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The Second International Workshop on the Biology of Sauropod Dinosaurs (part I)

The views expressed are those of the author and are not necessarily those of Scientific American.


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Diplodocid sauropods, artwork by Mark Witton.

ResearchBlogging.org

Sauropod dinosaurs are – in my somewhat biased opinion – among the most fascinating tetrapods that ever evolved. Exceeding all other terrestrial animals by an order of magnitude and famous for their extreme and often ridiculous necks, they were also remarkable in possessing an often elaborate degree of skeletal pneumatisation. Remember that sauropods were incredibly successful and were a persistent and obvious group of animals over a huge span of time. Sauropods pose a huge number of questions concerning behaviour, physiology, soft-tissue anatomy, reproduction, ecology and so on. Naturally, many of the questions we’d like to have answered just can’t be, given the limitations of the fossil record.

But in recent years a large number of scientists from diverse backgrounds have worked together in an concerted effort to better understand sauropod biology and determine the causes of their gigantism.

This research consortium, titled Research Unit 533 ‘Biology of the Sauropod Dinosaurs: the Evolution of Gigantism’ and funded by the German Research Foundation, is truly multidisciplinary, involving botanists, physiologists, biomechanists and other experts on living organisms – not just palaeontologists. A large number of technical papers have been produced by this research group, as has a very handsome multi-authored volume (Klein et al. 2011) [cover shown here]. Note that the group’s most influential publication – the major review of sauropod biology and evolution that is Sander et al. (2011) – is open-access and available free to all.

Palaeontologists near-universally agree on several aspects of sauropod biology. Sauropods were herbivores; they didn’t masticate their food or use gastroliths but almost certainly relied on rapid cropping and swallowing and hindgut fermentation; they possessed heterogenous, ‘bird-like’ lungs and a bird-like pneumatic system; and they laid clutches of hard-shelled eggs. There are some other ideas that are not exactly universally agreed on, but look increasingly well supported. One is that sauropods grew quickly (on par with precocial birds) and reached sexual maturity in their second decade. In modern animals, high growth rates like those seen in sauropods are only present in endothermic mammals and birds, and recent reviews of sauropod biology argue that – like mammals and birds – sauropods were most likely tachymetabolic endotherms (Sander & Clauss 2008, Sander et al. 2011). Another mostly accepted idea is that sauropods did not practise post-hatching parental care and that juvenile mortality was high.

One aim of the sauropod research group has been to determine how sauropods were able to grow so large. Clearly, no single factor led to gigantism in sauropods: numerous features were added piecemeal to produce the ultimate recipe for gigantism. These include a long neck, lack of reliance on mastication, avian-style lung, and production of numerous small young (Rauhut et al. 2011, Sander et al. 2011). The presence of the dinosaur bauplan contributed in some way to sauropod gigantism, since traits common to all dinosaurs (like parasagittal gaits and high growth rates) obviously allowed members of all dinosaurian lineages to evolve large body size with comparative ease.

Flow chart depicting evolutionary events that, combined, led to sauropod gigantism. From Sander et al. (2011).

With both our evolving understanding of sauropods, and the significant progress of the sauropod research group as required background knowledge, we now turn to the fact that the group recently hosted the second of its international workshops. Held at the University of Bonn, Germany, the meeting featured over 40 presentations on sauropods, given by researchers from all over the world. I wasn’t able to make the previous meeting (held in 2008), but am very pleased to report that I attended, and spoke at, this second one.

So – - three entire days devoted specifically to sauropod biology, physiology, reproduction, biomechanics and so on. As I said above, we can’t presently answer questions about such things as sauropod swallowing mechanics, pigmentation patterns, vocal abilities or mating postures, but – by the end of the meeting – we had certainly discussed, speculated about, and commented on, the majority of such issues.

Because the meeting was billed as a workshop – not just as a conference or seminar – discussion sessions followed each and every talk. This worked really well and it was typically all too easy to use up the 20 or so minutes of discussion allotted to each talk. In the text that follows, I haven’t discussed or even mentioned all the talks, but (as per usual) have mostly covered the ones that I found the most interesting, most enjoyable, or most memorable.

Reconstruction of a Massospondylus hatchling, from Reisz et al. (2005).

During the very first talk of the meeting, Robert Reisz discussed the large amount of new information he and his colleagues now have on the ontogeny and nesting behaviour of Massospondylus (note: not a sauropod, but a close relative of Sauropoda within the more inclusive clade Sauropodomorpha. A ‘prosauropod’). Much of this is unpublished so I won’t share it, but we’ve known for a while that juvenile Massospondylus are toothless, quadrupedal little animals, very different from the toothed, bipedal adults (Reisz et al. 2005). Does the association of those tiny babies with adults imply parental care? And what were the babies eating – were they provisioned by their parents or were they just eating something completely different?

Even at this very early stage of the conference, comments and questions were arising about neck posture, in particular because Robert said that Massospondylus most likely had a horizontal neck posture (a conclusion he reached following direct articulation of the fossil neck vertebrae). However, when you plug cervical vertebrae together in living animals, you never get the normal alert posture. I seem to remember a 2009 paper that took the trouble to point this out… we’ll be coming back to this issue later.

Photo of Tyrannosaurus by Scott Robert Anselmo, from wikipedia.

There followed a number of talks on sauropod growth rates, thermophysiology, digestion and feeding strategies. Chris Carbone spoke about his work on the ecology of Tyrannosaurus: a peculiar topic for a sauropod conference perhaps, but one with implications for several Mesozoic environments and foodwebs (Chris comes from a background in modelling energetic constraints in terrestrial predators and other animals: see Carbone et al. (1999)). You might think that the whole silly idea of the ‘scavenger rex’ is either dead or a non-issue, but it seems not to be so: one member of the audience implied strongly in the discussion section after the talk that T. rex’s morphology is inconsistent with hunting and only consistent with obligate scavenging. Err, what? The bottom line of Carbone et al. (2011) is that a hypothetical Maastrichtian habitat, realistically scattered with the carcasses of contemporaneous herbivores, would not provide enough available prey mass for a foraging T. rex, given physiological constraints. As I said to Chris after his talk, even this model is a best-case scenario, since there’s no one place in western North America where all the species listed in the analysis actually lived together. Sure, T. rex occurs from New Mexico all the way north to Saskatchewan, but Alamosaurus and various of the other dinosaurs included in the study don’t.

Reconstruction of Mamenchisaurus youngi by Steveoc 86, from wikipedia.

Two talks focused on the incredible Chinese mamenchisaurids, famous for their ridiculous necks (consisting of 16-17 vertebrae and, in cases, being four times as long as the body). In recent years a large number of new mamenchisaurid taxa have been named, and even the genus Mamenchisaurus itself now contains eight species. While these Mamenchisaurus species are superficially similar, it’s generally agreed that they likely aren’t close relatives. So it wasn’t really a surprise when a new cladistic analysis presented by Toru Sekiya scattered Mamenchisaurus to the four winds, though this was preliminary (one Mamenchisaurus species was recovered in a very counter-intuitive/startling position). It’s not as appreciated as it should be that some mamenchisaurids were truly enormous – there are mass estimates for some of the species that exceed 70 tons.

Europasaurus holgeri; photo by Ghedoghedo. It's perhaps not obvious from the photo how small this animal is (for a sauropod): about 6 m long.

José Carbadillo discussed the growth changes that occur in the vertebrae of the dwarf European titanosauriform Europasaurus [adjacent photo by Ghedoghedo]. For those who don’t know, this was an island-endemic dwarf sauropod, at most 6 m long and less than 1.5 m tall at the shoulder. The Europasaurus situation has become more complicated now we know that some animals reached skeletal maturity at much smaller body size than others – this seems to show that there are actually two europasaur taxa in the assemblage, both of which are dwarfs. Also on axial morphology, Francisco Gascó discussed the vertebral anatomy of the Spanish sauropods Losillasaurus and Turiasaurus, both of which seem to be part of the recently recognised non-neosauropod clade Turiasauria. You probably know that Francisco (aka Paco) blogs at El Pakozoico.

Francisco Gascó's opening slide, showing his excellent reconstructions of the Spanish turiasaurian sauropods Turiasaurus and Losillasaurus.

Three talks used computer modelling techniques (primarily finite element techniques) to analyse sauropod (and Plateosaurus) skull or pelvic structure. Phil Manning discussed synchrotron-based imaging work done on the skin of the famous Auca Mahuevo titanosaur embryo. I’ll hold off on saying anything further about this work, since the results are (understandably) embargoed.

Day two included sessions on the constraints of gigantism, feeding and digestion, and on reproduction and life history. Andreas Christian discussed something dear to my heart – the allometry of intraspecific fighting behaviour in animals and what it might mean for sauropods. Small animals can roll around and literally throw each other into the air [fighting cats from here], but this doesn’t work for big ones. They have to rely on body-barging or pushing. If sauropods did fight, it’s likely that this is what they did. Andreas has been a strong proponent of elevated neck postures in sauropods (his papers include useful work on neck posture and neck anatomy in ostriches, camels and other living animals) and his talks always include numerous amusing cartoons about the Necks Wars (an area we’ll return to in part II).

Digital reconstruction of a race-walking plateosaur, by Heinrich Mallison.

Heinrich Mallison discussed his new ideas about limb kinematics in long-tailed dinosaurs. Heinrich argues that we need to think anew about the importance of femoral retraction and protraction in dinosaurs and what it might mean for locomotion. Basically, he argues for speed-walking/race-walking dinosaurs where it’s the heavily muscled thigh and tail that provides the main power during fast movement, with the ankle being less important than traditionally thought. It all sounds pretty compelling but we know that some biomechanists who specialise on dinosaurs see problems with the idea. You can read all the details on Heinrich’s blog (dinosaurpalaeo), starting here. Heinrich also discussed possible resting postures for sauropods.

"Are fast-moving elephants really running?". Yes, it seems.

Bill Sellers also looked at the locomotor capabilities of sauropods, discussing evolutionary robotics and the construction of computer-generated models derived from laser scanning of mounted skeletons. John Hutchinson reviewed recent work on biomechanics in elephants, dinosaurs and other animals to see how they cope with the challenges of gigantism. Various preconceptions and assumptions are false and unreliable (such as that limb joints are always ‘more columnar’ in big animals than smaller ones). New work on elephant foot dynamics and the stresses transmitted through limb bone shafts paint an increasingly complex picture as goes the biomechanics and abilities of giant quadrupeds [adjacent running elephant image from RVC page here; used with permission]. And John was also interested in testing that age-old question of how big a land animal can become. His answer? Hmm, vaguer than you might like (unless you’re a big fan of Godzilla).

A session on food uptake and digestion included several talks by botanists working on the diversity and growth physiology of Mesozoic plants. Controversies over the composition of the Mesozoic atmospheric mean that radically different models need to be explored (some workers argue for high oxygen levels, others for much lower ones). Jennifer McElwain spoke about her fascinating work on plant-atmosphere interactions. Specially constructed greenhouses allow plants to be grown in simulated ‘prehistoric’ atmospheres.

Carole Gee discussed the plant foods available to sauropods and the nutritional values of those plants (see Gee 2011). Among the many plants available to sauropods, Araucaria species are particularly interesting in that they release a large amount of energy when retained for a long period in the hindgut. They are also particularly good at regenerating broken branches and tree-tops.

Baby diplodocids foraging on ferns, from Walking With Dinosaurs. (c) BBC.

Equisetum is also of special interest in the context of sauropod biology given that it was widespread across the Mesozoic world and is also energy-rich. Indeed, juvenile geese can fuel their growth demands on an Equisetum diet. I mentioned earlier that we think that sauropods grew at rates comparable to those of precocial birds. For some time now, those of us particularly interested in sauropod biology have regarded the apparently rapid growth of sauropods as a bit of an enigma. Surely, we mused, low-quality vegetation (ferns and the like) just can’t provide enough energy to fuel this sort of thing? So, we wondered, is it plausible that sauropods were somehow provisioned by their parents? Were babies provided with some sort of secretion produced by the mother, or did they feed from regurgitated, pre-digested plant slop or something? Such ideas are not ridiculous, since parental provisioning of babies is hardly unique to mammals: members of several bird groups produce ‘milk’ for their young, and there are frogs and caecilians that feed their young with special skin, eggs, or cloacal secretions. Yum. Regardless, it seems that these speculations (note: unpublished and technically off-the-record) are now unwarranted. Baby sauropods could apparently fuel their growth just fine on a diet of Mesozoic plants. And, yes, of course there is always the possibility that juveniles were omnivorous, snacking on insects and such on occasion.

L to r: Mike Taylor, Darren Naish, Vanessa Graff and Matt Wedel at Bonn. Also, the largest saurischian skull we could find.

On that note, time to call it quits. The remainder of my thoughts to appear in part II. You can read further thoughts on the meeting here at SV-POW! and note also that both Heinrich Mallison and John Hutchinson tweeted continually throughout the meeting under #SauroBonn. For previous Tet Zoo articles on sauropod biology and behaviour see…

Refs – -

Carbone, C., Mace, G. M., Roberts, S. C. & Macdonald, D. W. 1999. Energetic constraints on the diet of terrestrial carnivores. Nature 402, 286-288.

Carbone C, Turvey ST, & Bielby J (2011). Intra-guild competition and its implications for one of the biggest terrestrial predators, Tyrannosaurus rex. Proceedings. Biological sciences / The Royal Society, 278 (1718), 2682-90 PMID: 21270037

Gee, C. T. 2011. Dietary options for the sauropod dinosaurs from an integrated botanical and paleobotanical perspective. In Klein, N., Remes, K., Gee, C. T. & Sander, P. M. (eds). Biology of Sauropod Dinosaurs: Understanding the Life of Giants. Indiana University Press (Bloomington & Indianapolis), pp. 34-56.

Klein, N., Remes, K., Gee, C. T. & Sander, P. M. 2011. Biology of Sauropod Dinosaurs: Understanding the Life of Giants. Indiana University Press (Bloomington & Indianapolis).

Rauhut, O. W. M., Fechner, R., Remes, K. & Reis, K. 2011. How to get big in the Mesozoic: the evolution of the sauropodomorph body plan. In Klein, N., Remes, K., Gee, C. T. & Sander, P. M. (eds). Biology of Sauropod Dinosaurs: Understanding the Life of Giants. Indiana University Press (Bloomington & Indianapolis), pp. 119-149.

Reisz, R. R., Scott, D., Sues, H.-D., Evans, D. C. & Raath, M. A. 2005. Embryos of an Early Jurassic prosauropod dinosaur and their evolutionary significance. Science 309, 761-764.

Sander, P. M., Christian, A., Clauss, M., Fechner, R., Gee, C. T., Griebeler, E.-M., Gunga, H.-C., Hummel, J., Heinrich, M., Perry, S. F., Preuschoft, H., Rauhut, O. W. M., Remes, K., Tütken, T., Wings, O. & Witzel, U. 2011. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews of the Cambridge Philosophical Society 86, 117-155.

- . & Clauss, M. 2008. Sauropod gigantism. Science 322, 200-201.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. David Marjanović 7:40 am 12/19/2011

    I’m very happy that a cladistic analysis of the mamenchisaurids (…omeisaurids?) has finally been done! All those species assigned seemingly at random to Mamenchisaurus or Omeisaurus were a headache.

    Link to this
  2. 2. Jerzy New 8:28 am 12/19/2011

    I think the assumption that sauroods could grow so fast on plant food are overoptymistic.

    Question one is: so why elephants, rhinos, giraffe etc. grow so slow? Surely, percentage of absorbed energy is overestimated and energetic needs unrelated to growth (moving around etc) is ujnderestimated?

    Question two: is extrapolating growth curve of a goose-sized bird into dinosaur size sensible? Aren’t mass-to-volume effects kicking in at medium to near-adult size, for example size of food resource patches, foraging time, size of fermentation chamber, gut passage times, size of absorbing area of the interstines? And another constraint: by being independent, juvenile sauropods were in competition with adults for best foraging patches. Would it work?

    Cannot await biomechanics study of juvenile sauropods based on assumption that adults must have moved. Small juveniles should be incredibly overbuild and mobile critters.

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  3. 3. HowardRichards 12:53 pm 12/19/2011

    I’m curious about the statement that sauropods did not use gastroliths. The last I had heard on the subject (which is from a decade or more ago — I know, an eternity in an active science) was that gastroliths were usually found with sauropod fossils, and one sauropod in particular had apparently choked while trying to swallow a stone that was too large. Were these stones just accidental associations, or were they perhaps hoovered up by accident as the animal was eating?

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  4. 4. MikeTaylor 5:17 pm 12/19/2011

    Excellent write-up, thanks Darren. One correction: Mamenchisaurus cervical counts got up to 19, not just 17.

    Yes, David, it was good to see some phylogenetic techniques applied to the Mamenchisaurus/Omeisaurus complex. For some time the idea has been floating around that these two very speciose genera are intertwingled, but it seems from what was said at the conference that (while some species are misassigned), the genera are basically separate and distinguished by at least two significant characters: Mamenchisaurus has bifid posterior cercival and anterior dorsal neural spines, and procoelous anterior caudals; while Omeisaurus has unsplit spines throughout and amphiplatyan anterior caudals. Seems pretty convincing to me.

    Jerzy, we were also sceptical that juvenile sauropods could grow at altricial bird rates on vegetation without some kind of parental care, but now that we’ve spoken to some actual palaeobotanists and nutrition specialists, our doubts are dealt with. Not a problem: they could do it on Equisetum (horsetails), and there is no need to invoke the Nourishing Vomit of Eucamerotus hypothesis. The specific issues you raised have not been overlooked by the people who work on this stuff.

    HowardRichard, Oliver Wings has published the definitive work on sauropod gastroliths — it’s been the keystone of his career — and concluded that they were not used in digestion. See http://rspb.royalsocietypublishing.org/content/274/1610/635

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  5. 5. Heteromeles 5:23 pm 12/19/2011

    @Jerzy: My guess is that pneumaticity might make fast growth possible. Crudely, a sauropod has less tissue per cubic meter than an elephant does. In architectural terms, if an elephant is built like the Great Pyramid, a sauropod is built like the Colosseum.

    One question for Darren: does pneumaticity increase with sauropod size? And does it increase with size with conspecifics (e.g. do big bulls have bigger holes?)? If so, they one would expect sauropods to grow bigger and faster than elephants, simply because their mass scales at something less than height cubed. One would also expect smaller sauropods to have less complex lungs, proportionally heavier bones, and so forth, compared to the more skyscraping individuals.

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  6. 6. HowardRichards 6:14 pm 12/19/2011

    @Mike Taylor

    OK, so there were gastroliths, but no gastric mill. I suppose this means they ate the stones by accident? If so, they must have been feeding a good deal lower than is often portrayed. Or was there some other use for the stones? I know many animals eat earth for the minerals, but that’s usually clay, not stones.

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  7. 7. Jerzy New 5:08 am 12/20/2011

    @MikeTaylor
    Unconvinced. Among others, extrapolating the nutritional value of modern Equisetum backwards 100 million years is obviously shaky. Then, ecology of plant-herbivore interactions and herbivore competition goes mad here – why modern farmers don’t grow Equisetum instead of alfalfa and lucerne, herbivore pressure in the wild makes easy to eat and nutritious plants rare…

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  8. 8. naishd 6:28 am 12/20/2011

    Thanks for comments. On a diet of nutritious plants being sufficient to fuel sauropod growth, I of course agree with Mike’s comment (comment 4). Equisetum has been identified as a nutritious food source (22% protein in dry weight, with high phosphorus content) utilised by geese and swans, and also by caribou, bison, musk ox etc.

    Jerzy – you might misunderstand the issue: it isn’t that eating Equisetum turns you magically into a sauropod-style giant; rather, it’s that Equisetum could theoretically provide sufficient energy to fuel sauropod growth demands. But non-sauropods can also meet their nutritional demands from eating Equisetum too. Something else to consider is that birds and sauropods are far better at eating Equisetum than mammals, since birds and sauropods don’t chew (and hence aren’t so bothered by the abrasiveness of horsetail stems). There is every indication from nutritional scientists and digestive physiologists that horsetails release sufficient energy during fermentation to fuel the metabolism of big, endothermic herbivores: in fact, horsetails exceed grasses in this regard. See…

    Hummel, J. & Clauss, M. 2011. Sauropod feeding and digestive physiology. In Klein, N., Remes, K., Gee, C. T. & Sander, P. M. (eds). Biology of Sauropod Dinosaurs: Understanding the Life of Giants. Indiana University Press (Bloomington & Indianapolis), pp. 11-33.

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  9. 9. naishd 6:31 am 12/20/2011

    Other responses…

    Another Wings paper debunking the existence of gastroliths in sauropods is…

    Wings, O. 2007. A review of gastrolith function with implications for fossil vertebrates and a revised classification. Acta Palaeontologica Polonica 52, 1-16.

    Neck vertebrae in Mamenchisaurus: I did think 19 sounded correct, but on checking Upchurch et al. (2004) I saw that they give 17 for this taxon. What gives?

    Darren

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  10. 10. Dartian 6:32 am 12/20/2011

    Jerzy:
    why modern farmers don’t grow Equisetum

    Perhaps they should. Poultry farmers, anyway; wild geese – and their fast-growing goslings – are known to feed extensively on Equisetum. See:

    Thomas, V.G. & Prevett, J.P. 1982. The role of horsetails (Equisetaceae) in the nutrition of northern-breeding geese. Oecologia 53, 359-363.

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  11. 11. Dartian 6:34 am 12/20/2011

    Oops, cross-posting with Darren. Sorry.

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  12. 12. naishd 6:59 am 12/20/2011

    Dartian – hey, the more comments the merrier, seriously (you might know that we continually work hard behind-the-scenes to get MORE commenting here at SciAm blogs. Yes, progress is being made with the registration and all that).

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  13. 13. David Marjanović 7:03 am 12/20/2011

    Equisetum has been identified as a nutritious food source (22% protein in dry weight

    :-o

    extrapolating the nutritional value of modern Equisetum backwards 100 million years is obviously shaky

    Why? Is there any parsimonious reason to think much has changed?

    Neck vertebrae in Mamenchisaurus: I did think 19 sounded correct, but on checking Upchurch et al. (2004) I saw that they give 17 for this taxon. What gives?

    I bet it depends on the definition of “neck”. In birds, the third pair of long ribs is the first to contact the sternum, and therefore the vertebra they’re attached to is traditionally called the first dorsal by analogy to mammals.

    …Of course, in mammals, the first pair of long ribs contacts the sternum directly, without intervening sternal ribs. That doesn’t happen in sauropsids at all, AFAIK, and the sternum in birds is simply too far away from the first two pairs of long ribs to contact them directly or indirectly.

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  14. 14. naishd 7:05 am 12/20/2011

    Oops, I overlooked the comment from Heteromeles (comment 5)…

    “does pneumaticity increase with sauropod size? And does it increase with size with conspecifics (e.g. do big bulls have bigger holes?)?”

    A rough rule of thumb in pneumatic archosaurs is that the largest taxa are the most pneumatic, while the smaller ones may even apparently reduce their pneumaticity relative to the ancestral condition. So, giant brachiosaurs and titanosaurs are highly pneumatic (cervical vertebrae of Sauroposeidon, for example, are more than 80% air) while small dicraeosaurids have little pneumaticity relative to other flagellicaudatan diplodocoids (there is inconsistency, of course: small-bodied rebbachisaurids are crazy pneumatic). So, there’s a phylogenetic aspect to the amount of pneumaticity. But there’s an ontogenetic one as well: pneumatisation increases as an animal gets older, with pneumatic fossae and foramina increasing in number and becoming more elaborate with age. Matt Wedel is the go-to guy for this stuff, he may comment further. Hope this helps.

    Darren

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  15. 15. MikeTaylor 7:56 am 12/20/2011

    Lots to respond to here … I wish this crappy commenting system would provide a Preview facility, so I could use BLOCKQUOTE tags without gambling on my entire comment becoming unreadable. *sigh*

    Anyway …

    Heteromeles said “My guess is that pneumaticity might make fast growth possible. Crudely, a sauropod has less tissue per cubic meter than an elephant does.”

    Heteromeles asked “does pneumaticity increase with sauropod size? And does it increase with size with conspecifics (e.g. do big bulls have bigger holes?)?”

    Darren has already given a partial answer to this. But as always, your sauropod vertebra needs are best met over on Sauropod Vertebra Picture of the Week (clue’s in the question), specifically in the article Were the biggest sauropods the most pneumatic?. Enjoy at http://svpow.wordpress.com/2008/03/19/were-the-biggest-sauropods-the-most-pneumatic/

    HowardRichards asked “OK, so there were gastroliths, but no gastric mill. I suppose this means they ate the stones by accident? [and more questions]”

    I’m afraid I don’t know without reading the Wings paper. He is very much the go-to guy. If you care about gastroliths you need to read his stuff. What I do know from his work is that (A) yes, some sauropods probably had some stones in their guts, though the evidence is not 100% convincing; but (B) even when they had gastroliths, the quantities were pathetically inadequate for milling.

    Jerzy New wrote “Unconvinced. Among others, extrapolating the nutritional value of modern Equisetum backwards 100 million years is obviously shaky [snip]”

    Well, I am not knowledgeable enough to address your specific issues. All I can tell you is that, when talking to half a dozen palaeobotanists and nutritionists about this matter, and then they all unanimously said that available vegetation was sufficient to sustain atricial-bird levels of growth in juvenile sauropods, I lacked the courage to put my uninformed intuition up against their actual expertise. I guess you should contact them directly if you feel differently. Start with Carole Gee and Jurgen Hummel. Let me know when you’ve refuted them.

    Darren wrote: “I did think 19 sounded correct, but on checking Upchurch et al. (2004) I saw that they give 17 for [Mamenchisaurus]. What gives?”

    Interesting! I can tell you that Young and Zhao (1972), in the description of M. hochuanensis definitely enumerated 19 cervicals, giving measurements for each of them, and that I have verified this count in two separate casts of the holotype. I don’t know what Paul was thinking of in Upchurch et al. (2004:279).

    But:

    David Marjanovic wrote “I bet it depends on the definition of ‘neck’.”

    That is an excellent point, and one much overlooked in sauropod neck studies. We talk as though the neck and torso are clearly delineated separate units, but of course the cervical vertebrae shade into the dorsals. I can easily see how the 19th cervical of M. hochuanensis might be recategorised as a dorsal; but not the 18th.

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  16. 16. Andreas Johansson 8:22 am 12/20/2011

    Regarding the elephant, am I missing something? When I was taught that elephants can’t run, the (explicit) definition of running given involved all four (or two, for bipeds) feet being off the ground during part of each cycle, which doesn’t seem to be happening in that picture?

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  17. 17. naishd 9:07 am 12/20/2011

    Andreas: it turns out that many animals very much capable of running in the traditionally understood sense (e.g., certain birds, some horses) do not actually undergo a suspended phase when all feet are off the ground. For starters, look at the RVC papers listed here.

    Darren

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  18. 18. Jerzy New 10:19 am 12/20/2011

    @David Marjanović
    Try to eat any plant known to be edible to some other tetrapod, or any of the deadly poisonous plants closely related to edible plants.

    @naishd
    I think there is a misunderstanding there. No doubt Mesosoic vegetation was as lush as today’s tropics. Yet todays tropics don’t support herbivores growing so fast when the size of elephant. Animals in practice cannot grow as fast as plant resources avialable suggest.

    Paleobotanist or nutritionist is not likely to understand problems of scale at elephant-sized animals, or herbivore ecology.

    For example, precocial chicks of geese and ducks spend much of the day feeding under vigilance of parents. Would they have sufficent time to feed when we scale the size to half-grown sauropod?

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  19. 19. Jerzy New 10:37 am 12/20/2011

    Continued: imagine we scale a goose chick upwards. Size of a mouthful of food increases by square, mass of body to produce by cube. Animal would quickly need to feed over 24 hours per day. Or, simply, its growth would slow to match intake.

    Then is an issue of resources avialable. Imagine tasty plants grow randomly. Size of a feeding patch can be modelled by Poisson distribution (small patches are common, large patches are rare). Chick the size of a goose can find many suitable patches. When it grows, it must lose more and more time travelling to find food.

    Link to this
  20. 20. Heteromeles 12:08 pm 12/20/2011

    About extrapolating backwards on plants…
    1. This *probably* doesn’t apply to Equisetum, but
    2. It is a problem.

    The issue is that there are big differences between systems that are dominated by grazers or browsers, and those where the plants compete directly with each other for resources. When a plant predator is present, the dominant plants are those that are either immune to that predator, or (more commonly) the ones that recover better from grazing than the other plants do. A great example of this is California grasses vs. Great Plains grasses. The California grasses can’t tolerate the type of grazing they’d get under buffalo or cattle, and they were being grazed by megaherbivores only 10,000 years ago. Prairie grasses, of course, do great under ungulate grazing.

    This doesn’t apply to Equisetum, because as a group, they tend to have underground rhizomes that are fairly difficult to remove (think backhoe). I suspect farmers don’t grow equisetum because a) there’s not much use for it (unless you want a really green scouring pad), b) it’s difficult to harvest (the silica in the stem dulls steel just as it messes up vertebrate teeth), and c) it’s difficult to keep under control (due to those underground rhizomes and the way it dulls cutters). I’ve heard more complaints about how hard it is to get out of lawns than I have people (other than botanists) praising this group.

    Personally, I’m concerned about uncritical extrapolations of mesozoic conifers from modern ones than I am about extrapolations on equisetum. The extant species appear to have the same adaptations they’d need to survive dinosaur grazing.

    Final note: since Equisetum (I recall) has silica phytoliths, there should be evidence in coprolites about what dinosaurs were feeding on.

    Link to this
  21. 21. naishd 5:01 am 12/21/2011

    For Jerzy and Heteromeles – I don’t think your criticisms are fair in view of, you know, the work done and published by the nutritionialists, physiologists, botanists and sauropod experts who actually worked together on this issue. We know that sauropods grew quickly, at rates comparable to those of precocial birds. How could they get enough energy to fuel this growth? Answer: nutritional plants, including horsetails, provide sufficient energy. End of discussion.

    Coprolites: it’s about impossible to match coprolites to the species that produced them. Some putative sauropod coprolites from India preserve phytoliths and other fragments from grasses and other plants.

    So – - time to publish part II?

    Link to this
  22. 22. Jurassosaurus 9:38 am 12/21/2011

    David Marjanovic wrote:
    Why? Is there any parsimonious reason to think much has changed?

    Yes, evolution. Assuming that organisms today are the exact same as organism millions of years ago is a classic misapplication of uniformitarianism. Even taxa that appear to have changed very little morphologically, were likely very different genetically, behaviourally, and/or physiologically. How much of these changes would affect nutritional value I’m not sure, but Jerzy is absolutely right when he says that extrapolating the nutritional value of an extant plant back 100 million years is a shaky thing to do.

    I think folks have been getting the wrong impression from Hummel’s work. What he and others have shown is that if sauropods were alive today, they could sustain high growth rates on certain extant plants, even if they were running on an inefficient automatic endotherm metabolism. If we can find plants today that can do that, it is very likely that there were plants in the Mesozoic equally as capable (kind of a given seeing as how sauropods were very successful in their time, so the environments could obviously hold them).

    As for the sauropods grew like precocial birds mantra, I want to point out that we don’t actually know this. It has been assumed — based off some (mostly Sander) studies — that sauropods were fast growers, but to say that they grew like precocial birds is being disingenuous, however unintentional. As Jerzy pointed out earlier, one can’t simply take a regression line for birds between a couple hundred grams and 140kg, and then extrapolate it to the right a couple orders of magnitude. It violates a cardinal rule of statistics to do that. Regression lines are only good for the data they encompass. Going beyond that is assuming that the equation one has found is a real thing, and not just an equation good for animals between x and y body sizes. There is no guarantee that the distribution stays normal beyond those body sizes in either direction. Sander et al. are hardly alone in doing this. It is one of the most common and egregious errors in paleontology. Besides that one must also keep in mind that we are estimating the final masses of these animals, a number that varies wildly depending on what technique is used. We are also using static masses despite the fact that individuals within a population may differ substantial in their final adult masses (cf humans). Rarely have I seen a dino growth rate study that has incorporated a range of masses for their taxa. The final mass chosen is going to effect one’s final estimate for growth rate. There are a whole host of problems with estimating growth rates in dinosaurs. I suspect that much of this should be old news for those in the biz, yet despite all these caveats most dinosaur growth studies (e.g. Sander et al., Werning and Lee) fail to address these problems, or even use appropriate caution in their language. I don’t doubt that sauropods grew quickly (all large animals do), but we cannot compare the growth rate of multitonne dinosaurs to the growth rate either extant reptiles (which rarely reach 1 tonne), or extant birds (which don’t even come close to reaching 1 tonne). The best we can really hope for is to compare relative growth rates of dinosaurs to each other. It’s not very quantitative, but that is really all the data will let us do.

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  23. 23. yartar@yahoo.com 10:10 am 12/21/2011

    Jurassosaurus: wait a minute. You’re suggesting that mesozoic plants might have been different in nutritional value compared to living ones based on a hunch? An assumption that this must have been the case just because it…. must have been the case? That does not sound much like sound reasoning to me. I would think it conservative to assume that fossil horsetails were similar to modern ones in calorific value – this is conservative because growth in simulated mesozoic atmospheres make mesozoic plants more nutritious than living ones, not less.

    Link to this
  24. 24. Heteromeles 10:58 am 12/21/2011

    @NaishD: Hoo boy. That’s the last time I defend Equisetum. Or sauropod growth. Silly me.

    To reiterate: I’ve got no problem with the botanists’ work,

    Nor do I have a problem with Equisetum’s nutritional value,

    Nor do I have a problem with reported sauropod growth rates. I think it’s cool, and if pneumaticity increases with size, that would provide a handy mechanism, because they’d get less dense the bigger they got, which means they could grow faster than an organism that maintained constant density as it grew.

    The only piece of evidence I’d like to see is some equisetum phytoliths in a coprolite, because that would prove that dinosaurs of some sort ate equisetum. That would be useful evidence, right?

    Now, to take the baseball bat to some paleontological skulls: the problem with extrapolating from modern plants is that susceptibility to browsing changes *fast* in geological time. You can see this with loss of chemical defenses on island plants and currently with conifer seedlings in the northeastern US (which are being devastated by a horde of white-tailed deer), among many other examples. The fast changes occur in things like the position of buds and chemical defenses, and occur because the plants switch allocation from defending against some class of herbivores to competing against other plants. So far as I know, things like equisetum phytoliths don’t change quite so fast.

    The problem isn’t equisetum. It’s conifers. The stuff that the adult sauropods ate. I’ve seen far too many reconstructions where the dinosaurs are wandering through a modern-looking coniferous forest (usually a copy of a ponderosa forest, with sequoias in place of ponderosas, and ferns in place of flowers). It almost certainly didn’t look that way, simply because grazing pressure does some weird things to tree growth and reproduction, even when the trees are adapted to it.

    I’m not going to elaborate more, because the last time I posted, Darren jumped down my throat because he thought I was talking about equisetum when I said there’s a problem.

    Does this make sense?

    Link to this
  25. 25. ChasCPeterson 3:59 pm 12/21/2011

    In modern animals, high growth rates like those seen in sauropods are only present in endothermic mammals and birds

    Correlation.
    Causation.
    =/=.
    What is the proposed mechanism by which high metabolic rates are supposed to cause high growth rates?
    Where should I look for an answer to this question?

    juvenile sauropods could grow at altricial bird rates

    Wait, altricial or precocial? Because altricial birds grow much faster than precocial ones. Why? Because they are ectothermic while growing at those astronomical rates.

    I’ve had big problems with the claim that high growth rates are evidence for endothermy (or tachymetabolism) in dinosaurs for a long long time. I’d love to see some convincing arguments.

    Link to this
  26. 26. Owlmirror 6:05 pm 12/21/2011

    [[Coprolites: it’s about impossible to match coprolites to the species that produced them. ]]

    I found myself wondering if there might be some empirically testable correlation of poop to pooper. If it falls from a greater height and splats more, would that not imply sauropod? Are there no trace fossils of footprints near any dinosaur coprolites?

    How about parasite eggs? Do modern herbivores have well-distinguishable parasites that correlate to individual species? I seem to recall reading that they do, but I may be misremembering.

    Somewhat disappointingly, I see that there appears to be only one paper on dinosaur intestinal parasites. The field is wide open!

    Poinar,G & Boucot,A.J. 2006. Evidence of intestinal parasites of dinosaurs. Parasitology, 133 , pp 245-249 doi:10.1017/S0031182006000138

    Link to this
  27. 27. Jerzy New 4:13 am 12/22/2011

    There may be two direct ways to test parental feeding in sauropods.

    First, teeth and tooth wear in juveniles and immatures. Was it weaker than adults? Was it different? Especially that above there is also a suggestion that juveniles could be partially insectivores. Especially interesting would be half-grown immatures – here effects of enormous body size on resources would kick in.

    Second: I hear mantra that dinosaur trackways prove this or that. Do we know any fossil trackways of precocial birds (not necessary Mesosoic), and do they show more organized movements of adults and juveniles than dinosaurs? Or, even easier to check – take pictures of modern mudflats where families of geese, ducks, coots or waders fed. Do feet of adults and juveniles follow together? In my limited experience, feeding precocial chicks run independently around parents and their trackways would show little correlation with adult tracks.

    Link to this
  28. 28. MikeTaylor 4:46 am 12/22/2011

    ChasCPeterson notes the phrase “… juvenile sauropods could grow at altricial bird rates” and rightly asks “Wait, altricial or precocial?”

    My bad. I meant precocial, but typed altricial. Please mentally edit my earlier comment.

    Jerzy New wrote: “I hear mantra that dinosaur trackways prove this or that.”

    “Mantra”? You use that word a lot. I do not think it means what you think it does.

    Link to this
  29. 29. naishd 5:17 am 12/22/2011

    Dinosaur growth rates and physiology: I’m one of the worse people to talk about this issue, but anyway… It isn’t just that Mesozoic dinosaurs grew quickly (after all, ectothermic altricial birds and squids grow faster), it’s that they grew by continually depositing laminar fibrolamellar bone. I’ll quote from Sander et al. (2011):

    “Laminar fibrolamellar bone unequivocally indicates bone apposition rates only seen in endothermic vertebrates today. This is in agreement with data from growth mark records that indicate body mass gains of a few tons per year. Such growth rates are not seen in any living ectotherm (Case, 1978) and cannot be reconciled with the BMR of modern bradymetabolic terrestrial vertebrates but point to tachymetabolic endothermy in sauropods, at least during the phase of active growth (Sander et al., in press b).” (p. 132).

    Recent work has also shown that osteocyte lacunae size and nutrient foramina size in Mesozoic dinosaurs overlaps with that of endotherms, not with that of ectotherms. We seem to keep coming back to scepticism about dinosaur endothermy, but is there actually any evidence for ectothermy in Mesozoic dinosaurs? No, it just seems to come down to the ideas that, (a) dinosaurs were reptiles, and thus surely more like extant squamates and crocodilians, and (b) endothermy is stupid and inefficient, so ectothermy should be assumed. I’m not convinced by the logic here.

    Darren

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  30. 30. naishd 5:33 am 12/22/2011

    Jerzy (comment 27): in response, I would (as usual!!) remind you that we are limited in the data we have. There’s very little information on sauropod babies, certainly not enough to make meaningful statements about tooth wear. We do know that some diplodocids had narrower snouts than adults, and a dentition less restricted to the jaw tips, so it seems they were feeding in different fashion. As yet, there is no evidence that juvenile sauropods were eating anything ‘quirky’ with respect to adults.

    Tracks: juvenile sauropod tracks are not found in regular close association with adults; it seems that juveniles moved together, separately from adults (the ‘babies stayed in the middle of the herd’ is a total fabrication). While I’m here, there’s supposed to be a trackway that shows a baby sauropod running bipedally. This doesn’t make much sense, but so far it has only been reported in articles on the internet, not in print.

    Darren

    Link to this
  31. 31. David Marjanović 11:19 am 12/23/2011

    Login works again. Maybe it’s because I’ve switched from IE8 to Firefox 9. The problem with loading the main page has disappeared, too.

    Try to eat any plant known to be edible to some other tetrapod, or any of the deadly poisonous plants closely related to edible plants.

    The presence or absence of a toxin is just one difference. It’s not the kind of wholesale change in biochemistry that changes things like the protein content of a leaf.

    No doubt Mesosoic vegetation was as lush as today’s tropics. Yet todays tropics don’t support herbivores growing so fast when the size of elephant.

    Today’s tropics support… elephants.

    Paleobotanist or nutritionist is not likely to understand problems of scale at elephant-sized animals, or herbivore ecology.
    For example, precocial chicks of geese and ducks spend much of the day feeding under vigilance of parents. Would they have sufficent time to feed when we scale the size to half-grown sauropod?

    It’s strange of you that you assume the paleobotanists and nutritionists haven’t talked at all to the zoologists that are their coauthors and published behind their backs.

    You think growing sauropods wouldn’t have enough time to eat? Show me the math. I’m waiting.

    Continued: imagine we scale a goose chick upwards. Size of a mouthful of food increases by square

    ~:-| Are you sure? Mouths are three-dimensional.

    Then is an issue of resources avialable. Imagine tasty plants grow randomly. Size of a feeding patch can be modelled by Poisson distribution (small patches are common, large patches are rare). Chick the size of a goose can find many suitable patches. When it grows, it must lose more and more time travelling to find food.

    The more it grows, the less it depends on high-value food, because it can increase fermentation time more and more, till it can simply “graze” the forest itself.

    The only piece of evidence I’d like to see is some equisetum phytoliths in a coprolite, because that would prove that dinosaurs of some sort ate equisetum. That would be useful evidence, right?

    Sure. Problem is, terrestrial coprolites aren’t common, almost nobody has ever looked at the contents of Mesozoic terrestrial coprolites (the ones with the grass pollen, and the “king-size” coprolites assigned to Tyrannosaurus, are the only cases I know of!), and – apart from size – it would probably be impossible to assign a coprolite to anything more specific than “herbivorous archosaur”.

    I’ve seen far too many reconstructions where the dinosaurs are wandering through a modern-looking coniferous forest (usually a copy of a ponderosa forest, with sequoias in place of ponderosas, and ferns in place of flowers). It almost certainly didn’t look that way

    On this I fully agree!

    What is the proposed mechanism by which high metabolic rates are supposed to cause high growth rates?

    High metabolic rates allow high growth rates (as well as the rather slow ones of, say, humans) because growth is metabolism and consumes energy.

    Importantly, as you mention, high metabolic rates aren’t the same thing as endothermy. Endothermy requires metabolic rates above those found in most ectotherms, but it’s not an automatic consequence, and “high” covers a pretty broad range (sea cows and passeriforms are not in the same ballpark).

    Homeothermy is something else again.

    altricial birds grow much faster than precocial ones. Why? Because they are ectothermic while growing at those astronomical rates.

    Altricial chicks don’t use energy for anything but growth. They don’t move (much), and they don’t bother growing insulation, so their parents have to do that for them. I’m sure their ectothermy is a consequence of their astronomical growth rates rather than the other way around.

    I found myself wondering if there might be some empirically testable correlation of poop to pooper. If it falls from a greater height and splats more, would that not imply sauropod?

    What if sauropods pooped little pellets, like rabbits?

    Somewhat disappointingly, I see that there appears to be only one paper on dinosaur intestinal parasites. The field is wide open!

    The reason for why there’s just this one paper is that intestinal parasites simply don’t fossilize (under circumstances that have been encountered so far), except as eggs in coprolites.

    Especially interesting would be half-grown immatures – here effects of enormous body size on resources would kick in.

    Why at half adult size? Why not at 60 % or 10 % or 90 %? Why not at an absolute size instead of a relative one?

    Why do you pull numbers out of your ass? Do you even notice that that’s what you’re doing?

    Recent work has also shown that osteocyte lacunae size and nutrient foramina size in Mesozoic dinosaurs overlaps with that of endotherms, not with that of ectotherms.

    Smaller osteocyte lacunae = smaller cells (because of smaller genomes) = higher surface/volume ratio = potential for higher metabolism. Huge genomes and huge cells, as found in salamanders, don’t occur in tachymetabolic animals, and saurischian dinosaurs including birds have especially small ones.

    We seem to keep coming back to scepticism about dinosaur endothermy, but is there actually any evidence for ectothermy in Mesozoic dinosaurs? No, it just seems to come down to the ideas that, (a) dinosaurs were reptiles, and thus surely more like extant squamates and crocodilians, and (b) endothermy is stupid and inefficient, so ectothermy should be assumed. I’m not convinced by the logic here.

    Seconded.

    Link to this
  32. 32. JennDeland 10:02 pm 12/23/2011

    What’s a “diverse scientist?” Are you one? Or are you of the more boring, uniform variety? Or did you mean “diverse group?” If so, in what characteristics was the group diverse?

    Link to this
  33. 33. Jurassosaurus 2:42 am 12/24/2011

    My problem with the conclusions of Sander et al. is that they completely dismiss the multiple recorded cases we have of fibrolamellar bone growth in extant large reptiles (Reid, 1984, 1996, 1997, Ferguson et al. 1982, Chinsamy 2005, Tumarkin-Deratzian 2007). While one could argue the authors reasons for dismissal in the earlier papers from Reid, or Ferguson (the pictures aren’t that good in any of those papers), it just seems unreasonable to do so with the recent work by Tumarkin-Deratzian. Further, we have been steadily accumulating bone histology studies on other non-dinosaur species that also show fibrolamellar bone growth (Sauropterygians, rauisuchians, dinocephalians and as of SVP this year, pareiasaurs). None of these animals have ever been considered to be automatic endotherms. Couple that with our extant sample of fibrolamellar bone forming bradymetabolic critters and the supposed tight correlation between bone microstructure and thermophysiology is suddenly not so tight.

    Which brings us back to the initial problem. The argument that growth rate is tied to metabolism has always been a correlative one. Even as far back as Case’s seminal 1978 work, all that he found was a correlation. As ChasCPeterson alluded to, there is no mechanism behind it. There just seems to be this assumption that if one is tachymetabolic, this somehow magically allows for a high growth rate. But growth rate is going to be determined by both assimilation AND biomass conversion. In a world where all metabolisms are created equal then a tachymetabolic animal would grow faster than a bradymetabolic one, but tachymetabolic critters today (at least those that are constantly argued as having the type of MRs that dinosaurs should be compared to) have horrible biomass conversion rates ranging from 0.5% to 3% efficiency in small animals (Pough 1980) up to ~30% in mammals as large as humans. That we get high growth rates in extant automatic endotherms is something that is happening in spite of their thermophysiology, not because of it.

    Osteocyte lacunae data are interesting, but still too recent to say for certain what they mean. We currently don’t have a good sample of reptile data. I suspect that, much like bone microstructure and blood vessel shape, this will prove to be both variable within taxa (making for a good relative marker of growth rate, but a poor absolute marker), and unrelated to thermophysiology in the long run (like, every single other example that has been touted as a hallmark of a specific thermophysiological regime).

    We seem to keep coming back to scepticism about dinosaur endothermy, but is there actually any evidence for ectothermy in Mesozoic dinosaurs? No, it just seems to come down to the ideas that, (a) dinosaurs were reptiles, and thus surely more like extant squamates and crocodilians, and (b) endothermy is stupid and inefficient, so ectothermy should be assumed. I’m not convinced by the logic here.

    I feel that you are missing the point here. The argument has never been that “just because endothermy has all these problems, dinosaurs had to be ‘ectotherms’ since that was likely the plesiomorphic state.” It’s that none of the evidence put forth for dinosaurian endothermy actually counts as evidence for endothermy. Consider it this way:

    If one wanted to argue that dinosaurs were definitely “ectothermic,” one could just point out that dinosaur young were many orders of magnitude smaller than their adult forms (4,000 times smaller than the adults in Maiasaura, and even greater in sauropods). Such huge differences between hatching size and adult size are only seen in extant bradymetabolic animals. Dinosaurs also used their tails to drive their leg retractor muscles, resulting in large, hefty tails. Such tails are only seen in extant ectothermic animals.

    Now I’m betting neither of these examples are sitting well with you. They shouldn’t. All I’ve shown is something that happens to correlate with something else. That is probably as far as that relationship goes. However, this type of argument is exactly what we get with the erect stance = endothermy, high growth rate = endothermy, or the predator/prey ratio = endothermy arguments among many others. As ChasCPeterson already mentioned: just because two things correlate that doesn’t mean they are actually related.

    Schachner, Owerkowicz and Goodwin et al. all touched on this point at this year’s SVP. Thermophysiology is a complex subject, and something like tachymetabolic endothermy should not be viewed as a trait, but rather as a suite of traits that likely evolved in some kind of sequential, or iterative fashion. There is a trend, in dinosaur paleo, to associate tachymetabolic endothermy with any trait that is shared between dinosaurs, mammals, and birds. It’s become the bacon of paleo. It gets put on every dish regardless of whether it actually fits with the meal. More often than not, these traits that we have ascribed to endotherms only, are found to exist in extant reptiles and other bradymetabolic taxa too. We just hadn’t bothered to look before. Darren, you of all people should be familiar with this as your blog has repeatedly showcased examples where seemingly mammalian/avian only traits (e.g. play, parental feeding), have been found in reptiles, amphibians, or fish. This is no different.

    Refs:

    Chinsamy-Turan, A. 2005. The Microstructure of Dinosaur Bone: Deciphering Biology with Fine-Scale Techniques. JHU Press. Baltimore, MD. 216pgs ISBN: 080188120

    Ferguson, M. W. J., Honig, L.S., Bringas Jr, P., Slavkin, H.C. 1982. In vivo and in vitro development of first branchial arch derivatives in Alligator mississippiensis. Prog.Clin.Biol.Res. Vol.101:275–286

    Pough, H.F. 1980. The Advantages of Ectothermy for Tetrapods. Am.Nat. Vol.115(1):92-112

    Reid, R.E.H. 1984. Primary Bone and Dinosaurian Physiology. Geological Magazine 121:589–598.

    ________. 1996. Bone Histology of the Cleveland-Lloyd dinosaurs and of Dinosaurs in General. Part 1. Introduction to Bone Tissues. Brigham Young University Geology Studies. Vol.41:25–71.

    ________. 1997. “Dinosaurian Physiology: The Case for Intermediate Dinosaurs.” The Complete Dinosaur. Farlow, J.O. and Brett-Surman, M.K. eds.) Indiana U. Press. Pgs: 449 – 473. ISBN: 0253333490

    Tumarkin-Deratzian, A.R. 2007. Fibrolamellar bone in adult Alligator mississippiensis. Journal of Herpetology. Vol. 41. No.2:341-345.

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  34. 34. Jurassosaurus 2:52 am 12/24/2011

    Importantly, as you mention, high metabolic rates aren’t the same thing as endothermy. Endothermy requires metabolic rates above those found in most ectotherms, but it’s not an automatic consequence, and “high” covers a pretty broad range (sea cows and passeriforms are not in the same ballpark).

    Agreed. This is something that seems to be repeatedly lost in paleo papers. A high metabolism that is not “broken” for heat production (i.e. no uncoupling of mitochondrial reactions, and less unsaturated fatty acids in the cell membranes) will convert more energy towards biomass than a slower metabolism. And yes, that both tachy and bradymetabolic refer to quantifications that are based on energy consumption relative to some nebulous standard (what is this mythical “similar sized endotherm?”) doesn’t help matters. Sadly, it’s still the most accurate we can get without resorting to Paulian-style renaming schemes.

    Altricial chicks don’t use energy for anything but growth. They don’t move (much), and they don’t bother growing insulation, so their parents have to do that for them. I’m sure their ectothermy is a consequence of their astronomical growth rates rather than the other way around.

    Wait, what? I don’t think what you said made sense. Are you saying that ectothermy can’t = high growth rates, but high growth rates CAN = ectothermy? I’m pretty certain that this is a case of A equals B then B should equal A.

    Smaller osteocyte lacunae = smaller cells (because of smaller genomes) = higher surface/volume ratio = potential for higher metabolism. Huge genomes and huge cells, as found in salamanders, don’t occur in tachymetabolic animals, and saurischian dinosaurs including birds have especially small ones.

    It makes for a nice story, but as ever the details are far more complicated than this. While tachymetabolic birds might have smaller genomes than bradymetabolic reptiles, reptiles have smaller genomes than both tachymetabolic mammals and bradymetabolic amphibians (Olmo 2003, Vinogradov and Anatskaya 2006). Secondly, we have yet to find any statistical links between genome size and metabolism, longevity, or development in reptiles (Olmo 2003). Currently we have some correlative links between genome size and extinction risk (Vinogradov 2004) and genome size and mass-specific metabolic rate (Vinogradov 1995, 1997, Olmo 2003), but in the latter case, these statistical trends don’t even appear until one reaches “higher taxonomic levels.” Given the way cladists feel about ranks, these trends may just be phylogenetic pareidolia.

    On a side note, other than birds, what saurischian dinosaurs are you getting this “small genomes” data from?

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  35. 35. Jurassosaurus 2:54 am 12/24/2011

    Er, here are the refs for the last post. Apparently I have an itchy trigger finger at 3AM.

    Refs:

    Olmo, E. 2003. Reptiles: A Group of Transition in the Evolution of Genome Size and of the Nucelotypic Effect. Cyt.Genom.Res. Vol.101:166-171.

    Vinogradov. A.E. 2004. Genome Size and Extinction Risk in Vertebrates. Proc.R.Soc.Lond.B. Vol.271:1701-1705

    ________________ 1997. Nucleotypic Effect in Homeotherms: Body Mass Independent Resting Metabolic Rate of Passerine Birds is Related to Genome Size. Evolution. Vol.51:220–225

    _______________ 1995. Nucleotypic Effect in Homeotherms: Body-Mass-Corrected Basal Metabolic Rate of Mammals is Related to Genome Size. Evolution. Vol.49:1249–1259

    ________________, Anatskaya, O.V. 2006. Genome Size and Metabolic Intensity in Tetrapods: A Tale of Two Lines. Proc.R.Soc.B. Vol.273:27-32.

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  36. 36. David Marjanović 1:29 pm 12/24/2011

    That we get high growth rates in extant automatic endotherms is something that is happening in spite of their thermophysiology, not because of it.

    No, their thermophysiology is necessary for it, it’s just not sufficient. To build up proteins requires energy on every step of the way from initiating transcription to making peptide bonds. Fats and carbohydrates are similar, just less extreme. To support a high anabolism, you need lots of energy, and that requires a high catabolism that produces lots of heat. (Even digestion produces heat at the lowest level – hydrolysis of proteins, carbohydrates and fats produces heat.)

    If that heat is retained, you have an endotherm.

    To have enough energy for very fast growth, you need to produce lots of heat. There doesn’t seem to be a way around it.

    Altricial bird chicks don’t need to divert energy to growing insulation or moving, so they can put all the usable energy their high anabolism delivers into growth. I’m sure they produce enormous amounts of heat, they just don’t bother trying to keep it, because their parents do that for them.

    On a side note, other than birds, what saurischian dinosaurs are you getting this “small genomes” data from?

    Plenty of them. The osteocytes leave holes in fossil bone that are their exact size – and there’s a well-known correlation between cell and genome size. Did you read the Nature papers by Organ et al. a few years ago? (I’ll have to have another look at them, and see which of the papers you cite they cite.)

    some correlative links between genome size and extinction risk

    How was that determined?

    Link to this
  37. 37. David Marjanović 1:39 pm 12/24/2011

    In short, as far as I can see, a low biomass conversion ratio is necessary for fast growth. As Paul wrote in 1988, you need to waste a lot of energy in order to have a lot left.

    Link to this
  38. 38. Jurassosaurus 1:00 am 12/25/2011

    No, their thermophysiology is necessary for it, it’s just not sufficient. To build up proteins requires energy on every step of the way from initiating transcription to making peptide bonds. Fats and carbohydrates are similar, just less extreme. To support a high anabolism, you need lots of energy, and that requires a high catabolism that produces lots of heat. (Even digestion produces heat at the lowest level – hydrolysis of proteins, carbohydrates and fats produces heat.)

    If that heat is retained, you have an endotherm.

    That’s not how you get an automatic endotherm. While catabolic reactions do produce heat, they don’t produce a sufficient amount of heat to result in any significant endothermy. Bennett et al. (2000) tested this in Varanus exanthematicus by measuring their postprandial metabolic rates and heat production. The authors found that, despite increasing metabolic rate three times over RMR, endogenous heat production raised body temp by only half a degree. To produce enough heat to be an automatic endotherm you need to make reactions that only produce heat. Hence the evolution of uncoupling proteins in mammals and birds, or the shivering of endothermic insects, varanids, leatherbacks and various fish. One can also decrease the degree of saturated fatty acids in the cell membrane, resulting in an increase in sodium leakage, forcing the sodium potassium pumps to work harder in order to maintain osmolarity. The byproduct of all of this being heat.

    Note: none of these reactions result in greater energy availability, only greater energy use.

    To have enough energy for very fast growth, you need to produce lots of heat. There doesn’t seem to be a way around it.

    So then where are all the warm squid? Crocodylians grow faster than similar sized marsupials (Ruben 1995), yet they don’t appear to produce more endogenous heat.

    In short, as far as I can see, a low biomass conversion ratio is necessary for fast growth. As Paul wrote in 1988, you need to waste a lot of energy in order to have a lot left.

    That’s like saying one can build a house faster if one only uses a 10th of the needed materials, and just go back to the supply store more often. I don’t think one would have a very successful construction company with that motto.

    Me: some correlative links between genome size and extinction risk

    How was that determined?

    Yeah, I found that to be questionable too. Honestly I think it is bullcrap. According to Vinogradov:

    “The conservation status of these species was determined using the International Union for Conservation of Nature (IUCN) Red List of Threatened Species(http://www.redlist.org), which lists species of global conservation concern.

    The fractions of the total number of known species in different phylogenetic groups, which were assessed for conservation status, were also taken from the Red
    List database.”

    Going by the way some of the wording is used in this paper, I wouldn’t be surprised if the study was twisted in such a way to get government funding for the project, as I can think of numerous other biases that are likely to affect a species risk of extinction.

    Refs:

    Bennett, A.F., Hicks, J.W., Cullum, A.J. 2000. An Experimental Test of the Thermoregulatory Hypothesis for the Evolution of Endothermy. Evolution. Vol.54(5):1768-1773

    Ruben, J. 1995. The Evolution of Endothermy in Mammals and Birds: From Physiology to Fossils. Annu.Rev.Physiol. Vol.57:69-95

    Link to this
  39. 39. LeeB 1 5:41 pm 12/25/2011

    If increased metabolic activity results in a half degree rise in body temperature in a monitor lizard it should result in an even greater rise in temperature in a multi ton animal which has more difficulty in shedding heat due to its lower surface to volume ratio.
    The increased temperature should result in further increase in metabolism and hence more heat production; and for herbivores fermenting vegetation in the hind gut an increase in fermentation rate and yet more heat production from this.
    There seems to be a feedback loop here.
    And heat production from moving around will also tend to be retained in very large animals.

    So an interesting question would seem to be not whether or not dinosaurs were endotherms (which to me they do appear to be)but whether it was actually possible for a reasonably active multi ton organism to be an ectotherm.

    I suspect that unless the climate was very cold or they were living in water gigantothermy would prevent them from being ectotherms; and their metabolic rates would be kept constantly high by their body temperature.

    LeeB.

    Link to this
  40. 40. Jurassosaurus 8:02 pm 12/25/2011

    Lee – While metabolic reactions are temperature sensitive, a good way to avoid the runaway feedback loop you mention is to have enzymes change their conformation such that they reduce their substrate affinity. This would allow an animal with a high body temperature to avoid having an unnecessarily high metabolic rate.

    Link to this
  41. 41. LeeB 1 11:22 pm 12/25/2011

    Okay,

    but it might be possible for the enzymes to evolve to keep a high constant metabolic rate rather than a runaway one.
    One way or the other it looks like it would be easier for very large terrestrial animals to evolve endothermy
    than for small ones or aquatic ones to do so.

    LeeB.

    Link to this
  42. 42. Bogoslovsky 6:38 am 12/26/2011

    Good time of the day!
    I am very interested in author’s opinion about these two hypotheses :

    http://dinosaurtheory.com/index.html

    http://www.levenspiel.com/octave/dinosaurs.htm

    Link to this
  43. 43. David Marjanović 5:15 pm 12/26/2011

    That’s not how you get an automatic endotherm.

    I wasn’t talking about automatic endothermy. I was talking about how high metabolic rates are necessary for high growth rates.

    >>To have enough energy for very fast growth, you need to produce lots of heat. There doesn’t seem to be a way around it.<</

    So then where are all the warm squid?

    What kind of metabolic rates do they have? Are they like altricial chicks?

    Crocodylians grow faster than similar sized marsupials (Ruben 1995), yet they don’t appear to produce more endogenous heat.

    I said “very fast growth rates”.

    >>In short, as far as I can see, a low biomass conversion ratio is necessary for fast growth. As Paul wrote in 1988, you need to waste a lot of energy in order to have a lot left.<</

    That’s like saying one can build a house faster if one only uses a 10th of the needed materials, and just go back to the supply store more often. I don’t think one would have a very successful construction company with that motto.

    Not everything that doesn’t work is a metaphor. What I say is like saying you need to quarry the stones first, and then you need to move them against gravity. If your metabolism produces energy to waste, you can build the house quicker than if it produces just enough energy to do the job (let alone too little).

    Crocodiles again: Deinosuchus did get as big as many a dinosaur, but it took 50 years for it.

    So an interesting question would seem to be not whether or not dinosaurs were endotherms (which to me they do appear to be)but whether it was actually possible for a reasonably active multi ton organism to be an ectotherm.

    Paul has been saying the same (though he adds the metabolism of things like the heart to the equation!) since at least 1988…

    But this only takes care of adult sauropods, not of their hatchlings which did all the growing.

    It also doesn’t take care of the first dinosaurs, which were all well below 1 t.

    I forgot the ref (…quelle surprise… well, it was on the DML sometime in the last 2 years), but it was recently shown that even leatherback turtles are not gigantotherms. They’re large, they’re compact, they’re fairly well insulated by fat layers and stuff, and the constantly heat-generating limb muscles are inside the shell, and yet, that’s not enough – their body temperature is kept high(er than that of the surrounding water) and constant by an elevated basic metabolic rate. This means that no living example of a gigantotherm is known.

    Link to this
  44. 44. David Marjanović 5:21 pm 12/26/2011

    Squid have another advantage over vertebrates when it comes to growth: they’re capable of generating new muscle cells throughout life. Postembryonic vertebrates can only enlarge existing ones. I wouldn’t be surprised if that meant they can grow faster at the same energy expense.

    Also, bone and calcified cartilage cannot grow interstitially ( = from within). Bone growth at constant or anywhere near constant shape requires lots of work by osteoclasts. That’s an energy expense squid do without.

    Link to this
  45. 45. Jurassosaurus 1:04 am 12/27/2011

    I wasn’t talking about automatic endothermy. I was talking about how high metabolic rates are necessary for high growth rates.

    You literally said that high metabolic rates generate lots of heat, which if retained makes an animal an endotherm. That sure sounds like you were talking about automatic endothermy; unless you were referring to some non-bird/mammal taxa that fit the description above.

    Re: squid

    What kind of metabolic rates do they have? Are they like altricial chicks?

    Not sure. The most recent work on this (that I found) was from Seibel (2007). He found MSMR to vary substantially between species. He also found squid to have substantially higher MSMRs than similar sized mammals. However, the caveat to this is that it is only true when temperature corrected to various Q10s (the author corrected all MSMR, including mammals, to 5°C; which is a strange choice). The author also found MSMR to increase with increasing size, instead of what we typically see, but since each group had a different scaling exponent this is likely not true.

    All that aside, observations of live squid do seem to show that they are ectothermic homeotherms. So despite speedy growth we still don’t get toasty squid.

    Also in regards to altricial chicks, it’s difficult to get specific data, but Carpenter – in Eggs, Nests and Baby Dinosaurs – mentions that altricial chicks have resting metabolic rates that are lower than similar sized adult birds. It doesn’t really sound like these chicks are little dynamos.

    I said “very fast growth rates”.

    See the above mentioned Carpenter reference, as well as the “lack of toasty squid” bit. Incidentally, what is your quantified minimum for “very fast growth.” Are we still only focusing on altricial chicks here?

    If your metabolism produces energy to waste, you can build the house quicker than if it produces just enough energy to do the job (let alone too little).

    Again, I feel you are missing the point here. Automatic endotherm metabolism doesn’t create energy to waste, it creates waste energy (i.e. heat). This isn’t energy that can be co-opted for other uses, it is only heat (well, okay, it can be co-opted for warming). One can evolve enzymes that work best at the temperatures that this endogenous heat creates (increasing their efficiency), but you don’t wind up with a surplus of resources, which is what you seem to be implying.

    Crocodiles again: Deinosuchus did get as big as many a dinosaur, but it took 50 years for it.

    Erickson’s Deinosuchus study has been seen as a bit controversial by some in the field (e.g. Schwimmer, or Britton). That the data are based off of osteoderms only does not help matters. Different bones record growth differently, and osteoderms are likely poor indicators of actual growth rate (Klein et al. 2009 talk about issues with osteoderms). The long bones (tibia and femur) are much better suited to this. To put it another way, I and a few others who are far more qualified than me, don’t buy the extended juvenile growth rates argument for Deinosuchus. Ideally I’d like to see a revisit that used a tibia, or femur, but I’m not even sure if we have any of those.

    I forgot the ref (…quelle surprise… well, it was on the DML sometime in the last 2 years), but it was recently shown that even leatherback turtles are not gigantotherms. They’re large, they’re compact, they’re fairly well insulated by fat layers and stuff, and the constantly heat-generating limb muscles are inside the shell, and yet, that’s not enough – their body temperature is kept high(er than that of the surrounding water) and constant by an elevated basic metabolic rate. This means that no living example of a gigantotherm is known.

    I kind of remember what you are talking about. There was a paper by Bostrom and Jones back in 2007 that argued for variation in swim speed as a means of maintaining core body temperature. While metabolism has certainly increased in this case, it would be cheating to say that it is a higher metabolic rate that is keeping the turtle warm (the animal is doing work by locomoting. All animals warm up when moving around, the turtles are just capturing it under the fat). Further, Bostrom and Jones only used a mathematical model to predict the expected metabolic rate needed to maintain a certain temperature. Their model currently lacks any empirical data to support it (their results seemed to routinely go higher than published observations). While interesting, it does not negate gigantothermy as a means of thermoregulation. The authors merely try to incorporate behavioural aspects into the equation (since Paladino used only physiology). In terms of RMR, leatherbacks still fall within the “reptile” spectrum, with RMRs that are not statistically distinguishable from other sea turtles (Wallace & Jones 2008). Besides them we also have large crocodiles, tortoises and Komodo dragons that use these strategies (though only leatherbacks have ever been called gigantothermic [not surprising given that Paladino - who focuses on leatherbacks - coined the term]).

    Refs

    Klein, N., Scheyer, T., Tutken, T. 2009. Skeletochronology and Isotopic Analysis of a Captive Individual of Alligator mississippiensis Daudin, 1802. Fossil Record. Vol.12(2):121-131

    Seibel, B.A. 2007. On the Depth and Scale of Metabolic Rate Variation: Scaling of Oxygen Consumption Rates and Enzymatic Activity in the Class Cephalopoda (Mollusca). J.Exp.Biol. Vol.210:1-11

    Wallace, B.P., Jones, T.T. 2008. What Makes Marine Turtles Go: A Review of Metabolic Rates and their Consequences. J.Exp.Marine.Biol.Ecol. Vol.356;8-24

    Link to this
  46. 46. naishd 10:30 am 12/28/2011

    Jurassosaurus: whenever the subject of dinosaur endothermy comes up in discussion, you spend an inordinate amount of time seemingly arguing against the possible existence of tachymetabolic, ‘automatic’ endothermy in these animals (and other extinct archosaurs). I don’t mean to imply that there’s anything wrong with this – countering perceived ‘bad science’ is a crucial endeavour in my opinion (where would scientific blogging be without it?). So – let me get this straight – you think that dinosaurs weren’t tachymetabolic endotherms? I ask on the chance that you’re acting as devil’s advocate and are otherwise helping us to improve our arguments and better hone our angles of research.

    Anyway, I can see that there are pretty much always problems with the lines of evidence used to support the possibility of endothermy in Mesozoic dinosaurs (growth rates inferred from bone microstructure, erect gaits, long necks held erect, or held a long distance from the heart, inferred organ size, predator-prey ratios, cruising speed inferred from tracks, inferred migratory habits, isotope data, occurrence in cool climates, osteocyte lacuna size, vascular foramina size, inferred muscle mass and power output, presence of integumentary insulation, presence of complex feathers, etc. etc.). But this is surely linked to the fact that it’s just about impossible to find ironclad, convincing evidence of any sort of specific physiology in fossil animals. Could we infer with absolute confidence, for example, that true, cellular-level endothermy exists in fossil mammals, tunas and other scombroids, and lamnid sharks? I don’t know – there are always problem areas, inconsistencies or contradictions that, hypothetically, could lead to doubt (e.g., LAGs in some mammals and birds, proportionally small brains in tuna).

    Pointing to other fossil animals and saying “oh, but that bit of evidence is also present in [insert particular amniote clade]” isn’t satisfactory, since the metabolic status of those groups is virtually always no more the subject of agreement than that of dinosaurs. With reference to the groups listed in comment 33, dinocephalians have long been thought by have some sort of elevated metabolism (“partial endothermy” is a quote often used in association with this group) (contra comment 33), and elevated metabolic rates have been suggested for sauropterygians and fossil members of the crocodilian lineage based on histological and other data (contra comment 33). It’s been known for some decades (Reid has been saying it for long enough) that extant ectotherms can produce fibrolamellar bone (something that’s definitely understated in the palaeontological literature – and the individuals were not anomalous, nor one-offs, nor is fibrolamellar bone unique to the cold-tolerant American alligator) and it’s even been reported in such groups as temnospondyls; thus, one cannot point to fibrolamellar bone in isolation and use it as a guide for physiology, fair enough. But dinosaurs don’t _just_ grow fibrolamellar bone; they grew large amounts of it continuously, and they combined this with those other features inferred to be linked with endothermy. I remain impressed with the fact that Mesozoic dinosaurs inhabited cool and/or cold polar environments (definitely ‘cool’, despite arm-waving about the Mesozoic world being a perpetual hothouse), and that the aerobic constraints imposed by giant dinosaurian limb muscles indicate endothermy.

    Nature is not black and white and we’re all familiar with the idea that there are infinite shades of grey when it comes to behaviour, physiology and so on. Physiology in particular is a horribly complicated subject, and I’m certainly no physiologist (nor can I force myself to be especially interested in physiology, since it involves a great deal of chemistry). As regular Tet Zoo readers know, I’m perpetually frustrated by claims that certain bits of behavioural or anatomical complexity are unique to mammals and/or birds, since this is often loaded with the concept that squamates, crocs or turtles are in some way inferior to, or ‘lower than’, those special, magical mammals and birds. Living reptiles exhibit a diversity of often fascinating physiological strategies (just as do all other animals groups).

    But I resent the implication that pointing toward the probable presence of endothermy in Mesozoic dinosaurs is in any way disrespectful to, or unappreciative of, extant ectotherms. It isn’t cold-blooded: bad, warm-blooded: good; it’s about going where you think the evidence leads. And, so far as I can see, there isn’t any good evidence for ectothermy in dinosaurs and other ornithodirans: it just seems assumed based on the physiology of the extant animals conventionally called ‘reptiles’ (viz, excluding birds). Worse, it’s based on strange cherry-picking and cheating (I’m referring here to many of the claims from the Ruben camp about RTs, post-hepatic pumps, absence of avian-style pneumatic system and adequate sterna, and so on). Dinosaurs were not lizards or turtles, nor were they close relatives of modern crocodilians or all that like modern crocodilians in detailed anatomy or ecology, thus it is not obvious why they should have been like these animals in physiology. We will probably never, ever be sure about dinosaur physiology (and almost certainly not of the cellular-level stuff that we need to infer indisputable endothermy), but I still think that the bulk of evidence we now have is highly suggestive of true, tachymetabolic endothermy in Mesozoic dinosaurs (and pterosaurs). Are we ever going to do any better in palaeophysiology than say that things are “highly suggestive”? Hmm, probably not.

    Darren

    Link to this
  47. 47. Heteromeles 1:25 pm 12/28/2011

    As a botanist, I think these arguments are a great spectator sport. The biggest organisms around (things like redwoods, aspen clones and Armillaria clones) are indubitably ectothermic. They’re taller and heavier than dinosaurs too.

    Not that this matters one bit in arguments about dinosaur physiology, except that I’ll bet that sauropods “invented” redwoods, in that arboreal gigantism and rampant stump sprouting could have evolved as strategies to avoid sauropod browsing.

    Link to this
  48. 48. David Marjanović 6:34 pm 12/28/2011

    You literally said that high metabolic rates generate lots of heat, which if retained makes an animal an endotherm. That sure sounds like you were talking about automatic endothermy; unless you were referring to some non-bird/mammal taxa that fit the description above.

    I don’t know of anything that fits that description; I speculated about what might exist.

    All that aside, observations of live squid do seem to show that they are ectothermic homeotherms. So despite speedy growth we still don’t get toasty squid.

    Of course not. They live in water and aren’t insulated at all whatsoever.

    altricial chicks have resting metabolic rates that are lower than similar sized adult birds

    Interesting.

    Incidentally, what is your quantified minimum for “very fast growth.” Are we still only focusing on altricial chicks here?

    No, on the growth rates seen in most placentals and birds in general.

    Automatic endotherm metabolism doesn’t create energy to waste, it creates waste energy (i.e. heat).

    I suppose automatic endothermy (cell membranes that are unusually permeable to sodium ions) can only evolve once the basic metabolic rate is above a minimum. Otherwise, the first animal with such a mutation couldn’t produce enough ATP to keep the sodium pumps going fast enough and would simply die at a very young age indeed from complete lack of a membrane potential.

    ATP production is what I’m talking about.

    In terms of RMR, leatherbacks still fall within the “reptile” spectrum, with RMRs that are not statistically distinguishable from other sea turtles (Wallace & Jones 2008).

    Huh. In that case, I suppose they are gigantothermic after all. :-)

    The biggest organisms around (things like redwoods, aspen clones and Armillaria clones) are indubitably ectothermic. They’re taller and heavier than dinosaurs too.

    Photophosphorylation! :-) As long as the sun shines (and desiccation or heat don’t become limiting factors), plants have as much ATP as they want, and growth and reproduction are pretty much their only expenses, right?

    Link to this
  49. 49. Jurassosaurus 9:27 pm 12/28/2011

    Darren – In terms of personal beliefs I don’t see a problem with dinosaurs being “good reptiles” as Farlow once put it. I see no causal reason why dinosaurs couldn’t be active animals that had low metabolisms at rest.

    As a scientist though, I don’t really see any evidence for the thermophysiological state of any extinct animal. Even feathered maniraptorans could have used myogenic endothermy mixed with ectothermy similar to what we see in extant vultures and roadrunners. They could also have used “standard” tachymetabolic pathways similar to passerines and many other birds. Both are successful alternatives to the same environmental problems, and neither leave behind fossil evidence.

    I tend to get particularly passionate about this subject in dinosaurs because I grew up watching the pendulum sway from the “cold-blooded dead end” mentality to that of the “hot-blooded success story.” Changing the last two words in these phrases has never been the problem. The fact that thermophysiology should have any say on these results is a problem. Bakker and Paul (along with Desmond, Padian, Horner and many others) were successful in swaying public – and later scientific – opinion towards a more optimistic view of the Dinosauria, but all of these researchers have either alluded to, or just outright stated that success was contingent on having a high resting metabolism. Low metabolic rates need not apply. This never sat well with me since I could never see a reason why that should be so. Physiology is a complicated subject, and thermophysiology just increases this complication. That we can say anything about the physiologies of long extinct animals is amazing, but the huge holes we have in our data should mean that all conclusions based off them should remain guarded and cautious. This is why it is all the more frustrating to see studies that take correlative data and then stamp “tachymetabolic endothermy” onto the conclusions without ever considering why that should be so, or even considering alternative reasons for the correlation. My biggest pet peeve in the paleontological literature (I see it in other science fields as well, but dino paleo seems to be particularly rife with it) is the taking of small datasets and then making broad, sweeping generalizations that go well beyond what the data provide. This is particularly egregious when it comes to any paleo study that infers thermophysiology based off nothing more than the coincident association of a datapoint with an animal of a particular thermophysiology. My experience on the web has been that the appeal of tachymetabolic dinosaurs is so great that any study that appears to support that position goes by without a hint of skepticism, and often a fair bit of praise. For instance take the paper released this year by Roger Seymour, in which he found a correlation between femoral nutrient foramina and active metabolism. Now despite the author mentioning that this work was only preliminary, and despite showing varanids grouping with mammals, not doing any kind of phylogenetic correction, or considering other environmental variables (e.g. aquatic vs. terrestrial), most popular reports ran stories saying that this was more evidence that dinosaurs were endotherms in the same vein as mammals and birds, or that this was one more nail in the coffin of the ectothermic, bradymetabolic dinosaur.

    And yes Darren I do think it is still very much about a “cold-blooded = bad, warm-blooded = good” scenario. Padian has referred to it in terms such as this (and will shut out anyone who even talks to him about the alternative), Horner assumes it, and Paul takes it to such extremes that I actually think he is shocked that any reptile can exist at all in this day and age. That all three represent extremes of their own is a given, but the fact is that these are the guys that write the books and act as the creative consultants on TV shows. They are the most vocal, which gives them the most sway.

    Pointing out similar structures in other extinct non-dinosaurs is not meant to show that dinosaurs weren’t tachymetabolic, but instead to show that animals that have often been shoehorned into “cold-blooded” show the same types of evidence for inferred tachymetabolic endothermy as has been proposed for dinosaurs. If we see it in these other taxa then we should either: A) Start saying these other taxa were tachymetabolic critters as well, or B) Ask ourselves if what we are inferring is actually justified, and start looking for that infamous causal relationship.

    Regarding dinocephalians I don’t ever remember reading about “partial endothermy” in these guys. That was usually reserved for therocephalians and other critters more closely related to mammals. All that said I would like to point out that the evidence for the start of automatic endothermy in fossil synapsids is also pretty crappy. I’d be more vocal about it if I cared more about synapsids, but the same problems exist there as well. On the flip side, we don’t have any evidence that critters like Paleosaniwa, or baenids were bradymetabolic ectotherms either. While the EPB gives us some confidence in inferring it for some groups, the thermophysiology of practically ever extinct non-dinosaur has been assumed (not inferred, just taken as fact) based only on the phylogenetic position of the animals.

    You stated that dinosaurs weren’t crocs, lizards, or turtles, and I agree. But dinosaurs weren’t birds either. Another pet peeve of mine has been this trend in the paleo literature to make all dinosaur comparisons from a strictly avian point of view (even the qualifier “non-avian” implies that dinosaurs only matter in regards to the evolution of birds). Dinosaurs may have given rise to birds, but they also descended from animals more like crocodiles. I’m not sure why you understated it, but dinosaurs did share many things in common with crocs (e.g. large caudal musculature, femoral driven locomotion, similar braincast arrangements [up to ~coelurosaurs, then it gets more avian], presence of prefrontals and lacrimals, likely placement of some jaw muscles in various taxa). Accurate life history and physiological comparisons of dinosaurs need to involve comparisons to both groups (and even lepidosaurs, in order to help pick out traits that both extant outgroups may have obliterated). What we could seriously do with a reduction in are comparisons with mammals. For while the first dinosaurs may have shared their last common ancestor with crocodylians some 20 million years earlier, that was still almost 100 million years after the last common ancestor of dinosaurs and synapsids. If one is going to compare what some dinosaur may have done with what a mammal currently does, the least one can do is look to see if similar things are seen on the reptile-bird side first.

    To sum this rant up, thermophysiology is a complicated suite of non-fossilizable traits, and dinosaurs were a highly successful group of animals that had global distribution for some 165 million years. Given that extant animal groups don’t all fall under the same thermophysiological umbrella it is just as likely that dinosaurs did not as well. I think Seebacher was on the right track back in 2003 when he said that dinosaur thermophysiology should almost be taken on a case by case basis. Though with our current lack of data I think the best course of action would be to just not broach the subject at all (we don’t know, we currently can’t know, so we probably should stop acting like we do know). Just list the traits one sees in the dinosaur taxa one is talking about and act like the thermophysiology doesn’t matter at all; because in the end – especially for large animals – this is likely to be closer to the truth.

    Link to this
  50. 50. David Marjanović 6:56 am 12/29/2011

    If you’ve addressed my argument about high resting metabolism being necessary for high growth rates, I haven’t seen it…

    presence of prefrontals and lacrimals

    Birds still have lacrimals today. :-)

    Link to this
  51. 51. Jurassosaurus 10:34 am 12/29/2011

    If you’ve addressed my argument about high resting metabolism being necessary for high growth rates, I haven’t seen it…

    We’ve already been through this. Altricial chicks apparently don’t have high resting metabolisms. Squid don’t appear to have it either. If you would like more examples, leatherbacks have inferred growth rates on par with similar sized pinnipeds (Snover and Rhodin 2008). There is also Furcifer labordi which grows from hatchling to adult in about two months and is dead by five months, giving it one of the fastest growth rates and shortest lifespans of any vertebrate (Karsten et al. 2008).

    No data is available on resting metabolism in this taxon though, which is ostensibly the problem for any of these arguments regarding metabolic rate and growth. There are plenty of non-mammals and birds that grow as fast, or faster, but very little have had their metabolisms measured. The assumption that a high resting metabolism is necessary for high growth is a one sided one based mostly on mammal data and citations of Case 1978.

    Birds still have lacrimals today.

    I should have written that better. Dinosaurs have prefrontals and lacrimals. That is to say they retained two separate bones instead of one, which birds (squamates, and most other amniotes) have.

    In regards to your earlier mention of ATP production, I don’t think there is any inherent limitation to ATP production in any animal. After all we are talking about ATP efficiency and resting metabolism here. Resting metabolism can be anywhere from 1/2 to 1/100th the rate of active metabolism. As long as food is available and heat can be dissipated, metabolic rate seems able to continue to increase ad infinitum (Speakman and Krol 2010). Case in point: experimental manipulation of membrane lipid content was able to make the cellular membrane of a crocodile cell about as “leaky” and active as that of the cow (Wu et al. 2004), with the reciprocal being true as well. Despite increasing sodium/potassium pump concentrations to mammalian levels, the cells appear to be in no danger of running out of ATP.

    Refs

    Karsten, K., Andriamandimbiarisoa, L.Z., Fox, S.F., Raxworthy, C.J. 2008. A Unique Life History Among Tetrapods: An Annual Chameleon Living Mostly as an Egg. PNAS. Vol. 105(26):8980-8984

    Snover, M.L. Rhodin, A. G.J. 2008. Comparative Ontogenetic and Phylogenetic Aspects of Chelonian Chondro-Osseous Growth and Skeletochronology. In: Wyneken, J., Godfrey, M.H., Bels, V. (Eds.). Biology of Turtles. Boca Raton, FL: CRC Press, pp. 17-43

    Speakman, J.R., Krol, E. 2010. Maximal Heat Dissipation Capacity and Hyperthermia Risk: Neglected Key Factors in the Ecology of Endotherms. J.Anim.Eco. Vol.79(4):726-746

    Wu, B.J., Hulbert, A.J., Storlien, L.H., Else, P.L. 2004. Membrane Lipids and Sodium Pumps of Cattle and Crocodiles: An Experimental Test of the Membrane Pacemaker Theory of Metabolism. Am.J.Physiol.Regul.Integr.Comp.Physiol. Vol.287:R633-R641

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  52. 52. David Marjanović 5:56 am 12/30/2011

    Thank you, I’ll check out your refs sometime and shut up in the meantime.

    “An Annual Chameleon Living Mostly as an Egg” sounds impressive!

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  53. 53. Dartian 7:10 am 12/30/2011

    David:
    “An Annual Chameleon Living Mostly as an Egg” sounds impressive!

    It’s pretty neat, isn’t it? The reptile equivalent of a killifish. ;)

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  54. 54. Heteromeles 11:40 pm 12/30/2011

    @48 David: Actually, plants respire too. *Supposedly* the reason that the big redwoods occur in the temperate rainforest, not the tropics, is that the lower temperatures (at least during part of the year), decrease net respiration, meaning there’s more carbon to play with. There are some pretty big trees in the modern tropics, so I don’t entirely buy it. Additionally, the sequoia clade has a long evolutionary history, and they used to be much more widespread. Whether they’ve always grown to 100 m tall, or whether their current height is just an artifact of growing in the fog belt of the Pacific coast, is something I don’t know.

    As for fungi, they’re heterotrophs, just like animals. They have the small advantage that they live in their food, not on it, and if their mycelia get cut apart, they don’t die. That allows a few of them (like Armillaria) to get big. The fun thing about Armillaria is that it’s a pathogen, so those giant clones like the Humungus Fungus are almost certainly older than the trees they are currently infecting. There’s something vampiric about that…

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  55. 55. David Marjanović 11:09 am 12/31/2011

    The fun thing about Armillaria is that it’s a pathogen, so those giant clones like the Humungus Fungus are almost certainly older than the trees they are currently infecting. There’s something vampiric about that…

    Awesome.

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  56. 56. naishd 7:25 pm 01/1/2012

    Thanks, Jurassosaurus and others, for additional comments. Some responses to Jurassosaurus’s comment # 49…

    Ok, thanks for enunciating. I certainly don’t have a problem with the idea that some Mesozoic dinosaurs were heterotherms, that some were partial ectotherms like some extant birds, or that the normal metabolic rates of some dinosaurs were lower than those of average modern mammals and birds. We should expect Mesozoic dinosaurs to exhibit physiological variation on par with that of mammals and birds, and of course there’s the caveat that we’re wasting our time discussing this subject anyway since we can never know anything for sure. But the ‘good reptile’ model doesn’t cut it for me, in part because of all those polar dinosaurs (of diverse body sizes and shapes), and also because of work indicating that the metabolic costs associated with the powering of dinosaurian hindlimb musculature seemingly require endothermy (Pontzer et al. 2011).

    I’d like to add another caveat. I hope it’s clear from what I say and cover here on Tet Zoo that I certainly don’t regard endothermy as more interesting, or endothermic animals as ‘better’, than ectothermy and ectothermic animals. In fact I don’t really care what sort of physiology Mesozoic dinosaurs had, since (so far as I can tell) it’s agreed that the animals still looked the same, behaved the same, and got up to the same evolutionary shenanigans.

    I also want to add the possibly interesting point that approaches to this issue seem to differ depending on which culture you’ve been educated in. Here in the UK, my honest impression until just a few years ago was that ectothermy in dinosaurs was the accepted mainstream way of thinking, mostly because we have people like Benton, Norman, Milner and so on implying or stating that ectothermy is logical for dinosaurs and endothermy less so. It seems that things are different in the US, though I’m surprised to hear that some researchers are essentially close-minded on this subject. Is that really true? As noted above and in earlier comments, I think that true endothermy was likely for Mesozoic dinosaurs (and pterosaurs) due to certain key bits of evidence, not because I regard endothermy as cool, intuitive or more interesting than the possibility of ectothermy.

    Regarding some more select responses…

    Dinocephalians: agreed that discussions or claims of endothermy are usually reserved for cynodonts and lineages close to them, but it’s not too difficult to find suggestions in the literature that dinocephalians might have been in the early stages of evolving endothermy. Bakker of course regarded them as endotherms, and Kemp talks about a ‘therapsid grade’ in the evolution of endothermy (in between the ‘sphenacodontid grade’ and ‘eutheriodont grade’) in various of his books and articles.

    Crocs and such: non-avialan dinosaurs do/did of course share many characters with croc-branch archosaurs. But I stand by my assertion that Mesozoic dinosaurs were not “close relatives of modern crocodilians or all that like modern crocodilians in detailed anatomy or ecology”. You’ve pointed to similarities of caudofemoral and jaw musculature, brain anatomy and the presence of prefrontals and lacrimals (seriously? What the hell might this have to do with physiology and/or behaviour?). I think it’s more telling that – in strong contract to extant crocs – Mesozoic dinosaurs in general were fully terrestrial (viz, not amphibious), long-limbed animals that walked perpetually with ‘erect’ limbs*, powered by often enormous limb muscles. In a way, they seem intermediate between crocodilians and birds, but certainly not more like crocodilians than they are like birds.

    * Caveat required: many animals regarded as ‘erect-limbed’ don’t really hold their limbs directly beneath their bodies all of the time. You know this, I know this, we move on.

    By the way, I disagree with the idea that the term ‘non-avian dinosaur’/‘non-avialan dinosaur’ carries any implication that “dinosaurs only matter in regards to the evolution of birds”. Surely it’s more a term of convenience, used to reflect the fact that we’re not talking about the idiosyncratic lineage that made it into the Cenozoic. I try and use the term ‘Mesozoic dinosaurs’ when referring to dinosaurs that aren’t crown-birds, and sometimes this isn’t a bad alternative. It’s certainly less loaded.

    Refs – -

    Pontzer, H., Allen, V. & Hutchinson, J. R. 2011. Biomechanics of running indicates endothermy in bipedal dinosaurs. PLoS ONE 4(11): e7783. doi:10.1371/journal.pone.0007783

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  57. 57. Jurassosaurus 12:02 am 01/2/2012

    Darren – thanks for the info regarding cultural outlooks on dinosaurs. I admit I had a very American-centric view of things and had not thought the general outlook in the UK was all that different. As for close-mindedness, I would like to say that my experience talking to other paleontologists in the U.S. is that their view on dinosaur thermophysiology is more akin to yours in that they might have an idea of where they think the evidence is leading, but they don’t really care all that much since it doesn’t affect their view on dinosaurs anyway. There are just those few out there that see it as open-and-shut.

    Just some last bits for clarification before the embers completely go out on this post.

    Regarding Pontzer et al. The conclusions that were drawn regarding ectotherm aerobic power were based off of a generalized regression equation for standard metabolic rate. This resulted in some (many?) taxa having greatly underestimated aerobic abilities (e.g. the authors calculated an aerobic scope of 7x RMR in Heloderma suspectum, but empirical studies have found it to be closer to 30x [Beck et al. 1995]). There is also some question of whether the authors were looking at resting metabolic rate (which the paper says) or standard metabolic rate (which the regression equation was for). More importantly though, the final conclusions of the paper hold true only if the aerobic capacity argument does. I’ve actually gone on about this at length on my site so I’d rather not kick this hornets nest again, but sufficed to say there have been a number of studies within the past 30 years that have started to question the validity of this model for the evolution of endothermy (e.g. see Farmer 2001 and references therein).

    Re: the two skull bones. I only pointed them out as an example of detailed anatomy. I don’t think there is much physiological difference between one bone, or two smaller bones doing the same thing.

    While I agree that most dinosaurs were living lives quite different from most extant crocodylians, I would also have to say that this likely holds true for dinosaurs in comparison to most extant birds too. Both extant members of Archosauria are widely divergent from basal archosaurs, and even most dinosaurs. I think this is why a E.P.B. approach is so helpful, since it lets us weigh one trait in one radically different extant outgroup, to a similar or (preferably) the same trait in the other radically different outgroup, with implications for all the extinct guys.

    Refs:

    Beck,D.D., Dohm, M.R., Garland, T., Ramirez-Bautista, A., Lowe, C.H. 1995. Locomotor Performance and Activity Energetics of Helodermatid Lizards. Copeia. Vol.3: 577-585

    Farmer, C.G. 2001. “Parental care: A New Perspective on the Origin of Endothermy.” inn Gauthier, J.A., Gall, L.F.(eds). New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. Peabody Museum of Natural History, Yale University. pps. 389-412

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  58. 58. naishd 8:25 am 01/2/2012

    Interesting stuff. I saw your response to Pontzer et al., and their response to your response. While they might have underestimated the aerobic scope for some species, isn’t it plausible that their regression only made underestimates for the real exceptions? The unusually high aerobic scope of Heloderma is well known since the publication of Beck et al (1995), and it’s exceptional: that is, beyond what you’d expect based on other ectotherms (it doesn’t seem approached by that of varanids [aerobic capacity = from 7.0 to 13], the poster children for the Rubenite ectotherm movement). Indeed, that factorial aerobic capacity of 30.4 reported by Beck et al (1995) is “the highest … of any lizard measured to date”. I think Pontzer et al.’s response to you was pretty logical: “[T]he dinosaurs in our sample may be ectothermic, but have physiologies unlike any reptile seen today, able to maintain aerobic power at levels seen only in endotherms today. This is possible, but extraordinary claims require extraordinary evidence. Finally, the dinosaurs in our sample may be endothermic. This is the simplest explanation that fits our data, and therefore the explanation we support.”. The full text is here for anyone who wants to read it.

    Darren

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  59. 59. David Marjanović 6:15 pm 01/3/2012

    the ‘good reptile’ model doesn’t cut it for me, in part because of all those polar dinosaurs (of diverse body sizes and shapes)

    And not just the polar ones. The Jehol Group was a crocodile-free zone that is now thought to have had a rather temperate climate (though with less seasonal variation than otherwise comparable climates show today). AFAIK, the squamates, champsosaurs and amphibians were all small enough to hide somewhere for the winter. I wonder if Psittacosaurus dug burrows.

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  60. 60. David Marjanović 6:18 pm 01/3/2012

    Oops. I forgot the <blockquote> tag isn’t parsed here.

    Of course I agree that people who say “non-avian dinosaurs” need to be careful about whether that’s what they actually mean. Often they mean “stem dinosaurs”, “Mesozoic dinosaurs”, “extinct dinosaurs”, “non-eumaniraptoran dinosaurs”, “non-coelurosaurian dinosaurs” or suchlike.

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  61. 61. Halbred 3:40 pm 01/4/2012

    @David: I think it’s more likely that Psittacosaurus dug burrows than lived in lakes and rivers. LOL

    I didn’t realize that Jehol is thought to have had a temperate climate, and I could’ve sworn I read about one crocodilian from that formation, but I’ve been wrong before. If true, that’s really interesting. One wonders if more complex feather types (and the retention of multiple feather types in a single animal) evolved to combat more temperate climates? Birds up here in Alaska poof up their feathers to retain heat and it must be incredibly effective–it’s -3F right now and there are ravens and chickadees just hanging out, all poofed up.

    And of course I have to jump in and say something about our polar dinosaurs. All of our taxa from the North Slope–which was farther north than it is today–lived through months of darkness and temperatures that likely fell below freezing during the winters months. We only have one ectothermic animal in Alaska: the wood frog (Rana sylvatica) which is active for about five months out of the year and spends the rest of the time in a burrow, frozen solid.

    So I, for one, am a big believer in the “North Slope dinosaurs must have been endothermic” idea, and I would assume that, phylogenetically speaking, endothermy would be found in all of those dinosaurs’ more southern relatives (ceratopsids, pachycephalosaurs, duckbills, basal ornithopods, coelurosaurs).

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  62. 62. David Marjanović 9:02 am 01/8/2012

    I could’ve sworn I read about one crocodilian from that formation

    I just remembered Chimaerasuchus, but it’s from the Wulong Fm of Hubei, considerably farther south (in the north of the southern half of China) and probably a bit younger.

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  63. 63. JoseD 1:22 am 06/21/2012

    @Naishd

    “they didn’t masticate their food or use gastroliths”

    W/all due respect, I wouldn’t say that, given the following quote. Also, as Michael O. Erickson & William Miller pointed out (See the comments section: http://svpow.com/2009/12/02/your-cervical-ribs-are-probably-non-existent/ ), Wings’ analysis is majorly flawed.

    Quoting Sampson ( http://www.amazon.com/Dinosaur-Odyssey-Fossil-Threads-Life/dp/0520269896/ref=ntt_at_ep_dpt_1 ): “Nevertheless, occasional sauropod skeletons do show appropriately sized cobbles within the rib cage, suggesting that rock-filled gizzards may have been part of the digestive solution for at least some of these dinosaurian giants.”

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