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The Tet Zoo Manifesto

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


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As is so often the case, I find myself unable to make the time to finish the numerous Tet Zoo articles I want to complete and release upon the world. Through burning frustration and a desire to produce something, here’s this.

Night-time coots and geese, just because. Photo by Darren Naish.

Hmm, another goose. I think there might be a thing going on here. Image by Darren Naish.

Tet Zoo has now been going for more than eight years, yet there are still innumerable lineages that I have yet to write about at all, let alone discuss in anything approaching appropriate depth. However, thanks to my own biases, interests and priorities, there are several groups that have been a constant presence here, their stories repeated and revisited time and time again, often with updates and revisions that reflect new discoveries and the evolving state of our knowledge. While I certainly plan Tet Zoo to be a source of information on all the tetrapods, we might consider the subject areas listed below as those that form the core part of a Tet Zoo Manifesto. Links to key articles are included.

Lizards and frogs and snakes are awesome, even the small, plain-looking ones

Rhacodactylus leachianus henkeli and Tetrapod Zoology Book One (you can see part of Memo Kosemen's cover art); image by Ethan Kocak.

When it comes to tetrapods, I don’t think that there are any boring species. Look at all the frogs, lizards and snakes: you just have to look closely at these animals and read some of the work that’s been done on their ecology, biology, evolution and behaviour – they’re all fascinating. But the great frustration as goes animals like frogs, lizards and snakes is that good discussions devoted to them are all too often locked up in expensive, technical literature, and more needs to be done to bring it to the masses. Thanks (in part) to blogging, things are changing – and not too soon, since many amphibians and reptiles are of major conservation concern. Despite the annoying pull of charismatic megafauna, I’ve done my best to cover them when possible. There is still so much to do. Meanwhile…

‘Non-standard hypotheses’ are cool and interesting, worth knowing about, but ‘non-standard’ for very good reasons

The true origins of mammals, a controversial and little-known hypothesis.

If you read enough arcane literature, you’ll encounter assorted weird, wayward hypotheses about tetrapod evolution. I consider most of them interesting enough to warrant discussion. They don’t stand up well in view of the bulk of data, or our understanding of phylogeny or logic, but they sure are interesting. I’ve covered several such ideas on Tet Zoo…

Birds are dinosaurs, ‘birds’ and ‘dinosaurs’ grade into one another, and the more bird-like of non-bird dinosaurs were extremely similar to early birds

The bird-like non-bird Microraptor, a capable glider with elaborate feathering. Image by Emily Willoughby, used with permission.

Birds are dinosaurs, and virtually everyone who’s read the literature on Mesozoic birds and bird-like dinosaurs is familiar with the huge amount of anatomical data that supports this contention. And as we’ve come to know more about the life appearance of Mesozoic dinosaurs, it’s also become more obvious, and better appreciated, that feathered theropods were extremely bird-like in appearance – more bird-like than thought even by champions of the ‘birds are dinosaurs’ movement. Mesozoic dinosaurs are so well-covered in the blogosphere that I tend to avoid writing about them at Tet Zoo. Nevertheless, they’ve been a constant presence since the early years…

If we’re going to champion the birdiness of dinosaurs, or the dinosaurian nature of birds, it follows that birds of all sorts (yes, even the living ones) need to be included in literary reviews that cover dinosaurs. I’ve put my proverbial money where my mouth is and managed to get a major chapter on birds – all birds – into a major book on dinosaurs (Naish 2012). A push to review the fossil record of birds within the context of dinosaurian diversity is, in part, inspired by the fact that I see major problems with those reviews of the avian fossil record produced by Alan Feduccia.

Images by Emily Willoughby (top left), John Conway (right), and Matt Martyniuk (lower left).

The azhdarchid pterosaurs of the Cretaceous likely followed a ‘terrestrial stalking’ mode of life, and were a significant presence in the continental assemblages of the Cretaceous

A giant azhdarchid is a formidable beast. This illustration - from Witton & Naish (2013) - shows (A) Tyrannosaurus, (B) Romanian maniraptoran Balaur, (C) the long-necked giant azhdarchid Arambourgiania, and (D) a human, all to scale. Image by Mark Witton, from Witton & Naish (2013).

Some years ago now (2008!), Mark Witton and I published a key paper in which we argued that azhdarchid morphology, proportions, palaeoenvironment and palaeoecology best support the idea that they were terrestrial predators or omnivores, most likely specialised for a lifestyle that involved quadrupedal walking and the picking up of small prey items (Witton & Naish 2008). This model has been supported by most subsequent observations and analyses (Carroll et al. 2013, Vremir et al. 2013, Witton & Naish 2013), but it has also been challenged. It has some speculative zoology tie-ins as well…

The diversity of fossil crocodylomorphs is underappreciated and astonishing

Substantially simplified cladogram showing possible topology of crocodyliforms; image by Darren Naish.

All those archosaurs conventionally called ‘crocodilians’ are technically included together within the clade Crocodylomorpha; within this group, the major clade that includes all the more ‘crocodile-like’ lineages is termed Crocodyliformes. I still have yet to write about fossil crocodylomorphs at length: there are several articles on various of the crocodyliform groups, some of which now need to be replaced with wholly renovated versions, but most lineages remain untouched. Thanks to work on Wealden crocodyliforms (Salisbury & Naish 2012), and a great fondness for the marine thalattosuchians of the Jurassic and Cretaceous, I have, however, made a start…

Oh, a review article I wrote on the group (Naish 2001) is now very dated and is not as strong as it could be on croc diversity… I’d like to update it.

Sexual selection may have been an important driving force in the evolution of Mesozoic dinosaurs and pterosaurs

A selection of flamboyant ornithischian dinosaurs. Why were so many dinosaurs so very flamboyant? So that they could tell each other apart, or because - like many living flamboyant animals - their evolution was dominated by sexual selection? Image by Darren Naish.

Cover of the TREE issue that contains Knell et al. (2012): art by Mark Witton.

Together with colleagues, I’ve argued that the elaborate structures seen in the dinosaurs and pterosaurs of the Mesozoic – cranial crests, dorsal sails, head frills, horns and so on – most likely played important roles in sexual and social signalling, and likely evolved within the context of sexual selection pressure (Hone et al. 2012, Knell et al. 2012, 2013, Hone & Naish 2013).  While these structures may well have been used in thermoregulation, defence against predators and so on, sexual signalling was probably the main evolutionary force driving their diversity. This subject remains the topic of heated debate. The story so far is covered in the following Tet Zoo articles…

There are other subjects that have been a constant presence on Tet Zoo as well, including giant killer eagles, investigations of ‘mystery’ carcasses, speculative zoology, scientific approaches to cryptozoology, and the dinosaurs of the English Lower Cretaceous. But it’s the subjects listed above that can perhaps, I think, be considered the core components of the Tet Zoo Manifesto. And we’ll be visiting all of them again… in time.

Apologies, synapsid-fans, for the lack of mammals and kin. I guess they're just not as controversial. In the image here, Sturnus vulgaris rides Dama dama; photo by Dave Hone.

Refs – -

Carroll, N. R., Poust, A. W. and Varricchio, D. J. 2013. A third azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana. In: Sayão, J. M., Costa, F. R., Bantim, R. A. M. & Kellner, A. W. A. International Symposium on Pterosaurs, Rio Ptero 2013, Short Communications. Universidad Federal do Rio de Janeiro: pp 40-42.

Hone, D. W. E. & Naish, D. 2013. The ‘species recognition hypothesis’ does not explain the presence and evolution of exaggerated structures in non-avialan dinosaurs. Journal of Zoology 290, 172-180

- ., Naish, D. & Cuthill, I. C. 2012. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia 45, 139-156.

Knell, R., Naish, D., Tomkins, J. L. & Hone, D. W. E. 2012. Sexual selection in prehistoric animals: detection and implications. Trends in Ecology and Evolution 28, 38-47.

- ., Naish, D., Tomkins, J. L. & Hone, D. W. E. 2013. Is sexual selection defined by dimorphism alone? A reply to Padian and Horner. Trends in Ecology and Evolution http://dx.doi.org/10.1016/j.tree.2013.02.007

Naish, D. 2001. Fossils explained 34: Crocodilians. Geology Today 17 (2), 71-77.

- . 2012. Birds. In Brett-Surman, M. K., Holtz, T. R. & Farlow, J. O. (eds) The Complete Dinosaur (Second Edition). Indiana University Press (Bloomington & Indianapolis), pp. 379-423.

Salisbury, S. W. & Naish, D. 2011. Crocodilians. In Batten, D. J. (eds). English Wealden Fossils. The Palaeontological Association (London). pp. 305-369.

Vremir, M., Kellner, A. W. A., Naish, D. & Dyke, G. J. 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS ONE 8: e54268.

Witton, M. P. & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3: e2271.

- . & Naish, D. 2013. Azhdarchid pterosaurs: water-trawling pelican mimics or “terrestrial stalkers”? Acta Palaeontologica Polonica doi: http://dx.doi.org/10.4202/app.00005.2013

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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Comments 27 Comments

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  1. 1. Sebastian Marquez 12:20 am 04/8/2014

    When I think manifesto, I think unkept salt and pepper beard… hopefully 8 years of serious blogging hasn’t given you one!

    I for one am glad to be able to read about oft-overlooked members of the clade. And no, I’m not sucking up because I’m waiting for ratites part II. Mostly not anyway!

    Link to this
  2. 2. naishd 5:35 am 04/8/2014

    Ratites part II has been delayed for a very good reason — incoming paper in top-tier journal…

    Link to this
  3. 3. Andreas Johansson 7:06 am 04/8/2014

    Speaking of crocs and underappreciation, something that’s way undercovered in anything resembling popular accounts is the non-crocodylomorph croc-line archosaurs; aetosaurs, rauisuchians, etc. Surprisingly so as the they include seriously big carnivores.

    (Apparently the to-be-prefered formal name of croc-line archosaurs is now … Pseudosuchia. Can’t help but find that a bit annoying.)

    Link to this
  4. 4. naishd 10:13 am 04/8/2014

    I did actually cover aetosaurs way back in these articles…

    Your Triassic armadillodiles
    The armadillodile diaries, a story of science ethics

    It’s all looking dated now, so needs revamping. I never published my rauisuchian stuff but have been meaning to do so for ages. As for the name Pseudosuchia — I agree, I would prefer to use Crurotarsi. At the moment the community is inconsistent as to which name is preferred.

    Link to this
  5. 5. John Harshman 1:39 pm 04/8/2014

    1. There can by definition be no good excuse for the delay of Ratites Part II.

    2. It would be great to have more about various non-dinosaurian archosaurs in your copious free time.

    3. And shouldn’t your obsession with Benedict Cumberbatch be a clearly stated section of the manifesto?

    Link to this
  6. 6. Gigantala 3:02 pm 04/8/2014

    “a capable glider”

    I thought Dyke et al. 2013 made it clear that it wasn’t?

    Link to this
  7. 7. naishd 3:14 pm 04/8/2014

    We (Dyke et al. 2013) concluded that Microraptor suffered from extensive drag and was highly inefficient, yes.. I didn’t mean to imply that it was super-efficient or specialised. ‘Capable’ will do.

    Oh: Benedict Cumberbatch (comment # 5)… hey, it’s Mark Witton’s illustration, not mine!

    Link to this
  8. 8. irenedelse 3:46 pm 04/8/2014

    No need for excuses, Darren. Benedict Cumberbatch is well placed on the Most Adorable Tetrapods list, closely tied with otters, kittens, feisty little geckos, Emily Willoughby’s microraptors and the baby crocodiles at the end of Lake Placid.

    Link to this
  9. 9. Andreas Johansson 4:26 pm 04/8/2014

    @Darren: The 2007 armodillodile article refers to an upcoming revelation about aetosaur appearance. Has it been revealed yet and if so what was it?

    Link to this
  10. 10. Tayo Bethel 9:30 pm 04/8/2014

    More killer eagles, croc-line archosaurs and underappreciated bird groups. Or a new take on some more familiar ones–the evolution of accipitrids, for instance. and … how about giant predatory geckos of the future? Geckos the size of small dogs :)

    Link to this
  11. 11. Jerzy v. 3.0. 4:38 am 04/9/2014

    More tetrapods!

    Link to this
  12. 12. DavidMarjanovic 7:31 am 04/9/2014

    Ratites part II has been delayed for a very good reason — incoming paper in top-tier journal…

    Oho.

    *Homeric drool*

    Link to this
  13. 13. Heteromeles 9:52 am 04/9/2014

    So what was it with the bats back there? Did I dream it all, or was that just a diversion?

    Anyway, let me know where to buy my little green book and cheap suit. On with the revolutio…never mind.

    Link to this
  14. 14. Heteromeles 11:41 am 04/9/2014

    Off topic, but there are a couple of websites out there that let people check if a website is vulnerable to the heartbleed bug. These include http://lastpass.com/heartbleed/ and http://filippo.io/Heartbleed/.

    It looks like blogs.scientificamerican.com was vulnerable, but it’s since been fixed. The bad news is that those of us who are paranoid may want to change our passwords here.

    Link to this
  15. 15. JoseD 3:20 pm 04/9/2014

    Naishd: “It’s all looking dated now, so needs revamping. I never published my rauisuchian stuff but have been meaning to do so for ages. As for the name Pseudosuchia — I agree, I would prefer to use Crurotarsi.”

    That reminds me: How is 1 supposed to pronounce “rauisuchian” & “Crurotarsi”? Also, I agree w/Andreas Johansson in that we need more popular stuff about “non-crocodylomorph croc-line archosaurs”. Also also, some popular stuff about non-mammalian synapsids would be cool.

    Link to this
  16. 16. DavidMarjanovic 6:09 pm 04/9/2014

    Oh, and, the PhyloCode is against Pseudosuchia because it includes Suchia while implying the opposite.

    Link to this
  17. 17. Dartian 5:44 am 04/10/2014

    Hmm. Shouldn’t a manifesto come with a slogan of some kind? How about “Tetrapod zoologists of the world, unite!”? ;)

    Link to this
  18. 18. naishd 6:13 am 04/10/2014

    Thanks for comments. Andreas Johnson (comment # 9) asks “The 2007 armodillodile article refers to an upcoming revelation about aetosaur appearance. Has it been revealed yet and if so what was it?”. When I was in Stuttgart, I was shown an aetosaur specimen (not a new one: it had been put into storage during the 1940s) where the dorsal osteoderms were covered with a thick (c. 20 mm), smooth, continuous layer of what I was told was a preserved mass of soft tissue. So, I came away from that specimen thinking that aetosaurs were like softshell turtles: that is, that the bony armour was actually obscured in life by a thick, continuous layer of skin and other tissue. I later discussed this specimen with several experts on Triassic croc-group archosaurs, one of whom knew it from personal examination. The ‘soft tissue layer’ was no such thing, but, rather, a preservational artefact – a layer of calcite or such that had formed around the specimen. I don’t know if the specimen has been published (it was amazingly complete, fully articulated, and with a complete skull), or if its taphonomic history has been discussed in print.

    As for a manifesto slogan (comment # 17)… yes, Dartian, I’d go with that :) Or “All tetrapods, all the time”: that works too.

    Link to this
  19. 19. naishd 6:41 am 04/10/2014

    On comment # 16: “Thus he places the true crocodiles (both living and fossil) within a taxon that he calls “Pseudosuchia” – which means false crocodiles!” (Charig & Milner 1990, p. 135). Err, not that I support the rest of the argumentation used in that particular contribution.

    Ref – -

    Charig, A. J. & Milner, A. C. 1990. The systematic position of Baryonyx walkeri in the light of Gauthier’s reclassification of the theropoda. In Carpenter, K. & Currie, P. J. (eds) Dinosaur Systematics: Approaches and Perspectives. Cambridge University Press, pp. 127-140.

    Link to this
  20. 20. irenedelse 9:22 am 04/10/2014

    I’ll add my voice to those asking for more of the smaller, less-well-know (or apparently banal but with weird traits or behavior) animals. Even mammals ;-) The voles article was a fascinating read. A thing I especially like in TetZoo is the way you learn to see ordinary critters in a new light. Either they are seriously weird if you dig a little, or they are members of a larger, diverse group… Or both!

    Link to this
  21. 21. JoseD 10:58 am 04/10/2014

    Just making sure my questions in Comment #15 aren’t forgotten about.

    Link to this
  22. 22. John Harshman 1:32 pm 04/10/2014

    Just in case you don’t have enough to do, how about something on dicynodonts? I’m wondering, for exmaple, how this exceedingly cool paper has held up over the last 11 years:

    Thulborn, T., and S. Turner. 2003. The last dicynodont: An Australian Cretaceous relict. Proceedings of the Royal Society of London, Series B 270:985-993.

    Link to this
  23. 23. naishd 3:46 am 04/11/2014

    Woo-hoo, comment # 23 :)

    The Cretaceous dicynodont (comment # 22): I’ve heard positive things about the identification of the specimen as pers. comms. from some therapsid specialists, and there’s a 2009 review paper by Fröbisch that does cite Thulborn & Turner (2003) in a favourable context (Fröbisch 2009). Otherwise, it hasn’t been mentioned in several recent (2013 and 2014) papers on kanemeyeriiforms: this makes me curious, but might be due to the fact that those papers are dedicated to discussion of Triassic taxa. I will ask Christian Kammerer and Michael Maisch.

    Ref – -

    Fröbisch, J. 2009. Composition and similarity of global anomodont-bearing tetrapod faunas. Earth-Science Reviews 95, 119–157.

    Link to this
  24. 24. naishd 3:59 am 04/11/2014

    JoseD (comment # 15): I think I’m the last person that should be providing advice on pronunciation. With my accent, ‘rauisuchian’ is pronounced ‘raow-(as in ‘how’)-sook-ee-un’; ‘Crurotarsi’ is ‘cruur-oh-tar-see’.

    And, yes, more croc-line archosaurs and non-mammalian synapsids coming here, hopefully later this year. I have so much incomplete stuff on these animals sitting around, including a whole series on the different non-mammalian synapsid groups. Yes, all of them.

    Link to this
  25. 25. naishd 4:23 am 04/11/2014

    Cretaceous dicynodont: I’ve just been ‘talking’ about it with Christian Kammerer on twitter – he says that the specimen ‘looks consistent’ with a therapsid identification, but that it lacks derived characters that might confirm such an identification. In other words, the identification looks plausible, based on general similarity, but isn’t convincing and requires substantial scepticism. Christian also reminds me that Agnolin et al. (2010) suggested an alternative identification: baurusuchid crocodyliform. I had forgotten this. They state…

    “Regarding the Cretaceous dicynodont, Thulborn & Turner (2003) indicated that with this record the biochron of this group expanded more than 100 million years after their supposed extinction. Although a thorough revaluation [sic] of the Australian Cretaceous dicynodont goes beyond the scope of the present paper, similarities with some baurusuchian crocodyliforms (e.g. Baurusuchus pachecoi; Riff & Kellner 2001) are striking. Among these traits are the presence of an anterolateral fossa, a large canine-tooth, and very small postcanine tooth. Thus, in light of the similarities between the Alderley dicynodont and baurusuchian crocodyliforms, a re-evaluation of the affinities of this fragmentary specimen is warranted” (p. 293).

    Ref – -

    Agnolin, F. L., Ezcurra, M. A., Pais, D. F. & Salisbury, S. W. 2010. A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: evidence for their Gondwanan affinities. Journal of Systematic Palaeontology 8, 257–300.

    Link to this
  26. 26. DavidMarjanovic 9:39 am 04/13/2014

    Oh, it has a postcanine tooth!?! Kannemeyeriiforms aren’t supposed to have any ever, are they?

    With my accent, ‘rauisuchian’ is pronounced ‘raow-(as in ‘how’)-sook-ee-un’;

    Where do you put the first i?

    Link to this
  27. 27. Affluence14009669 6:38 am 05/2/2014

    As a student currently studying a Zoology degree and hoping to specialize in Reptilian and amphibian behavioral ecology . I found the section on ‘Sexual Selection’ to be fascinating and i would love to read more on the environmental factors contributing to a species evolution. Could someone please refer me to good articles on a similar topic but more directly related to the evolution or behavior of Reptiles or Amphibians?

    I look forward to the next blog entry.
    Shannon Mitchell
    University of Pretoria
    South Africa
    u14009669

    Link to this

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