ADVERTISEMENT
  About the SA Blog Network













Tetrapod Zoology

Tetrapod Zoology


Amphibians, reptiles, birds and mammals - living and extinct
Tetrapod Zoology Home

A brief history of sengis, or elephant shrews

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


Email   PrintPrint



Zanj elephant shrew (Rhynchocyon petersi); image by Joey-Makalintal, licensed under the Creative Commons Attribution 2.0 Generic license.

Macroscelideans – the elephant shrews or sengis – are an exclusively African group of animalivorous placental mammals, famous for their long, mobile snouts [adjacent image of a rhynchocyonine sengi by Joey Makalintal]. They have long tails, proportionally elongate limbs, and range in size from 10 to 30 cm, and from 50g to over 500g. Digital reduction and elongate, often fused, distal limb segments are in keeping with often saltatorial habits: sengis are speedy runners, but also adept at leaping when avoiding obstacles and predators. Limb bone fragments of fossil taxa are similar to the corresponding parts of living taxa and suggest that fossil forms were similar in locomotor abilities. Close relatives of living species (some belonging to the same genera, such as Rhynchocyon) are known from the Miocene onwards, with molecular clock data indicating that aridification events in Africa drove diversification events within the crown-clade (Douady et al. 2003).

Reconstructed skull of the Early Miocene myohyracine Myohyrax oswaldi (after Patterson 1965).

Paleogene macroscelideans were more diverse but none are represented by especially good remains. The oldest taxa belong to the Middle and Late Eocene group Herodotiinae, recognisable due to molariform upper fourth premolars, a wide mesial cingulum on the upper molars and other dental characters. Herodotiines appear to be the sister-group to a clade that contains all other macroscelideans. Within this latter clade, Metoldobotes from the Oligocene seems to be sister-taxon to a Rhynchocyoninae + Myohyracinae + Macroscelidinae clade (Tabuce et al. 2001). Metoldobotes is the biggest fossil macroscelidean yet reported, but even it was only slightly larger than the biggest living species (Patterson 1965). Metoldobotes resembles living sengis in tooth form but has more bulbous tooth cusps. Its enlarged, procumbent lower third incisor possesses a lingual groove of unknown function (to my knowledge, no-one has yet suggested that it was a venomous sengi that used that groove to deliver venom! Tooth grooves are widespread in mammals and other tetrapods and are frequently unrelated to the production or presence of venom).

Lower jaw of Mylomygale spiersi from the Pleistocene of South Africa, from Patterson (1965). The discovery site of this specimen was - according to Broom - "about half a mile to the north of the cave which yielded the Taungs man-ape skull".

Among the more interesting of fossil sengis is Mylomygale of Pliocene Africa. This taxon has large, complex, strikingly rodent-like cheek teeth and was almost certainly a rodent-like herbivore. The Miocene myohyracines (like Myohyrax, illustrated above) were superficially hyrax-like and were initially thought to be hyraxes. Like hyraxes, their molariform teeth indicate that they were browsing herbivores though, again, the biggest taxa were probably only slightly larger than the largest living sengis.

Traditional anatomical hypotheses linked macroscelideans with Archonta, Eulipotyphla or Glires. These proposed relationships were always problematic in view of the vaguely ‘ungulate-like’ form of macroscelidean teeth and limb bones (Simons et al. 1991). Their current inclusion within Afrotheria and close to various Paleogene taxa traditionally classified as condylarths does make more sense.

For previous Tet Zoo articles on afrotherians, see…

Refs – -

Douady, C. J., Catzeflis, F., Raman, J., Springer, M. S. & Stanhope, M. J. 2003. The Sahara as a vicariant agent, and the role of Miocene climatic events, in the diversification of the mammalian order Macroscelidea (elephant shrews). Proceedings of the National Academy of Sciences 100, 8325-8330.

Patterson, B. 1965. The fossil elephant shrews (family Macroscelididae). Bulletin of the Museum of Comparative Zoology, Harvard University 133, 295-335.

Simons, E. L., Holroyd, P. A. & Bown, T. M. 1991. Early tertiary elephant-shrews from Egypt and the origin of the Macroscelidea. Proceedings of the National Academy of Sciences 88, 9734-9737.

Tabuce, R., Coiffait, B., Coiffait, P.-E., Mahboubi, M. & Jaeger, J.-J. 2001. A new genus of Macroscelidea (Mammalia) from the Eocene of Algeria: a possible origin for elephant-shrews. Journal of Vertebrate Paleontology 21, 535-546.

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!

Nature Blog Network

Follow on Twitter @TetZoo.

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





Rights & Permissions

Comments 92 Comments

Add Comment
  1. 1. llewelly 2:11 pm 06/15/2013

    Elephant shrews: More closely related to elephants than to shrews.

    It is interesting that 3 of 6 afrotherian orders have very long, sensitive noses. (The other 3 afrotherian orders also have long sensitive noses, but perhaps not unusually so among mammals. )

    Link to this
  2. 2. Gigantala 4:49 pm 06/15/2013

    Wasn’t Zalambdalestes historically thought to be one? Of course, now it’s generally considered another kind of eutherian, but still.

    Link to this
  3. 3. AlHazen 10:21 pm 06/15/2013

    A few years back (late 1990s? early 2000s?) there was a claim made that Macroscelideans were close to one bunch of Northern Hemisphere “condylarths”– Lousiinae? maybe? (*)
    Strongest piece of evidence seems to have been “fused distal limb elements”: there was a photo of a fossil tibia-fibula, with the fibula merging with the tibia a bit above the mid-point, in the (Nature? Science?) article that looked strikingly Macroscelidean-like. I thought at the time that the evidence was far from conclusive: a few features that could easily be convergent.
    Has there been further discussion of this hypothesis? Or better, have better and more complete specimens turned up to support or “de-support” it?

    (*) As I recall it, Hyopsodontids were mentioned… but it seemed as if the people who were most concerned thought Hyopsodontidae was ripe for, ummm, disaggregation, and the proposal was that Macroscelidea might be close to some member of “traditional” Hyopsodontidae which wasn’t at all close to Hyopsodus. (Striving to attach names only to monophyletic groups is perhaps a good idea when the phylogeny has been reasonably well worked out, but for the foreseeable future I think it might be good to keep the name Condylarthra, understanding it to mean “That menagery of early Cenozoic Eutherians that hasn’t been sorted out yet”!)

    Link to this
  4. 4. BrianL 5:00 am 06/16/2013

    @AlHazen:

    It was indeed hyopsodontids of some stripe. This, along with suggestions that the likes of phenacodids might also be afrotherians and that some definite afrotherians such as embrithopods have their earliest representatives outside Africa, let people to say that Afrotheria itself might not have originated in Africa. Given how poorly known Paleocene African faunas are, and that overall the constituent clades do seem to be strongly tied to Africa in their earliest history, I’d say that’s circumstantial evidence at best. All those non-African Paleogene afrotheres, if indeed all afrotherian to begin with, aren’t very basal at all. They could all constitute early immigrants from Africa, much like metatherians, bats and primates were early immigrants to Africa in the Paleogene.

    As for Condylarthra, I think maintaining it gives the illusion of it really meaning something. I’d much prefer its constituent clades to be considered *incertae sedis* for the time being and Condylarthra itself to be retired or restricted to a much smaller subset of those clades.

    And senghis…do we know why they were able to survive the influx of Laurasian taxa into Africa while they were apparently still unable to colonise Eurasia? Even aardvarks and hyraxes colonised Eurasia for some time!

    Link to this
  5. 5. naishd 6:51 am 06/16/2013

    Thanks for comments…

    The Northern Hemisphere ‘condylarths’ argued to be close to macroscelideans are the apheliscine hyopsodontids: ‘core’ hyopsodontids were always found to be well away from Macroscelidea in the resulting trees (Zack et al 2005).

    The louisinids (or lousinines) from the Paleocene and Eocene of Europe, North America, north Africa and possibly Asia have also been included within Macroscelidea at times. More recently, Tabuce et al. (2001) recovered them as the sister-group to a clade that includes Proboscidea, Hyracoidea, Perissodactyla and Phenacodontidae (this corresponds to Archibald’s (1998) Taxeopoda). One ‘louisinine’, Microhyus, was recovered as close to Macroscelidia by Tabuce et al. (2001).

    Refs – -

    Archibald, J. D. 1998. Archaic ungulates (“Condylarthra”). In Janis, C. M., Scott, K. M. & Jacobs, L. L. (eds) Evolution of Tertiary Mammals of North America. Volume 1: Terrestrial Carnivores, Ungulates, and Ungulatelike Mammals. Cambridge University Press, pp. 292-331.

    Tabuce, R., Coiffait, B., Coiffait, P.-E., Mahboubi, M. & Jaeger, J.-J. 2001. A new genus of Macroscelidea (Mammalia) from the Eocene of Algeria: a possible origin for elephant-shrews. Journal of Vertebrate Paleontology 21, 535-546.

    Zack, S., T. A. Penkrot, J. Bloch and K. D. Rose. 2005. Affinities of the “hyopsodontids” to elephant shrews and a holarctic origin of Afrotheria. Nature 434, 497-501.

    Link to this
  6. 6. Metridia 4:13 pm 06/16/2013

    Speaking of murky Paleogene affiliations of the placental cohorts/superorders, what does TetZoo think of the idea that the common ancestor of placental mammals originated after the KT boundary? That the earliest Afrotherians include some erstwhile notoungulates/’meridiungulates’? It’s also remarkable to think that the post-Cretaceous world was so species-poor, if all the diverse placentals now coalesce to one post-Cretaceous ancestor. What are the lineages of birds that predate the K-T boundary?

    Refs:

    O’Leary, M., et al. (2013) “The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals” Science 339: 662. DOI: 10.1126/science.1229237

    Hacket, S.J., et al. (2008) “A Phylogenomic Study of Birds Reveals Their Evolutionary History” Science 320: 1763. DOI: 10.1126/science.1157704

    Link to this
  7. 7. David Marjanović 4:15 pm 06/16/2013

    Striving to attach names only to monophyletic groups is perhaps a good idea when the phylogeny has been reasonably well worked out, but for the foreseeable future I think it might be good to keep the name Condylarthra, understanding it to mean “That menagery of early Cenozoic Eutherians that hasn’t been sorted out yet”!

    As mentioned above, the term for that isn’t “Condylarthra”, it’s “Eutheria incertae sedis”. In phylogenetic nomenclature, names are labels on trees.

    Link to this
  8. 8. Heteromeles 8:11 pm 06/16/2013

    So perhaps we should call them shrew elephants instead of elephant shrews?

    I’ve got the dumbass question, as always: during the paleogene, Africa was an island. How do we get deep-time phylogenetic links to contemporary mammals on other continents, especially those in the northern hemisphere? Absent some radically good evidence of vicariance (which doesn’t apply to sengis, AFAIK), convergence might be a better explanation for paleogene afrotherians outside Africa.

    Link to this
  9. 9. John Harshman 10:16 pm 06/16/2013

    What are the lineages of birds that predate the K-T boundary?

    Hard question to answer. At least 7 if you believe that Vegavis is a presbyornithid and that we know where presbyornithids fit in the anseriform tree. Given all that, there must also be Cretaceous representives of at least stem members of these lineages: 1) Anatidae, 2) Anseranatidae, 3) Anhimidae, 4) Galliformes, 5) Neoaves, 6) Palaeognathae; makes 7 with presbyornithids. There are a number of other proposed Cretaceous crown group avian fossils, but few of them are good enough to make much of.

    Now, if you want to go with time-calibrated trees, I get 39 lineages crossing the K/T boundary from the Hackett et al. tree. That’s with no attempt to estimate uncertainty, of which there is plenty, of many varieties. Note that this also doesn’t count any lineages that crossed the K/T but became extinct later, only those with living descendants.

    Link to this
  10. 10. CS Shelton 10:44 pm 06/16/2013

    For mammals, at minimum there’s one marsupial, one placental, and one monotreme that made it, but I second metridia’s curiosity. How many lines of each were there? It sucks that small species preserve the worst on land, and they’re the only things left when the biosphere craps out.

    Link to this
  11. 11. CS Shelton 10:51 pm 06/16/2013

    Oh, and it’s interesting and totally makes sense that dinos may still have outnumbered mammals in diversity after the K-T, doesn’t it?

    Link to this
  12. 12. CS Shelton 11:13 pm 06/16/2013

    Sorry to spam, but I found this a long time ago and it’s pure awesome. Cute and interesting sengi videos!

    Link to this
  13. 13. Metridia 11:18 pm 06/16/2013

    @John Harshman- Thanks. I look forward to when they try to reconstruct the stem Neoaves as they did for mammals in the O’Leary et al. paper. The compression of the diversification of Neoaves shown in Hackett et al. does suggest a rapid adaptive radiation- perhaps paralleling that of Paleocene mammals.

    Is it just me, or does all of this coalesce to form a new picture of just how severe the K-T event was? Little surprise not one nonavian dinosaur made it- barely anyone else did either.

    Conditional on support future research of course. Since so much bird diversity rests in Neoaves, finding fossils of Neoaves in the Cretaceous would be key. But the results from O’Leary et al., if confirmed, suggest that we needn’t expect to find current diversity reflected in number of ancestors that crossed the K-T boundary.

    @CS Shelton- Don’t forget the St Bothans ‘multituberculate’- that’s four.

    Link to this
  14. 14. CS Shelton 12:16 am 06/17/2013

    I’m extremely far from an expert, but I remember reading about that. I’d love to get a better vision of that time period. Testudines were really successful back then, right? What a weird world.

    Link to this
  15. 15. naishd 3:15 am 06/17/2013

    More later.. but, with colleagues, I currently have an ms in review on the timing of the crown-bird radiation. I can’t scoop the results but, once the paper’s out, I’ll talk about this issue at length.

    Re: afrotherians outside of Africa – yes, Afro-Arabia was an island for much of the Paleogene, but it’s thought that there must have been some terrestrial connection(s) between Africa and Europe early on in the Paleocene, since both regions share small mammals like adapisoriculids, omomyiforms and zegdoumyid rodents. In fact, Afro-Arabia might not have become completely isolated until the Oligocene.

    Darren

    Link to this
  16. 16. Tayo Bethel 5:00 am 06/17/2013

    Dr. Naish:

    Looking forward to your discussion on Neoaves… reading your chapter in The Complete Dinosaur at the moment. Its fascinating. Wonder what the world would be like if more flighted rhattites had survived the Great Extinction …

    Link to this
  17. 17. vdinets 5:18 am 06/17/2013

    Sengis, my favorite African mammals! I still don’t understand why they are all lumped into one family, considering that Rhynchocyon is so distinctive… One of just two higher-level splits in Mammalia I am ready to accept anytime.

    Link to this
  18. 18. David Marjanović 6:03 am 06/17/2013

    Is it just me, or does all of this coalesce to form a new picture of just how severe the K-T event was? Little surprise not one nonavian dinosaur made it- barely anyone else did either.

    Seconded.

    @CS Shelton- Don’t forget the St Bothans ‘multituberculate’- that’s four.

    …I’ve never heard that the non-chiropteran mammal from St Bathans (no connection to Star Wars!) had been identified as a multituberculate. All I know is the phylogenetic analysis in the original paper, which puts it into a polytomy with the other primary branches of crown-Mammalia. Do you have a reference?

    I currently have an ms in review on the timing of the crown-bird radiation

    I just came home yesterday from a conference of the European Association of Vertebrate Palaeontologists that had a session by the SAPE (Society of Avian Palaeontology and Evolution). The abstract volume will be uploaded on http://www.eavp.org/ at some point. Behold:

    Robert A. DePalma, David A. Burnham, Larry D. Martin (deceased) & Amanda R. Falk: A new bird from the latest Maastrichtian of North America

    “Here, we report a new ornithurine [sensu BAND – Euornithes] bird specimen from the Hell Creek Formation. The fossil consists of a partially articulated skeleton, and is the most complete specimen of its kind thus far discovered in the formation. It is also the first terrrestrial ornithurine bird species to be described from the Hell Creek. The skeleton was preserved in a medium- to fine-grained laminated clay-pebble conglomerate that was deposited in a low-energy stream channel that had a high sedimentation rate. The site is stratigraphically close to the K-T boundary (<20 m below the boundary), within the HC III floral zone (DePalma 2010), and dates to approximately 65 MYA. Overall morphology of the skeleton is consistent with a water-marginal habitat, and specific morphology, more notably the shoulder and hip region, is reminiscent of modern Gruiformes. A phylogenetic study places it as a basal member of the Rallidae within the phylogeny proposed by Livezey [and Zusi]. The highly advanced and derived morphology of the specimen closely resembles modern forms, and indicates that more basal forms may have existed closer to the initial emergence of the Gruiformes at some point earlier in the Cretaceous. Van Tuinen et al. (2006 [cited as 2004 below]) suggested that superordinal groups of extant birds began to emerge around 100 million years ago, followed by modern orders 90–80 million years ago, and diversification occurring rapidly thereafter, a theory consistent with the present specimen.

    Literature Cited
    DePalma, R. 2010. Geology, Taphonomy, and Paleoecology of a Unique Upper Cretaceous Bonebed near the Cretaceous-Tertiary Boundary in South Dakota: Master’s Thesis, University of Kansas.
    van Tuinen, M., and Dyke, G. 2004 [cited as 2006 above]. Calibration of Galliform Molecular Clocks using Multiple Fossils and Genetic Partitions. Molecular Phylogenetics and Evolution 30(1): 74-86.”

    Alas, the authors compared their partial articulated skeleton only to extant rallids, not to known Paleogene stem-rallids. Nikita Zelenkov ripped into this in the question session. I missed the fact that they used the data matrix by Livezey & Zusi, which appears to have a character selection heavily biassed towards precladistic hypotheses, in particular Wetmore’s (1960) classical classification. Given all this and Brochu’s and my work on calibration dates and their effects, I think that this animal may no more be a rallid than Neogaeornis and the heavily reconstructed Polarornis are gaviids.

    I haven’t heard of Vegavis being identified specifically as a presbyornithid; the original paper puts it into a trichotomy with Presbyornithidae and Anatidae. However, what happened to Teviornis? That one (from Mongolia) was described as a Late Cretaceous presbyornithid.

    Link to this
  19. 19. David Marjanović 6:06 am 06/17/2013

    Oh, I should have mentioned the Hell Creek “loriid”. That may be another good analogue, except it’s known from way less material.

    Link to this
  20. 20. M.Ziegler 7:06 am 06/17/2013

    So, I’m commenting here for the first time to drop this:
    Myoglobin sequence data says that moles, echidnas, elephants and hyraxes had aquatic ancestors:

    http://phenomena.nationalgeographic.com/2013/06/13/one-protein-shows-elephants-and-moles-had-aquatic-ancestors/

    Mirceta, S. et al., 2013. Evolution of Mammalian Diving Capacity Traced by Myoglobin Net Surface Charge. Science, 340(6138).

    Link to this
  21. 21. John Harshman 9:09 am 06/17/2013

    I haven’t heard of Vegavis being identified specifically as a presbyornithid; the original paper puts it into a trichotomy with Presbyornithidae and Anatidae. However, what happened to Teviornis? That one (from Mongolia) was described as a Late Cretaceous presbyornithid.

    Vegavis: close enough, and requires the same number of extant taxa; given some resolutions, add one to the number of lineages crossing the K/T, which would make 8.

    Teviornis: The great thing about Vegavis is that there’s so much material; Teviornis is much more fragmentary. And Clarke & Norell didn’t like it.

    Clarke, J. A., and Norell, M. A. 2004. New Avialan Remains and a Review of the Late Cretaceous Nemegt Formation of Mongolia. American Museum Novitates 3447:1-12.

    Link to this
  22. 22. BrianL 11:36 am 06/17/2013

    I’m disappointed in anyone still seriously suggesting modern neornithean ‘families’ in the Cretaceous. What is this, the 19th century? Alas, alas that so many paleornithologists seem to be of the non-cladistic mindset.

    That being said, a rail-like morphology and ecology would make sense for the ancestral neornithean, given that rails are essentially multifunctional jacks of all trades: They walk, swim, climb, dive, fly, run, are ancestrally omnivorous, reasonably fecund and capable dispersers. A generalised ecology like that makes sense for both this ancestral neognath and for a K-Pg boundary survivor. From that perspective, it only makes sense for a Cretaceous neornithean to have been rail-like.

    As for the isolation of Afro-Arabia in the Paleogene, it does not seem to have been very complete. Mind, after the earliest Paleogene it would seem that few highly terrestrial taxa crossed (primates, rodents and ancestral herpestoids may be exceptional in that they, especially the first two, have made oversea voyages on other occassions. Herpestoids not much so, but they did reach Madagascar at least.) The crossing by anthracotheres, embrithopods, stem-desmostylians and anthracobunids are less exceptional in that all of these may have been more or less semi-aquatic: island hopping is very much on the cards in their case and may have taken place in both directions in a complex fashion of colonisation and re-colonisation. In the same vein, protosirenids and stem-pyrotheres (if indeed afrotherian) may have island-hopped to South America from Africa.

    Regarding mammals crossing the K-Pg boundary, let’s not forget gondwanatheres, meridiolestids (I hope I remembered that name correctly) and whatever *Chronoperates* was, if indeed it was from the Cenozoic. I’d also like to mention *Quinornis*, a Paleocene Chinese bird that may be non-neornithean.

    Link to this
  23. 23. BrianL 11:38 am 06/17/2013

    I forgot to remember that a South American anthracothere has recently been described, though it dates from the Miocene. Perhaps another case of a transoceanic mammalian traveler from Africa?

    Link to this
  24. 24. Jerzy v. 3.0. 1:46 pm 06/17/2013

    What was the continent map then? I guess narrow sea crossings made plenty of possibilities for small mammals to colonize on vegetation rafts.

    Link to this
  25. 25. Yodelling Cyclist 2:18 pm 06/17/2013

    Is it just me, or does all of this coalesce to form a new picture of just how severe the K-T event was? Little surprise not one nonavian dinosaur made it- barely anyone else did either.

    Seconded.

    Yeeeessss…..but there are some odd exceptions, at least in the southern hemisphere. Sebecosuchids made it across the KT boundary while retaining quite large body sizes, and adapted to be terrestrial predators (implying that something large and worth eating made the transition with them).The descendants of Waimanu and large bodied turtles also made the leap while all other marine reptiles and birds got eliminated. Photosynthetic colonial corals seem to have made it through (despite suffering enormous losses) as well while rudists died out – almost the reverse of what you would predict for the scenario in which the skies were darkened and phytoplankton dies, leaving the marine ecosystem to tick over relying on trace photosynthesis and stored nutrients (including material washed off the land).

    The KT was a big hit but there are some odd survivors. There must have been some viable refugia with clearish skies, possibly in the more southern lattitudes.

    In short it would probably be ok to time-travel back to the early Danian – I’m reasonably sure I could find some worthwile dive sites.

    Link to this
  26. 26. BrianL 2:37 pm 06/17/2013

    @Yodelling Cyclist:
    *Waimanu* is from the Paleocene, and I wouldn’t put much faith in stem-penguins existing at the end of the Cretaceous. At least not in the sense of stem- to penguins and only penguins. The closest thing around may have been the ancestral neoavian…if that.

    Link to this
  27. 27. Yodelling Cyclist 2:48 pm 06/17/2013

    Ah yes, on closer reading you may well be right. However this paper:

    Slack, K.E. et al Mol Biol Evol (June 2006) 23 (6): 1144-1155.

    strongly suggests some sort of proto-penguin shore bird making it through the transition, and as far as I’m aware there are no records of aqua flyers in fresh water.

    Link to this
  28. 28. John Harshman 4:02 pm 06/17/2013

    I’m disappointed in anyone still seriously suggesting modern neornithean ‘families’ in the Cretaceous.

    What is inherently absurd about such a claim? Are you suggesting that taxonomic ranks have some objective content? I think what you’re really objecting to is putting fossils into modern families without sufficient evidence. That’s the real problem. You need a phylogenetic analysis with enough clear, independent synapomorphies to make convergence unlikely. (You also need to clarify the phylogenetic definition of the family — branch-based or node-based?)

    Slack, K.E. et al Mol Biol Evol (June 2006) 23 (6): 1144-1155.

    The conclusion makes sense if you agree with the assumptions: 1) that the Paleogene fossil is at least a stem-penguin, 2) that the topology is otherwise correct, 3) that the mt tree has been rendered ultrametric correctly. I will say that the very quick, very dirty calibration (using Vegavis alone) of the Hackett et al. tree that I have mentioned above also puts the split between penguins and their living sister group at around 71ma, and given the Hackett et al. topology this demands a great diversity of neoavians across the K/T boundary.

    One might also consider Ericson, P. G. P., C. L. Anderson, T. Britton, A. Elzanowski, U. S. Johansson, M. Källersjö, J. I. Ohlson, T. J. Parsons, D. Zuccon, and G. Mayr. 2006. Diversification of Neoaves: Integration of molecular sequence data and fossils. Biology Letters 2:543-547.

    Link to this
  29. 29. John Harshman 4:07 pm 06/17/2013

    Returning to the subject (which I’m sorry to be hijacking), I have seen it claimed in a book that I can’t now locate that elephant shrews have extraordinarily strong and rigid spines, to the extent that a full-grown human can stand on one without ill effects on the shrew. Any experience with this?

    Link to this
  30. 30. Yodelling Cyclist 4:11 pm 06/17/2013

    I accept that Waimanu and proto-penguins may not be such a good example of a medium sized air-breathing marine species surviving the KT boundary. My apologies.

    Can I try again with the Dyrosauridae?

    Link to this
  31. 31. naishd 4:15 pm 06/17/2013

    Thanks to all for the excellent and entertaining comments. Some really brief responses…

    – there is mention of an (as-yet-unpublished) Cretaceous penguin in the literature: memory tells me that it’s from Chatham Island. I believe it’s referred to in Gerald Mayr’s book on Paleogene birds.. I will check.

    – the claim about the rigid spine on the shrew (comment # 29) refers to the hero shrew (Scutisorex), not to a sengi. It is indeed said in the literature that one of these animals can withstand the weight of a man and survive but there is substantial scepticism about such claims and – so far as I’ve been able to tell – it has never come remotely close to being verified. This issue has formed the basis of various vigorous late-night pub-based discussions.

    Darren

    Link to this
  32. 32. BilBy 4:16 pm 06/17/2013

    #29 @John Harshman – I think that is actually the hero shrew – a soricid from central Africa.

    Link to this
  33. 33. BilBy 4:16 pm 06/17/2013

    Damn, beaten to it by Darren

    Link to this
  34. 34. Metridia 5:21 pm 06/17/2013

    @David #18- no, you are right, i meant it is a lineage of similar age to the multituberculates- but it was part of a polytomy, so it’s not known to be any closer to the multituberculates.

    Others- thanks, definitely did not know about the gondwanatheres etc.!

    Link to this
  35. 35. Christopher Taylor 7:35 pm 06/17/2013

    That being said, a rail-like morphology and ecology would make sense for the ancestral neornithean, given that rails are essentially multifunctional jacks of all trades

    I agree. Also, since the Wetmore-esque ‘Gruiformes’ have now been divided between nearly all the major neoavian lineages, and diverging fairly early in at least the ‘higher land-bird’ and ‘higher water-bird’ lineages, I’ve wondered if the ‘gruiform’ characteristics might be the plesiomorphic characters for Neoaves as a whole.

    Link to this
  36. 36. Metridia 12:04 am 06/18/2013

    @Yodelling Cyclist-

    A couple points- do we know the sebecosuchids, dryosaurids, that other weird crocodylomorph from the Wyoming Eocene with the long ghost lineage, and marine turtles were actually large across the K-T? Further, they may be the exception that proves the rule. Crocodylomorphs may have a broad diet and require little food, while many marine turtles eat jellyfish, which themselves can thrive as part of disturbed, overfished ecosystems. Marine turtles can range far across the ocean, while crocodylians can hide/hibernate in burrows.

    That said, it does seem like places in the southern hemisphere might have been a likely refugia for a meteor strike in the northern hemisphere, proceeding in a northwestern direction (e.g. Schultz and D’Hondt (1996); Geology 24: 963-967)

    Link to this
  37. 37. Dartian 2:31 am 06/18/2013

    Regarding specific examples of mammalian survivors across the K-Pg boundary; at the genus level, there are regrettably few taxa that are currently known from both the Mesozoic and the Cenozoic. Most such purported cases have subsequently been challenged (e.g., the early ‘primate’ Purgatorius, which is actually known with certainty only from Palaeocene deposits). However, the early ‘condylarth’ Protungulatum is one mammalian taxon that is now known to have made it through the end-Cretaceous mass extinction (Archibald et al., 2011).

    This, obviously, has potential implications for our understanding of the overall phylogeny of (placental) mammals, but unfortunately, we don’t currently have any good idea of exactly what kind of mammal Protungulatum was. As mentioned, it has traditionally been regarded as a condylarth or a proto-ungulate, but Archibald et al. (2011) note that it’s not certain if it’s even a placental mammal at all.

    Reference:
    Archibald, J.D., Zhang, Y., Harper, T. & Cifelli, R.L. 2011. Protungulatum, confirmed Cretaceous occurrence of an otherwise Paleocene eutherian (placental?) mammal. Journal of Mammalian Evolution 18, 153-161.

    Link to this
  38. 38. David Marjanović 4:56 am 06/18/2013

    Hyaenodontidae reached Asia from Africa in the Palaeocene.

    *Quinornis*

    Qinornis. The q is not what you think it is; the closest sound in English is “ch”.

    I forgot to remember that a South American anthracothere has recently been described, though it dates from the Miocene.

    Wow.

    Perhaps another case of a transoceanic mammalian traveler from Africa?

    Are there any in North America?

    What was the continent map then?

    Look it up. http://www.scotese.com/ is a good place to start (though don’t trust the coastlines too much).

    Sebecosuchids made it across the KT boundary while retaining quite large body sizes, and adapted to be terrestrial predators (implying that something large and worth eating made the transition with them).

    I’m not sure about that. Baby crocodiles are independent very soon, and they can grow arbitrarily slowly. Body size is also rather plastic evolutionarily.

    Also, it seems that only one clade made it, composed of Sebecidae and its closest relatives. I need to look up the latest phylogeny again…

    large bodied turtles

    The really big ones, the protostegids, died out along with the ammonites and the rudists. Only the jellyfish-eaters survived. Jellyfish are disaster taxa, as we’re observing right now. (See comment 36.)

    Photosynthetic colonial corals seem to have made it through

    They can bleach, switch to eating, and regain their symbionts a few months later, right?

    it would probably be ok to time-travel back to the early Danian –

    The sound of the thunder would be deafening.

    However this paper:

    Slack, K.E. et al Mol Biol Evol (June 2006) 23 (6): 1144-1155.

    strongly suggests some sort of proto-penguin shore bird making it through the transition

    BZZZT! How was that calibrated, and what are the error margins?

    (I’ll look it up myself in a few hours.)

    the very quick, very dirty calibration (using Vegavis alone) of the Hackett et al. tree that I have mentioned above also puts the split between penguins and their living sister group at around 71ma

    That calibration is old and far outside the clade of interest. Both of these factors bias the results toward too old divergence dates (Brochu 2004a, b, Journal of Paleontology; me & Laurin 2007, Syst. Biol.; some amount of review in me & Laurin 2013, Geodiversitas, open access).

    Can I try again with the Dyrosauridae?

    No, because their young lived in freshwater. :-) Or at least they’re completely absent from the marine record, while juvenile mosasaurs are common in the same deposits up to the end of the K.

    Freshwater ecosystems are largely detritus-based.

    Others- thanks, definitely did not know about the gondwanatheres etc.!

    Also, adapisoriculid stem-eutherians – the Cretaceous Deccanolestes is one. Also also, Taeniodonta (which may or may not belong to Placentalia) – the Cretaceous Schowalteria belongs there. Also also also, Leptictida (which may or may not belong to Placentalia) – the Cretaceous Gypsonictops may belong there. Clearly outside Placentalia, there are the stem-eutherian Cimolestes, and several lineages of multituberculates. Not sure how many metatherians.

    (e.g., the early ‘primate’ Purgatorius, which is actually known with certainty only from Palaeocene deposits)

    …and not even earliest Palaeocene ones. As I was told last SVP meeting, it is not one of the Four Horsemen that show up immediately after the apocalypse: Protungulatum, Oxyprimus, Mimatuta, Baioconodon.

    Link to this
  39. 39. naishd 5:10 am 06/18/2013

    The “South American anthracothere” – Arretotherium meridionale – is from Panama. Quite a few North American anthracotheres have long been known: I would have to check the paper again, but I don’t recall there being anything about a possible Africa –> Central America crossing being inferred, only a southward spread from North America.

    Darren

    Link to this
  40. 40. Dartian 5:29 am 06/18/2013

    Darren:
    The “South American anthracothere” – Arretotherium meridionale – is from Panama.

    That’s right, it lived on the North American landmass, not on the South American.

    I don’t recall there being anything about a possible Africa –> Central America crossing being inferred, only a southward spread from North America.

    According to the authors (Rincon et al., 2013) the closest relatives of this new Central American anthracothere lived in North America – as one would expect for geographical reasons.

    Reference:
    Rincon, A.F., Bloch, J.I., MacFadden, B.J. & Jaramillo, C.A. 2013. First Central American record of Anthracotheriidae (Mammalia, Bothriodontinae) from the early Miocene of Panama. Journal of Vertebrate Paleontology 33, 421-433.

    Link to this
  41. 41. Yodelling Cyclist 10:49 am 06/18/2013

    @Metridia (and indeed to all): First off, thank you for being patient with a non-biologist. I’m going to stiuck with this argument, however, as either there is something wrong with the existing hypothesis, or something fundamental which I don’t understand (which is more likely).

    With regards crocodilian survival: much is made of their ability to hunker down and survive long periods without food. This is great, and would surely allow a large terrestrial croc to survive the extinction event. One could imagine an animal passively watching over the months to years as the skies clear and the ferns start to break out. Then what? It’s 24 months later and the only prey that appears to be available are very small mammals and detritivourus invertebrates. Evolution of larger mammals capable of supporting a large terrestrial animal predator will take centuries. No individuals will make it that far. Evolution literally takes generations, extinction takes one bad night. Maybe the only sebecosuchids to make it through the KT were in fact small, hitherto unknown species which subsequently evolved into larger taxa very similar to those from the end of the Cretaceous. That would solve the problem, but honestly I think the idea of some kind of medium to large herbivore surviving somewhere, a surviving working (albeit hugely damaged) ecosystem in short, is more plausible.

    Time demands that I can’t respond to every good counter point, but I would observe that corals that eject their algal symbiotes then exist as all-but filter feeders – the lifestyle which the rudists excelled at. The rudists didn’t survive, so there’s something more there.

    Turtles eat jellyfish, jellyfish thrive in overfished environments. All true, but the jellies are predators themselves, and heavily dependent on the plankton. A disaster that can annihilate the ammonites by plankton eradication should be seriously harming the jellyfish – but maybe they can make it.

    Dyrosauridae juveniles living in freshwater: ok, but that’s a devastated ocean they’ll grow up to inherit. Maybe that does get them through.

    The Danian was 4 million years long. Post-impact things have to calm down within a decade (at a massively pessimistic estimate). A century later there would be blue skies.

    Link to this
  42. 42. Yodelling Cyclist 1:50 pm 06/18/2013

    Also:

    the exception that proves the rule

    Personally, I really, really hate that expression. If a rule has an apparent exception, either the rule is wrong or the exception is only apparent without being actual.

    In science we can’t have exceptions to every rule – preciously the opposite, there must be no exceptions. Atomic orbitals don’t “sometimes” contain three electrons yet I’m still pretty happy with the Pauli exclusion principle.

    Link to this
  43. 43. Heteromeles 3:05 pm 06/18/2013

    Since I actually set a time-travel story in the mid-Paleocene, I’d suggest that it’s about the safest, most boring place to travel to in the last 100 myr or so.

    The nearest analog would be highland New Guinea. Yeah, safe like that. Bring along some *good* crops to plant. Still, it’s safer than the Cretaceous, which would have been like highland PNG plus dinosaurs. That would kind of suck for even the hardiest survivalists.

    Anyway, the problem with the Danian isn’t the remnants of the impact winter, it’s also whatever was going on with the Deccan traps and probably wild weather of the sort we’re experiencing now. Long droughts, strong storms, lots of erosion, and weedy ecosystems. The ecosystems would have been fairly simple in many places: a few dominant trees over a simple understory, and if some disease came along to take out one or the others, things would get bad.

    As for what crocodilians survived the K-T, I think we can answer that by looking at Australia. How do Salties and Freshies survive problems like, oh, loss of large terrestrial vertebrates, crappy weather, invasions by things like cane toads and weeds? These are a crude analog for the Danian.

    Link to this
  44. 44. Yodelling Cyclist 3:34 pm 06/18/2013

    How do Salties and Freshies survive problems like, oh, loss of large terrestrial vertebrates, crappy weather, invasions by things like cane toads and weeds?

    Well, there are still macropods in Aus much larger than the mammals that supposedly survived the KT.

    Secondly the sebecosuchids are alleged to be terrestrial – they likely wouldn’t be able to draw effectively on fish or other aquatic food sources that salties utilise. The skulls are quite different. Maybe, as I say, only some dwarf sebecosuchid survived and repopulated, but we can’t use the get out of having them hide in the rivers and streams like the eusuchids, and we can’t just wave our hands and say they could cope with very little food. The environment is apparently denuded of medium sized herbivores for millenia. The putative surviving herbivores don’t have to be non-avian dinosaurs. Big squamates, surprisingly big mammals, chelonians or just birds might do the job. Or some herbivorous suchian similar to simosuchus, of some form.

    Link to this
  45. 45. John Harshman 4:21 pm 06/18/2013

    That calibration is old and far outside the clade of interest.

    I can see “far outside the clade of interest”. But why “too old”? It’s almost the same age as the node it attempts to calibrate here, which seems perfect.

    Link to this
  46. 46. David Marjanović 4:58 am 06/19/2013

    (I’ll look it up myself in a few hours.)

    I… sort of forgot.

    But why “too old”? It’s almost the same age as the node it attempts to calibrate here, which seems perfect.

    You need both old and young ones compared to the clade you want to date cladogeneses in – you can’t date one node alone anyway.

    Link to this
  47. 47. vdinets 6:08 am 06/19/2013

    Just for the record, at least two crocodilian species (American alligator and Siamese crocodile, if I remember correctly) have been observed feeding on fruit. And these were well-fed captive individuals.

    Link to this
  48. 48. naishd 6:31 am 06/19/2013

    Cases of occasional herbivory and frugivory in crocodiles, caimans and alligators were covered on Tet Zoo ver 2 back in 2008. Go here. Also worth a look: alligators vs water melons!

    Darren

    Link to this
  49. 49. David Marjanović 9:10 am 06/19/2013

    Found it. The only two calibration points for the figure shown in the main text were Waimanu and Vegavis. The supplementary information goes on to state that there was a third calibration point, of middling age and far outside, the divergence between emu and cassowary at a wholly guesstimated 30 to 35 Ma ago (the oldest fossil that could calibrate this is 25 Ma old, so you need silly assumptions about the speed of morphological evolution to arrive at a date 10 to 15 Ma earlier).

    The supp. inf. goes on to state: “95% confidence intervals were calculated but are not shown.” They’re kept secret, they’re not even published in the supplementary information. Isn’t that embarrassing?

    Link to this
  50. 50. John Harshman 9:34 am 06/19/2013

    You need both old and young [calibration points] compared to the clade you want to date cladogeneses in – you can’t date one node alone anyway.

    While that may all be true, it seems irrelevant to your original objection that a particular calibration point was “too old”.

    Link to this
  51. 51. Heteromeles 10:33 am 06/19/2013

    Back to #42: The exception proves the rule is, indeed, irritating. Problem is, the ideas that rules are absolute comes from physics, not biology. Even in physics, rules are regularly broken. One good example is the small problem of expressing time and gravity in quantum mechanics, and expressing the wave/particle duality in general relativity.

    Getting back to rules in ecology and evolution: yes, there are rules that control both evolution and ecology. The problem is determining which ones apply most strongly. The physical laws that most strongly govern ecology and evolution on an alpine glacier are rather different than those that control the ecology and evolution in the rainforest below, even though both systems may be strongly coupled.

    Bottom line is not to expect absolutes in biology. Feel free to yell at anyone who uses “the exception proves the rule” though. Personally, I think we should all feel privileged every time we have enough data points to posit a hypothesis, and leave the prating about rules to the amateurs.

    Link to this
  52. 52. Heteromeles 10:47 am 06/19/2013

    The simple answer for how animals survived the K-T is refugia. More specifically, I’d focus on jumbled mountain ranges that, due to topography and location on the globe, survived the K-T disaster relatively intact. There may have even been dinosaurs in these systems. The limit on these areas is that they were relatively small, and like urban parks, they were too small to support breeding populations of large endothermic herbivores and carnivores.

    For those who want to derive some numbers for the upper limit of a refuge, we can look at a couple of theories:

    –the theory of island biogeography, specifically as it applies to parks. For decades there have been studies of how species disappear from parks as a function of size and isolation, and it shouldn’t be impossible to figure out how big a park would be to support, say, a breeding population of sebecosuchids. Perhaps Komodo dragons can be substituted for sebecosuchids, since they occur in multiple small islands.

    –Fire and landscape: there’s some interesting research associated with Jon Keeley (USGS) about how landscapes affect the propagation of wildfires. The tl;dr version is that topography matters more than vegetation. A place like Malibu Canyon, which is a fairly big, linear canyon facing the direction of the predominant Santa Ana winds, burns extremely well any time there’s a wind and an ignition within it, which is why fires in Malibu Canyon commonly make the news. Nearby canyons with a palmate topography (canyons branching off at all angles, with no preferred direction) rarely if ever burn, because no matter which way the wind blows, a fire that gets into these canyons only burns a small spot before jumping to the next ridge.

    While we don’t know where all the mountain ranges were at the K-T boundary, we can figure out where many of them were. We can also figure out how big these areas were, and (crudely) how large a species could be supported in each refuge. In a way it’s cheating, because we already know the answer. Still, it would be a good exercise for some paleogeographer to run through.

    Link to this
  53. 53. Yodelling Cyclist 3:55 pm 06/19/2013

    First off I should apologise if I came across as yelling. I’m passionate about the physical sciences and sometimes I don’t phrase things well. I apologise for any offence caused.

    I would also point out that the inconsistencies between quantum physics and GR, without wishing to have a deep discussion about either (as I am no where even close to the levels of understanding required to have such a discussion), are considered proof that either or both are inadequate, and as such should not be considered universal “rules”, merely excellent, excellent, staggeringly good, models. It is the presence of a counter example that destroys the rule, not which validates it.

    Finally I would argue that at a fundamental level the “rules” governing evolution on glacier will be exactly the same as in a rainforest environment. The definition of an organisms “fitness” will definitely be different, but natural selection will grind on relentlessly in both environments.

    In the specific case of the KT extinction I would suggest that the “rule” that no land animal above x kg (I’ve definitley heard 10kg) survived may be too strict a conclusion to draw based on the available evidence.

    Link to this
  54. 54. ralaven 6:15 pm 06/19/2013

    The issue brought up by yodelling cyclist – the exception proves the rule – is a classic example of a language change meaning that an expression is thought to mean the opposite of what it actually means.

    The issue is what ‘prove’ means. In this case prove means test – similar to its use in the phrasing ‘proving a dough’ where the last rise is a test that the yeast is working. So to say that the exception proves the rule is to say that it tests it. I.e is it a good rule or does this exception mean that the rule is not a good one. So the expression actually means exactly what YC stated – “It is the presence of a counter example that destroys the rule, not which validates it”.

    Link to this
  55. 55. Heteromeles 6:33 pm 06/19/2013

    Finally I would argue that at a fundamental level the “rules” governing evolution on glacier will be exactly the same as in a rainforest environment. The definition of an organisms “fitness” will definitely be different, but natural selection will grind on relentlessly in both environments.

    Not really. If it helps, think about how to optimize clothing for a high-mountain glacier, vs. clothing for a tropical rainforest. The critical requirements for creating health and safety are different in each environment. In one environment, you have to keep an organism from freezing to death, then keep it fed in an environment with little biomass of any sort. In the other environment, disease is a huge issue (with a side order of poisonous organisms. Other major issues are, dehydration, overheating, and navigation. Biomass is not limited, but edible biomass may well be. Keep food edible and water potable are going to be a problem in the tropical forest, but much less of a problem on a glacier.

    I’m doing this by analogy, but if you look at the insects in aeolian ecosystems vs. those in tropical rainforests, you’ll see much of the same distribution.

    Link to this
  56. 56. Yodelling Cyclist 7:54 pm 06/19/2013

    I think we’re considering different “levels of rule” here, and so this may well come down to a failure , at least on my part, to articulate clearly.

    I would consider a very general statement, such as, “an organism must be able to secure sufficient nutrients to grow, maintain itself, and then breed in order for it’s genes to be transmitted” to be a rule (or to be more formal, a functioning axiom for biology) as it is as near a universally true statement as I can imagine for a biological system. I would not consider the statement, “an organism must be able to survive an air temperature below 273K” to be a rule. It is a practical upshot of the basic constraints of biology if we are considering life on a glacier, and but it requires additional specifying criteria to be found true. It is not true, as you say, in a normal tropical rain forest (on earth), but the my first statement is true in both cases and so is I classify it as a rule.

    My original bug was with what I perceived to be a general tendency to say that the KT impactor produced so much ejected debris and induced fires with their concomitant soot to such a degree that the entire earth was blanketed with an opaque layer that blocked photosynthesis for long enough to eliminate all those components of ecosystems so dependent on photosynthesis that they could not survive months in the dark, and a significant temperature drop potentially lasting years (nuclear winter scenarios are scarily similar to ice ages, and though I accept the Cretaceous was a hot world, an impact on the described scale would still be really hard for terrestrial poikilotherms). This is, as I understand it, the proposed kill mechanism for herbivorous non-avian dinosaurs and indeed everything else that failed to survive. There is a corollary: everything that survives the impact winter then has to survive in the post impact ecosystem which will reach a new equilibrium fairly rapidly (centuries). If you’re a large terrestrial carnivore, you need something to eat, and you can’t wait for the mammals to evolve something tasty – they’re not that quick. In the oceans the corals have to start photosynthesising within a few years or the reef will break down under sediment and algae – and besides why are all the rudists dead – this should be heaven for them? Then there’s the really odd problem: surviving amphibians. Hot house cretaceous amphibians suddenly plunged into months of darkness, 10K+ temperature drops lasting years and probably acid rain should really be dying off, or just gone altogether if these effects are truely global. So I make this observation: there is something bit more subtle happening here, there are likely refugia, most importantly with clear skies, and working out why some animals survived and spread from these points and others simply went under is a question I can’t answer.

    That rant aside, it’s very far from the theme of the original blog post, and short of major field expeditions – probably to Antartica (what is under the ice ?!?!? :-) ) this is all speculation, and fun though it is I’m in danger of looking like the nutter in the corner – if indeed I’m not already.

    Link to this
  57. 57. Jerzy v. 3.0. 8:38 pm 06/19/2013

    Survival of land crocodiles may indeed come from ability of juveniles to stop growth during lack of food and perhaps breed in shrunken size. This assumption may be testable on Paleocene croc skeletons. Whether adult Paleocene crocs could “hunker down and fast” as long as adult Nile crocodiles is probably not testable. Neither we know whether adult dinosaurs couldn’t fast as long as Nile crocodiles.

    One little-known fact is that Galliform birds share this ability. Apparently some scientist maintained a domestic chick for months as a little fluffy chick by giving it precise amount of food, and later let it grow into a normal, reproducing hen.

    Alternative is that we underestimate Paleocene crocs’ aquatic abilities and their ability to feed on small prey.

    @52 I also toyed with the idea whether K/T survival could be explained by survival of very small refuges (size of hectares or single square kilometers), capable of supporting only small animals. However, it is difficult to avoid quick re-colonization of the surrounding land by plants and then dinosaur herbivores.

    Link to this
  58. 58. John Harshman 9:01 pm 06/19/2013

    You may be omitting what may be the major cause of death from the impact, the infrared pulse cause by re-entry of ejecta into the atmosphere. Ability to hide under non-flammable objects (rocks, a foot or so of water or soil, etc.) may have been highly selected for, for about 20 minutes.

    Robertson, D. S., M. C. McKenna, O. B. Toon, S. Hope, and J. A. Lillegraven. 2004. Survival in the first hours of the Cenozoic. Geological Society of America Bulletin 116:760-768.

    Link to this
  59. 59. Yodelling Cyclist 10:28 pm 06/19/2013

    @Jerzy3.0: The possibility of breeding as a juvenile would be extremely useful in this scenario.

    Refugia on the scale you suggest would be…odd, I think. With dust and soot in the atmosphere, I’m more thinking of very large areas where the dust would not be so concentrated, permitting serious preservation of plant life. A possibility is very close to the southern pole. If the non-avian dinosaurs of region habitually migrated north in the winter where as crocodylians and others hibernated then this would be a decent possible explanation (assuming that maybe the polar vortex keeps the dust at bay). Interestingly doing a little googling (when I should be writing my thesis) reveals some suggestions that there is greater preservation of floral diversity across the KT boundary in South America than North America.

    Because the readership here knows much more than I: what is the mammal radiation like with respect to the southern hemisphere? In other words, are southern hemisphere mammals more diverse post impact than the northern hemisphere? Do the surviving lineages appear to radiate from the south?

    for about 20 minutes

    Hehehe. Duck and cover.

    Link to this
  60. 60. Yodelling Cyclist 10:32 pm 06/19/2013

    Actually, thinking about it, if the refuge is in the south, the south would look more archaic. The huge radiation would be in the northern hemisphere as the handful of survivors radiated massively into the novel niches that are left. Mammals might be conserved in the south, and novel in the north.

    Link to this
  61. 61. naishd 3:53 am 06/20/2013

    Wow, outstanding example of thread drift :) Interesting to see how we got to here, from sengis.

    Darren

    Link to this
  62. 62. David Marjanović 5:48 am 06/20/2013

    While that may all be true, it seems irrelevant to your original objection that a particular calibration point was “too old”.

    You’re misquoting me. I said “old”, not “too old” – you need both old ones and new ones, both outside and inside the clade of interest. The constraint in question is old and outside – if it’s used alone, the results will be biased toward too old ages.

    And you need maximum ages on a few (or, in more recent programs, probability distributions on calibration dates).

    me & Laurin 2007
    open-access pdf of me & Laurin 2013

    The issue is what ‘prove’ means. In this case prove means test – similar to its use in the phrasing ‘proving a dough’ where the last rise is a test that the yeast is working.

    That doesn’t work. The expression exists in German as well, and there it’s die Ausnahme, die die Regel bestätigt, the exception that confirms the rule. Prüfen, “test”, isn’t in there.

    This is, as I understand it, the proposed kill mechanism for herbivorous non-avian dinosaurs and indeed everything else that failed to survive.

    Oh no, it’s just one part of it. The heat pulse and of course the fires have been mentioned. And then there’s…

    – Such an impact locally ignites the air, yielding lots of nitrogen oxides. They immediately annihilate the ozone layer,
    – are seriously poisonous,
    – and eventually rain down as nitric acid, together with the sulfuric acid produced from the anhydrite at the impact site and the carbonic acid derived from the dolomite at the impact site as well as from the fires. This acid appears to have sterilized the top of the ocean.
    – It also appears to have washed all kinds of nasty stuff out of the continents. Beryllium and aluminium for instance.
    – Carbon dioxide! Greenhouse gas.

    Is it known which corals survived? There are deep-water corals that should have had much less trouble than the shallow-water ones. Were there any deepwater rudists?

    Then there’s the really odd problem: surviving amphibians.

    Some actually did die out. They didn’t all sail through unscathed. Many of the survivors, as far as the biased fossil record can tell us, belonged to freshwater ecosystems, so survived the same way freshwater crocodiles did. And many radiations conspicuously began in the Paleocene.

    what is the mammal radiation like with respect to the southern hemisphere? In other words, are southern hemisphere mammals more diverse post impact than the northern hemisphere? Do the surviving lineages appear to radiate from the south?

    Only South America has a known fossil record of that time… and there, you have:
    – a huge diversity of meridiolestidans cut down to Peligrotherium in the Paleocene and Necrolestes in the Miocene;
    – surviving gondwanatherians of probably unchanged low diversity;
    – IIRC, there’s a multituberculate in the K but none in the Cenozoic of all of Gondwana (in Laurasia, the ptilodontoids and taeniolabidoids thrive, though the djadochtatheres are gone);
    – two teeth called Monotrematum in the Paleocene, no monotremes before or after;
    – meta- and eutherians that must have immigrated from North America showing up in the… I think mid-late Paleocene, but I’d need to check, and the early Paleocene (Danian) terrestrial fossil record of South America is very scanty in general. In any case, none have yet been found in the Cretaceous.

    Link to this
  63. 63. David Marjanović 5:56 am 06/20/2013

    This page lists one meta- and two eutherians from the same site and age as Peligrotherium and Monotrematum; that’s supposed to be Danian, but South American correlation is really hard. I need to check a paper on the Itaboraian (latest Paleocene) I read recently.

    Link to this
  64. 64. vdinets 9:38 am 06/20/2013

    I think small refugia with clear skies are physically impossible. A larger polar refugium formed by a mechanism similar to the one responsible for the ozone hole might be possible, but it would be nice to ask a meteorologist about this. If you need small terrestrial refugia, areas of active volcanism are much better candidates.

    I don’t understand how acid rains could sterilize the ocean surface but not the freshwater ecosystems. Could it be that freshwater hard-skeleton animals are less sensitive to acidification? And, by the way, didn’t rudists have massive shells that would be very difficult to build in acidic environment?

    Some amphibians and a few squamates can survive being frozen (supposedly for decades, if not centuries, in the case of Siberian salamander). It is claimed that the largest extant freeze-proof one is the box turtle. Chinese alligators survive months of sub-zero temperatures in underground burrows.

    Link to this
  65. 65. Yodelling Cyclist 12:07 pm 06/20/2013

    You see? This is a really fun topic. Or I’ve gone too far in my KT induced nutter-dom. One of the most bizarre side effects of the KT mass extinction event is that it can, as Darren points out, generate massive thread drift as long as 65 million years after the event. :-)

    @ David Marjanović:

    And then there’s…

    I hadn’t forgotten that list, I just didn’t bring it up. It does raise a good point though: ozone depletion and catastrophic acid rain are rarely classed as amphibian friendly events. If anything it makes it more likely that there have to be places where species can survive in relatively benign conditions. A global oceanic acidification to the point of actually sterilising the photic zone globally requires such a release of material and energy that everything should be dead. Crudely assuming diffusion from the point source (such that a point on the opposite side of the globe is poisoned to the point of only just killing every damn thing in the plankton) of an impact requires staggering ocean death counts, it becomes really unlikely that anything comes through, let alone jellyfish that require plankton to feed.

    Could all these fresh water survivors be due to taphonomic bias towards such environments?

    Also, thank you very much for the mammal species list. Sadly, I don’t think there’s enough data to draw a conclusion. Very interesting though, learned much. Maybe not all you tried to teach, but much.

    The CO2 being a greenhouse gas won’t save you from the debris and ash, particularly if (as suggested) the particles reach the stratosphere. To much light, even in the infra red is blocked. Things have to get cold.

    Actually it’s kind interesting what global oxygen levels would have looked like post KT. If most of the terrestrial plant biomass actually did burn, with subsequent rotting of additional dead biomass and photosynthesis dropped off for a year or more, ppO2 must have been decreased somewhat.

    Oceanic Be leaching? Was that actually significant? I had to pay a goddamn fortune for a Be tube recently. I know most of that cost was due to toxicity and handling difficulties, but it’s really a quite rare element.

    With regard to deep water corals: these are not photosynthetic. Some photosynthetic (via algae of course) species did survive.

    With regards rudists, yet more googling seems to indicate that they particularly thrived in the warm waters of the tropics and lower latitudes, even to the point of displacing corals. The cold may have done from them, ultimately.

    Pet peeve #429: “ignite the atmosphere”. Usually ignition (for chemists) describes a process in which a thermal run away occurs i.e. (for combustion reactions) enough energy is released to provoke further combustion. If you burn N2 in O2 this does not happen – the reaction endothermic – not enough energy is released to propagate the combustion (thank heavens), so yes NOx species will form from the impact, but the global atmosphere doesn’t go up like gasoline.

    @vdinets:

    Some amphibians and a few squamates can survive being frozen (supposedly for decades, if not centuries, in the case of Siberian salamander). It is claimed that the largest extant freeze-proof one is the box turtle. Chinese alligators survive months of sub-zero temperatures in underground burrows.

    Sure, but these are species which have, gradually, adapted to the cold, or at least cold spells. The KT thermal pulse and impact winter will have come on suddenly, in a very warm Cretaceous world. Were we to gather a selection of tropical amphibians from around the modern globe, I doubt that any of them would walk off a year in the dark, with temperatures 10K (or more) below their adapted range, showered with acid rain and the removal of all prey but the detritivores. At the end of that period, these populations have to survive a continued cool period with high UV exposure, as a follow up. Plus, let’s put a small number of diminutive crocodiles into this study.

    No, things can’t be this bad globallY. Clear skies have to appear somewhere soon after the impact. Just somewhere with corals, turtles, some crocodylians, amphibians, some mammals, no ammonites, no non-avian dinosaurs, no pterosaurs or any of the rest of the zoo of large marine reptiles. No rudists allowed. It’s weird.

    Link to this
  66. 66. vdinets 12:22 pm 06/20/2013

    Yodelling Cyclist: weren’t there some high mountains on the planet at that time? If there were, it means that no matter how warm the world was, some species were cold-adapted and could hibernate through the whole thing. They would also be the ones adapted to UV radiation.

    As for the marine environment, the event would cause a major deforestation and a spike in surface erosion. What killed a lot of marine animals but not jellyfish or corals was probably not a total loss of plankton, but just the opposite, a massive bloom of toxic algae. Note that plankton can photosynthesize at very low light levels, i.e. under snow-covered sea ice.

    Link to this
  67. 67. Yodelling Cyclist 12:47 pm 06/20/2013

    @vdinets: Not sure about the mountains. Good thought. Are there many high-altitude amphibians today?

    As for low light level photosynthesis: I would be surprised if there would be enough to support a toxic bloom on the scale proposed. There has to be an energy source to permit chemical reduction. Notably red tides don’t happen under ice! Otherwise, it’s great. It would allow for mass death to extend to areas with clear skies.

    The idea of total plankton loss is really derived from the loss of ammonites but retention of nautiloids.

    Link to this
  68. 68. Yodelling Cyclist 12:58 pm 06/20/2013

    Or, put another way:

    http://imgur.com/r/funny/eQ5A99k

    Link to this
  69. 69. vdinets 4:34 pm 06/20/2013

    There are lots of high-altitude amphibians in the Andes. Also, a lot of amphibian lineages (including remarkably high proportion of “primitive” groups such as tailed frogs, Hynobiids and giant salamanders) live in cold, clear mountain rivers.

    Increased runoff would have to continue for a long time to fill the oceans with enough nutrients to cause algal blooms. By that time the skies would be clear again.

    Ammonites had more complex shells, with fractal-shaped septae (or whatever they are called) and thick mother-of-pearl layers. These shells were almost certainly a lot heavier than those of nautiloids… and more difficult to build in acidic environment.

    Link to this
  70. 70. LeeB 1 7:04 pm 06/20/2013

    A number of hot climate amphibians live in desert areas and survive by digging themselves into the mud at the end of the wet season and aestavating until it rains again.
    Frogs in Australia and Africa do this and some survive for well over a year underground.
    Given the hot climate in the Cretaceous this may have been a common adaptation amongst amphibians living in seasonal climates at the time.
    Most would be underground and thus shielded from climatic perturbations at the end of the Cretaceous.
    Other amphibians live in fresh water in areas with limestone or dolomite rocks, the dissolution of these rocks would act as a buffer against the acidification of the fresh water.
    And some photosynthesizing corals in the genera Leptoseris, Agaricia and Craterastrea live in very deep water, sometimes at 120m or so, the amount of light is very small but their symbiotic algae are adapted to this and can still photosynthesize.
    So the water depth would protect them from acidification of the surface waters.

    LeeB.

    Link to this
  71. 71. David Marjanović 6:03 am 06/21/2013

    I don’t understand how acid rains could sterilize the ocean surface but not the freshwater ecosystems.

    See comment 70: it depends on the local rocks. The acid rain of the 80s was a catastrophe in granitic Scandinavia, but hardly had an effect in the calcareous parts of the Alps.

    Could all these fresh water survivors be due to taphonomic bias towards such environments?

    Probably. I’ll need to check.

    The CO2 being a greenhouse gas won’t save you from the debris and ash,

    Oh, of course not. It’ll make the world hot right afterwards. It’s one more kill mechanism, that’s why I put it in the list of kill mechanisms!

    Speaking of which, I forgot two more kill mechanisms:
    – Tsunami.
    – The impact itself, an earthquake topping 12.4 on the Richter scale.

    particularly if (as suggested) the particles reach the stratosphere.

    This, and the long darkness, came from the original idea that the ejecta from the impact were mostly dust. This was shown to be clearly wrong several years ago; the ejecta were mostly sizable fragments that contributed to the heat pulse instead of staying in the air. It did probably get dark for a while (not a year, I guess!), but that’s due to the soot from the wildfires which I can’t imagine to have reached the stratosphere in significant amounts.

    Actually it’s kind interesting what global oxygen levels would have looked like post KT. If most of the terrestrial plant biomass actually did burn, with subsequent rotting of additional dead biomass and photosynthesis dropped off for a year or more, ppO2 must have been decreased somewhat.

    But then, lots and lots of respirators were dead, too.

    Oceanic Be leaching? Was that actually significant?

    Probably not much… but I don’t know how much research there is on this.

    I had to pay a goddamn fortune for a Be tube recently. I know most of that cost was due to toxicity and handling difficulties, but it’s really a quite rare element.

    Not that much; it’s just usually bound up in silicates that aren’t soluble in water of normal pH ranges.

    Al, however, is very common.

    With regards rudists, yet more googling seems to indicate that they particularly thrived in the warm waters of the tropics and lower latitudes, even to the point of displacing corals. The cold may have done from them, ultimately.

    The cold probably didn’t last long enough to cool the oceans down.

    But bivalves are among the filter feeders that tend to do less well in mass extinctions. They have a comparatively high metabolism – they need a lot of food, and their planktonic larvae already need it because their eggs have no yolk. Brachiopods and sponges are well represented in the postapocalyptic assemblages of the earliest Paleocene; they have low metabolism and yolk-rich eggs.

    Ammonites: planktonic larvae (known from the fossil record), got hit very hard in every large mass extinction and completely died out last time; nautiloids: entire life cycle pretty far down in the sea, yolk-rich eggs.

    Pet peeve #429: “ignite the atmosphere”.

    Huh. I’m surprised this comes up often enough to become a pet peeve. :-)

    What killed a lot of marine animals but not jellyfish or corals was probably not a total loss of plankton, but just the opposite, a massive bloom of toxic algae.

    Interesting idea. It should be testable; dinoflagellates, at least, leave chemical signatures.

    The idea of total plankton loss is really derived from the loss of ammonites but retention of nautiloids.

    By no means only that.

    Given the hot climate in the Cretaceous this may have been a common adaptation amongst amphibians living in seasonal climates at the time.

    Well, it was too hot for deserts to exist, or nearly so.

    And some photosynthesizing corals in the genera Leptoseris, Agaricia and Craterastrea live in very deep water, sometimes at 120m or so, the amount of light is very small but their symbiotic algae are adapted to this and can still photosynthesize.

    Wow! I didn’t know that! How closely related are these genera to each other?

    Link to this
  72. 72. LeeB 1 6:53 am 06/21/2013

    Leptoseris and Agaricia are in the Agariciidae; Craterastrea is in the Coscinaraeidae.
    I checked some figures for these corals and Leptoseris has several records from the Pacific ocean and Red Sea between 143 to 165m deep.
    Agaricia from the Atlantic had a record of 119m.
    My memory for Craterastrea was out a bit; it is restricted to parts of the western Indian ocean in deep waters or very turbid shallower waters and its distribution has only started to become clear; so it’s depth distribution has not been studied; but it reaches or exceeds 60m in the Chagos where it was common at those depths, the divers studying it there were unable to dive deeper.
    However Montastrea from the Faviidae has been recorded at 92m in the Atlantic ocean and Porites from the Poritidae at 95m in the Pacific.
    It is only in the last decade or so that divers using rebreather equipment and remotely operated underwater vehicles have brought to light the common occurrence of very deep occurring zoothanthellate corals on what are termed mesophotic reefs.
    The maximum depth at which corals in the genera above have been found keeps increasing, although Leptoseris does seem to be the deepest.

    LeeB.

    Link to this
  73. 73. Andreas Johansson 8:30 am 06/21/2013

    The atmosphere masses about 5 petatonnes, about 1 petatonne of which is oxygen. Acc’d to an estimate I got from Krebs’s The Basics of Earth Science, the world’s plants mass a mere 740 gigatonnes (0.00074 petatonnes), the burning of which ought have a neglible direct impact on the atmosphere’s oxygen content.

    Link to this
  74. 74. Heteromeles 12:07 pm 06/21/2013

    Two general, non-trivial points:

    1. Most atmospheric oxygen (70-80%) comes from unicellular marine algae, not land plants. These reproduce quite quickly.

    2. Wildfires never burn uniformly. There are always areas that are skipped over, as mentioned above in #52, and even in a “global conflagration,” a lot of land won’t burn. There’s actually an emerging science around how wildfires burn across landscapes, because it turns out to be one of the key factors in determining which homes burn in wildfires. As an aside, the other factor is how the home is fire-proofed. The amount of fuel on the landscape doesn’t matter nearly as much.

    Link to this
  75. 75. Zoovolunteer 2:28 pm 06/21/2013

    One other point that might have been important – the time of year when the impact occurred. Incubation times for many egg-laying reptiles is of the order of 120 days or so, and if the impact occurred at the start of the nesting season at least a few nests might have survived to hatch even if the adults were all killed off. I expect any birds nesting near the pole were migrants, so if the impact occurred during the southern summer they might have not had to face the full rigour of the effects either until they returned north in the southern autumn. None of this would have prevented massive casualties of course, but it might have resulted in at least nucleus populations missing the worst in the first few months post-impact. Personally I rather like the idea of Antarctica being a kind of fall-out shelter for the world’s fauna, and I think if it had not been habitable the post-KT world would have turned out very differently.

    Link to this
  76. 76. Yodelling Cyclist 3:41 pm 06/21/2013

    Once again, thank you all for taking time to discuss this. I’m loving the discussion. Even when I’m wrong.

    @ David Marjanović & LeeB1:

    Is it known which corals survived? There are deep-water corals that should have had much less trouble than the shallow-water ones. Were there any deepwater rudists?

    Why should a deepwater photosynthetic organism have an easier time than a shallow water one? The light reaching both is being attenuated by the atmosphere. It may even be worse for a deep dwelling species as there may be additional silt in the water column. I would point out that this did not happen gradually over a century, permitting corals to build up at progressively shallower depths. This is thick atmospheric ash developing over days and persisting for long periods. This only works as a survival scenario if those same deepwater species also thrive in shallow water.

    Plus, apparently, an enormous pH drop and the addition of Be (which I strongly question being leached in significant quantities!).

    Finally, David has observed that the corals should switch to filter feeding. At the same time as all the plankton dies.

    Huh. I’m surprised this comes up often enough to become a pet peeve.

    I’ve had to tutor undergrads doing (very) basic thermodynamics. It does when they seem to think that adding oxygen to anything is exothermic.

    The cold probably didn’t last long enough to cool the oceans down.

    Well, I appreciate that the two things are different, and exhibit different chemistries, but consider the (much less energetic) Tambora eruption. It is difficult to disentangle effects from the climactic minimum at the time, but cooling seems to last 10 years or so after the eruption. The upper layers of the ocean will respond. They respond seasonally, after all.

    @Andreas Johansson: Well, that’s a damn good argument for little effect on the oxygen concentration, thank you.

    @Heteromeles: The algae has to die too.

    So, another attempt to clarify.

    Summarising from above people seem to agree that:

    a.) The firestorm shouldn’t burn everything (but does have to burn enough to generate enough ash to kill enough plants to kill the large herbivores).

    b.) The oceans have to get acidic enough, cold enough and the skies dark enough to kill the plankton, ammonites, rudists and enough fish to wipe out most of the marine reptiles, even unto the far side of the earth (but leave plankton enough for sufficient jellyfish to feed turtles, some coral to make it through).

    c.) The amphibians might survive if living in high altitude chalk streams which would protect them.

    d.) The sebecosuchians that started all this…I think the consensus from the above is that they have to be surviving by being represented by small species across the KT, or by juveniles being able to breed, or being more generalist and less terrestrial than has been previously assumed.

    I still think some kind of refuge is plausible, but I accept that it is hard to prove, and does require some odd omissions in its fauna (and probably flora). I also still think the deep south maybe the place to survive. Nuclear winter models (alas, all found merely through googling) seem to suggest that the polar vortex offers some protection against the ash.

    Link to this
  77. 77. Yodelling Cyclist 3:52 pm 06/21/2013

    Actually, pursuant on the nuclear winter analogy, her’s a nice paper:

    http://www.atmos-chem-phys.net/7/2003/2007/acp-7-2003-2007.pdf

    Caveats: the planet is different in the 21st century from the Cretaceous, the situation being modelled is smaller, and all the usual caveats for an atmospheric chemistry paper. That said, it does suggest that the temperature effects of a sub- and tropical nuclear war (or possibly impact) would be less at high lattitudes, particularly in the opposite hemisphere.

    Link to this
  78. 78. Jerzy v. 3.0. 6:54 pm 06/21/2013

    As far as I understand, many K/T survivors are extremely poor dispersers. Which speaks against that just one continent or part of the globe was refugium for the world’s fauna.

    BTW, any idea how freshwater clams survived K/T boundary? They are, together with freshwater fish and amphibians, very sensitive to water pollution. Amphibians are among the groups best surviving the K/T event. So I would look away from chemical pollution as the most important factor in K/T extinctions.

    Link to this
  79. 79. LeeB 1 7:09 pm 06/21/2013

    The deep water corals are buffered against sudden temperature and pH changes.
    People have experimented with Leptoseris fragilis in the Red Sea taking deepish water specimens and transplanting them to both shallower and deeper depths; after a year most survived.
    So specimens of coral adapted to mesophotic conditions and growing at the shallow end of their depth range might well survive if the light levels dropped; it would be equivalent to them being suddenly transplanted to deeper water.
    Furthermore they could feed on all the dead plankton drifting down into the depths for a while; and all the plankton did not die, some tough species adapted to extreme conditions increased in numbers and would become a further food supply for the corals.
    Also some deep water adapted corals also live in turbid water or under overhangs and in cave entrances in shallow water, after being hit by Tsunamis broken pieces of these may be available to grow in the open under low light conditions and turbid water.
    I wonder how much the acidification of shallow marine waters is buffered on coral or rudist reefs when the corals or rudists are mainly dead and dissolving.

    LeeB.

    Link to this
  80. 80. Heteromeles 2:09 am 06/22/2013

    Here’s a rather strange idea for a refugium: India. At the K-T, it was approximately halfway around the planet from the impact site, and anything that could survive the Deccan Trap eruptions probably was in better shape to survive post-Impact than species in more calm parts of the world.

    The other thing to remember is that non-avian dinosaurs probably survived the K-T. All they had to do was not survive in populations big enough to keep from going extinct. Think about how big a park is necessary to keep a stable population of elephants alive (at something like, perhaps 3 animals/mile), and you’ll see what I mean.

    Link to this
  81. 81. David Marjanović 9:34 am 06/22/2013

    Why should a deepwater photosynthetic organism have an easier time than a shallow water one? The light reaching both is being attenuated by the atmosphere. It may even be worse for a deep dwelling species as there may be additional silt in the water column. I would point out that this did not happen gradually over a century, permitting corals to build up at progressively shallower depths. This is thick atmospheric ash

    As I just said, this scenario probably did not happen. The ejecta was not ash, it was mostly pebbles. (Well, and water vapor. A site in New Zealand preserves evidence for chaos in the water cycle after the impact, lasting for thousands of years.)

    Only your point about silt stands.

    Plus, apparently, an enormous pH drop

    Yep, in the surface layer. Planktonic foraminifera participated in the mass extinction, benthic foraminifera didn’t even notice.

    and the addition of Be (which I strongly question being leached in significant quantities!).

    Again, I only mentioned Be and Al as two examples, and then emphasized that Al is much more common.

    a.) The firestorm shouldn’t burn everything (but does have to burn enough to generate enough ash to kill enough plants to kill the large herbivores).

    Also, the cheirolepidiacean conifers died out worldwide, with one possible local exception I vaguely remember.

    As far as I understand, many K/T survivors are extremely poor dispersers.

    Details, please.

    BTW, any idea how freshwater clams survived K/T boundary?

    The same way as the rest of the freshwater ecosystems?

    and anything that could survive the Deccan Trap eruptions probably was in better shape to survive post-Impact than species in more calm parts of the world.

    Good point. India does seem to have harbored some survivors and delivered them to Laurasia around the Paleocene-Eocene boundary.

    On the other hand, it’s not clear if anything survived on Madagascar.

    Link to this
  82. 82. Jerzy v. 3.0. 7:41 pm 06/22/2013

    @81
    I meant: how well freshwater clams survived K/T?

    About dispersal – tuatara and Liopelma on NZ, Australian monotremes, marsupials etc, Andean fauna, assorted salamanders – many Mesozoic living fossils seem to stay where they survived K/T. Which speaks against that one region acted as refugium from which fauna migrated across the planet by multiple rafting on tree rafts or whatever.

    Link to this
  83. 83. Metridia 2:07 am 06/23/2013

    @yodelling cyclist- yeah I wasn’t being very precise when I said exception proves the rule. I just meant that the crocodilians may have had some special qualities that allowed them to survive. Hard avoid special pleading here, but .. As others have pointed out mere estivation is not really satisfying as an explanation for surviving a multiyear catastrophe, although the ability to grow “arbitrarily slowly” is more appealing. And body size is quite plastic evolutionarily. This all really requires a systematic discussion of what the constraints were, and what loopholes and refugia these may have engendered- ie detritus-based ecosystems, clear skies in the south, etc.- and what organisms may have been in position to benefit while others weren’t.

    On that note, I want to throw out there that I want to throw out one more complication- the fact that marine photosynthesizers are often not light-limited- or at least there are many adapted to living at the base if the photic zone,and I think the importance of ocean acidification or other geochemical perturbations shouldn’t be forgotten, as far as marine extinctions go.

    Link to this
  84. 84. Metridia 2:24 am 06/23/2013

    Oops I see others have mentioned acidification and low light adaptation… But anyway, the transition to low light growers in the ocean should have been relatively seamless due to high habitat connectivity, compared to the land. Also exactly how low and for how long was sunlighted attenuated?

    Link to this
  85. 85. David Marjanović 7:28 am 06/23/2013

    I meant: how well freshwater clams survived K/T?

    All I know is that there were unionoids before and after.

    About dispersal – tuatara and Liopelma on NZ, Australian monotremes, marsupials etc, Andean fauna, assorted salamanders – many Mesozoic living fossils seem to stay where they survived K/T.

    Don’t exaggerate this. The monotremes must have been on Outer Gondwana, but where exactly isn’t yet possible to tell, what with Monotrematum in the early Paleocene of South America. There is at present no evidence for Cretaceous metatherians anywhere in Gondwana. Be more specific about the “Andean fauna”. Of the salamanders, amphiumids, sirenids, and scapherpetids (meanwhile extinct) must have survived in North America and stayed there; the Cretaceous proteid Paranecturus described in the latest JVP issue is likewise from North America, but later proteids have occurred all the way to the Caucasus; P. further implies a Cretaceous ancestry for Rhyacotriton and/or the plethodontids; and the hynobiids may have been restricted to Asia at the time, as they are today, but in the Mio- and Pliocene they showed up in Europe. The cryptobranchids probably survived in Asia, but show up in North America soon after the boundary. The ancestors of the Ambystomatidae-Dicamptodon-Salamandridae clade may have survived in North America or Europe (the Paleocene Ukrainian Seminobatrachus seems to be an ambystomatid).

    *sigh* My paper with Michel Laurin that presents the latest lissamphibian timetree was scheduled to be published on May 21st, and I submitted the corrected proofs and the copyright form in time for that. The week after the date, I wrote to the journal and was informed they have a backlog that’ll take “a few weeks” to work through. Isn’t that a strange place to have a backlog? As opposed to review or the production of the page proofs, I mean.

    Link to this
  86. 86. vdinets 2:36 am 06/24/2013

    There is a Soviet sci-fi novel written in the 1950s, titled “The Flaming Island”. In it, an asteroid lands on earth and forms an island. It contains some chemical compound that is a catalyst, capable of making nitrogen burn and produce a previously unknown kind of oxide (as you know, there are a few kinds already). Evil capitalists set the island on fire and it gradually consumes the atmosphere, so the capitalists begin charging people for oxygen. But the Soviet Union launches ballistic missiles that land around the island, creating a huge wave and extinguishing the fire.

    Link to this
  87. 87. Heteromeles 4:34 pm 06/24/2013

    @vdinets: personally, I prefer War with the Newts, but you’re right, we in the west don’t properly appreciate Soviet SF.

    Still, someone should write a satiric SF story about how 21st Century capitalists are intent on creating a P-T style extinction crisis by deoxygenating the sea (through massive carbon dumps into the atmosphere, which trigger massive release of subsea methane clathrates that, as Peter Ward would have it, turn the seas purple and the sky green). This would be done on the theory that they’ll be able to control what few resources are left (and have a simple enough system that they could run things rationally). They would set themselves up as old-style irrigation kings and (manic cackle) “Rule the World!”

    I wish I believed they were that smart.

    Link to this
  88. 88. vdinets 6:43 am 06/25/2013

    Heteromeles: my personal favorite in Soviet sci-fi is this book: http://thomas-hersey.wiki.uml.edu/file/view/Roadside%2BPicnic.pdf

    Link to this
  89. 89. Jerzy v. 3.0. 5:22 pm 06/25/2013

    @vdinets
    I also read “Monday begins in Saturday”. Not so deep, but lots of laughs, especially the cat. Sort of Harry Potter concept invented 40 years before Rowling, more lighthearted, without children (all characters are adults working at the institute scientifically researching magic) and poking fun at Soviet bureaucracy – much as Rowling criticizes British society.

    Link to this
  90. 90. vdinets 5:04 am 06/26/2013

    Jerzy: there is a sequel called “The Tale of Troika”, it has some funny zoological characters, like a talking bedbug constantly preaching the supremacy of insects over mammals.

    Link to this
  91. 91. Yodelling Cyclist 11:13 am 06/27/2013

    Ok, NOW we have awesome thread drift.

    Link to this
  92. 92. ralaven 8:52 pm 06/30/2013

    My previus comment:

    “The issue is what ‘prove’ means. In this case prove means test – similar to its use in the phrasing ‘proving a dough’ where the last rise is a test that the yeast is working.”

    David M’s response: “That doesn’t work. The expression exists in German as well, and there it’s die Ausnahme, die die Regel bestätigt, the exception that confirms the rule. Prüfen, “test”, isn’t in there.”

    First response – just because it’s the same wrong in German doesn’t mean it isn’t wrong in both. Fetus is spelt incorrectly (foe) in both British English (though no longer in most scientific circumstances) and German. the error arises form the same place.

    My argument is that from the Etmyologicon (Mark Forsyth). The original phrase is Cicero’s – exceptio probat regulam in casibus non exceptis – so prove is there in the original

    Link to this

Add a Comment
You must sign in or register as a ScientificAmerican.com member to submit a comment.

More from Scientific American

Scientific American Dinosaurs

Get Total Access to our Digital Anthology

1,200 Articles

Order Now - Just $39! >

X

Email this Article

X