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Choeropotamids — better known than you thought, perhaps

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


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Let’s face it, there’s an extraordinary number of fairly obscure Paleogene artiodactyl groups that are only familiar if you’re a specialist. I’ve recently had the enjoyable task of writing about all of them for a major in-progress book project (details to come), and today I’d thought I’d share text on one – just one – of those fairly obscure groups. My apologies to the authors who work on these animals and consider them dear friends rather than obscure oddballs. Anyway…

Amphirhagatherium model constructed, I think, by Jörg Erfurt and Hans Altner; image by DagdaMor, licensed under Creative Commons Attribution 3.0 Unported license.

Choeropotamids are one of several anthracothere-like groups from the European Eocene and Oligocene, mostly known from jaws and teeth [image above by DagdaMor]. Oh, what are anthracotheres? Anthracotheriids or anthracotheres are an Eocene-Pleistocene group of suiform-like artiodactyls, often imagined as hippo prototypes and frequently implicated in hippopotamus ancestry. Note that anthracotheres are not to be confused with anthracobunids, a group of tethytheres close to sirenians and/or proboscideans.

Several choeropotamid taxa were originally included within Anthracotheriidae but the realisation that the taxa concerned are united by a distinctive pattern of premolar dentition led to the idea that they should be included within a new group termed Haplobunodontidae, named in 1941. Haplobunodontidae was eventually shown to be synonymous with Choeropotamidae, named by Richard Owen in 1845 (Hooker & Thomas 2001). Key features used to unite choeropotamids include an incisiform lower canine, a short diastema between the first and second lower premolars, and bunoselenodont* molars (Hooker & Thomas 2001). Tooth form indicates that choeropotamids ate fruit and leaves (an idea supported by gut contents known for Masillabune from Messel) with the caniniform anterior teeth at least suggesting the possibility of occasional faunivory.

* This means that the molars combine both mound-shaped (= bunodont) cusps as well as the semi-lunate (= selenodont) cusps.

Excellent skulls of the late choeropotamid Tapirulus from Quercy, France, from Costeur & Berthet (2011).

Jörg Erfurt and Hans Altner's Amphirhagatherium model again, this time with a prototype that lacks the final integument; note also the conference poster in the background. Photo by Darren Naish.

Later members of the group (like Lophiobunodon and Tapirulus) have more selenodont teeth and hence are likely to have been more dedicated to herbivory. Thick enamel in Choeropotamus suggests that it fed on thick-skinned fruit. Cuisitherium from the Ypresian of France is the oldest choeropotamid and Amphirhagatherium from the upper-most Eocene or lower-most Oligocene of Germany is the youngest. Increasing seasonality and cooler climates at the end of the Eocene may have caused the extinction of this mostly northern European group.

We have a reasonably good idea of what live choeropotamids might have looked like thanks to the nice specimens from Messel. A really good life-sized, accurate model of Amphirhagatherium is displayed at the Institute of Geosciences at Martin-Luther-University, Halle-Wittenberg, Germany and is shown here. I believe that it was constructed by Jörg Erfurt and Hans Altner (I may be wrong!), and its construction and appearance are described in Erfurt & Altner (2003). I’ve seen the model myself at conferences and have even photographed it. Can I find those photos right now? No, but I’ll add them here when I do [UPDATE: found them, obviously].

For previous Tet Zoo articles on artiodactyls, see…

Refs – -

Costeur, L. & Berthet, D. 2011. A new skull of Tapirulus from the late Eocene of France. In Lehmann, T. & Schaal, S. F. K. (eds) The World at the Time of Messel: Puzzles in Palaeobiology, Palaeoenvironment and the History Early Primates. Senckenberg Gesellschaft für Naturforschung, pp. 40-41.

Erfurt, J. & Altner, H. 2003. Habitus-Rekonstruktion von Anthracobunodon weigelti (Artiodactyla, Mammalia) aus dem Eozän des Geiseltales. Veröffentlichungen des Landesamtes für Archäologie 57, 153-175.

Hooker, J. J. & Thomas, K. M. 2001. A new species of Amphirhagatherium (Choeropotamidae, Artiodactyla, Mammals) from the Late Eocene Headon Hill Formation of southern England and phylogeny of endemic European ‘anthracotherioids’. Palaeontology 44, 827-853.

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

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





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  1. 1. DavidMarjanovic 7:26 am 07/7/2014

    “Anthracobundon”

    Missing o in the first figure caption: Anthracobunodon.

    Link to this
  2. 2. naishd 7:28 am 07/7/2014

    You’re quick off the mark :) (but I’d already caught that).

    Link to this
  3. 3. Andreas Johansson 11:17 am 07/7/2014

    Clearly Anthracobunodon stole the name from some better deserving anthracobunid …

    The book project sounds interesting. Can you tell us if it’s all artiodactyls, or also covers other Palaeogene critters?

    Link to this
  4. 4. naishd 11:19 am 07/7/2014

    The book covers EVERYTHING.. its working title is The Vertebrate Fossil Record. This is why I’ve been killing myself with fish over the past year and then some…

    Link to this
  5. 5. BrianL 11:29 am 07/7/2014

    Can you tell us which parts you are doing? I assume you aren’t doing it entirely by yourself? I am very interested in the project.

    So, what was hunting choeropotamids? Messel does not have that many larger predators apart from crocodiles, does it? It seems reasonable to suppose that *Gastornis* doesn’t count. Speaking of which, when are we going to find a *Gastornis* preserved as Lagerstätten in Messel?

    Link to this
  6. 6. Heteromeles 11:30 am 07/7/2014

    Gee, and here I thought that Anthracobunodon meant “coal bunny.” Great to get educated. So it’s a bandicoot on the front end, a chevrotain in the middle, and a mongoose tail? Weird critter. (note to the uninformed: I’m being slightly sarcastic and very whimsical here).

    Link to this
  7. 7. keesey@gmail.com 11:52 am 07/7/2014

    I’ve been planning to use taxidermy to recreate extinct species (although in a different group of amniotes) for a while — my skills are not yet up to the task, but some day…. Nice to see someone else trying it! I wonder what the skin is from.

    Link to this
  8. 8. keesey@gmail.com 11:58 am 07/7/2014

    Wait, it that model of Anthracobunodon or Amphirhagatherium, as the filename says?

    Link to this
  9. 9. naishd 12:31 pm 07/7/2014

    When I photographed the model, it was Amphirhagatherium, but that name is now regarded as synonymous with Anthracobunodon… I’ve been following literature that treats the latter as the senior name but, now that I check, I think it’s the other way round. I’ll check later.

    Link to this
  10. 10. irenedelse 1:12 pm 07/7/2014

    Naming fossil species after characteristics of their teeth, sure, especially when you only have the teeth… But “Anthraco-something”, because you found the type specimen in a coal mine? Weird. It’s not like the animal lived in one when alive!

    Link to this
  11. 11. irenedelse 1:41 pm 07/7/2014

    @BrianL:

    What was hunting Choeropotamids? Alligators and crocodiles must have taken a big part part. Several species of medium to large crocodilians were found in the Geiseltal lagerstatte, plus big snakes (boa and python), and for mammalian predators, some Hyaenodontids. The mammals were not very big, though, and Choeropotamids probably featured on the menu of the big reptiles.

    Link to this
  12. 12. SeanMcCabe 2:08 pm 07/7/2014

    So where do they fall on the artiodactyl tree? Are they allied to Anthracotheres or something else? By their timing and overall look a Dichobunoid (If that group is recognized today?) placement seems probable… answers?

    Link to this
  13. 13. naishd 3:42 pm 07/7/2014

    Ok… it turns out that there is some difference of opinion as to whether Anthracobunodon Heller, 1934 is synonyomous with Amphirhagatherium Deperet, 1908. I had somehow missed that Hooker & Thomas (2001) – cited extensively above – argue that the two should be combined. So, I’m now changing the article above such that the name Amphirhagatherium, not Anthracobunodon, appears throughout.

    As for the possible phylogenetic position of these animals, ‘convention’ (e.g., McKenna & Bell 1997) would have it that they’re part of Anthracotherioidea, somewhere in the mess that includes dichobunoids and not too far from hippos and anoplotherioids. Some recent phylogenetic studies that combine a molecular backbone with morphological data from extant and fossil taxa find some anthracotheres close to cetancodontamorphans and others close to ruminants… I’ll return to this issue later, have run out of time.

    Link to this
  14. 14. Allen Hazen 4:26 pm 07/7/2014

    Not exactly off-topic, but tangential: when do (you, the majority of pale-mammal specialists, the man on the Clapham omnibus) think the last common ancestor of the Artiodactyla lived? These guys (Choeropotamids) date from the Ypresian: early Eocene. (But the Ypresian seems to have lasted something like eight million years, so: do we know whether Cuisitherium was early, middle or late Ypresian?) But you report in comment #13 (without, though, sounding dogmatically committed to it!) an opinion that they belong to the Anthracotherioidea so the common ancestor of Anthracotherioidea and non-Anthracotherioid Artiodactyles would be before that.

    Worse, Tylopoda seems to be outside (Anthracotherioidea+Suina+Pecora)(*). I take it that the common ancestor of Tylopoda and other Artiodactyla was definitely Paleocene (if not earlier!)?

    (*) Evidence (here’s my excuse for posting!) for this keeps coming in! There’s a very recent “Nature” article — I’ll post a reference when I’ve had a chance to look it up again — on the evo-devo of mammalian digit reduction. Tylopods, Suines and Pecorans all concentrate on digits III and IV, but the detailed embryology (patterns of gene expression and such) of how they suppress the outer digits differs: so there are developmental traits (outer digit reduction by route 1 vs. outer digit reduction by route 2) which appear to separate Tylopoda from Suina+Pecora.

    Link to this
  15. 15. Allen Hazen 4:40 pm 07/7/2014

    References– TWO papers in the 3 July 2014 issue of “Nature”:
    –Cooper et al., vol. 511, pp. 41-45,
    –Lopez-Rio et al., vol. 511, pp. 46-51.
    Cf. also the commentary (with a neat diagram summarizing the results) by Huang and Mackem in the same issue, pp. 34-35.

    Link to this
  16. 16. jayb61 8:50 pm 07/7/2014

    As a non Academic I want to thank Darren for a great rollercoaster ride through the Dictionary.

    Interesting article though.

    Link to this
  17. 17. DavidMarjanovic 3:55 am 07/8/2014

    I’ve been planning to use taxidermy to recreate extinct species (although in a different group of amniotes) for a while — my skills are not yet up to the task, but some day…. Nice to see someone else trying it! I wonder what the skin is from.

    …I don’t think there’s any real skin in this so-called model.

    Link to this
  18. 18. Andreas Johansson 4:38 am 07/8/2014

    The book covers EVERYTHING.. its working title is The Vertebrate Fossil Record. This is why I’ve been killing myself with fish over the past year and then some…

    Oh, that sounds really interesting. And massive.

    Link to this
  19. 19. Dartian 6:48 am 07/8/2014

    David:
    I don’t think there’s any real skin in this so-called model

    I’m not so sure about that; the hair looks pretty real to me. Palaeoartists occasionally use real skin (sometimes dyed) of extant mammals to cover their reconstructions.

    BTW, why do you refer to it as a “so-called” model?

    Link to this
  20. 20. irenedelse 8:09 am 07/8/2014

    @Dartian:

    “Palaeoartists occasionally use real skin (sometimes dyed) of extant mammals to cover their reconstructions.”

    That’s how I understood it too. Not a taxidermied specimen of the fossil animal, but a model fitted with real pelt to make it more life-like. Maybe not great scientific interest, and fragile obviously, but impressive as a museum exhibit.

    Link to this
  21. 21. Heteromeles 3:33 pm 07/8/2014

    By the way, if we time the next two posts *just* right, Darren will feel the pressure to write another article just as TetZooCon comes along… Hmmmm.

    Link to this
  22. 22. artiofab 5:13 pm 07/8/2014

    In re: Allen Hazen at #14,

    All the modern representatives of Artiodactyla diverged from one another in either (at latest) the earliest earliest Eocene or (most probably) the Paleocene or (who knows?) the latest Cretaceous. Based on the fact that some molecular clocks for eutherian/placental mammals somewhat break near the K-Pg, it seems likely that early-Pg mammalian evolution was fast enough to permit the divergence of Artiodactyla within the Paleocene.

    Link to this
  23. 23. SeanMcCabe 5:33 pm 07/8/2014

    #23

    Wait, are you saying eutherians as a whole evolved in the latest Cretaceous? Molecular clocks put lemurs alone at between 80-66 Ma, with 75-70 Ma being most likely.

    Link to this
  24. 24. Stripeycat 6:55 pm 07/8/2014

    Remember though that those are only minimal dates. The actual divergence could be as far back as the Big Bang. (After all, absence of evidence is not evidence of absence; and we’re all entitled to our own opinions.)

    Link to this
  25. 25. naishd 7:00 pm 07/8/2014

    Aww maaan, over 23 comments already? :)

    For those who might not quite get it, comment # 24 is another hilarious reference to the comment war still going on over in May’s ratite evolution article. Panbiogeography vs the world.

    Link to this
  26. 26. Allen Hazen 7:43 pm 07/8/2014

    Artiofab (#22): Thanks. That is about what I thought the current view was. … As far as I know there is no current consensus on what the … nearest non-artiodactyl Paleocene relatives of A. were. A lot of older literature (20th Century: really ancient!) pointed to the “Arctocyonid” (*) Chriacus, but apparently more complete specimens of Chriacus look less artiodactyl-like. There was a note in some Chinese journal a few years ago (I might be able to find a more detailed reference, but it’s not on my computer desktop right now)about something with dental resemblances to early Artiodactyls, but I haven’t seen anything more about it.

    (*) It may actually be an Arctocyonid, sensu something or other: scare quotes only because the phylogenetic affinities of a lot of Palaeogene mammals seem to be even more mysterious than we used to think!

    Link to this
  27. 27. Allen Hazen 7:53 pm 07/8/2014

    RE comment #26:
    Here’s what I said in a comment on a 2009 Tetrapodzoology post, with a (not very detailed, sorry) reference:
    Here’s a topic I’d love to see someone knowledgeable discuss: as between Chriacus, Ganungulatum and space aliens, which on the basis of available evidence is more likely to be closely related to Artiodactyls? (Sorry: Ganungulatum was described by Ting et al. in the 2007 “Vertebrata Palasiatica” with a suggestion that it might be close to the origins of the Artiodactyla, and I have seen no further discussion or comment at all. The origins of the extant “Ungulate” orders are… a mystery wrapped in an enigma wrapped….!)

    Link to this
  28. 28. SeanMcCabe 8:12 pm 07/8/2014

    Am I missing something here?

    Link to this
  29. 29. Heteromeles 12:39 am 07/9/2014

    Hey, how many of those paleocene mammals were even mammals? I mean, the teeth are so “stem,” who knows what clade they’re actually in?

    Link to this
  30. 30. DavidMarjanovic 5:09 pm 07/9/2014

    BTW, why do you refer to it as a “so-called” model?

    *blink* …Wow, I must have been ridiculously tired. In hindsight, I must have been referring to the fact that it’s called a model in the caption. ~:-|

    Wait, are you saying eutherians as a whole evolved in the latest Cretaceous? Molecular clocks put lemurs alone at between 80-66 Ma, with 75-70 Ma being most likely.

    The oldest known eutherian is Juramaia, probably from the beginning of the Late Jurassic, in any case from the Jurassic. There are lots of nodes between the origin of Eutheria and that of Placentalia.

    Anyway, no, the split between lemurs and lorises has long been put in the Eocene based on molecular data, which is also where the sparse fossil record locates it. Molecular divergence dating studies need to be calibrated, and that’s tricky business that requires a good fossil record and very good knowledge of it.

    It may actually be an Arctocyonid, sensu something or other: scare quotes only because the phylogenetic affinities of a lot of Palaeogene mammals seem to be even more mysterious than we used to think!

    Quite. Just wait till Thomas Halliday publishes the phylogenetic analysis from his thesis (presented at last year’s SVP meeting). Chriacus features prominently… but not close to artiodactyls.

    Hey, how many of those paleocene mammals were even mammals? I mean, the teeth are so “stem,” who knows what clade they’re actually in?

    …They’re all clearly mammals, though. Crown-group mammals.

    Link to this
  31. 31. DavidMarjanovic 5:14 pm 07/9/2014

    …More to the point, however, it is almost entirely unclear how many of the Paleogene eutherians that don’t fit into an extant “order” were placentals ( = crown-group eutherians).

    Link to this
  32. 32. Heteromeles 11:24 pm 07/9/2014

    Thanks for the correction, David.

    Link to this
  33. 33. artiofab 1:11 pm 07/10/2014

    Sean McCabe’s comment at #23 illustrates an example of molecular clocks saying weird things. If lemurs diverged from other primates 75-70 Ma, then all the preceding divergences in Placental phylogeny must have also taken place by that time. Therefore, there should be Cretaceous crown group xenarthrans, afrotheres, and boreoeutheres. And even though we have Cretaceous mammal fossils, none of them seem assignable to any of these modern groups: there are no Cretaceous rabbits, sirenians, bats…

    Allen Hazen at #26: paleomammalogists are pursuing all possible leads as to what late Cretaceous or Paleocene beasts are the sister group to Artiodactyla. The animals formerly known as condylarths might have some connection to the origins of modern perissos and artios, or they might just be an extinct sidebranch of eutherian (or placental?) evolution. It’s troublesome.

    Link to this
  34. 34. SeanMcCabe 10:18 am 07/11/2014

    I’ve heard the lemur divergence date variously across the internet and it all seems to trace back to Horvath et al (2008), thought it could go back further or to another paper.

    Link to this
  35. 35. DavidMarjanovic 4:39 am 07/12/2014

    Well, what did Horvath et al. (2008) say about that date? Often that’s hidden in the supplementary information – which most journals put outside the paywall.

    Link to this
  36. 36. keesey@gmail.com 5:50 pm 07/15/2014

    “Not a taxidermied specimen of the fossil animal, but a model fitted with real pelt to make it more life-like.”

    What do you think taxidermy is?

    http://www.realdeerforms.com/taxidermy_forms_3.jpg

    Link to this

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