Week Of Wonders: Coryphodon

16 12 2009

Good tidings and well-wishes!

When asked to cite my favorite sub-discipline of biology by interested parties, I often find myself at an uncharacteristic loss for words. As an academic marriage of geology and bio, my beloved field of paleontology certainly can’t qualify as a finalist for this distinction. This fact results in a three-way tie between evolutionary studies (which, I hardly need tell my fellow nerds, covers an enormous intellectual area), psychobiology (which nicely combines my love of the humanities and social sciences with my passion for evolutionary biology), and the centuries-old subject of comparative vertebrate anatomy.

This latter science is a beautiful thing in that it so very often lends an enormous amount of scientific credence to the notion that ‘looks can be deceiving’. For the proponents of this science have shown that their beloved domain can do much more than assist us in our efforts to ascertain the identities of the various chimeras which have proclaimed their existence to the scientific community through the ages: it can also reveal that those creatures which, at first glance, appear to be entirely mundane are actually far more interesting than anything which we could have possibly imagined. Last spring, I utilized this column to feature the strange case of Sivathertium: a moderately-large giraffid which, according to most any initial inspection, resembled a moose with an elongated skull. Nearly six months later, I’d like to draw the attention of my readership to the anatomical story of another bizarre animal: Coryphodon sp. of the Eocene.

Let’s begin by examining the animal’s skeleton as displayed below:

Coryphodon sp. Skeleton (Courtesy of Wikipedia)

Mammal enthusiasts are likely to assume that this beastie was merely a type of prehistoric Hippopotamus as suggested by its relatively stout limbs, barrel-like chest, and fearsome jaws.

However, perhaps we should now compare it to a skeleton of an actual Hippopotamus:

The two aren’t exactly uniform in composition, are they?

In their excellent book, “Mammoths, Sabertooths, And Hominids: 65 Million Years Of Mammalian Evolution In Europe”, Jordi Augusti and Mauricio Anton write:

“the skeleton of Coryphodon [is] a mixture of traits reminiscent of those of different kinds of animals. The trunk vertebrae have surprisingly weak neural spines for such a big animal [(Coryphodon was approximately 1 meter in height and 2.25 in length)], suggesting a partly amphibious lifestyle, like that of modern hippos. The long bones of the limbs resemble in structure those of heavy perissodactyls like rhinos and tapirs, while the feet, retaining all five digits, are like those of modern elephants in structure. In side view, the head vaguely resembled that of the Paleocene arctocyonids, with huge canines, although this animal was not an omnivore like the latter, but a specialized vegetarian.”

Coryphodon foot reconstruction, which, as the authors have pointed out, really resembles that of an elephant more than anything else.

Although Coryphodon certainly bore distinct resemblances to various members of the artiodactyla, perissodactyla, proboscidea, and arctocyonidae, this intriguing herbivore owed its phylogenetic allegiance to none of these groups. So what the hell was it?

The animal actually belonged to the extinct order pantodonta: one of the first groups of herbivorous mammals to truly attain relatively large sizes.  A list of the group’s distinguishing characteristics may be located here.

Restorations of some pantodonts of the North American Paleocene. A. Coryphodon. B. Barylambda. C Titanoides primaevus. D. Caenolambda. E. Pantolambda cavirictus. E. Pantolambda bathmodon. (Courtesy of paleocene-mammals.de)

As the preceeding image indicates, pantodonts were a wonderfully diverse lot despite their aforementioned similarities. While our hippo-like Coryphodon likely behaved in the manner of the modern creature to which its skeleton was compared at the onset of this article, Barylambda was built like an eccentric ground sloth and likely acted accordingly, Titanoides was a fairly large terrestrial herbivore whose dietary habits largely consisted of tough vegetation, and Pantolambda was a vaguely cat-like creature which nevertheless maintained an herbivorous diet. For an immeasurably more complete description of these incredible organisms, do go here.

A behind-the-scenes look at the Coryphodon cranial reconstruction which was recently employed at the AMNH's recent 'Extreme Mammals' exhibit.

There are certainly many more questions to be answered concerning this magnificent group of creatures (most notably, that of ‘to what other congregation of mammals is the pantodonta most closely related?’), and one would hope that they will soon be answered with the advent of additional research and a host of rising specialists.

May the fossil record continue to enchant us all!




4 responses

17 12 2009
Zach Miller

Coryphodon! There is SOME trace evidence (footprints) that this genus existed in Alaska, though aside from the correponding time period and rather generalized print, it’s tough to pin it down.

18 12 2009

Interesting… I’d never heard of any sort of ichno-fossil related to Coryphodon. Where in Alaska was it located?

23 12 2009
Zach Miller

I’m not sure anymore…I learned about it so long ago. I think it’s in the southeast.

19 06 2010
Weekly Spotlight: Barylambda « The Theatrical Tanystropheus

[…] whose appearance and, in all probability, lifestyle superficially resembled those of extant hippos. In that article, I showcased the considerable range of pantodont diversity by including the following illustration […]

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