Since the entelodonts look pretty much like over-sized warthogs, I assumed they would all be part of the family Suidae. But, it turns out they are at different ends of the cetartiodactyl clade.
Cetartiodactyla is a group containing the artiodactyls, or even-toed ungulates, and cetaceans, such as whales, sea cows and relatives. (The story of how they came to be classified together is a fascinating one, but that will have to be for another time.) I made a very simple cladogram (a type of evolutionary tree diagram) over Cetartiodactyla based on what I could find on Wikipedia:
So, according to this, the entelodonts would be more closely related to cetaceans and hippos than to pigs and boars (Suina is a more inclusive group than the family Suidae that I mentioned before: Suina includes Suidae, which are Old World pigs, and the small family Tayassuidae, which are New World pigs).
Still, entelodonts look so similar to warthogs; they even have fairly similar jugal (cheekbone) processes, which is the topic of this investigation.
A
warthog skull, showing the pronounced outgrowths of the cheekbone
(just under
the eye socket), similar to those of the entelodonts (and ceratopsians), albeit
broader.
Picture from http://www.africahunting.com/before-after-hunt/7615-warthog-dipped-skull-opinions-wanted.html
Perhaps this is yet another case of convergent evolution, although maybe more intimate, as the warthogs are at least closer to the entelodonts than either are to the ceratopsian dinosaurs. Also, this makes me think I ought to check if there may be more cases of similar cheekbone anatomy within the cetartiodactyl clade. The more animal groups we compare with, the more accurate the picture will be – more complicated, surely, but more accurate.
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