The Giraffe-Rhino-Musk Deer-Hippo Things

Trivia question: what combines the characteristics of a giraffe, a musk deer, a rhino, and a hippo? Give up? It's the dinoceratans.

The order Dinocerata includes only one family (similar to Tubulidenta aka the aardvark) known as the uintatheriids, the namebearer for said family shown in the first picture of this post. We'll review Uintatherium and its relatives below.

-Basal Uintatheriines:

• Prodinoceras, upper left, is the earliest known and basalmost of the known uintatheriid dinoceratans. It contains one known species, P. martyr, from the Late Paleocene of Mongolia and China. At approx. 9.5ft long, it was a rather large animal, and had the characteristic fangs that other members of the subfamily would share.
• Probathyopsis, below Prodinoceras is another basal uintathere and the latter's sister genus. It too is from the Late Paleocene, but is located in Wyoming and Colorado, containing P. harrisorum, P. praecursor, and P. lysitensis. Several have considered separating this and its sister genus into a new family within Dinocerata, which would be known as Prodinoceratidae.

-Advanced Uintatheriines:

• Tetheopsis, top middle, is one of the three "classic" uintatheres, with six ossicones (which I've alluded to in a giraffe post) and large fangs, which our two basal uintatheriines had as well. Its two species are T. speirianus (formerly in invalid genus Loxolophodon) and T. ingens, named by famous rivals Cope and Marsh, respectively. 
• Bathyopsis is one of the earlier of the advanced uintatheriines, which only had a pair of small ossicones on the snout. Like almost all dinoceratans, it is known from the US, specifically Colorado and Wyoming, containing B. fissidens.
• Eobasileus is another of the classic uintatheres, and possessed the biggest ossicones and canines. At 13ft long and 8000lbs in weight, it is also the biggest uintathere. At least three genera are synonymous with this one, including the aforementioned Loxolophodon. It contains only one species, E. cornutus, found in Colorado, Wyoming, and Utah. Obviously they were very boring in real estate choices.
• Uintatherium, the classic uintathere and the one that gives the entire family its name. Dinosaurs are the infamous factour in the equally infamous Bone Wars, but in fact, uintatheres, especially Uintatherium, played a major focal point as well, with the genus being described my big-bearded Marsh himself. There is only one genus, U. anceps, which was more widespread, located in California, Utah, Texas, and Wyoming, existing alongside Eobasileus in two states. Its canines were 12in long, aka pants-crappingly big.

And then things really get wacky...

Enter Gobiatherium, the advanced uintatheriid from Mongolia and China. Notice how instead of ossicones, it has a globular snout (how much it slopes and its exact appearance up to debate), how narrow and long its skull is, and how, surprise, there are no fangs. What in heck is it? For now we consider it a gobiatheriine uintatheriid. But many consider it to be its own family, Gobiatheriidae (remember the "a" after "Gobi"). For now in technical terms it "heck if we know".

The small-brained dinoceratans lasted until the Mid Eocene, where they promptly died off. Their weak teeth, adapted to a diet of leaves, couldn't save them and were eventually replaced by the previously covered brontotheres. But there's so much more we don't know. Where did they come from? What specifically are they related to? Why are they so ugly? Only time can tell.

Seriously, look at that.

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Uintatherium - Dmitry Bogdanov

Dinoceratan Diversity - Yours truly, aka Connor Ross

Gobiatherium - Tim Morris (you might be reading this from the FB page, so hi, Tim)

Uintatherium...again - Nobu Tamura

Sources:

en.wikipedia.org

paleodb.org

The Dinosaur Heresies, by Robert Bakker

National Geographic Prehistoric Mammals, by Alan Turner

The Illustrated Encyclopedia of Dinosaurs and Prehistoric Creatures - Mammals, by R. J. G. Savage