#oreodont

Florida Oreodont (Mesoreodon floridensis)

Mesoreodon is an extinct genus of terrestrial herbivore of the family Merycoidodontidae, subfamily Merycoidodontinae (the oreodonts), Odd-toed ungulates, endemic to North America during the Whitneyan stage of the Oligocene-Miocene epochs (33—20.6 mya) existing for ~ 12.4 million years.

"Dust to Dust" Megacerops/Merycoidodon/Mesohippus/Subhyracodon/Leptomeryx/Alligator Paleogene, 34 million years ago, White River Formation This was posted last week on my Patreon, available to $10 supporters!

It's rare that you get dust storms like this in the late Eocene. The world has been drying since the hothouse ended, and as a result the forests have been shrinking. The tropical jungles still make up most of the land area, but proper savannahs have begun to emerge. Although the grasses will really come into their own in the Miocene, an unexpected extended dry spell has allowed some grasses to replace an open fern-scape. Dealing with this interesting climactic change forces animals to gather around shrinking water sources, bringing a variety of organisms together. First up, we have Megacerops: A brontothere the size of an elephant. Horns on the nose exhibited a great variety of shapes, potentially depending on sex and age. In the past, this led to the creation of a bajillion species, until now we have like two. They may have been herding animals, browsers that lived in humid forests. As they receded, the brontotheres had less leaves and more grass, and so the Megacerops died as the land dried. Much like dinosaurs, there have been outlandish hypotheses behind their extinction, including disease and "racial senesence" - the idea that somehow, your lineage can get old and "degraded" somehow until your entire family tree just dies of old age. These individuals don't know that, though. The dryness hasn't kicked in just yet, and so for them, it's simply a more uncomfortable-than-usual Tuesday. I like the Eocene, it has what I call the Extinct Big Horny Pachyderm Trio (brontotheres, dinoceratans, embrithopods). I dunno why there were so many of them, but I like them and think they're just goofy guys. Rolling around in the mud, we have the hornless Subhyracodon, a variety of rhinoceros. Just like modern rhinos, these guys are wallowing around to keep cool and wet in the heat. In the background, we have Merycoidodon, rolling up with vast herds. Namesake and perhaps most famous of the oreodonts, named after those big teeth, sorta like mountains. We think that in front of their eyes, there may have been scent glands used to mark their territory. These were extremely common animals, and their teeth are some of the more common ones you might observe in the midwestern badlands of the United States. There are also Mesohippus, a three-toed horse the size of a dog. Their mouths were narrow, and built for browsing on leaves and twigs, instead of grass. Just like modern horses, I'm portraying them as skittish and quick to flee - but in this case, for good reason.

Alligator prenasalis is stalking them. The length of a man, Mesohippus are quite good-sized prey, and this individual exploits the presence of a communal watering hole to snag unsuspecting creatures.

And finally, the teensy-tiny members of the crowd - Leptomeryx, a deer-like critter the size of a cat. They mingle amongst the bigger members of the herd, using them for protection while avoiding being bumped around by their compadres.

here's today's #Paleostream sketches!!! we had a shorter flocking today to save energy for #PaleostreamCon2025 (which is in ~2 hours at the time of posting 😉)

today we sketched just Duonychus, and Brachycrus

Merycochoerus is such a goober. While being a oreodont it had little to do with your typical oreodont, which was usually a sheep sized, rather short snouted herbivores from the Oligocene and Miocene. It's skull structure suggests the presence of a short trunk, but it also shows that these animals were fighting a lot since they are often covered in healed wounds.