Xenopermian Biota of the Ural Sea: Brontopator chapsia, a hippodont dicynodont

The Xenopermian is a collaborative effort between Scott, Raven, Zach and myself to outline a very different, speculative world. In some ways this is not all that different than the exercises of Dougal Dixon, After Man and The New Dinosaurs. Rather than speculating on what the dinosaurs would be like if they had not gone extinct, much like his New Dinosaurs or the Spec World Project, or project into the future with After Man or The Future is Wild, our team asked the question of ‘what if the Permian Extinction did not happen?

This is the next post about the fauna of the Xenopermian in the Ural Sea region. We have talked about a ‘fossil’ and a faux controversy associated it with. We have talked about the geological staging differences in the XenoPermian timeline, and have even talked about the differences in the world in general under such a different period. We have generalized about the fauna, but now we want to get into specifics. In our first post, we talked about the first faunal member of the Xenopermian, Graviloricanasus roma, a pseudochelonid and very derived pareiasaur. Then we talked about Elyardia hensonii, a very derived anomodont. Then we talked about the alternate pterosaur, Maralae whittoni.  Another time we talked about the trematosaurine temnospondyl Chronoperifronius thassalicus.  Post before last, we looked at the walrodont, Psittacops makradens.   The last post we looked at the desmodont dicynodont, Palonatator beccus.

Today we are sticking with the dicynodonts.  It will be the last dicynodont post for some time.  However, we are looking today at another branch that has been nicknamed the 'hippodonts' since they have developed in parallel in form (somewhat) and function (more so) to the hippopotamuses of our timeline.  The parallel evolutionary example we will work with today is Brontopator chapsia.

Brontopator chapsia is an example of another fictional and derived member of the clade Thassalothere which are a clade of the dicynodonts, an important group within the anomodonts.  These are in turn therapsids like the gorgons, therocephalians and cynodonts.  That last is inclusive of the mammals like you, you darned dirty ape, you!

During the great Evolutionary Churn of the XenoPermian, when the Siberian Traps did a 10 million year long sustained eruption instead of the bursty nastiness causing the Permian Triassic mass Extinction, the dicynodonts branched out into different clades.  The dicynodonts were already very successful herbivores and as the innovation took place within the clade, the dicynodonts started to exploit new resources.  One of these was the waterways.  The dicynodonts took to the water, despite not really being semi aquatic in OTL, and found a very unexploited set of niches with the lack of aquatic herbivores at the time.  The basal most thassalothere took to the swampy regions.  From there, they branched out into what would be informally called the hippodonts (river dwellers), walrodonts (sea residents) and desmodonts (swamp dwellers).

The hippodonts look like the strange cousins of Placerias.   They are big and portly and spend most of their time in the water.  They munch on the aquatic plants and come on land to graze at night.  While there is no grass in the XenoPermian, there are plenty of low herbaceous conifers and fast growing ferns.  They live in small herds and birth live young.

  

Brontopator chapsia is pretty generic for a hippodont.  They have a semi sprawled front leg stance and can and do charge predators.  Their thick skulls and semi forward facing tusks make them a serious hazard for predators.  They do protect their young and do not have large litters, rather one or two at a time.  Their young are more developed than the desmodont and walrodonts'.  However, they are still birthed on land.

One species of hippodont, not B. chapsia, actually seems to do some minor intentional environmental engineering and digs side pools to the rivers which they live.  In there, they raise their young, defended from even the reptilomorph and temnospondyls lurking in the rivers. This cousin does have a problem with reptilomorphs though.  The communally nesting variety can and will take over unoccupied hippodont ponds.  The repitlomorphs are not a match one on one, but when they have taken over a pond, they will enmass defend it.    That many reptilomorphs get rather hungry when they are sitting in the defense for so long.  They'll eschew eating the eats, but they can take down baby hippodonts in the area.

Brontopator chapsia is common in the short rivers running into the Ural Sea.  Cousins of their's are present in most rivers draining into the Tethys and in some draining into the Panthalassa.  Two species even migrate from the Transpangaea Mountains down into the Megavongo.

Their biggest predators are the gorgonopsids.  They are large enough to take down an adult B. chapsia.  However, the gorgons prefer munching on the young or sick.  The second most deadly are the venomous felid-like therocephalians that will ambush a herd, take a bite and run, letting its poison kill whatever it bit.  The large adult B. chapsia will pull through.  However, the young or old will not.  Temnospondyls are a problem as well when the herd takes to the water: they can wait crocodile like in the water to attack and pull young under the water for a kill.  This is rather risky given the strength of a stab by the hippodont tusks.

The hippodonts will last to the XenoPermian Jurassic Mass Extinction.  However, an Elvis Taxon would arise in the Cretaceous from a NeoDicynodont clade.  This mimicing lineage would die out in the Cretaceous-Eocene Extinction at the Mesozoic/Allozoic boundary.  Examples of competing parallel evolution would take place during the Allozoic, with dicynodonts, therocephalians and mammals duking it out up until the Pleistocene for the ecological niche.  However, the true hippodonts were gone 200 million years earlier.