Proplacerias

***Proplacerias*** is an original extinct genus designed and collaborated by User:GurgiFan57. It lived in what is now Africa, Eurasia, and the Americas during the mid-Triassic and the early Jurassic, from 235.4 million to 187.1 million years ago, making it one of, if not the last dicynodonts that had ever existed. *Proplacerias* came in nine known species, although seven other species may have been present.

## Appearance and anatomy

*Proplacerias*, depending on a species, varied in size from 0.6 to 2.5 meters (2 to 8 feet) long and had a mass of between 8.6 to 90.7 kilograms (19 to 200 lbs). In general appearance, *Proplacerias* closely resembled *Lystrosaurus*, in which it may have descended from, but with a more distinctive skull shape, giving it slight reminiscence to ceratopsian skulls. Like other dicynodonts, *Proplacerias* had very short snouts and no teeth except for the tusk-like upper canines. *Proplacerias* is generally thought to have had a horny beak like those of turtles, for shearing off pieces of vegetation, which were then ground on a horny secondary palate when the mouth was shut. The jaw joint moved backwards and forwards with a shearing action, instead of the more common sideways or up and down movements. It is thought that the jaw muscles were attached unusually far forward on the skull and took up a lot of space on the top and back of the skull. As a result, the eyes were set well forward on the skull, and the face was short. Features of the skeleton indicate that *Proplacerias* moved with a semi-sprawling gait.

## Behavior and ecology

*Proplacerias* lived in various environments at the end of the middle Triassic and early Jurassic period, being one of the most common synapsids of its time on Earth. *Proplacerias* may have been either a solitary animal that lived alone outside of mating season, or a social animal that lived in small to large herds, depending on a species.

### Diet

*Proplacerias* was a herbivore and adapted to feed on any of the ferns, horsetails, roots, and tuber-like plants of its time. Although its jaw joints were once thought to be weak, it was later realized by paleontologists that its jaws were strong, due to the animal eating some of the tough vegetation, giving it a powerful bite for its sizes.

### Behavior and intelligence

*Proplacerias* is thought to have had low intelligence as with other dicynodonts.

### Reproduction

*Proplacerias* may or may not have mated for life, producing a clutch of between 6 and 18 eggs. Once hatched, the young were capable of standing, walking, and running within just hours. The adults most likely taught their young how to find and forage for food, etc.

## Trivia

When fossils of *Proplacerias* was first discovered in 1970s, it was once thought to have been a species of *Lystrosaurus*, but in 2017, it was discovered that it was actually part of the separate genus and contained several species.

It is thought that *Proplacerias* may have survived the Triassic-Jurassic extinction event, with the following scenarios that may or may not have happened:

Growth marks in fossilized tusks suggest that *Proplacerias* living in South America ~201.3 Mya could enter a prolonged state of torpor analogous to hibernation.

The suggestion that *Proplacerias* was helped to survive and dominate by being semi-aquatic has a similar weakness: although sauropodomorphs become more abundant in the Cañón del Colorado Formation's Jurassic sediments, they were much less numerous than *P. precedens* and *P. araripensis*.

The most specialized and the largest animals are at higher risk in mass extinctions; this may explain why the unspecialized *P. regilla* survived while the larger and more specialized *P. penicillata* perished along with all the other large dicynodonts of the late Triassic. Although *Proplacerias* generally looks adapted to feed on plants similar to *Dicroidium*, which survived to the Early Jurassic, the larger size of *L. maccaigi* may have forced it to rely on the larger members of the *Glossophyllum* flora, which did not survive the end-Triassic extinction.

Only the 2.2 meter (7.2 feet) long coelophysoid *Megapnosaurus* and the large neotheropod *Dilophosaurus* appear to be large enough to have preyed on the Jurassic *Proplacerias* species, and this shortage of predators may have been responsible for a *Proplacerias* population boom in the Early Jurassic.

According to Dan Henderson, "Perhaps the survival of *Proplacerias* was simply a matter of luck".