Placerias (meaning 'broad body')[2] is an extinct genus of dicynodonts that lived during the Carnian to the Norian age of the TriassicPeriod (230–215 million years ago). Placerias belongs to a group of dicynodonts called Kannemeyeriiformes, which was the last known group of dicynodonts before the taxon became extinct at the end of the Triassic.
Description
P. hesternus compared to a human
Placerias was one of the largest herbivores in the Late Triassic, measuring 3.5 metres (11 ft) long and weighing up to 800–1,000 kilograms (1,800–2,200 lb).[3][4][5] The largest skull found had a length of 68 centimetres (26.8 in).[6]
Placerias had a powerful neck, strong legs, and barrel-shaped body with possible ecological and evolutionary parallels with the modern hippopotamus, spending much of its time during the wet season wallowing in the water and chewing at bankside vegetation.[5]Placerias was closely related to Ischigualastia and similar in appearance.[7]Placerias used its beak to slice through thick branches and roots with two short tusks that could be used for defence and for intra-specific display. The genus exhibits two morphs, one with short tusks and one with long tusks, which is inferred to be sexual dimorphism, with the longer-tusked individuals presumably being males.[8]
Life restoration of Chinle formation where Placerias (lower right) coexists with Coelophysis (lower left) and Postosuchus (top left)
Placerias was originally considered the last of the dicynodonts, although other Late Triassic dicynodonts, such as Lisowicia[10] and Pentasaurus[11] have since been discovered.[a]
^A report of a dicynodont fossil from the Cretaceous Period[12] proved to be neither Cretaceous nor a dicynodont; it proved to be a specimen of a diprotodontidmarsupial that probably dates to the Pliocene or Pleistocene.[13]
^Kammerer, Christian F (2018). "The first skeletal evidence of a dicynodont from the lower Elliot Formation of South Africa". Palaeontologia Africana. 52: 102–128. ISSN2410-4418.
