However, the name was found to be preoccupied by the therapsid.

As a therapsid, Diictodon shared many features with modern day mammals.

This therapsid lived on open plains during the early to middle Triassic period, roughly 230-245 million years ago.

Should it turn out to be a therapsid, the extinction date for this group would be pushed forward almost 45 million years.

This was a medium-sized therapsid, with a skull about twenty cm in length.

One species, O. sakamenensis, is the only therapsid yet known from Madagascar.

In fact, they said, tetraceratops is the oldest known therapsid and not a pelycosaur, as was formerly believed.

Alrausuchus is an extinct genus of biarmosuchian therapsid from Russia.

Bienotherium was a therapsid from the Early Jurassic of China.

There has been some controversy as to whether Tetraceratops is a therapsid or a more basal pelycosaur.

Megawhaitsia is an extinct genus of large therapsid, potentially a therocephalian.

However, unlike any other therapsid, the choanae are short and extend only from the level of the fourth incisor back to the first canine.

According to a phylogenetic analysis conducted along with its initial description, Raranimus is considered to be the basalmost therapsid.

Tetraceratops is the oldest known therapsid.

The largest carnivorous therapsid was the aforementioned Anteosaurus.

Malasaurus is an extinct genus of therocephalian therapsid which existed in Russia.

The dinocephalians evolved from a pelycosaur-like therapsid that lived in the late Cisuralian epoch.

It is considered to be a dicynodont by some paleontologists; others think Galechirus is a younger form of a larger therapsid.

Bullacephalus is an extinct genus of biarmosuchian therapsid belonging to the family Burnetiidae.

Traversodon is a genus of therapsid.

Raranimus is an extinct genus of therapsid of the Middle Permian.

With the general absence of therapsid remains from Olson's Extinction, different hypotheses have developed in order to explain the group's origins and initial diversification.

Biarmosuchus is an extinct genus of biarmosuchian therapsid that lived around 255 mya during the late Permian period.

Titanophoneus ("titanic murderer") is a carnivorous dinocephalian therapsid from the Middle Permian.

Hipposaurus ('horse lizard') is an extinct genus of therapsid that lived in the Late Permian.