It was described in 2009 from a partial skull found in 1998 from the Dashankou locality of the Qingtoushan Formation, outcropping in the Qilian Mountains of Gansu, China.

If Tetraceratops is a therapsid, as has recently been proposed, it would be the oldest and most basal one known, surpassing Raranimus in age by several million years.

This has left a morphological and temporal gap in the fossil record during which the origin of therapsids must have occurred[7] called Olson’s Extinction.

[8][9] 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.

[11] Below is a cladogram modified from Liu et al., 2009 depicting the phylogenetic relationships of Raranimus with therapsids that occur in Olson's Gap highlighted:[1] Haptodus Dimetrodon Tetraceratops Raranimus Biarmosuchus Hipposaurus Herpetoskylax Lycaenodon Lemurosaurus Proburnetia Burnetia to mammals Gorgonops Lycaenops Cyonosaurus Biseridens Patranomodon Suminia Stenocybus Syodon Titanophoneus Estemmenosuchus Styracocephalus Jonkeria