In the large reptile tree (LRT, 1308 taxa) pareisaurs split after Stephanospondylus into two clades: 1) traditional pareiasaurs and 2) turtle-ancestor pareiasaurs (Fig. 1). Only the latter clade develop distinct supratemporal horns.
On a recent trip
to the Sam Noble Oklahoma Museum of Natural History in Norman, Oklahoma, USA, I studied a pareiasaur horn, OMNH 708 (Fig. 2). For over a century elginiid pareiasaurs were only known from Scotland. This year other elginids were reported from China (Liu and Bever 2018), and others were reported in 2005 from Eastern Europe (Bulanov and Yashina 2005). OMNH 708 represents yet another specimen, perhaps the first from the Late Permian Karoo beds of South Africa. (Please, let me know of not so.)
The OMNH specimen
is much larger than the Scottish and Chinese specimens (Fig. 2), more in the size range of ancestral pareiasaurs and Stephanospondylus.
The only question that remains is
is this really a pareiasaur horn? Or has everyone misinterpreted it? It really looks like a cow or bison horn (Fig. 4), but its origin in Permian strata prohibits that.
Say, ‘hello’, to convergence, once again.
Bulanov VV and Yashina OV 2005. Elginiid pareisaurs of Eastern Europe. Paleontological Journal 39(4):428–432.
Liu J and Bever GS 2018. The tetrapod fauna of the upper Permian Naobaogou formation of China: A new species of Eliginia (Parareptilia, Pareiasauria). Papers in Paleontology 2018: 1-13.
Newton ET 1893. On some new reptiles from the Elgin Sandstone: Philosophical Transactions of the Royal Society of London, series B 184:473-489.