Procolophon trigoniceps (Owen 1876) Late Permian to Early Triassic was considered a parareptile and as a candidate sister to the turtles (Reisz and Laurin 1991), but it is neither. Tsuji (2006) nested Procolophon with Owenetta, but they are not closely related. Here Procolophon is derived from Diadectes. Pentaedrusaurus and Hypsognathus are sister taxa.

Distinct from Diadectes, the skull of Procolophon has a shorter rostrum, a larger orbit and the quadratojugal "horns" are greatly enlarged and laterally separate from the rest of the skull. The maxilla rose to separate the naris from the lacrimal. The jugal was shorter and did not descend onto the "horn". The postorbital portion of the skull was greatly reduced.

The neural spines were narrower. The tail was shorter. The ribs were broadest around the belly, not the chest.

The coronoid was split into anterior and posterior coronoid bones. The humerus was hour-glass shaped. The manus and pes were relatively larger.

The ilium had no posterior process. The pubis and ischium were not fused. The hind limbs were relatively longer.

Carroll RL and Lindsay W 1985. Cranial anatomy of the primitive reptile Procolophon. Canadian Journal of Earth Sciences 22, 1571-1587.

DeBraga M 2001. The postcranial anatomy of Procolophon (Parareptilia: Procolophonidae) and its implications for the origin of turtles. PhD thesis, University of Toronto.

DeBragra M 2003. The postcranial skeleton, phylogenetic position and probable lifestyle of the Early Triassic reptile Procolophon trigoniceps. Canadian Journal of Earth Sciences 40: 527-556.

Dias-DaSilva S, Modesto SP and Schultz CL 2006. New material of Procolophon (Parareptilia: Procolophonoidea) from the Lower Triassic of Brazil, with remarks on the ages of the Sanga do Cabral and Buena Vista formations of South America. Canadian Journal of Earth Sciences 43, 1685-1693.

Gilmore CW 1928. New Fossil Reptile from the Triassic of New Jersey. Proceedings of the United States National Museum 73(7):1-8.

Liu J and Bever GS 2015. The last diadectomorph shed light on Late Palaeozoic tetrapod biogeography. Biology Letters 11:2015011. Online

Owen R 1876. Descriptive and Illustrated Catalogue of the Fossil Reptilia of South Africa in the Collection of the British Museum. London, British Museum (Natural History).

Watson DMS 1914. Procolophon trigoniceps, a cotylosaurian reptile from South Africa. Proceedings of the Zoological Society of London 1914, 735-747.

Zaher M, Coram RA and Benton MJ 2018. The Middle Triassic procolophonid Kapes bentoni: computed tomography of the skull and skeleton. Papers in Palaeontology 2018:1–28. doi: 10.1002/spp2.1232

wiki/Procolophon