Cranial osteology and a new diagnosis of the late Permian pareiasaur Nanoparia luckhoffi (Broom, 1936) from the Karoo Basin of South Africa, and a consolidated pareiasaurian phylogeny

Abstract

Pareiasaurs were an enigmatic and diverse group of parareptilian herbivores of the middle and late Permian. Nanoparialuckhoffi was erected in 1936 but remains the least well-known member of four “dwarf” pareiasaurs that comprise Pumiliopareiasauria. After new preparation of the holotype, we present the first detailed cranial description of Nanoparialuckhoffi and a new diagnosis for the taxon based on seven autapomorphies: (1) an additional bone on the posterior margin of the cheek flange between the squamosal and quadratojugal; (2) a pyramidal-shaped parietal; (3) a very short, square lacrimal; (4) paired prepalatal foramina positioned anterolaterally on the internal premaxillary palatal flange; (5) notch on anteromedial border of the choana; (6) a ventral flange formed by the lateral margin of the internal tabulars; and (7) tabulars that extend posteriorly further than the supratemporals. We find evidence supporting a juvenile ontogenetic state for the holotype, including small skull; unossified open cranial sutures; an unossified dorsal braincase; and fewer marginal teeth than most pareiasaurs. An updated phylogeny recovers Nanoparia as a sister taxon to Provelosaurusamericanus from Brazil and remains a constituent member of Pumiliopareiasauria. Keywords: Nanoparia, Pumiliopareiasauria, Pareiasauria, Parareptilia, late Permian, Gondwana.