Cranial morphology and phylogenetic relationships of the Middle Permian pareiasaur Embrithosaurus schwarzi from the Karoo Basin of South Africa

Abstract

Pareiasaurs were globally distributed, abundant, herbivorous parareptiles of the Middle to Late Permian, with the basal-most members found in the Middle Permian of South Africa. These basal taxa were particularly abundant and went extinct at the end of the Gaudalupian (Capitanian) at the top of the Tapinocephalus Assemblage Zone. Currently four taxa are recognized in this group: Bradysaurus seeleyi, B. baini, Nochelesaurus alexanderi and Embrithosaurus schwarzi, but they are all poorly understood. We here present the first detailed cranial description and updated diagnosis for Embrithosaurus schwarzi. No cranial autapomorphies were identified. However, Embrithosaurus schwarzi is a distinct taxon in this group, based on its unique dentition and using a combination of cranial features. It has nine marginal cusps on all maxillary and mandibular teeth, and wider maxillary teeth than in the co-occurring taxa, due to the marginal cusps being arranged more regularly around the crown, and the apex of the crown lacking the long, central, three-cusped trident. Our updated phylogenetic analysis recovers the four Middle Permian South African taxa as a monophyletic group for the first time, which we call Bradysauria, comprising a clade including Embrithosaurus, Bradysaurus baini and a polytomy including Nochelesaurus and Bradysaurus seeleyi.

Bone Microstructure of Pareiasaurs (Parareptilia) from the Karoo Basin, South Africa: Implications for Growth Strategies and Lifestyle Habits

“…Caution should nonetheless be exercised since differences in bone histology could also be the consequence of incorrect taxonomic identifications of pareiasaur remains from the Tapinocephalus AZ, and thus rather reflect inter‐specific variability. Indeed, preliminary results of an ongoing taxonomic revision of pareiasaurian material from the Tapinocephalus AZ (Van den Brandt et al, ) show that specimen SAM‐PK‐9137 could possibly belong to the species Nochelesaurus alexanderi (M. Van den Brandt, 2016 pers. comm).…”

Cranial morphology of the middle Permian pareiasaurNochelesaurus alexanderifrom the Karoo Basin of South Africa

“…2015; Benton 2016; Liu & Bever 2018; Van den Brandt et al . 2020). These basal taxa are therefore important as they form a baseline from which to investigate the origin, diversification and subsequent distribution of the group.…”

“…In the first in a series of papers designed to update the anatomy, taxonomy, phylogeny and stratigraphic ranges of basal South African pareiasaurs, Van den Brandt et al . (2020) produced an updated cranial description and diagnosis for Embrithosaurus schwarzi . We included a new phylogenetic analysis in which we recovered the basal South African taxa as a monophyletic group for the first time, which we named the Bradysauria.…”

Oxygen isotopes and ecological inferences of Permian (Guadalupian) tetrapods from the main Karoo Basin of South Africa

“…Bradysaurus baini, B. seeleyi, Embrithosaurus schwarzi and Nochelesaurus alexanderi (Lee, 1997;Van den Brandt et al, 2019). As the pareiasaur specimens sampled are not all well J o u r n a l P r e -p r o o f 8 preserved, only six could be reliably identified with three Bradysaurus bainii, two Embrithosaurus schwarzi and one Nochelesaurus alexanderi; the remaining seven specimens cannot be identified to genus and are referable only to the family level (pers.…”

“…The absence of a significant difference between the median values of the different groups (Wilcoxon test pvalues > 0.18; Fig.5) indicate that dinocephalians, therocephalians, and the pareiasaurs could have shared a similar terrestrial lifestyle.This study of the lifestyle of pareiasaurs through a geochemical proxy, the δ 18 O p values from the phosphate group of the apatite, is in alignment with previously published studies that interpreted pareiasaurs as a fully terrestrial taxon. It is important to stress that this study focused only on middle Permian pareiasaurs from the Karoo Basin of South Africa, which are the oldest pareiasaurs known (Van denBrandt et al, 2019), and that different results might be obtained from analyses of later species.Stable oxygen and carbon isotope compositions of phosphate apatite of teeth and bones were analyzed to investigate the debated ecological lifestyle of middle Permian pareiasaurs and the dinocephalian Anteosaurus. Our results demonstrate that the aquatic ecology of the rhinesuchid specimen is strongly supported by its low δ 18 O p value, the lowest of the horizon.…”