A new species of burnetiid (Therapsida, Burnetiamorpha) from the early Wuchiapingian of South Africa and implications for the evolutionary ecology of the family Burnetiidae

Abstract

Burnetiidae is a family of basal therapsids that is known from sequences of late Permian (Lopingian) age from southern and eastern Africa and European Russia. Recent discoveries of related genera within the broader clade Burnetiamorpha have added to our understanding of morphological variation in the group but have eroded the list of characters defining the family Burnetiidae. We describe a new burnetiid taxon, Leucocephalus wewersi gen. et sp. nov., and argue that Burnetiidae can be defined by, among other characters, the presence of two bosses on the ventrolateral surface of suborbital bar and zygomatic arch, high skull angulation between the orbits, and a median frontal crest that becomes wider and lower posteriorly. The new specimen was found in the early Wuchiapingian Tropidostoma Assemblage Zone of the Main Karoo Basin and, along with previous discoveries, indicates that the family reached its greatest diversity and abundance in the early Wuchiapingian. Diversity declined into the later Wuchiapingian and Changhsingian. Although the clade Burnetiamorpha, including the family Burnetiidae, contains at least 11 genera, each of these is exceptionally rare, with most represented by only one specimen. This could be attributed to a genuine ecological characteristic or may be the result of biogeographical factors, particularly if the Main Karoo Basin was on the periphery of their range.

Effects of taphonomic deformation on geometric morphometric analysis of fossils: a study using the dicynodontDiictodon feliceps(Therapsida, Anomodontia)

“…Although a number of synapsid species are represented by large sample sizes ranging into the hundreds of specimens ( Smith, Rubidge & Van der Walt, 2012 ; Codron et al, 2017 ), the group also includes numerous stratigraphically and phylogenetically important species represented by very few individuals (e.g., all but one species in the therapsid subclade Burnetiamorpha are known from a single skull; Sidor, 2015 ; Day et al, 2018 ). Ideally, analyses of synapsid morphological disparity should include both abundant taxa as well as rare species.…”

The original boneheads: histologic analysis of the pachyostotic skull roof in Permian burnetiamorphs (Therapsida: Biarmosuchia)

“…The diverse but relatively short‐lived tapinocephalid clade is restricted to the Guadalupian (~ 260 Ma; middle Permian, Barghusen, ; Rubidge, ; Kammerer, ; Olroyd & Sidor, ), whereas burnetiamorphs persisted until the end of the Permian, with 11 genera currently recognized (Day et al. ). Importantly, burnetiamorphs developed a wide range of bony adornments on their skulls, including crests, bosses, and dome‐like thickenings, which can be tied to their relatively speciose fossil record (Padian & Horner, ; Sidor et al.…”

A new burnetiid from the middle Permian of Zambia and a reanalysis of burnetiamorph relationships

“…A subsequent paper (Day et al . 2018) using the same underlying dataset recovered a similar topology, with Bullacephalus + Pachydectes outside of Burnetiidae.…”

“…We find that the cladistic conclusions of Day et al . (2016, 2018) do not withstand a detailed restudy of the constituent characters and character states. Instead, our study bolsters earlier proposals of burnetiamorph phylogeny that recognize an expansive Burnetiidae divided into the subclades Proburnetiinae and Burnetiinae.…”

“…at least eight in Herpetoskylax , 8–9 in Leucocephalus ; Sidor & Rubidge 2006; Day et al . 2018). No complete mandibles are known for burnetiines, but most of the jaw is preserved in BP/1/5387 (holotype of Bullacephalus jacksoni ) and it is generally similar to those of other burnetiamorphs (with four preserved teeth, but given that this is only the posteriormost section of the tooth row, more were probably present).…”