Abdalodon diastematicus: a new Cynodont From Upper Permian South Africa

A new taxon of cynodont from the Tropidostoma Assemblage Zone (upper Permian) of South Africa, and the early evolution of Cynodontia

Author:

Kammerer

Abstract:

A new taxon of early cynodont, Abdalodon diastematicus gen. et sp. nov., is described. The new taxon is represented by a single skull from the upper Permian Tropidostoma Assemblage Zone (AZ) of the Beaufort Group (Karoo Basin, South Africa), which was previously referred to Procynosuchus delaharpeae. Abdalodon is distinguished from Procynosuchus by the presence of only four upper and three lower incisors, fewer postcanines, a well-developed depression on the lateral surface of the maxilla posterior to the canine root, a tall mandibular symphysis forming a distinct ‘chin’, a relatively short snout, and weak or absent interdigitation of sutures in the interorbital region. These features are shared with the only other Tropidostoma AZ cynodont, Charassognathus gracilis. Abdalodon is distinguished from Charassognathus by its postcanine morphology, the presence of an expanded masseteric fossa, inset postcanine tooth rows, a broader interorbital region, and proportionally shorter temporal region. Most strikingly, Abdalodon has a lengthy diastema between the canines and postcanines on both the maxilla and the dentary. Charassognathus has a short diastema between the upper canine and postcanines, but not the lowers, and diastemata are absent from the tooth rows of Procynosuchus. Phylogenetic analysis recovers Abdalodon as the sister-taxon of Charassognathus, forming a clade (Charassognathidae fam. nov.) at the base of Cynodontia. These taxa represent a previously unrecognized radiation of small-bodied Permian cynodonts. Despite their small size, the holotypes of Abdalodon and Charassognathus probably represent adults and indicate that early evolution of cynodonts may have occurred at small body size, explaining the poor Permian fossil record of the group.

Mupashi migrator: a new Karenitid Therocephalian From Upper Permian Zambia

The first karenitid (Therapsida, Therocephalia) from the upper Permian of Gondwana and the biogeography of Permo-Triassic therocephalians

Authors:

Huttenlocker et al

Abstract:

Therocephalians were an ecologically diverse group of therapsids whose long stratigraphic record and widespread distribution during Permian and Triassic times make them important for understanding biogeographic patterns during a major faunal transition. Here, we describe a new therocephalian, Mupashi migrator gen. et sp. nov., from the upper Madumabisa Mudstone Formation (upper Permian) of Zambia's Luangwa Basin. The specimen has a long snout with a maxilla–vomerine contact on the hard palate, a high antecanine tooth count and numerous postcanines, and a conspicuous boss on the dentary angle whose structure is identical to that of the Russian baurioid Karenites. Additional endocranial anatomy, including palatal and braincase features, are revealed by high-resolution X-ray computed tomography and described in detail in light of the growing availability of tomographic data for therapsids. A phylogenetic analysis of 56 therapsid taxa and 136 cranial and postcranial characters recovers Mupashi as the sister taxon to Karenites, placing the pair between basal ictidosuchid-grade baurioids and the later Triassic bauriamorphs. Parsimony optimizations of geographic occurrences are ambiguous regarding the origination centers of therocephalian subclades. However, the patterns are suggestive of either (1) rapid, early dispersal events of Eutherocephalia and its major subgroups from a Laurasian center during the early–late Permian or, more likely, (2) within-province diversifications with occasional dispersal events occurring between provinces. Regardless, these associations strengthen the hypothesis that unknown but effective dispersal routes to high latitudes were available to therapsids and other tetrapods at least until early–late Permian times.

Pre Mammalian Permian Therapsids Were Hairy: Evidence From Upper Permian Coprolites

Microbiota and food residues including possible evidence of pre-mammalian hair in Upper Permian coprolites from Russia

Authors:

Bajdek et al

Abstract:

Coprolites (fossil faeces) provide direct evidence on the diet of its producer and unique insights on ancient food webs and ecosystems. We describe the contents of seven coprolites, collected from the Late Permian Vyazniki site of the European part of Russia. Two coprolite morphotypes (A, B) contain remains of putative bacteria, cyanobacteria, fungi, protists, invertebrate eggs, arthropod elements, undigested bone and tooth fragments, fish scales and elongated hair-like structures with hollow interiors. Content, size and shape of the coprolites together with the associated body fossil record suggest that the most probable scat-producers were carnivorous tetrapods; the bone-rich morphotype A reveals short food retention time and a fast metabolism and is therefore assigned to therapsid carnivores whereas morphotype B with rarer and degraded bones are assigned to archosauromorphs or other non-therapsid carnivores. The general coprolite matrix contains abundant micron-sized spheres and thin-walled vesicles which are interpreted as oxide and phosphatic pseudomorphs after microbial cells. From analyses of the undigested bones, we infer that they represent remains of actinopterygian fish, a therapsid and unrecognizable parts of amphibians and/or reptiles. Additionally, hair-like structures found in one coprolite specimen occur as diagenetically altered (oxide-replaced) structures and moulds (or partly as pseudomorphs) in a microcrystalline carbonate-fluoride-bearing calcium phosphate. This suggests that the latest Permian therapsids probably were equipped with hair-like integument or hairsuit. If true, this is by far the oldest evidence of this mammalian character in the stem group of mammals.

Lende chiweta: a new Burnetiamorph Biarmosuchian Therapsid From Upper Permian Malawi

Lende chiweta, a new therapsid from Malawi, and its influence on burnetiamorph phylogeny and biogeography

Authors:

Kruger et al

Abstract:

The Chiweta Beds of Malawi have yielded a diverse late Permian fossil tetrapod fauna that correlates with that of the Cistecephalus Assemblage Zone of the South African Karoo Supergroup. Amongst the fossil therapsids from the Chiweta Beds is the well-preserved skull and lower jaw of a burnetiamorph, a group of biarmosuchians with numerous bosses and swellings on the skull. This specimen was reported in a preliminary paper in 2005 as the first burnetiamorph described outside of South Africa and Russia. Reanalysis of the morphology and phylogeny of this specimen places Lende chiweta, gen. et sp. nov., as the sister taxon to the clade formed by Proburnetia (Paraburnetia (Pachydectes, Bullacephalus, Burnetia, Niuksenitia)). The greatest diversity of this basal therapsid group is from South Africa, with six of nine described genera and a stratigraphic range that extends from the middle Permian Tapinocephalus Assemblage Zone to the upper Permian Dicynodon Assemblage Zone. Bearing in mind the constraints that govern fossil preservation, current data suggest that what is now southern Africa may have been the area of origin for burnetiamorphs. Under this premise, what is now central Africa represented a corridor that allowed migration of representatives of the group between the southern and northern portions of Pangea during the late Permian.

A new Emydopoid Dicynodont From Upper Permian Tanzania

Distinctive emydopoid dicynodont (Therapsida, Anomodontia) mandibles from the Permian Ruhuhu and Usili formations (Songea Group), Ruhuhu Basin, Tanzania

Authors:

Angielczyk et al

Abstract:

Dicynodont therapsids were discovered in the Permian Usili Formation (Ruhuhu Basin, Tanzania) in the 1930s and in the Permian Ruhuhu Formation in the 1960s, with further collections being made in 2007, 2008, and 2012. Here we describe two fragmentary mandibles that represent a new morphotype of emydopoid dicynodont. One specimen was collected in the middle fossiliferous horizon of the Ruhuhu Formation, and the other originated in the overlying Usili Formation. Three synapomorphies support the placement of these specimens in the emydopoid subclade Kingoriidae: mandibular fenestra occluded by the dentary; curved ridge that follows the profile of the symphysis present on the edge between the anterior and lateral surfaces of the dentary; and posterior dentary sulcus absent. The specimens may represent a new dicynodont species, a previously known species for which mandibular material was unknown, or an intraspecific variant of Dicynodontoides nowacki. Regardless of which of these options is correct, the specimens constitute the first taxon with a stratigraphic range extending from the likely middle Permian middle fossiliferous horizon of the Ruhuhu Formation into the late Permian Usili Formation. They also improve our understanding of the middle Ruhuhu tetrapod fauna, which previously consisted only of Endothiodon tolani.