Euptychognathus

Euptychognathus bathyrhynchus While the genus Euptychognathus was not named until 2011, fossils of Euptychognathus have been known since the middle of the 20th century. In 1942, German palaeontologist Friedrich von Huene named a new species of Dicynodon, Dicynodon bathyrhynchus, from a single skull (GPIT-PV-117020) discovered in what is now recognised as the Usili Formation in Tanzania. The skull was discovered Ernst Nowack on an expedition to the Usili Formation with his wife Maria Nowack between 1934 and 1936, who sent the skull to Germany to be examined. while others synonymised it with Dicynodon lacerticeps (e.g. Brink in 1986). One of the major issues affecting the matter is that the skull has been heavily reconstructed with plaster, with a particularly large section of skull below the naris (nostril opening) being entirely reconstructed and putting its proportions into question. While the original holotype specimen was discovered in Tanzania, these three additional specimens all come from the Karoo Basin in South Africa. Among the many specimens collected was the nearly complete skeleton of a dicynodont, formerly catalogued as TSK 14 but now accessioned in the Natural History Museum, London as NHMUK PV R 37005. TSK 14 was thoroughly described by British palaeontologist Gillian King in 1981. She identified NHMUK PV R 37005 as a specimen of Dicynodon trigonocephalus, a species originally described from South Africa, as they both had similarly short and broad skulls with wide temporal fenestra, among other features. When Kammerer and colleagues revised the taxonomy of Dicynodon in 2011, they determined that the unusual proportions of the holotype of D. trigonocephalus was due to compression of the skull, and that in fact is a distorted specimen of D. lacerticeps, synonymising the two species. They also assigned all dicynodontoid (a dicynodont subgroup that includes Dicynodon and its close relatives) specimens from Tanzania and Zambia, including NMHUK PV R 37005, to Dicynodon huenei (a species originally recognised from Tanzania). D. huenei itself would come under revision in 2019 by Kammerer, who now recognised the species as belonging to the genus Daptocephalus instead. However, he also acknowledged that he and other authors had been overly conservative in lumping all the Tanzanian and Zambian dicynodontoids under the single species D. huenei. He restricted D. huenei to only some specimens from Tanzania, and recognised other Tanzanian specimens as belonging to a new species of Dicynodon (D. angielczyki). The taxonomy and affinities of the Zambian specimens, namely NHMUK PV R 37005, was left up in air, however, but were implicitly stated to not belong to either of the two species recognised from Tanzania and that they were being re-examined. The taxonomy of NHMUK PV R 37005 and other Zambian dicynodontoids was finally revised in 2025 by Kammerer, Angielczyk and Fröbisch, where they were recognised as belonging to multiple species of lystrosaurids. This revision followed a series of expeditions to the Luangwa Basin from 2009 to 2019 by a multi-institutional research group studying the Permo-Triassic fossils of eastern Africa, which collected additional specimens of the Zambian "Dicynodon trigonocephalus" represented by NHMUK PV R 37005. Kammerer and colleagues identified these specimens as belonging to a new species of Euptychognathus. They named the new species Euptychognathus kingae in honour of Gillian King for her work describing and analysing the skeleton of the species in 1981, among her many other contributions to the study of dicynodonts. Geological background of the Ruhuhu Basin with the Usili Formation in blue, where the holotype of Euptychognathus was discovered Unlike many other Permian dicynodontoids, fossils of Euptychognathus are known from multiple sedimentary basins across several different countries. In Tanzania, where it was originally discovered, E. bathyrhynchus is known from the Usili Formation of the Ruhuhu Basin, in Zambia from the Madumabisa Mudstone Formation of the Luangwa Basin as well as the Zambezi Basin, which straddles both Zambia and Zimbabwe. The South African records come from the Balfour Formation, part of the historic Beaufort Group of the Karoo Basin. The stratigraphy of the Beaufort Group has been well-studied and subdivided into a series of discrete biozones with distinct faunal assemblages, which can be correlated with other basins globally, particularly southern and eastern Africa. Despite being widespread across multiple basins, the comparative rarity of Euptychognathus fossils has historically made it unsuited for biostratigraphic correlations. In the Karoo, the stratigraphic range of Euptychognathus has not been strictly determined, but specimens of E. bathyrhynchus have been recovered from deposits that cover the Cistecephalus and Daptocephalus Assemblage Zones. These assemblage zones have been radiometrically dated to 256.6 ± 0.1 million years ago at the base of the Cistecephalus AZ to roughly 252 million years ago at the top of the Daptocephalus AZ (coinciding with the end of the Permian period), bracketing the age of Euptychognathus to within this timespan. The ages of the upper Madumabisa Mudstone and Usili formations have not been precisely dated and correlating them with the biozones of the Karoo Basin has been inconsistent. Recent work following the expeditions from 2009-19 indicates that both the Madumabisa Mudstone and Usili formations in part correlate to the upper Cistecephalus and lower Daptocephalus AZs. ==References==