On the stratigraphic range of the dicynodont taxon Emydops (Therapsida: Anomodontia) in the Karoo Basin, South Africa
Date
2005
Authors
Angielczyk, Kenneth D.
Fröbisch, Jörg
Smith, Roger M. H.
Journal Title
Journal ISSN
Volume Title
Publisher
BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH
Abstract
The dicynodont specimen SAM-PK-708 has been referred to the genera Pristerodon and Emydops by various authors, and was used to
argue that the first appearance of Emydops was in the Tapinocephalus Assemblage Zone in the Karoo Basin of South Africa. However, the
specimen never has been described in detail, and most discussions of its taxonomic affinities were based on limited data. Here we
redescribe the specimen and compare it to several small dicynodont taxa from the Tapinocephalus and Pristerognathus assemblage zones.
Although the specimen is poorly preserved, it possesses a unique combination of features that allows it to be assigned confidently to
Emydops. The locality data associated with SAM-PK-708 are vague, but they allow the provenance of the specimen to be narrowed down
to a relatively limited area southwest of the town of Beaufort West. Strata from the upper Tapinocephalus Assemblage Zone and the
Pristerognathus Assemblage Zone crop out in this area, but we cannot state with certainty from which of these biostratigraphic divisions
the specimen was collected. Nevertheless, SAM-PK-708 is an important datum because it demonstrates that the stratigraphic range of
Emydops must be extended below its widely-accepted first appearance in the Tropidostoma Assemblage Zone. This range extension is
significant because it implies that the divergence between the emydopid and dicynodontid lineages must have occurred no later than
Pristerognathus Assemblage Zone times, and that most of the major lineages of Permian dicynodonts had emerged by a relatively early
point in the history of the group.