Immaturity vs paedomorphism: a rhinesuchid stereospondyl postcranium from the Upper Permian of South Africa
Date
2004
Authors
Pawley, Kat
Warren, Anne
Journal Title
Journal ISSN
Volume Title
Publisher
BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH
Abstract
The postcranial skeleton of a medium-sized rhinesuchid from the Late Permian Dicynodon Assemblage Zone of South Africa is
described. The well-preserved, articulated specimen consists of a partial skull, vertebral column and ribs, pectoral girdle, proximal limb
elements, and ventral scales. Interesting features rarely preserved in stereospondyls include the extensive ventral scales and the
pectinate anterior border of the interclavicle. SAM-PK-K10021 is of an average size for a rhinesuchid, but possesses a poorly ossified
postcranial skeleton in comparison to larger rhinesuchid specimens. The scapulocoracoid lacks an ossified coracoid plate, the humerus
lacks a supinator process, and the femur lacks a well-developed internal trochanter and adductor blade. Despite its relatively large size,
SAM-PK-K10021 is an immature stage of a large rhinesuchid, thus contributing to our knowledge of the changes to the postcranial
skeleton that occur during ontogeny. The assessment of heterochronic processes, especially paedomorphism, in the postcranial
skeleton of temnospondyls, and the implications for cladistic analysis, are discussed.