Article: The rhynchosaur Howesia browni from the Lower Triassic of South Africa
Publication: Palaeontology
Volume:
38
Part:
3
Publication Date:
October
1995
Page(s):
665
–
685
Author(s):
David W. Dilkes
Abstract
Howesia browni is a rhynchosaur (Reptilia: Archosauromorpha) known from a single locality in the Cynognathus Assemblage Zone (Beaufort Group: Burgersdorp Formation) near the town of Aliwal North, Eastern Cape Province, South Africa. Howesia is diagnosed by the following autapomorphies: (1) multiple rows of small, conical teeth on medially expanded maxillaries that lack longitudinal, occlusal grooves; (2) multiple rows of small, conical teeth on dentaries; (3) a broad ventral process of the squamosal that does not extend below the middle of the lower temporal fenestra; (4) a medial shelf on the quadrate ramus of the pterygoid; (5) contact between the ectopterygoid and jugal reduced to less than half of the distal expansion of the ectopterygoid; (6) deep pockets on the neural arches of the posterior dorsals and sacrals; and (7) posteriorly inclined and tall proximal caudal neural spines. A preliminary phylogenetic analysis demonstrates that Rhynchosauria can be rediagnosed by seven synapomorphies: (1) a beak-shaped premaxilla; (2) a single, median external naris; (3) contact between the premaxilla and prefrontal; (4) depression on the dorsal surface of the frontal; (5) depression on the dorsal surface of the postfrontal; (6) fused parietals; and (7) flat occlusion. Howesia is the probable sister taxon to the clade of Rhynchosaurus, Stenaulorhynchus, Scaphonyx and Hyperodapedon.