Abstract
Abstract. The Late Permian dicynodont Digalodon rubidgei Broom and Robinson, 1948, is redescribed based on reanalysis of the holotype and newly recognized referable specimens. Digalodon can be diagnosed by the presence of a long "beak" sharply demarcated from the caniniform process; an extremely tall zygomatic ramus of the squamosal, with a thickened, "folded-over" dorsal margin; raised parietal "lips" along the lateral edges of the pineal foramen; and a broad posterolateral expansion of the parietal, excluding the postorbital from the back of the skull roof. Inclusion of Digalodon in a recent analysis of anomodont phylogeny recovers it as a kistecephalian emydopoid, specifically as the sister taxon to the clade containing the remaining kistecephalians. Four definite specimens of Digalodon are known, but several additional specimens lacking tusks, the swollen pineal "lips", and a thickened zygoma may represent sexually dimorphic females or juveniles. Specimens of Digalodon are restricted to the central portion of the Karoo Basin, in the area around Graaff-Reinet, and are part of a characteristic fauna probably representing a limited time span.
Highlights
Emydopoidea is one of the three major groups of “advanced” dicynodont therapsids
Emydopoids are common in the early Late Permian of South Africa, with hundreds of specimens recovered from the Tropidostoma and Cistecephalus assemblage zones (AZs) of the Karoo Basin (Smith et al, 2012)
There are three specimens we consider definitely referable to Digalodon rubidgei: B 42, Bernhard Zipfel (BP)/1/157, and RC 469
Summary
Emydopoidea is one of the three major groups of “advanced” dicynodont therapsids (therochelonians sensu Kammerer and Angielczyk, 2009). Broom and Robinson (1948) distinguished Digalodon from Dicynodon (sensu lato, including Diictodon, Oudenodon, and various other taxa – see Kammerer et al, 2011) by its broad parietal exposure in the intertemporal region They noted (correctly) that this represents a primitive character common in small-bodied dicynodonts like Pristerodon and most emydopoids. Most recently, Angielczyk et al (2009) reconsidered the synonymy of Digalodon and Dicynodontoides, and concluded that Digalodon represents a distinct taxon possibly related to Emydops They referred two additional specimens to D. rubidgei (RC 469 and USNM 22941), but noted that these referrals were tentative pending a full redescription of the species.
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