Pelanomodon is an extinct genus of dicynodont therapsids that lived in the Late Permian period. Fossil evidence of this genus is principally found in the Karoo Basin of South Africa, in the Dicynodon Assemblage Zone.[1] Lack of fossil record after the Late Permian epoch suggests that Pelanomodon fell victim to the Permian-Triassic extinction event.
The name Pelanomodon can be broken up into three parts; “pelos” meaning mud, “anomo” meaning irregular and “odon” meaning tooth. Together, this suggests Pelanomodon to be a mud dwelling anomodont (a group of therapsids that are characterized by their lack of teeth).[2] The Karoo Basin during this period was characterized by its extensive flood plains,[3] so to hypothesize a mud based habitat for this genus is not far fetched.
Pelanomodon is in the family Geikiidae along with Aulacephalodon and Geikia. Aulacephalodon is believed to have lived alongside Pelanomodon in the Karoo Basin, where as records of Geikia have been discovered in Scotland and Tanzania. Pelanomodon is primarily characterized and distinguished from Aulacephalodon by its lack of tusks.[1] Other crananial features have been used by paleontologists to establish two species of Pelanomodon; P. moschops and P. rubidgei. However, recent analysis points to the conclusion that these may in fact the same species.[1]
The fossil record of Pelanomodon is principally made up of both complete and partial skulls. It is for this reason that morphology of the skull is used to distinguish Pelanomodon from other genus in the Geikiines family. The absence of tusks is a significant feature that is used to differentiate Pelanomodon from Aulacephalodon, in addition to bosses on the post orbital bar and twisting of the zygoma.[1] Pelanomodon is distinguished from Geikia due to its longer temporal fenestra and snout, lesser developed oesophageal crest and flush pineal foramen.[1]
In addition to these distinctions, Pelanomodon's skull has many other characteristic features. One of the most apparent of these features being that its skull is wider than it is tall, resulting in a triangular shape, when viewed dorsally.[1] In connection with this, the temporal fenestra angle out posterolaterally.[1] Compared to other dicynodonts, the external naris is retracted and located relatively high on the snout.[1] Likewise, the orbits are also placed higher than is typically seen in dicynodonts.[1] In accordance with other Anomodonts, Pelanomodon have cheek teeth but lack their molar teeth.[2] In addition, like other therapsids, the premaxilla extends on the ventral side in order to form a secondary palate.[1]
Pelanomodon was first discovered by Robert Broom, in the Karoo Basin of South Africa, in 1913. Its classification was based on a nearly complete skull, missing only the lower jaw.[4] The species was originally named Dicynodon moschops, however, in 1969 an analysis done by A. W. Keyser reclassified the specimen as Pelanomodon moschops.[5] Another species, Pelanomodon rubidgei, was classified by Broom in 1938, and was established from a complete skull found in the same region, by S. H Rubidge.[6]