On kannemeyeriiform dicynodonts from the Shaanbeikannemeyeria Assemblage Zone of the Ordos Basin, China

Shaanbeikannemeyeria is a common tetrapod from the lower part of the ErmayingFormation of the Ordos Basin, China. There are taxonomical questions surrounding this genus,such as the validity of the genus, and how many species are included within it. Several specimenshave been collected since 1978. Shaanbeikannemeyeria first appeared from the top of theHeshanggou Formation. These specimens are described to clarify the diagnostic characters, theindividual variations and the phylogenetic position of Shaanbeikannemeyeria. Only one species,S. xilougouensis, is recognized. It is characterized by the following autapomorphies: occiputstrongly inclined relative to the palate such that the skull is much shorter basally than dorsally,sword tip-like premaxillary posterodorsal processes, tall and dorsally-convex cutting blade on themedial edge of the dorsal surface of the dentary, reflected lamina with a separated posteroventralprocess, and 15 dorsal vertebrae. This species shows variations on the cranial morphology,such as the occiput height relative to the width, the snout tip (sharp or obtuse), the shape of theorbital portion of the zygomatic arch, and the shape of caniniform process. Some variationscould be ontogenetically related, such as the development of the caniniform process and tusk, theposterior extension of the maxilla on the zygomatic arch, the distance between the frontal andthe premaxilla, the intertemporal bar width, and the exposing degree of the parietals. Based onpostcranial bones, the second dicynodont genus (possibly Parakannemeyeria) is present in thelower Ermaying Formation.