Daqingshanodon

Daqingshanodon is an extinct genus of dicynodont therapsid from the Late Permian of Inner Mongolia, China. The type species D. limbus was described in 1989 from a single skull found in the Naobaogou Formation.[1] Daqingshanodon belongs to a group of dicynodonts called cryptodonts. It is the smallest known cryptodont, and the only one known from China. Like other cryptodonts, it has a pair of rounded nasal bosses above its nostrils and a ridge of bone on the upper jaw called the postcaniniform process. Daqingshanodon has a pair of elongated, recurved tusks extending from its beak-like snout. It is distinguished from other dicynodonts by the presence of a distinct ridge running along the side of the skull from below the eye socket to the area around the tusks. The skull of Daqingshanodon is less than 10 centimetres (3.9 in) long, yet this specimen is thought to have been an adult on the basis of its well-developed nasal bosses.[2]

Daqingshanodon Temporal range: Late Permian
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Therapsida
Clade:	†Dicynodontia
Clade:	†Cryptodontia
Genus:	†Daqingshanodon Zhu, 1989
Type species
†D. limbus Zhu, 1989

In his 1998 study of dicynodont biogeography, paleontologist Spencer G. Lucas synonymized Daqingshanodon with Dicynodon, forming the species Dicynodon limbus.[3] Most of the features used to distinguish Daqingshanodon as a distinct genus were also seen in specimens of Dicynodon. In 2011, a study of Dicynodon species included D. limbus in its phylogenetic analysis. D. limbus was placed among the cryptodonts, which are only distantly related to Dicynodon. With this phylogenetic placement, the genus Daqingshanodon was reinstated for D. limbus. Below is a cladogram from the 2011 analysis:[2]

Bidentalia

Cryptodontia    Keyseria       Daqingshanodon      Oudenodontidae    Oudenodon       Tropidostoma     Australobarbarus             Odontocyclops     Idelesaurus        Rhachiocephalidae    Rhachiocephalus     Kitchinganomodon      Geikiidae      Aulacocephalodon     Pelanomodon       Geikia                Dicynodontoidea    Interpresosaurus     Elph     Katumbia       Gordonia       Delectosaurus       Vivaxosaurus       Dicynodon         Daptocephalus       Dinanomodon     Peramodon           Lystrosauridae       Turfanodon     Kannemeyeriiformes

References

1. Zhuh, Y. (1989). "The discovery of dicynodonts in Daqingshan Mountain, Nei Mongol (Inner Mongolia)" (PDF). Vertebrata PalAsiatica. 27 (1): 9–27.
2. Kammerer, C.F.; Angielczyk, K.D.; Fröbisch, J. (2011). "A comprehensive taxonomic revision of Dicynodon (Therapsida, Anomodontia) and its implications for dicynodont phylogeny, biogeography, and biostratigraphy". Journal of Vertebrate Paleontology. 31 (Suppl. 1): 1–158. doi:10.1080/02724634.2011.627074.
3. Lucas, S.G. (2001). "Permian". Chinese Fossil Vertebrates. New York: Columbia University Press. pp. 71–88. ISBN 978-0-231-08483-3.