Shantungosuchus

Shantungosuchus
Temporal range: 161.2–99.6 Ma

Late Jurassic - Late Cretaceous

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Crocodylomorpha
Clade: Mesoeucrocodylia
Genus: †Shantungosuchus
Species
  • †S. chuhsienensis Young, 1961 (type)
  • †S. hangjinensis Wu et al, 1994
  • †S. brachycephalusYoung, 1982
Synonyms

Shantungosuchus is an extinct genus of Cretaceous crocodyliform found in China. It includes three species: Shantungosuchus chuhsienensis and S. brachycephalus, which were both described by Yang Zhongjian – usually referred to as "Young" – in 1961 and 1982, and S. hangjinensis, which was described by Xiao-Chun Wu et al in 1994. S. chuhsienensis is the type for this genus.

Etymology

The primary part of Shantungosuchus' name comes from Shan-tung, the Wade-Giles romanization of Shandong (simplified Chinese: 山东; traditional Chinese: 山東; pinyin: Shāndōng; Wade–Giles: Shan1tung1), a province located on the eastern coast of the People's Republic of China, where it was first discovered. The second part, suchus is a Latin word meaning "crocodile".

Description

S. chuhsienenis was first described from an articulated skeleton that was preserved as an impression of its ventral surface. Its small size, slender body, and triangular skull made it distinct from other atoposaurids.[1]

Shantungosuchus belongs to Protosuchia, a group of early crocodilian relatives that were all rather small in size, about 1 meter in length, and terrestrial rather than aquatic.[2] They are most easily distinguished from other crocodylians by their short premaxilla and maxillas, a transversely broad shelf on the jugal bone, and a pair of posterolaterally divergent ridges on the pterygoid, and two large depressions on the sphenoid bone. The angular shape of the rest of the skull is absent from the posterolateral section of the jaw. The dentaries near the symphysis are superficially asymmetrical. All known forms of Shantungosuchus also have a square-shaped fossa on the jugal, and a leaf-shaped palatine bone.

Taxonomy

Two of the species of Shantungosuchus, including the type, were described by Yang Zhongjian (referenced here as C.C. (Chung Chien) Young) in 1961. Since the description of S.chuhsienensis, there has been uncertainty about the placement of the genus. It was suggested to be an atoposaurid by several different authors from the 1960s to the 1980s,.[3][4][5] However, in Xiao-Chun Wu's 1994 description of S. hangjinensis, he noted the bones were more similar to the family Protosuchidae rather than Atoposauridae, and proposed to classify it as such.[1]

Protosuchia has recently been considered a paraphyletic grouping of early crocodyliforms. Protosuchia is now commonly split into two groups: the basal family Protosuchidae, which is a true clade, and a group of basal crocodyliforms more closely related to Hsisosuchus and Mesoeucrocodylia. Shantungosuchus is included in the latter grouping, as it is more closely related to mesoeucrocodylians than the protosuchid protosuchians.[6]

Distribution and habitat

Shantungosuchus chuhsienensis, aside from being the type species, is also the oldest. It was found in upper Jurassic deposits in its namesake Shandong province. Also from the Jurassic of Shandong is S. brachycephalus.[1] S. hangjinensis, however, is slightly younger, and is found in the lower Cretaceous Luohandong Formation of Outer Mongolia.[1] The Luohandong formation provides clues to Shantungosuchus' environment. For instance, S. hangjinensis likely shared its habitat with fish such as Sinamia, the turtle Orodsemys, and another species of crocodile-like reptile called Ikechosaurus, and several types of dinosaurs- though none have been identified to the level of genus.[7][8]

See also

References

  1. 1 2 3 4 Wu, Xiao-Chun. Donald B. Brinkman, and Jun-Chang Lu. A new species Shantungosuchus from the Lower Cretaceous of Inner Mongolia (China) with comments on S. chuhsiensis Young, 1961, and the phylogenetic position of the genus. Journal of Vertebrate Paleontology, 1994, 14(2):210-229.
  2. ↑ Colbert, Edwin H., Morales, Michael. Minkoff, Eli C., Colbert's Evolution of the Vertebrates: A History of the Backboned Animals through Time. Fifth Edition. 2001. Wiley-Liss. p.183
  3. ↑ Buffetaut, E. (1982). Radiation évolutive, paléoécologie et biogéographie des Crocodiliens mésosuchiens. Mémoires de la Société Géologique de France, 60, 1-88.
  4. ↑ Clark, J.M. (1985). A new crocodylomorph from the Late Jurassic Morrison Formation of western Colorado, with a discussion of relationships within the "Mesosuchia". Master's thesis, Univ. of California, Berkeley, 85 pp.
  5. ↑ Buscaloni , Angela D. and José Luis Sanz. (1988). PHYLOGENETIC RELATIONSHIPS OF THE ATOPOSAURIDAE (ARCHOSAURIA, CROCODYLOMORPHA). Historical Biology, 1988. Vol. 1. pp. 233-250.
  6. ↑ Pol, D.; Ji, S.; Clark, J.M.; Chiappe, L.M. (2004). "Basal crocodyliforms from the Lower Cretaceous Tugulu Group (Xinjiang, China), and the phylogenetic position of Edentosuchus" (PDF). Cretaceous Research. 25: 603–622. doi:10.1016/j.cretres.2004.05.002.
  7. ↑ Lucas, Spencer G., 2001. Chinese Fossil Vertebrates. New York. University of Columbia Press. p. 169.
  8. ↑ Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
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