Open Paleo

Chaoyangsauridae

Zhao et al., 2006 Type genus Chaoyangsaurus

Its genera lived 165.3–132.6 million years ago Middle Jurassic–Early Cretaceous

Chaoyangsauridae is a family of small, early-diverging ceratopsian dinosaurs from Asia (and possibly Europe, if the German genus Stenopelix belongs here). They are among the earliest known marginocephalians, with the oldest remains dating to roughly 160 million years ago in the Late Jurassic and others extending into the Early Cretaceous. Its members bore sharp beaks for snipping off leaves and only a very small frill, retaining many primitive features while already showing the rostral bone that characterizes ceratopsians. Han and colleagues (2015) recover Chaoyangsaurus, Xuanhuaceratops, Yinlong and Hualianceratops as a weakly supported clade, sister to Psittacosaurus, with that pair the sister group of the remaining neoceratopsians.

Diagnosis

  1. Semicircular process near the mandibular glenoid
  2. Flat dorsal surface of the squamosal bearing a stalked quadrate process
  3. Deep sulcus dividing the quadrate condyles
  4. Laterally ridged angular
  5. Reduced predentary
  6. Rostrally converging dentary margins

Genera placed directly in Chaoyangsauridae

  • Chaoyangsaurus Zhao et al., 1999 Tithonian–Berriasian (149.2–137.1 Ma)China
  • Hualianceratops Han et al., 2015 Callovian–Oxfordian (165.3–154.8 Ma)China
  • Stenopelix Meyer, 1857 Berriasian–Valanginian (143.1–132.6 Ma)Germanyunder dispute
  • Xuanhuaceratops Zhao et al., 2006 Tithonian (149.2–143.1 Ma)China
  • Yinlong Xu et al., 2006 Callovian–Oxfordian (165.3–154.8 Ma)China

Synonyms

Name Type Reason
Chaoyoungosauridae nomen nudum The superfamily Chaoyoungosauroidea of Zhao (1983), lowered to a family by Olshevsky (1991); unavailable, because its type genus was itself a nomen nudum until Chaoyangsaurus was named.

References

  1. Zhao, X.; Cheng, Z.; Xu, X.; Makovicky, P. J. (2006). A new ceratopsian from the Upper Jurassic Houcheng Formation of Hebei, China. Acta Geologica Sinica 80(4): 467-473.

    Described Xuanhuaceratops and proposed Chaoyangsauridae, modified from a name of Zhao (1983), as all taxa closer to Chaoyangsaurus youngi than to Triceratops or Psittacosaurus.

    zhao2006a
  2. Han, F.; Forster, C. A.; Clark, J. M.; Xu, X. (2015). A new taxon of basal ceratopsian from China and the early evolution of Ceratopsia. PLOS ONE 10(12): e0143369. Public Library of Science (PLoS). doi:10.1371/journal.pone.0143369

    Revised diagnosis of Chaoyangsauridae; recovered as monophyletic outside Neoceratopsia.

    han2015a
  3. Zhao, X. (1983). Phylogeny and evolutionary stages of Dinosauria. Acta Palaeontologica Polonica 28(1-2): 295-306.

    Proposed the superfamily Chaoyoungosauroidea, with a short diagnosis, for the then-unpublished genus Chaoyoungosaurus.

    zhao1983a
  4. Olshevsky, G. (1991). A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2: 1-196.

    Lowered Chaoyoungosauroidea to the family Chaoyoungosauridae, noting that both names were nomina nuda.

    olshevsky1991a