page_title: Heterodontosauridae
section_title: Distribution
hierarchical_section_title: Heterodontosauridae / Distribution
caption_attribution_description: Biogeographic distribution in time for heterodontosaurids included in the phylogenetic analysis. Localities for included taxa are plotted on an Early Cretaceous (Berriasian-Valanginian) paleogeographic map (Smith et al. 1994) and recent time scale (Gradstein and Ogg 2009). Abbreviations for taxon localities and biogeographic areas: 1 Echinodon 2 Fruitadens 3 Kayenta heterodontosaurid 4 Tianyulong 5 Manidens 6 Abrictosaurus, Lycorhinus, Heterodontosaurus, Pegomastax A Africa As Asia E Europe NA North America SA South America.
context_page_description: Heterodontosauridae is a family of early ornithischian dinosaurs that were likely among the most basal members of the group. Although their fossils are relatively rare and their group small in numbers, they lived across all continents except Australia for approximately 100 million years, from the Late Triassic to the Early Cretaceous.
  Heterodontosaurids were fox-sized dinosaurs less than 2 metres in length, including a long tail. They are known mainly for their characteristic teeth, including enlarged canine-like tusks and cheek teeth adapted for chewing, analogous to those of Cretaceous hadrosaurids. Their diet was herbivorous or possibly omnivorous.
context_section_description: While originally known only from the Early Jurassic of southern Africa, heterodontosaurid remains are now known from four continents. Early in heterodontosaurid history, the supercontinent Pangaea was still largely intact, allowing the family to achieve a near-worldwide distribution. The oldest known possible heterodontosaurid remains are a jaw fragment and isolated teeth from the Laguna Colorada Formation of Argentina, which dates back to the Late Triassic. These remains have a derived morphology similar to Heterodontosaurus, including a caniniform with serrations on both anterior and posterior edges, as well as high-crowned maxillary teeth lacking a cingulum. Irmis et al. (2007) tentatively agreed that this fossil material represents a heterodontosaurid, but stated that additional material is needed to confirm this assignment because the specimen is poorly preserved, while Sereno (2012) only stated that this material may represent an ornithischian or even specifically a heterodontosaurid. Olsen, Kent & Whiteside (2010) noted that the age of the Laguna Colorada Formation itself is poorly constrained, and thus it wasn't conclusively determined whether the putative heterodontosaurid from this formation is of Triassic or Jurassic age. The most diverse heterodontosaurid fauna comes from the Early Jurassic of southern Africa, where fossils of Heterodontosaurus, Abrictosaurus, Lycorhinus, and the dubious Geranosaurus are found.
  Undescribed Early Jurassic heterodontosaurids are also known from the United States and Mexico, respectively. In addition, beginning in the 1970s, a great deal of fossil material was discovered from the Late Jurassic Morrison Formation near Fruita, Colorado in the United States. Described in print in 2009, this material was placed in the genus Fruitadens. Heterodontosaurid teeth lacking a cingulum have also been described from Late Jurassic and Early Cretaceous formations in Spain and Portugal. The remains of Echinodon were redescribed in 2002, showing that it may represent a late-surviving heterodontosaurid from the Berriasian stage of the Early Cretaceous in southern England. Dianchungosaurus from the Early Jurassic of China is no longer considered a heterodontosaurid; though one late surviving Asian form is known (Tianyulong).
caption: Biogeographic distribution of heterodontosaurids in time
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