Distribution
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 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. 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).
Read more about this topic: Heterodontosauridae
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