Abstract
We report a new ichthyopterygian assemblage from Lower Triassic horizons of the Prida Formation at Fossil Hill in central Nevada. Although fragmentary, the specimens collected so far document a diverse fauna. One partial jaw exhibits isodont dentition with blunt tipped, mesiodistally compressed crowns and striated enamel. These features are shared with the Early Triassic genus Utatsusaurus known from coeval deposits in Japan and British Columbia. An additional specimen exhibits a different dentition characterized by relatively small, rounded posterior teeth resembling other Early Triassic ichthyopterygians, particularly Grippia. This Nevada assemblage marks a southward latitudinal extension for Early Triassic ichthyopterygians along the eastern margin of Panthalassa and indicates repeated trans-hemispheric dispersal events in Early Triassic ichthyopterygians.
Highlights
Ichthyosaurs were among the most enduring and successful Mesozoic marine reptile groups, appearing in the Early Triassic and persisting some 150 million years until their extinction in the Late Cretaceous (McGowan & Motani, 2003)
Nevada has been an important source of Triassic marine reptile fossils since the 19th Century producing abundant and well-preserved Middle Triassic (Leidy, 1868; Merriam, 1905; Merriam, 1908; Merriam, 1910; Sander, Rieppel & Bucher, 1994; Sander, Rieppel & Bucher, 1997; Frobisch, Sander & Rieppel, 2006; Frobisch et al, 2013) and Late Triassic
The type locality of Utatsusaurus is in the Osawa Formation of Japan (Shikama, Kamei & Murata, 1978), whereas the type localities of Grippia and Chaohusaurus are in the Vikinghøgda Formation (= “Sticky Keep Formation” of older references) of Spitsbergen (Wiman, 1929; Wiman, 1933; Hounslow et al, 2008) and the Nanlinghu Formation of Anhui Province, China (Young & Dong, 1972), respectively
Summary
Ichthyosaurs were among the most enduring and successful Mesozoic marine reptile groups, appearing in the Early Triassic and persisting some 150 million years until their extinction in the Late Cretaceous (McGowan & Motani, 2003). The fossil record of early ichthyopterygians (the clade comprising ichthyosaurs and close relatives) includes a variety of morphologically disparate taxa from widespread localities in Asia, North America and the Arctic. Most of these assemblages are broadly contemporaneous, all being late Spathian (late Early Triassic) in age. Nevada has been an important source of Triassic marine reptile fossils since the 19th Century producing abundant and well-preserved Middle Triassic (Leidy, 1868; Merriam, 1905; Merriam, 1908; Merriam, 1910; Sander, Rieppel & Bucher, 1994; Sander, Rieppel & Bucher, 1997; Frobisch, Sander & Rieppel, 2006; Frobisch et al, 2013) and Late Triassic
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