Mammal and bird trackways in the Miocene Horse Spring Formation, Clark County, Nevada
The Thumb Member of the Miocene Horse Spring Formation contains a vertebrate track assemblage of mammal (camel and carnivore) and avian footprints. Camelid tracks identified are Lamaichnum alfi, Lamaichnum macropodum, and Lamaichnum etoromorphum. Carnivore tracks include canid tracks (Canipeda sp.) and a possible felid track ( Felipeda? sp.). One canid trackway records a c-shaped pattern, which is apparently the fist documentation of a rotary gallop gait in Miocene canids. Five types of bird tracks, four of which are previously undescribed, also occur. They are: (1) Alaripeda lofgreni, (2) Avipeda sp. A, (3) Avipeda sp. B, (4) Anatipeda sp. A, and (5) a new, previously undescribed track type in the Morphofamily Gruipedidae; A summary of the eight known Miocene track-bearing formations (including the Horse Spring Formation) in the western United States indicates that an ichnofacies of Miocene mammal and bird tracks associated with lacustrine deposits is beginning to become apparent.
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