Paper No. 7-2
Presentation Time: 8:30 AM-4:30 PM
INITIAL DESCRIPTION AND IDENTIFICATION OF LARGEST KNOWN LONGNOSE GAR, LEPISOSTEUS BEMISI, FROM THE GREEN RIVER FORMATION OF WYOMING, U.S.A
The lower Eocene Green River Formation (48.5-53.5ma) of Fossil Lake in southwest Wyoming was a tropical/subtropical freshwater paleoenvironment in a volcanically active area. Within the Green River Formation, the Fossil Butte Member (52ma) is a layer of rock famous for an abundance and variety of exceptionally preserved fossils. Among the largest organisms found in the Green River are gar (Lepisosteiformes). Four species of gar have been described from the Fossil Butte Member sediments of the Green River Formation: Masillosteus janei, Atractosteus atrox, Atractosteus simplex, and Lepisosteus bemisi. The specimen we examined is currently housed at the Wyoming Dinosaur Center (Specimen ID JJSF-2012-001) and is an example of the excellent preservation common to the Split Fish layer of the Fossil Butte Member in which it was discovered. Based on the locality of the specimen and numerous diagnostic features; the size, elongated jaw, number of caudal rays, the pointed build of the teeth, and lack of a supraoccipital bone, we identify specimen JJSF-2012-001 as a specimen of Lepisosteus bemisi, commonly referred to as the Green River longnose gar. Specimen JJSF-2012-001 is also the largest L. bemisi specimen described to date, with a total length (TL) of 1655 mm, 45 mm longer than the largest previously known specimen. The quality of preservation and the detail of preparation of this specimen will allow for considerable future research that will enrich our understanding of L. bemisi and related gar.