Fig. 23. Mioplosus, a fairly common perch from Fossil Butte. Length of original, 30 cm. Collection of American Museum of Natural History.
Fig. 24. Priscacara, a small bass that is common in the Fossil Butte fish beds. Length of original, 13 cm. Collection of University of Wyoming.
The one genus for which no close living relatives can be found is Priscacara ([Fig. 24]). The family Priscacaridae is thought to be related to the bass. The family is known only from the Eocene. The size of Priscacara is extremely variable. The body is deep and nearly round like that of the common sunfish, the head blending in well with the body and its contours. The most distinguishing feature of Priscacara is the series of strong, stout spines supporting the anal and dorsal fins. These spines may have acted as cut-waters for better swimming and/or they may have protected Priscacara from its more voracious relatives.
AMPHIBIANS.
To date, no amphibian fossils are known from Fossil Butte. They must have been present, as this class of animals is recorded from Devonian rocks more than 350 million years old and from rocks younger than those at Fossil Butte. Living amphibians are typified by frogs, toads, and salamanders. The lack of amphibian remains at Fossil Butte is more likely due to nondiscovery than nonexistence.
REPTILES.
Reptile fossils are very abundant in the Green River and Wasatch formations. Also a jaw of the three-horned Triceratops is known from the Cretaceous part of the Evanston Formation.
Small lizards are normally represented only by jaw fragments and vertebrae. Their remains are most often found by a process of washing and screening of the sediments containing the fossils. Snakes are also represented in the Green River Formation. Remains of these animals are also often restricted to jaws and vertebrae. A complete skeleton of a fossil boa, Boavus idelmani, has been recovered from the Green River Formation and is the most complete fossil snake from North America (Schaeffer and Mangus 1965).