Amphibians are extremely rare fossils in the Fossil Butte Member (FBM). Only 2 species have been identified.
One possible explanation for this scarcity of amphibians is the alkalinity of Fossil Lake's water. The lake was supersaturated with calcium carbonate, making the pH around 8 or 8.5. Amphibians generally prefer a neutral pH of 7. It is possible amphibian specimens washed into Fossil Lake from a connecting stream with a neutral pH.
Fossil Amphibian Species
Aquatic Salamander - Paleoamphiuma tetradactylumOrder Urodela, Family Sirenidae
The 4 modern species of the Sirenidae family (commonly known as sirens) are found in warm climates of the southeastern United States and northern Mexico. Sirens are the only omnivorous salamanders, the rest being strict carnivores.
Like its living relatives, P. tetradactylum had a toothless jaw and very small front limbs. However, modern sirens totally lack hind limbs, unlike P. tetradactylum. The specimen pictured is 1.3 feet long.
Frog - Aerugoamnis paulusOrder Anura, Family Anomocoela
Anura species are amphibians lacking tails, such as frogs. Only one specimen of this species has been found in the FBM.
The fossil is split, meaning a part and a counterpart are displayed on 2 opposing slabs of rock. One slab contains an almost complete, articulated skeleton. The other slap contains a poor impression of the bone.
Last updated: October 3, 2017