Vertebrates were preserved too, including the scutes of "Borealosuchus", the crocodile that was an early clue to the mild Eocene climate of Western North America. Fish are common. The fossils of the herring-like "Knightia", sometimes in dense layers, as if a school had wandered into anoxic water levels and were overcome, are familiar to fossil-lovers and are among the most commonly available fossils on the commercial market. There were two genera of indigenous freshwater stingray, "Heliobatis" and "Asterotrygon". Approximately sixty vertebrate taxa in all have been found at Green River. Besides fishes they include at least eleven species of reptiles, and some birds and one armadillo-like mammal, "Brachianodon westorum", with some scattered vertebrae of others, like the dog-sized "Meniscotherium" and "Notharctus", one of the first primates. The earliest known bats ("Icaronycteris index"