Fossils of the extinct red panda Parailurus anglicus were excavated in China in the east to Britain in the west. In 1977, a single tooth of Parailurus was discovered in the Pliocene Ringold Formation of Washington. This first North American record is almost identical to European specimens and indicates the immigration of this species from Asia. In 2004, a tooth from a red panda species never before recorded in North America was discovered at the Gray Fossil Site in Tennessee. The tooth dates from 4. 5–7 million years ago. This species, described as Pristinailurus bristoli, indicates that a second, more primitive ailurine lineage inhabited North America during the Miocene. Cladistic analysis suggests that Parailurus and Ailurus are sister taxa. Additional fossils of Pristinailurus bristoli were discovered at the Gray Fossil Site in 2010 and in 2012. The discovery in Spain of the postcranial remains of Simocyon batalleri, a Miocene relative to the red panda, supports a sister-group relationship between red pandas and bears. The discovery suggests the red panda's "false thumb" was an adaptation to arboreal locomotion — independent of the giant panda's adaptation to manipulate bamboo — one of the most dramatic cases of convergent evolution among vertebrates.