All About Gray Fossil Site's Red Panda

Bristol’s Panda (Pristinailurus bristoli), found only at the Gray Fossil Site, is an ancient North American relative of the living Red Panda (Ailurus fulgens). Known from intact skeletons, it is the most complete fossil ailurid from North America and most complete ailurine found anywhere else in the world.

Etymology

Its genus name (Pristinailurus) comes from the Latin word pristinus meaning “former” or “previous”, and Ailurus for the living Red Panda (Ailurus fulgens) to which the fossil species is closely related. The species name (bristoli) is named for Larry Bristol who discovered the first fossils from Bristol’s Panda. Commonly, this species is also known as “Bristol’s Appalachian Panda.” The word “panda” itself is derived from the Nepalese term nigalya poonya, which means “bamboo-eater,” a reference to the diets of the living Red Panda and the unrelated Panda Bear (Ailuropoda melanoleuca).

Habitat & Distribution

Bristol’s Panda is special because it is one of only two ailurine pandas known from North America. The other is an unnamed Parailurus species from Washington State, and it is known by a single tooth. Although the living distribution of Bristol’s Panda was undoubtedly more expansive, fossils are known only from the late Miocene-early Pliocene locality of Gray, Tennessee. The environment in which it lived was a forested region with a subtropical climate as evidenced by the alligator and other fossils unearthed here.

Physical Attributes                               

Bristol’s Panda differs from the Red Panda in a number of ways, the most obvious being its much larger size. The fossil panda would have weighed 8 to 15kg (17 to 33lbs) in life, compared to the modern Red Panda which averages 5kg (11lbs). The skull of Bristol’s Panda is not as domed and it lacks a sagittal crest suggesting a weaker bite. However, its snout was longer with larger incisors and canines. The upper carnassial is also longer and not as wide, suggesting that it was not as dependent on plant matter as part of its diet.

Bristol’s Panda shares several physical characteristics with the modern Red Panda which point to climbing ability. They both have a long tail for counterbalance, broad paws with recurved semi-retractable claws, and a nimble body with powerful muscles in the forelimbs and lower back. There are some major differences between the ancient and modern red pandas. Several aspects of Bristol’s Panda’s anatomy hint at a more terrestrial existence than its living relative. Compared to the tree-dwelling Red Panda, Bristol’s Panda has proportionally shorter and more robust forelimbs while the hind limbs were significantly longer. This body plan is typical of carnivorans such as civets, small cats, and certain foxes that actively hunt on the ground while retaining considerable climbing ability.

Skull and head comparison of Bristol's Panda (left) and Red Panda (right).

We see further evidence of a terrestrial lifestyle in Bristol’s Panda in the arrangement of its wrist and finger bones. The modern Red Panda has particularly well-developed “false thumbs” on its front paws that form an effective clamp for gripping tree trunks and thin branches. The false thumbs of Bristol’s Panda are proportionally much smaller. This suggests less frequent usage of the “false thumbs” and overall less time spent in the higher branches of trees.

Size comparison between the Bristol's Panda and the Red Panda. Note
the larger size and proportionally shorter forelimbs, longer hind limbs,
and longer body in the Bristol's Panda.

Ecology & Behavior

The body proportions of Bristol’s Panda were those of an active and agile predator that spent most of its time on the ground but could readily climb trees when necessary. Like many small forest-dwelling carnivorans it was probably nocturnal and solitary, perhaps sleeping in burrows during the day and emerging at night to forage. Together with the Woodland Badger (Arctomeles dimolodontus), Bristol’s Panda is the most commonly found small carnivoran found at the Gray Fossil Site. This suggests that these animals had a relatively high population density, which is typical of small mammals with versatile diets. For Bristol’s Panda, the menu would have included various small animals and fruits, as well as eggs and insects, all of which are typically abundant in forested habitats. With food sources available all year round, Bristol’s Panda may have required small territories.

References & Further Reading

Wallace SC (2011). “Advanced Members of the Ailuridae (Lesser or Red Pandas – Subfamily Ailurinae)”. pp 43-59 in AR Glatston (ed), Red Panda: Biology and Conservation of the First Panda <Book>

Salesa MJ, Anton M, Morales J (2005). “Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas”. PNAS 130(2): 379-382 <Full article>

Wallace SC, Wang X (2004). “Two new carnivores from an unusual late Tertiary forest biota in eastern North America”. Nature 431: 556-559 <Full article>

Roberts MS & Gittleman JL (1984). “Ailurus fulgens”. Mammalian Species 222: 1-8 <Full article>