The fossil jaw was missing its front and back ends, and the cheek teeth in the middle had been broken off. However, based on the fact that the roots of the missing teeth provided a tooth count of three (two premolars and one molar), this jaw likely belonged to a specialized meat eater in the cat family. Other carnivores, such as canines and hyenas, tend to have more cheek teeth in their jaws, allowing them to eat a more generalized diet. Cats, on the other hand, specialize in processing soft tissues of their prey using the trenchant cheek teeth in their upper and lower jaws.
As we picked scattered fragments on the slope, we noticed that some appeared to be sticking out from the rocks below them. These bones were not all on the surface. We did a little bit of brushing and realized that multiple bones were half-buried in the ground. The arrangement of the fossil limb bones and mixed pebbles indicated that the fossils had been concentrated here by flowing water in a creek or near a delta. An impromptu meeting was called over the radio, and within the hour the entire expedition had gathered at this site.
After our trip leader, Xiaoming Wang, approved a preliminary excavation, we got to work on exposing more bones just beneath the surface. At this point we knew only that this was a relatively rich site for fossils, but nothing in particular seemed out of the ordinary. Concentrated fossil deposits, or bone beds, are not a rare occurrence in other fossil-rich regions of the world, although this would be one of the first bone beds to be found in Tibet. We set up a grid system to map the locations of the bones in three-dimensional space.
By the third day of the excavation, we had a sizable list of mammal species that could be identified from the fossils we pulled out of the bone bed, now known as locality ZD1001 (ZD for Zanda, 10 for the year 2010, and 01 for the first site to be discovered that year). In addition to the antelopes, horses, and rhinos, we added a fox and a badger to the list. But nothing prepared us for what we found next.
After finding five or six antelope limb bones, we were ready to take some of the fossils out in larger chunks to save time, when we brushed away the sand to find the forehead of a skull among the limb bones. Thinking we could have a skull to go with the numerous antelope fossils, we brushed and chipped away the surrounding regions with great anticipation. By the time most of the eye sockets and the snout were uncovered, we stopped as disbelief sank in: This looked like the top of a cat skull.
Species in the mammal group Carnivora are among the most carnivorous and specialized of all predators. These species usually occur in small populations compared with their more abundant prey, and this difference lowers the probability of finding bones of carnivores preserved as fossils. That is why we could not believe our eyes when a catlike skull emerged from our brushstrokes. The eye sockets of this critter were round and broad, and the exposed part of its snout was short, its braincase rounded. The unmistakable sagittal crest for the attachment of powerful jaw muscles added to our increasing confidence in this discovery of the first fossil cat from Tibet.
And that was only the first surprise. We covered the skull in plaster bandages and carved a chunk of rock containing it out of the ground to take back to the laboratory. It was not until later in the year that we finally saw what we had, the skull skillfully extracted from its plaster sarcophagus by paleontological preparator Howell Thomas of the Natural History Museum of Los Angeles County. Subsequent preparation of additional plaster casings from the site provided additional fossils of the same species, and collections in 2012 brought the total count of fossils representing this cat species to seven, belonging to at least three individuals. Research into the identity of these cats commenced in 2011, involving the joint efforts of scientists from seven research institutions around the world.
The fossils represent a new species of extinct big cat. Anatomical features unite it with the snow leopard as a unique lineage adapted to the high-altitude, low-temperature environment of the Himalayas. The presence of fossil relatives of the snow leopard’s prey, such as sheep, antelope, and pika, indicates that the fossil cat may have had a similar diet and environment as its living relative. The new fossils are between 5.95 million and 4.10 million years old. This week the species is finally presented to the world as the oldest known fossil big cat. Its name, in honor of the snow leopard-loving daughter of supporters of research at the Natural History Museum of Los Angeles County, is Panthera blytheae, or Blythe’s panther.