The Tibetan Plateau and the formidable Himalayan mountains to the south are known as the “Roof of the World,” with towering peaks and expansive high-altitude plains. Explorations over the past century, either for scientific or for personal, spiritual or nationalistic purposes, are immortalized in books, documentaries and urban myths. My team’s expeditions to Tibet began without much fanfare. Our goal was simple: to systematically document the fossils present in the remote western reaches explored previously by geologists but not vertebrate paleontologists.
Since 2006 we have focused our efforts in a stretch of badlands in the Zanda Basin. Zanda’s badlands cover an area larger than Yellowstone National Park and are transected by a river called the Langqen Zangbo, which flows westward into India. A group of us makes the pilgrimage yearly from Los Angeles to Beijing, where we set off in field vehicles on the seven-day cross-country trip to western Tibet. The final descent from the plateau into the basin is a sight to behold no matter how many times I return here for field work: With the permanently snowy peaks of the Himalayas as the backdrop, our vehicles snake through barren cliffs that take us backward through time as we pass deeper and deeper rock layers. Reminders of the perils of the expedition can be seen at the bottom of the cliffs, where fallen and crushed cars remain year after year. We finally reach the level of the Langqen Zangbo, where the small town of Zanda sits on a terrace overlooking the majestic river valley.
August 2010 started as a typical field season, except that it was the first time since our wedding that my wife, Juan, and I were on an expedition together. (We met while doing fieldwork in the northern Tibetan Plateau in 2005.) I was a graduate student at the University of Southern California and she at the University of Alberta. Our drivers skillfully navigated the intricate valleys on dirt trails to bring us close to rock exposures that looked promising from our satellite maps. We parked the vehicles just off the trail and split into small groups to search for fossil remains of extinct mammals and other animals.
We stopped as disbelief sank in: This looked like the top of a cat skull.
Feeling caged in between the cliffs, I proposed to hike directly to the top with Gary Takeuchi, a good friend and experienced field paleontologist from the Page Museum of Rancho La Brea in Los Angeles. Juan decided to take another route, going up a different hill while prospecting. Gary and I bee-lined to the top of the cliffs, where the view was much better. Much to our dismay, we found no traces of fossils, not even a fragment. We received a call over the two-way radio from Juan; She had found some fossil bone fragments on a gentle slope about halfway down the adjacent hill. After getting the sense that the fragments were significantly weathered, Gary and I pressed on over the ridge into the unknown. Not a few minutes passed before we received another radio call, this time from Qiang Li of the Chinese Academy of Sciences; he took a look at what Juan has found and urged us to join them for further examination.
Without having found even a single piece of bone, Gary and I called off our hike and met Juan and Qiang. As we approached we could see numerous fist-sized fossil bone fragments scattered throughout the flat area they were standing in. Picking through them like an old lady picking through a basket of fruit, I looked for diagnostic bits and pieces to identify at least some of the fossils to a specific group of animals. (Almost all were mammals.) Toe bones of horses and rhinos, and limb bones of extinct antelopes were immediately apparent. Most of those species were already known from previous collections in the basin, so I was not greatly impressed with Juan’s find.
Then I saw a broken lower jaw that belonged to a carnivore.
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.
Z. Jack Tseng is a Frick postdoctoral fellow at the American Museum of Natural History.