protoceratops

This is a story about the ancient environments of Protoceratops, the diminutive, plant-eating dinosaur that first thrilled the world 80 years ago when Roy Chapman Andrews cabled reports of its existence to the United States (see Fig. 1). Andrews' teams had found the remains of the beast and its eggs, demonstrating for the first time that dinosaurs laid eggs. The discovery was made at the remote Flaming Cliffs area in the Gobi Desert in southeastern Mongolia. As remote as Mongolia was from the United States of the 1920s, however, the 70-million-year-old world Andrews unearthed was infinitely farther removed.
      As it turned out, that world was perhaps too far removed from Andrews, because much of what he concluded has since become suspect. In 1995, researchers from the American Museum of Natural History showed that Andrews' Protoceratops eggs actually belong to Oviraptor. Oviraptor, a creature whose name (literally "egg thief") belies its motherhood, was actually guarding its own nest. With the eggs shown to belong to another dinosaur, what did we really know about Protoceratops? Since 1993, I have traveled regularly with Japanese Mongolian Expeditions to the Gobi Desert to find some answers.
      The Gobi is still remote. Planes fly into Beijing, Seoul, and Osaka, but then the isolation sets in: To reach our research sites, we have to fly to Ulan Baator and then ride in converted Russian troop carriers for three days on bumpy dirt trails (or no trails) to the heart of the Gobi Desert (see Fig. 2).
      With temperatures exceeding 110^o F, the Gobi is as inhospitable as it was in Chingis (or Genghis) Khan's day. It consists primarily of plateaus paved with chert pebbles that glisten from incessant polishing by dust-laden winds. A few scrubby shrubs struggle to survive. Peeking out from beneath the plateaus are soft and treacherous sandy exposures, the remnants of the 70 million-year-old dinosaur-bearing landscapes.
      Our expeditions haul gas and water with lumbering, overloaded Russian trucks that commonly founder in the pliant sands and must be dragged free (see Fig. 3). Cables are attached, go taut, wheels spin, and cables snap: it is always a rather uncertain process at best. We carry some food, but much we buy on the hoof (literally) from nomadic herdsmen who raise sheep and goats for meat and keep camels and horses for transportation, milk, cheese, and an alcoholic yogurt called airag.
      We cannot carry all the water needed for six weeks. Instead we hunt for wells using old Russian maps and the advice of local herdspeople. The wells were built in the 1960s and consist of large, low cement pyramids, each with a long handle and a trough. Most no longer function, and the housings and troughs have weathered into large, useless cement slabs. Some functioning wells yield surprises: at one well, after fighting biting flies and hauling about 80 gallons of water, bucket by bucket, the last bucket brought up a dead bird.
      The modern-day Gobi takes its toll on all who live there. For those of us unaccustomed to these conditions, it can be brutal. What was it like 70 million years ago when the dry sands that trapped our expedition were part of the living landscape?
      The answer was found, along with specimens of Protoceratops, at Tugrikin-shireh in the south central Gobi Desert. Tugrik, as it is commonly known, is the richest fossil locality that I have ever seen. The skulls and postcranial bones of Protoceratops are everywhere and five or six complete skeletons were found along a horizon that we dubbed "Protoceratops Row" (see Fig. 4). Why was Protoceratops so abundant at Tugrik? Did it live there, or were its remains somehow concentrated into an extremely rich deposit?
      The evidence that Protoceratops lived at Tugrik came from the 1994 discovery of two nests full of babies. The nests are small, bowl-shaped depressions that contain as many as 15 babies, each about 6 inches long (see Fig. 5). In both nests, the babies' heads are oriented in the same direction, facing away from the ancient prevailing winds. Protoceratops must have lived at Tugrik if it built nests there.
      What was Tugrik like 70 million years ago? The answer is in the sands. We recognized large dipping surfaces, hundreds of meters long, which could be unambiguously reconstructed as the lee faces of gigantic ancient sand dunes (see Fig. 6). These ancient dunes were the kind that occur in modern dune-rich deserts, such as the Sahara. The ancient Tugrik dunes were large; as high as 80 feet and, given their size and distribution, they must have been extensive. Windblown sand dune fields---sand seas---are today called ergs. The ubiquitous sand that surrounded us was ubiquitous 70 million years ago: Protoceratops lived in the midst of an erg.
      What was a nice dinosaur like Protoceratops doing in a place like this? The skull bones and teeth indicate Protoceratops was well-suited to cropping and shearing plants. And yet this was not the kind of environment in which one might expect much vegetation. Again, Tugrik surprised us. Some of the ancient lee sides of the dunes preserve forests of beautifully lithified plant roots intertwined with insect burrows (see Fig. 7). This suggested that despite the desert environment, Tugrik was rich and productive. We can speculate that the ancient denizens of Tugrik were adept at obtaining moisture, perhaps from early morning dew. Tugrik must have been a thriving ecosystem, as the fossils reflect an abundance of life.
      Why it ended remains a mystery. At Tugrik, it appears that life was snuffed out by the relentless migrating sand dunes. Most likely, they stilled the nests of embryos and caused the deaths along Protoceratops Row. Protoceratops and its cohorts may have mastered living in a sand sea, but one suspects that this extreme environment, like its modern counterpart, allowed few missteps.