Sauropod dinosaurs—like the Diplodocus (dip-LOW-duh-cus) in the Dinosaurs and Fossils Gallery—had big bodies and teeny heads. Their fragile skulls were paper-thin in places. This means sauropod heads are among the rarest of dinosaur finds. Paleontologists have found about a dozen skulls from the Jurassic Period (208-144 million years ago), but no complete Cretaceous Period (144-65 million years ago) skulls in North America. Until now.
Scientists at Dinosaur National Monument in Utah are studying four Cretaceous sauropod skulls found in their quarry over the past few years. All four are the same type, from a new species that lived about 100 million years ago. And the skulls are unusually well preserved. (Sauropod skulls aren't single bones, but collections of very delicate bones. When the animals died, the heads usually separated from the bodies and the skulls fell apart or scavengers scattered them. The fragile pieces usually didn't fossilize.)
Sauropods were very common in the middle part of the age of dinosaurs, the Jurassic Period. But they became rarer in the Cretaceous. The skulls may offer valuable clues to the evolution and eventual extinction of this impressive group of beasts.
A lucky break
The paleontologists at Dinosaur National Monument found one extremely well preserved and articulated (not in pieces) skull, a second disarticulated skull (with all its pieces), the snout from a third animal, and the brain case of a fourth. Who knows? There may be many more in the quarry.
How did four skulls end up together? Scientists can't know for sure. The quarry site was a stream or river 100 million years ago. Maybe a herd of dinosaurs was crossing the river and these animals drowned. Or maybe they died during a drought, waiting beside a dried-up river, and a later flash flood washed all the bones together.
The Minnesota connection? Nature's little miracle...
Science Museum paleontologists found this intact juvenile Diplodocus skull at Poison Creek Quarry, near Buffalo, Wyoming. It's about 150 million years old, and from the Jurassic Period, not the Cretaceous. The thin, juvenile bones make this skull even more delicate than other sauropod skulls and an even luckier find. It's so well preserved that you can see a row of small replacement "bud" teeth coming in along the upper jaw.
The remains of other dinosaurs were also found in the quarry—including the adult Diplodocus, one of the Camptosaurs, and the Apatosaurus femur on display in the Dinosaurs and Fossils Gallery. 150 million years ago, the quarry was a flood plain. The bodies of the dinosaurs that died there piled up in quiet backwaters, and sediments buried the bones and preserved them. Because so many skeletons from the quarry were still articulated, we know that the water wasn't moving fast and scavengers didn't disturb the bodies. These conditions also helped to preserve this skull.
A treasure map
This is a section of SMM paleontologist Bruce Erickson's map of the Poison Creek quarry. You can just see the snout of the Diplodocus skull peeking out from under the articulated neck bones of an adult Diplodocus. (The adult skeleton shown in this map is the one mounted in the Dinosaurs and Fossils Gallery.)