Many dinosaur species are known from scant remains, with some estimates suggesting 75% are known from five or fewer individuals.Auroraceratops rugosuswas typical in this regard when it was named in 2005 based upon a single skull from the Gobi Desert in northwestern China. But that is no longer the case.
In the intervening years, scientists have recovered fossils from more than 80 individualAuroraceratops, bringing this small-bodied plant-eater into the ranks of the most completely known dinosaurs. It is now one of the few very early horned dinosaurs known from complete skeletons.
In a collection of articles appearing asMemoir 18in theJournal of Vertebrate Paleontologythis week, researchers from theUniversity of Pennsylvania,Indiana University of Pennsylvania, theChinese Academy of Sciences,Gansu Agricultural University, and other institutions describe the anatomy, age, preservation, and evolution of this large collection ofAuroraceratops.
Their analysis placesAuroraceratops, which lived roughly 115 million years ago, as an early member of the group Ceratopsia, or horned dinosaurs, the same group to whichTriceratopsbelongs. In contrast toTriceratops,Auroraceratopsis small, approximately 49 inches (1.25 meters) in length and 17 inches (44 cm) tall, weighing on average 34 pounds (15.5 kilograms). WhileAuroraceratopshas a short frill and beak that characterize it as a horned dinosaur, it lacks the “true” horns and extensive cranial ornamentation ofTriceratops.
“When I first saw this animal back in 2004, I knew instantly it was a new kind that had never been seen before and was very excited about it,” says paleontologistPeter Dodson, senior author on the work and a professor with appointments in Penn’sSchool of Veterinary MedicineandSchool of Arts and Sciences. “This monograph onAuroraceratopsis long-awaited.”
In 2005, Dodson and his former students Hai-Lu You and Matthew Lamanna namedAuroraceratops(in Latin, “dawn’s horned face”) in honor of Dodson’s wife, Dawn Dodson. You, along with fellow Chinese scientist Da-Qing Li—both authors on the current work—and collaborators followed up on the discovery, identifying more than 80 additional examples of the species, from near-hatchlings to adults.
Eric Morschhauser, lead author who is now on the faculty at Indiana University of Pennsylvania, completed his Ph.D. under Dodson at Penn, focused on characterizingAuroraceratopsusing this robust dataset.
Auroraceratopsrepresents the only horned dinosaur in the group Neoceratopsia (the lineage leading to and including the large bodied ceratopsians such asTriceratops) from the Early Cretaceous with a complete skeleton. This exclusiveness is significant, the researchers say, because horned dinosaurs transitioned from being bipedal, like their ancestors, to being the large rhinoceros-like quadrupedal animals most people think of as horned dinosaurs during the later parts of the Cretaceous.
“Before this study,” says Morschhauser, “we had to rely onPsittacosaurus, a more distantly related and unusual ceratopsian, for our picture of what the last bipedal ceratopsian looked like.”
Auroraceratopspreserves multiple features of the skeleton, like a curved femur and long, thin claws, that are unambiguously associated with walking bipedally in some dinosaurs.
“It can now provide us with a better picture of the starting point for the changes between bipedal and quadrupedal ceratopsians,” adds Morschhauser.
Peter Dodson is a professor of anatomy in the University of Pennsylvania School of Veterinary Medicine’s Department of Biomedical Sciences and a professor of paleontology in the School of Arts and Sciences’ Department of Earth and Environmental Science.
Eric Morschhauser is an assistant professor of biology at Indiana University of Pennsylvania and a research associate of the Carnegie Museum of Natural History in Pittsburgh. He earned his doctorate studying with Peter Dodson at the University of Pennsylvania Department of Earth and Environmental Science in 2012.
This research was funded by the National Science Foundation (Grant NSF EAR 1024671), the National Geographic Society (Grant 8930-11), University of Pennsylvania, Jurassic Foundation, 2009 National Science Foundation /Ministry of Science and Technology East Asia and Pacific Summer Institutes program (Grant OISE-0913833), National Natural Science Foundation of China (Grant 41072019), Chinese Academy of Sciences, and Gansu Geological Museum.