It has been a good year for horned dinosaurs. The recent description of Mojoceratops, the discovery of
Understanding the significance of the newly-described dinosaur requires a little background information. As with tyrannosaurs, horned dinosaurs are organized via a nested tree of different groups, with each term marking a different degree of specificity. Within this scheme the Ceratopsia is the most inclusive group—containing everything from early forms such as Yinlong all the way to Triceratops—whereas the Ceratopsidae is subset of this larger group which includes the stereotypical quadrupedal herbivores with gnarly frills and horns on their faces. Ceratopsians which sit near the base of the horned dinosaur family tree have been found in China before, but the new Chinese Science Bulletin paper is the first notice of one of the specialized ceratopsids from the area.
Named Sinoceratops zhuchengensis, the new dinosaur is represented by the top portion of a skull and a partial frill discovered in the approximately 75-million-year-old rock of Shandong, China. From what is known of it, Sinoceratops appears to have been a centrosaurine ceratopsid, or, in other words, belonged to the subset of ceratopsid dinosaurs with large nasal horns and small frills which includes Styracosaurus and Pachyrhinosaurus. Given that the scientists placed it at the base of the centrosaurine family tree, Sinoceratops does not share some of the specializations seen among other members of the group, but its archaic traits may indicate what the ancestors of the first centrosaurines were like. Provided further discoveries support the hypotheses put forward in the new paper, Sinoceratops may act as a transitional form which could help explain how the centrosaurine dinosaurs evolved and may even indicate that ceratopsid dinosaurs evolved in Asia before dispersing to North America.
Still, as the new paper points out, among the most important aspects of the discovery of Sinoceratops is that it shows that ceratopsids were present in China. As is well known among paleontologists, there is a remarkable correspondence between the Late Cretaceous dinosaurs of North America and Asia—tyrannosaurus, hadrosaurs, ankylosaurs, pachycephalosaurs, and others—but until now ceratopsids seemed to have stuck to North America. Now we know otherwise, although the fact that it took so long to find the bones of a ceratopsid in Asia may be indicative of barriers—in terms of geography or environment—that prevented this group of horned dinosaurs from proliferating in Asia as they did in North America.
XU Xing, WANG KeBai, ZHAO XiJin & LI DunJing (2010). First ceratopsid dinosaur from China and its biogeographical implications Chinese Science Bulletin, 55 (16), 1631-1635 DOI: 10.1007/s11434-009-3614-5