蒙古戈壁上白垩统的暴龙类额骨(英文)

记述了发现于蒙古戈壁查干泰格地点的一块额骨。短的眶缘和矢状脊的存在等特征表明,该标本属于暴龙超科。查干泰格地点出露的地层被认为属于森诺曼-桑托期的巴音沙拉组,新材料的发现为上白垩统下部非常稀少的暴龙类恐龙记录增添了新的内容。     

A New Mass Mortality of Juvenile Protoceratops and Size-Segregated Aggregation Behaviour in Juvenile Non-Avian Dinosaurs

Background

Monodominant bonebeds are a relatively common occurrence for non-avian dinosaurs, and have been used to infer associative, and potentially genuinely social, behavior. Previously known assemblages are characterized as either mixed size-classes (juvenile and adult-sized specimens together) or single size-classes of individuals (only juveniles or only adult-sized individuals within the assemblage). In the latter case, it is generally unknown if these kinds of size-segregated aggregations characterize only a particular size stage or represent aggregations that happened at all size stages. Ceratopsians (“horned dinosaurs”) are known from both types of assemblages.

Methods/Principal Findings

Here we describe a new specimen of the ceratopsian dinosaur Protoceratops andrewsi, Granger and Gregory 1923 from Mongolia representing an aggregation of four mid-sized juvenile animals. In conjunction with existing specimens of groups of P. andrewsi that includes size-clustered aggregations of young juveniles and adult-sized specimens, this new material provides evidence for some degree of size-clustered aggregation behaviour in Protoceratops throughout ontogeny. This continuity of size-segregated (and presumably age-clustered) aggregation is previously undocumented in non-avian dinosaurs.

Conclusions

The juvenile group fills a key gap in the available information on aggregations in younger ceratopsians. Although we support the general hypothesis that many non-avian dinosaurs were gregarious and even social animals, we caution that evidence for sociality has been overstated and advocate a more conservative interpretation of some data of ‘sociality’ in dinosaurs.