Psittacosaurus Juvenile Herds

Juvenile-only clusters and behaviour of the Early Cretaceous dinosaur Psittacosaurus

Authors:

1. Qi Zhao (a,b)
2. Michael J. Benton (a)
3. Xing Xu (b)
4. Martin J. Sander (c)

Affiliations:

a. School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK a

b. Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China

c. Division of Paleontology, Steinmann Institute, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, D-53115 Bonn, Germany.

Abstract:

It has hitherto been hard to prove that any association of juvenile dinosaurs represents original behaviour rather than sedimentary accumulation, and it has been hard also to determine the ages of such juveniles. A previously described specimen, which consists of an ‘adult’ Psittacosaurus with 34 fully articulated juveniles, turns out to be a composite: the ‘adult’ skull has been added, and in any case it is below breeding age. Other juvenile-only clusters have been reported, but the best examples that likely reflect behaviour rather than sedimentary accumulation are specimens from the Early Cretaceous Lujiatun beds in NE China, which were entombed beneath pyroclastic flow deposits. A remarkable juvenile-only cluster of Psittacosaurus shows clear evidence of different ages (five 2-year olds and one 3-year old) based on bone histological analysis. These juveniles may have associated together as a close knit, mixed-age herd either for protection, to enhance their foraging, or as putative helpers at the parental nest.