Taxonomy, Cranial Morphology, and Relationships of Taxonomy, Cranial Morphology, and Relationships of

摘要

IN 1922, WELL-PRESERVED FOSSILS of the first parrot-beaked dinosaur were discovered in Early Cretaceous horizons in the Gobi Desert of Mongolia. Now referred to a single species, Psittacosaurus mongoliensis, these remains include a growth series from hatchlings to adults. In subsequent years, 15 species have been added to the genus Psittacosaurus and a second genus, Hongshanosaurus, was recently described, all from Early Cretaceous rocks in Asia. Although the second genus and about one-half of the species attributed to Psittacosaurus are potentially invalid, Psittacosaurus remains the most species-rich dinosaurian genus, with interspecific variation concentrated in the skull and dentition. This paper reviews evidence differentiating the named genera and species of psittacosaurs, outlines major cranial changes in a growth series from hatchling to adult in Psittacosaurus mongoliensis, and provides evidence of two species groups within the genus.