Psittacosaur Growth Rates

Summary

The focus of this article centers around the histological examinations of several different specimens of psittacosaurs so as to determine the overall rate of growth of a psittacosaur. This data could then be used to determine if psittacosaurs were able to compete with other species during that time. Such data could hold insights as to why this particular dinosaur went extinct. Since dinosaurs are relatively rare finds and single specimens are often all that is found of a species at any one time, it becomes necessary to study changes in ontogeny, being that this is one of the only ways to infer the life history of individuals. Several samples of long bones from psittacosaurs that ranged from juvenile to adult specimens were subjected to several tests and measurements to determine growth patterns in psittacosaurs at different life stages. The findings show that as psittacosaurs grew, the vascular structure within the bones changed and became more complex. Such a change allowed not only for fast development within the psittacosaur, but also the ability to be more active and competitive.

Review

The study presented by Erickson and Tumanova examines the microstructure within the long bones of seven specimens of the ceratopsian dinosaur known as psittacosaurus monogoliensis. The desired results from this study are an understanding of the growth a psittacosaur undergoes at different stages in its life. A set of such data would help researchers to understand the variation in psittacosaur growth. With this, one could compare the growth of a psittacosaur to that of other dinosaurs and also bird and mammal species of the Cretaceous period when this dinosaur existed, in order to see whether or not psittacosaurs were at an actively competing level with these other species. Since dinosaur finds are relatively rare, and it is even less common to find several of one species at a given location, it becomes difficult to infer life history of that specimen. By using histological data of the fossils however, one can examine many different aspects of individual life histories across a field of specimens by using only one set of data.

By comparing the growth rates of different specimens of psittacosaurs, one can infer a portion of the life history of individual psittacosaurs, regardless of morphological changes that may be present from individual to individual. To determine this, a range of psittacosaurus specimens was needed, spanning from juvenile to adult in age and size. The long bones, meaning bones that are significantly longer than they are wide, were selected. Three bones in particular, the tibiae, femora and humeri from seven different psittacosaurs were chosen for histological analysis. This was done by cutting one-millimeter thin sections of the selected bones and viewing the thin sections under a petrographic microscope at magnifications between 20 and 400 x and examining, among other things, the growth lines in the thin sections