1998/04/10 by David K. Smith · 8 citations
Earth and Planetary Sciences · Mathematics · #Evolution and Paleontology Studies #Morphological variations and asymmetry #Paleontology and Evolutionary Biology
paper · doi:10.1080/02724634.1998.10011039
openalex publication_date 1998/04/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
Population variation in Allosaurus fragilis is estimated using a principal components analysis. Specimens included in this analysis were found at Como Bluff, Dry Mesa, Dinosaur National Monument, Canyon City, and Cleveland-Lloyd quarries. Except for the material identified as Allosaurus (Saurophaganax) maximus, there is only one species of Allosaurus indicated in the Morrison Formation. Almost all of the variables on all elements load heavily on the first principal component, a size factor. Loading patterns on the successive components contribute to a correspondingly low shape influence. Some of the elements display two clusters along the allometric trajectory, probably reflecting sexual dimorphism. The non-Cleveland-Lloyd specimens tended to be larger than those from Cleveland-Lloyd, but there is no evidence of consistent evolutionary or geographic trends. A comparison of the second principal component, interpreted as the main shape factor, for Allosaurus with that of Plateosaurus showed that there was less shape variation in the theropod. This result may be of systematic importance.