Morphometric analysis of the gull Larus (Aves:Laridae) with implications for small theropod diversity in the Late Cretaceous

Abstract

This project analyzed morphological diversity in the modern gull (Aves: Charadriiformes) genus Larus. Measurements of the post-cranial skeletons were made on specimens from six species of Larus and analyzed using Principal Component Analysis (PCA). Similar analyses were conducted on a series of theropod taxa. Landmark-based geometric morphometric analysis was conducted on skulls of gulls and analyzed using PCA. Results show that the gull species are very similar for the morphological parameters analyzed, only differing in overall body size and cannot be easily distinguished based on their skeletal morphology. These results were used as a modern analogue for inferring species diversity in the theropod fossil record. The implications of this study suggest that skeletal morphology may not be able to distinguish closely related species of non-avian theropods. This suggests that the species diversity of extinct non-avian theropods was likely higher than can be of determined from their skeletal remains.