Re-examining ratio based premaxillary and maxillary characters in Eudromaeosauria (Dinosauria: Theropoda): Divergent trends in snout morphology between Asian and North American taxa

摘要

The clade Eudromaeosauria predominantly comprises medium to large Late Cretaceous Laurasian dromaeosaurids. Because many specimens are fragmentary, the maxilla has frequently been used to infer the proportions of the entire snout. Given the strong relationship between snout shape and feeding behaviour, such inferences have potentially important palaeobiological implications, but they should ideally be justified by explicit analysis. Maxillae have also been hypothesized to have high interspecific variability and are used to erect new taxa. However, many maxillary characters are based on proportions that may vary ontogenetically, sexually, and randomly within species, as well as phylogenetically. Proportionate characters are often unjustifiably coded in terms of discrete states even when they represent a continuum of variation.