CHARACTER ANALYSIS OF THEROPODA: A BRIEF STUDY CONFINED TO BRAINCASE CHARACTERS AND FOCUSING ON BASAL TAXA

Phylogenetic study of basal Theropoda has largely been ignored historically due to a paucity of specimens, but recent discoveries of many basal theropods and development of new technologies have encouraged a new interest in the study of these early theropods. Because paleontology is limited by the specimens available for study, the effort to collect more data often results in the attempt to find and use as many characters as possible in phylogenetic studies. This study arises from an interest in assisting researchers in the use of braincase characters for their analyses. Until recently, braincases where considered to be conservative and of not much use for phylogenetic studies. In this study, 51 braincase characters derived from 3 recent phylogenetic studies (Carrano, Benson, and Sampson 2012; Smith, et al. 2007; Turner, et al. 2007) were analyzed by tracing the character history in the phylogenetic program Mesquite against a tree constructed from the aforementioned papers. This analysis aims to identify characters falling into 1 of 3 groups: 1) characters which support this phylogeny, 2) characters which contradict the hypothesized relationships between taxa or suggest that the characters reflect environmental rather than genetic constraints, and 3) characters which require a more complete scoring to provide information on the type of pattern reflected by the character history. At least 16 characters are possible synapomorphies or generally support the tree and at least 5 characters seem to be contrary to the relationships hypothesized in the tree.