Читать книгу Hadrosaurs - David A. Eberth - Страница 40

A new systematic analysis is presented here for the explicit purpose of exploring the nature of putative phylogenetic relationships between a range of more derived non-hadrosaurian ornithopods. Twenty-four taxa (Appendix 2.1) were selected for this analysis because they are known from generally well preserved skulls and/or skeletons, and have been reasonably well described. A significant number of additional taxa have been named in very recent years but these are, on the whole, more fragmentary, and their addition to the analyses materially affects the resolution and stability of tree topology. These have been removed a priori. More comprehensive analyses incorporating these additional taxa, as well as more basal ornithopods, are being considered in more detail elsewhere (Norman, in press). Lesothosaurus (based on the descriptions of Thulborn [1970, 1972], and the supplementary information from Sereno [1991]) is used as the outgroup taxon (Butler et al., 2008) in order to polarize character-states. The character-states and their codings are presented in Appendix 2.2, and these comprise a suite of 92 characters that have been generated after reassessment and revision of previously published character lists (e.g., Norman, 2004; McDonald et al., 2010; Prieto-Márquez, 2010; Wu and Godefroit, 2012). Unusually, compared to the general trend in the literature, the number of characters used is fewer rather than greater. The data matrix was constructed in MacClade 4.06 (Maddison and Maddison, 2003), and the analysis was undertaken using PAUP* 4.0b10 (Swofford, 2002). All characters were equally weighted, and were first analyzed as “unordered” using the Branch and Bound search option (and the analysis was run twice using ACCTRAN and DELTRAN optimizations). Because a substantial number of characters used in this analysis are multistate in nature, a second run was undertaken using the “ordered” character option. The matrix was again analysed using Branch and Bound search option and was run under both ACCTRAN and DELTRAN optimization protocols.

2.23. Iguanodon bernissartensis. Reconstruction of the skeleton, modified from an earlier original drawing by Gregory S. Paul (from Brett-Surman, 1997).