Meeting Abstract

59.6  Jan. 7  Crocodylian Phylogeny & Cranial Ecomorphology SADLEIR, R.W.; Univ. of Chicago, Field Museum rsadleir@uchicago.edu

Conflicting phylogenetic signals, character homoplasies, and character atavisms typify crocodylian phylogeny. Most phylogenetic ambiguity involves Gavialis and Tomistoma, for whom a secondary signal showing 70% of the characters supporting incongruent topologies is associated with their slender skull. Slender-snout skulls are one of five identified eusuchian cranial morphotypes thought to reflect functional or ecological specialization. Using concentrated changes tests, the effect of ecomorphology on cranial character state gains in phylogeny was tested for transitions among general, blunt, and slender ecomorphs. 120 published cranial characters were tested on the gains of three skull ecomorphs using a 92-taxon morphological phylogeny, a 13-taxon molecular phylogeny, and a 62-taxon combined-data phylogeny. In addition, trees were reduced to 11 taxa to test the effect of taxonomic sample size on hierarchical signals identified by reverse successive weighting. Because concentrated changes requires resolved tree polytomies, its analytical power is limited. Therefore, �tree-free� character compatibility tests of character independence were conducted on the morphological data matrix. Test results suggest ecomorphs affect cranial character state gains in phylogeny. Concentrated changes identify 52 character state changes that significantly correlate with transitions to the slender ecomorph, and 40 character state changes that significantly correlate with transitions to general and blunt ecomorphs on morphological, molecular, and combined-data tree topologies. Since cranial ecomorphs affect character state transitions, non-phylogenetic variables could mislead crocodylian phylogeny by affecting cranial morphology.