Meeting Abstract
P1.199 Saturday, Jan. 4 15:30 Macroevolutionary Impact of Hypothesized Artiodactyl Key Innovations O’BRIEN, H.D.; Ohio University haley.d.obrien@gmail.com
Many fruitful macroevolutionary studies focus on extreme differential survivorship of phenotypically similar clades, such as the ungulate orders Artiodactyla and Perissodactyla. Although similar in phenotype, life history, and historic diversity, there are 14-fold more artiodactyl taxa. This pattern of extant diversity coupled with a rich fossil record renders ungulates an intriguing model to investigate mammalian evolutionary trends. Here, novel phylogenetic comparative methods and fossil-based evidence are used to examine whether hypothesized artiodactyl key innovations (foregut fermentation [FF] and thermoregulatory cranial vasculature [TCV]) have influenced ungulate diversification and extinction rates. First, diversification and extinction rates were calculated from a time-calibrated mitochondrial phylogeny of Euungulata. Three peaks in diversification were identified: the middle Eocene, the early Miocene, and across the Pliocene and Pleistocene, when the majority of modern taxa arise. Next, presence/absence of FF and TCV were mapped onto the phylogeny, and binary-state speciation and extinction analyses were used to calculate trait dependent diversification rates. Among extant taxa, these rates are not significantly different for each proposed key innovation—likely due to significant trait distribution overlap among living ungulates. Therefore, these traits were sought in fossil specimens, using osteological correlates for TCV and dental proxies for FF. Data from fossils reveals that few extinct ungulate clades overlap in distribution of TCV and FF, and that the origins of these specialized features coincide temporally with peaks in diversification rates. Incorporation of diversification patterns among extinct taxa supports the hypothesis that unique digestive and thermoregulatory physiologies are contributing to the generation of modern ungulate diversity.
