Meeting Abstract
21.2 Jan. 5 New Insights into Phanerozoic Oxygen Levels and their Impact on Evolution VANDEN BROOKS, J. M.; Arizona State University john.vandenbrooks@asu.edu
Variation in atmospheric oxygen levels has the potential to be one of the main drivers of long-term vertebrate evolution through the Phanerozoic. Recent models of the evolution of atmospheric oxygen through time have hypothesized a large spike in oxygen from below modern day levels in the Devonian to upwards of 30% of the total atmospheric composition in the Permian, followed by a drop to as low as 12% in the early Triassic. Such large changes in oxygen would have had significant impacts on vertebrate development and evolution. Previous research by the author has shown that varying oxygen levels have a large impact on the development of Alligator mississippiensis. These effects include changes in growth rate, the timing of developmental events, bone density, phosphate concentration within the bones, and mortality rates. Additionally, oxygen has been shown by other research groups to have an effect on the development and short-term evolution of various insect groups (e.g. body size and tracheal diameter in Drosophila melanogaster). This modern data is reviewed here and then used to critically examine changes and trends observed in both the vertebrate and insect fossil record. It has long been known that some giant insects existed during the time of hyperoxia, but here we look past the outliers for a more in depth analysis of changes through time. In the vertebrate record, the results demonstrate strong correlation between changes in allometric relationships (e.g. head/body size ratios) in both reptilimorphs and temnospondyls and the modeled variation in atmospheric pO2. Patterns of origination and extinction are also shown to be correlative with changing pO2. The fossil data is presented here and discussed with respect to the modern analyses.
