Fossil Calibration Database
The Fossil Calibration Database is an open-access database that curates vetted calibrations that meet the five Best Practices outline by Parham et al. (2012). James Parham and I led a series of NESCent Working Group meetings bringing together a group of 25 paleontologists, molecular biologists and programmers to launch this database.
The Fossil Calibration Series at Palaeontologia Electronica publishes peer-reviewed fossil calibrations which are accessioned directly to the Fossil Calibration Database. Articles describing the phylogenetic and stratigraphic justifications for 135 fossil calibrations have been published to date, and we are actively seeking new contributions.
The Fossil Calibration Database was created with funding from the NESCent (NSF EF-0905606) award “Synthesizing and Databasing Fossil Calibrations: Divergence Dating and Beyond” (to DTK and JFP) and is supported by Palaeontologia Electronica. An Encyclopedia of Life BioSynC Synthesis Meeting award (to JFP) was critical to the conception of the database.
Dating the Avian Tree of Life
One of my broader interests is the timing of the radiation of modern birds, and how fossil and molecular data inform our understanding of this event. Across dozens of studies, there has been a high level of disparity between fossil ages and molecular divergence dates for major avian clades. Kristin Lamm, Jessica Ware, and I showed that this disparity is more pronounced for younger clades. This is counter-intuitive from the perspective of the fossil record, which in general becomes more complete towards the present. Thus , the pattern suggests that model misspecification in molecular dating analyses may be an important driver of disparity. Expanding on these empirical observations, Matt Phillips and I found solid evidence for tree compression / extension operating in empirical analyses of mitochondrial and nuclear datasets. Our preferred scenario for the modern avian radiation posits just a handful of lineages crossing the K-T boundary, followed by a rapid radiation in the Paleocene and Eocene.
HIstorical patterns in the perceived completeness of the fossil record is another related area of interest. Clint Boyd and I have mapped out the pattern of discoveries filling in stratigraphic gaps in the avian fossil record across the last century. Our data show a pronounced uptick in improvement in the last few decades, but also suggest we may be approaching an era of diminishing returns in terms of pushing back the origination dates for major groups of birds. We also note the profound effect of applying phylogenetic methods to existing fossils, which accounts for a substantial part of the improvement above and beyond new fossil discoveries. We're working on extending the method to accommodate completely extinct groups like non-avian dinosaurs.