PROSPECTING FOR STASIS IN THE AGE OF BIG DATA

The first section of Chapter 9 of Steve Gould’s The Structure of Evolutionary Theory is titled “What Every Paleontologist Knows,” referring to one of the central aspects of punctuated equilibria (PE): morphological stasis. The forms of species tend not to change significantly over geologic time, a fact central to biostratigraphy (as noted by Eldredge and Gould, 1977). Numerous studies before and after Eldredge and Gould (1972) have demonstrated stasis prevails in the fossil record in many taxonomic groups and time intervals, yet paradoxically, challenges are still made to PE.

Because of stasis, species often have long durations, sometimes spanning millions of years. Such species durations are fundamental data in many studies. A duration is determined by the first and last appearance of a species, with stasis involving minimal morphological change between these. Unfortunately, many published species durations—as well as data in online repositories—are not supported by curated specimen data or photographic records of specimens that represent first and last appearances, or points in between. When duration data are not tied to corresponding specimen data, users of these data have limited means to verify taxonomic assignments, or independently evaluate reported durations or stasis.

Here we recommend modest changes to the standard practice of systematic paleontology that will eventually expand the number of examples of stasis and, more generally, better substantiate taxon durations: 1) systematists should clearly identify voucher specimens that represent temporal occurrences of species, especially first and last appearances; and 2) high-quality photographs of such voucher specimens (as well as types) should be placed in open access websites and be assigned public domain or Creative Commons licensing. We outline how the novel data generated by these changes to systematic practice could be integrated with existing online databases to provide readily verifiable evidence for hundreds of more instances of stasis, dramatically magnifying the putative evidence for “What every paleontologist knows.” We explore the proposed approach by investigating the temporal occurrence data that are currently available for several iconic marine invertebrate species that represent a variety of clades and time intervals.