Using Big Data Methods to Understand Mesozoic Fish Diversity and Predation
Over the last 500 million years there have been numerous extinction events that have led to the diversification of animals. Non tetrapod vertebrates (fishes) do not display the same turnover events as other vertebrate groups. It is hypothesized that the ‘Big Five’ mass extinction events did not have a firsthand effect on fish diversity. Fish diversification is thought to drive the Mesozoic Marine Revolution (MMR) - the rapid adaptation to shell-crushing and drilling predation in benthic organisms throughout the Mesozoic era. The lack of representation of fish in existing fossil compendia is a big confound to our understanding of fish turnover events and marine revolutions. The aim of this project is to map the biodiversity of fishes and address these hypotheses by cataloguing the existence of thousands of species in the Cretaceous and Jurassic eras.
A database was created using google scholar to sort through research papers, museum collections and books. Fossil fishes from the Cretaceous and Jurassic era were catalogued according to occurrences, regional stages, environment and taxonomic categories. The data was cleaned for visualization to analyze distribution of species by regional stage, distribution of genera by regional stage, global distribution of species in each regional stage and distribution of species by Cretaceous stage (lower or upper) as well as Jurassic stage (lower, middle and upper). The data collected was compared to the Paleobiology Database (PBDB) the existing compendia on fossil fishes.
Results showed that the newly created Jurassic database was 51% larger than the existing PBDB data, and the newly created Cretaceous database was 30% larger than the existing PBDB data. The data also shows a huge decline in fish diversity at the end-Jurassic, with low diversity in the early Cretaceous, and another huge decline in the Cenomanian-Turonian, none of which was apparent in the PBDB data. In contrast, there’s a diversity spike at the Toarcian, which suggests that fishes were not affected by that Ocean Anoxic Event which eliminated some bottom-dwelling invertebrates.
The data collected so far supports the hypothesis that fishes do have different extinction events when compared to bottom dwelling invertebrates, and are more like marine reptiles, ammonoids and other free-swimming species. Further time series analysis and ecological/phylogenetic comparisons will reveal patterns and further our understanding in macroevolution.