The impact of the Pull of the Recent on extant elasmobranchs
Pimiento, Catalina; Benton, Michael (2020), The impact of the Pull of the Recent on extant elasmobranchs, Dryad, Dataset, https://doi.org/10.5061/dryad.6hdr7sqw4
Modern elasmobranchs have a long evolutionary history and an abundant fossil record. Many fossil taxa have living representatives. However, the representation of extant taxa in the fossil record is unknown. To begin to understand the geological history of extant elasmobranchs, here we assess the quality of their fossil record. We do so by assessing the Pull of the Recent (herein, POR). The POR can bias the fossil record because the rather complete record of living taxa allows palaeontologists tobridge time bins where fossils are absent. We assessed the impact of the POR by quantifying the proportion of extant elasmobranchs that have a fossil record, but do not occur in the last 5 million years. We found that the POR does not affect orders and families, but it does affect 24% of elasmobranch genera. Although modest, the impact of the POR in extant elasmobranch genera is higher than that found in other taxa. Overall, the geological history of elasmobranchs contradicts the usual assumption that the fossil record becomes worse backwards in time. This is the case across geographical regions and tooth size, further suggesting that sampling intensity and outcrop availability can help explain the POR effect on sharks and rays.
We gathered a list of all extant elasmobranchs (class: Elasmobranchii) from FishBase (http://www.fishbase.org) using the R package “rfishbase” (Boettigeret al.2012)and cross-referenced it with Weigmann (Weigmann 2016). In total, we gathered a list of 1,163 species, 193 genera, 58 families and 12 orders. Then, we downloaded all available fossil occurrences of these taxa from the Paleobiology Database (http://paleobiodb.org/)using the package “paleobioDB” (Varelaet al.2015). Because our objective was to assess the completeness of the fossil record of living taxa in the last 5 million years, we limited our search to the Neogene and the Quaternary. Additional records were found in Shark-References (http://shark-references.com). In total, we studied 310 publications not previously entered in the Paleobiology Database, adding new fossil occurrences for 58 genera and 59 species. We searched for records using valid names and their synonyms.
We assessed the number of extant taxa (at the order, family, genera and species level) that have a fossil record in the in the Neogene and Quaternary (the last 23 myr), recording fossil occurrences in seven geological time bins as follows: early Miocene (Aquitanian and Burdigalian), middle Miocene (Langhian and Serravallian), late Miocene (Tortonian and Messinian), early Pliocene (Zanclean), late Pliocene (Piacenzian), early Pleistocene (Gelasian and Calabrian), and late Pleistocene (Middle and Upper). Whenever an age covered multiple time bins (e.g. Pliocene), we counted it in all bins covered (e.g. both the early and late Pliocene). Based on this number, we calculated the proportion of taxa that do, and do not have a record in the Pliocene or Pleistocene (Sahney and Benton 2017; Jablonski, et al.2003). We also recorded the geographical distribution of the fossil occurrences [based mainly on the Paleobiology Database and Cappetta (2012)], categorized tooth size [macro-teeth: >1cm of crown height; micro-teeth: <1cm; based on Cappetta (2012)], and assessed the effect or POR across regions and tooth size.
Supplemenatry references. Additional references found in shark-refences.com
Table S1. Genera of extant elasmobranchs and their fossil presence or absence across time bins.
Table S2. Species of extant elasmobranchs and their fossil presence or absence across time bins.
Table S3. Genera of extant elasmobranchs and across geographic regions and tooth type.
H2020 Marie Skłodowska-Curie Actions, Award: 663830