DOI: 10.5061/dryad.6hdr7sqw4
title: The impact of the Pull of the Recent on extant elasmobranchs

description: 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.
description: We gathered a list of all extant elasmobranchs (class: Elasmobranchii) from FishBase (http://www.fishbase.org) using the R package “rfishbase” (Boettiger<i>et al.</i>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” (Varela<i>et al.</i>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 <i>extant </i>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<i>, et al.</i>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: &gt;1cm of crown height; micro-teeth: &lt;1cm; based on Cappetta (2012)], and assessed the effect or POR across regions and tooth size.
description: <strong>Supplemenatry references. </strong>Additional
 references found in shark-refences.com
 <strong>Table S1.</strong> Genera of extant
 elasmobranchs and their fossil presence or absence across time
 bins. <strong>Table S2.</strong> Species of
 extant elasmobranchs and their fossil presence or absence across time
 bins. <strong>Table S3. </strong>Genera of
 extant elasmobranchs and across geographic regions and tooth
 type.