The impact of the Pull of the Recent in extant elasmobranchs

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.