The impact of the pull of the Recent on the fossil record of tetrapods

Question: Why has there been an apparently exponential rise in the global diversity of life on land in the past 120 million years? Hypothesis: Most of the apparent rise in diversity is an artefact of improved sampling towards the present day. A particular bias, the Pull of the Recent (POR), affects those fossil taxa with living representatives, by artificially inflating their numbers. Organisms: The fossil record of tetrapods (amphibians, reptiles, mammals, and birds). Methods: Compare lists of extant families and genera with totals and proportions that do, and do not, have fossil records in the Plio-Pleistocene. Results: The POR extends its influence back to the early Eocene, accounting for at most 6.1% of the increase in tetrapod family diversity and 1.3% of generic diversity. Small animals, insectivores, and birds are most affected by the POR, perhaps because of their delicate skeletons. Conclusion: The POR does not significantly distort the pattern of diversification, suggesting that the massive expansion of tetrapod biodiversity in the past 120 million years is largely a real biological pattern.