Reassessment of the possible size, form, weight, cruising speed, and growth parameters of the extinct megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), and new evolutionary insights into its gigantism, life history strategies, ecology, and extinction

Abstract

Otodus megalodon (Lamniformes: Otodontidae) is an iconic Neogene shark, but the lack of well-preserved skeletons has hampered our understanding of various aspects of its biology. Here, we reassess some of its biological properties using a new approach, based on known vertebral specimens of O. megalodon and 165 species of extinct and extant neoselachian sharks across ten orders. Using the median neurocranial and caudal fin proportions relative to the trunk proportion among non-mitsukurinid/ non-alopiid lamniforms, we show that O. megalodon could have had a slender body and possibly reached about 24.3 m in length. Allometric considerations indicate that a stout body plan like the extant white shark (Carcharodon carcharias) for O. megalodon could have incurred excessive hydrodynamic costs, further supporting the interpretation that O. megalodon likely had a slenderer body than C. carcharias. A 24.3-m-long O. megalodon may have weighed around 94 t, with an estimated cruising speed of 2.1–3.5 km h-1. A reanalysis of vertebral growth bands suggests a size at birth of 3.6–.