Use of nursery areas by the extinct megatooth shark Otodus megalodon (Chondrichthyes: Lamniformes)

Abstract

Nursery areas are fundamental for the success of many marine species, particularly for large, slow-growing taxa with low fecundity and high age of maturity. Here, we examine the population size-class structure of the extinct gigantic shark Otodus megalodon in a newly described middle Miocene locality from Northeastern Spain, as well as in eight previously known formations (Temblor, Calvert, Pisco, Gatún, Chucunaque, Bahía Inglesa, Yorktown and Bone Valley). In all cases, body lengths of all individuals were inferred from dental parameters and the size-class structure was estimated from kernel probability density functions and Gaussian mixture models. Our analyses support the presence of five potential nurseries ranging from the Langhian (middle Miocene) to the Zanclean (Pliocene), with higher densities of individuals with estimated body lengths within the typical range of neonates and young juveniles. These results reveal, for the first time, that nursery areas were commonly used by O. megalodon over large temporal and spatial scales, reducing early mortality and playing a key role in maintaining viable adult populations. Ultimately, the presumed reliance of O. megalodon on the presence of suitable nursery grounds might have also been determinant in the demise of this iconic top predatory shark.

Ontogenetic growth pattern of the extinct megatooth shark Otodus megalodon—implications for its reproductive biology, development, and life expectancy

“…Yet, deciphering the life-history strategy of prehistoric sharks is often challenging because the vast majority of species are represented by teeth as their poorly mineralised cartilaginous skeleton usually does not fossilise (Cappetta 2012). In this regard, our vertebra-based study is a rare exception, where the life-history traits for Otodus megalodon proposed here have a significant bearing on various hypotheses and biological issues, such as its potential use of nursery grounds (Pimiento et al 2010;Herraiz et al 2020), its proposed competition with Carcharodon carcharias during the early Pliocene (Boessenecker et al 2019), and ontogenetic effects on its thermophysiology (Ferrón 2017). However, addressing these issues is beyond the scope of this paper primarily because our study rests on multiple assumptions, such as growth bands in IRSNB P 9893 representing annual cycles and the unconventional application of VBGF to a single individual (see Materials and Methods).…”

Body length estimation of Neogene macrophagous lamniform sharks (Carcharodon and Otodus) derived from associated fossil dentitions

“…Pimiento and Balk (2015) repeated this process to analyze spatial and temporal macroevolutionary body size trends in O. megalodon. This method has since propagated into numerous studies of O. megalodon (Reolid and Molina, 2015;Trif et al, 2016;Grant et al, 2017;Razak and Kocsis, 2018;Herraiz et al, 2020).…”

“…Carcharodon carcharias is the largest macrophagous shark alive today, achieving maximum body lengths of arguably 6 to 7 m (Gottfried et al, 1996;Castro, 2012;McClain et al, 2015). Otodus megalodon represents the largest macrophagous shark that ever lived, with contentious adult estimates ranging from 10 to more than 30 m (Dean, 1909;Randall, 1973;Bendix-Almgreen, 1983;Gottfried et al, 1996;Pimiento et al, 2010;Pimiento and Balk, 2015;Reolid and Molina, 2015;Trif et al, 2016;Grant et al, 2017;Razak and Kocsis, 2018;Shimada, 2002aShimada, , 2019Herraiz et al, 2020). This longstanding interest in body size of the world's largest marine macropredators has been shared by professional paleontologists and the public alike.…”

“…It was then proposed that these equations may be an appropriate analog to estimate body size of O. megalodon, given that C. carcharias represents the largest extant macrophagous shark. All subsequent studies (Pimiento et al, 2010;Pimiento and Balk, 2015;Reolid and Molina, 2015;Trif et al, 2016;Grant et al, 2017;Razak and Kocsis, 2018;Herraiz et al, 2020) mentioned have since used the Shimada (2002a) equations to estimate the size of O. megalodon. However, K-12 students applied Shimada's (2002a) equations to a 3D printed model of an associated dentition (i.e., multiple teeth from a single individual) of O. megalodon (UF-VP-311000), resulting in a range of body length estimates from 12 to 45 m for this single individual (Grant et al, 2017).…”

Biomechanical insights into the dentition of megatooth sharks (Lamniformes: Otodontidae)

“…3). This may explain why the ontogenetic change in O. megalodon teeth mimics the modifications that took place during their evolution within Otodontidae 53,54,57,58 . We propose that the morphological differences among otodontid dentitions may not be the result of selection acting on those traits but are simple sequelae of size variation.…”