Figure 1.

Simplified family-level phylogenetic hypothesis of Lamniformes showing all extant clades and †Otodontidae (A: dagger [†] indicates extinct), and silhouette depiction of fossil vertebral column of †Otodus megalodon (B). A, Current understanding of lamniform phylogeny demonstrating that a large portion of the phylogenetic tree remains unresolved due to conflicting results based on various molecular and morphological studies (Sternes et al., 2023 and references therein); although the placement of †Otodontidae is tentative and other extinct families are not depicted in this tree, the main point of this illustration is to demonstrate that †Otodontidae lies outside of Lamnidae (both clades highlighted in bold letters) where clades containing one or more species with regional endothermy (indicated by an asterisk [*]) do not share an immediate common ancestry (Sternes et al., 2023). B, Reconstructed vertebral column and its total measured length by Cooper et al. (2022) based on an incomplete associated vertebral set from the Miocene of Belgium; this specific specimen (IRSNB P 9893) was previously estimated to have come from an individual that measured 9.2 m in total length, including the head and caudal fin (Gottfried et al., 1996) based on the modern white shark, not accounted for by Cooper et al. (2022).