Southern higher-latitude lamniform sharks track mid-Cretaceous environmental change

The mid-Cretaceous (Albian and Cenomanian, 113–93.9 Myr) marked a transformative interval of shark evolution during which lamniforms (mackerel sharks) diversified as dominant marine predators. Yet, their radiation dynamics relative to major biotic turnovers delimiting the Albian–Cenomanian Cenomanian–Turonian boundaries are incompletely understood. Here, we use high-resolution dental fossil record track changing morphological disparity tooth size through succession assemblages from higher-palaeolatitude (up ∼ 58°S) settings in Australia. Our geometric morphometric analyses evolutionary model fitting reveal stable throughout late Albian–late Cenomanian. By contrast, lamniform increased early Turonian, might reflect local habitat differences and/or intraspecific variability heterodonty. Nevertheless, clade-specific partial increases evident among small-bodied carchariids, couple with trend towards larger teeth proxy for body-size coeval anacoracids. We correlate these signals recovery after Oceanic Anoxic Event 2, severely disrupted latest Cenomanian ecosystems apparently instigated disjunct responses communities occupying epeiric versus outer neritic environments.