Gavialoidea is presently composed of only two extant
crocodylian species, the Indian gharial Gavialis gangeticus, and
the false gharial Tomistoma schlegelii , both from southeast Asia.
However, Gavialoidea displays a rich and near-cosmopolitan
diversity in the fossil record, with over 40 species currently
recognized. Several of these gavialoids are recovered from
Cenozoic deposits in the Mediterranean region, with many
assigned historically to the genus Tomistoma . However, recent
phylogenetic analyses do not typically recover these species as
closely related to the false gharial, with several fossil species
in need of taxonomic revision. Here, we present a detailed
re-evaluation of one of these species, Tomistoma cairense from
the Middle Eocene Mokattam Formation of Egypt, based on the holotype skull and several referred specimens. Supplemented by endocranial anatomy revealed
via computed tomography (CT), we identify numerous anatomical differences with T. schlegelii
and other gavialoids, including the approximately contemporaneous Egyptian species, Eogavialis
africanum and Paratomistoma courti . These differences are reinforced through phylogenetic analysis
under maximum parsimony, in which T. cairense is recovered as a gavialoid that does not cluster with
T. schlegelii or Mediterranean taxa. We erect a new genus name for T. cairense , with the resultant new
combination of Herugavialis cairensis diagnosed by several characteristics, including telescoped orbits.
An apparent decline in Mediterranean gavialoid diversity during the Late Eocene–Oligocene is potentially
driven by a reduction in habitat, as a result of global cooling and declining eustatic sea level.
Warming in the Miocene might have facilitated a subsequent rebound in gavialoid diversity, prior to
the extirpation of crocodylians in the Mediterranean region in the Late Miocene, which might have
been caused by the Messinian Salinity Crisis. The taxonomic revision of additional Mediterranean
gavialoid species should facilitate greater insight into their evolutionary history and demise.