Within Metriorhynchoidea, the Metriorhynchidae displayed extreme adaptions for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin,[5] and probably gave live birth, seemingly uniquely among archosaurs.

[8] Mark T. Young and colleagues in 2024 defined Thalattosuchia in the PhyloCode as "the largest clade within Crocodylomorpha containing Macrospondylus bollensis and Thalattosuchus superciliosus, but not Protosuchus richardsoni, Notosuchus terrestris, Peirosaurus tormini, Anteophthalmosuchus hooleyi, Deltasuchus motherali, Pholidosaurus schaumburgensis, Dyrosaurus phosphaticus, and Crocodylus niloticus (the Nile crocodile)".

[2] Indeterminate remains possibly belonging to thalattosuchians have been reported from the Early Jurassic (Sinemurian) of Chile and France.

[10] In 2023 a basal teleosauroid was reported from the earliest Jurassic (Hettangian-Sinemurian) of Morocco, representing one of the oldest known thalattosuchians.

[10] While abundant during the Jurassic, their fossil record during the Early Cretaceous is scarce, and generally confined to low latitudes.