Estimating divergence times of lizardfishes and their allies (Euteleostei: Aulopiformes) and the timing of deep-sea adaptations

The divergence times of lizardfishes (Euteleostei: Aulopiformes) are estimated utilizing a Bayesian approach in combination with knowledge of the fossil record of teleosts and a taxonomic review of fossil aulopiform taxa. These results are integrated with a study of character evolution regarding deep-sea evolutionary adaptations in the clade, including simultaneous hermaphroditism and tubular eyes. Divergence time estimations recover that the stem species of the lizardfishes arose during the Early Cretaceous/Late Jurassic in a marine environment with separate sexes, and laterally directed, round eyes. Tubular eyes have arisen independently at different times in three deep-sea pelagic predatory aulopiform lineages. Simultaneous hermaphroditism evolved a single time in the stem species of the suborder Alepisauroidei, the clade of deep-sea aulopiforms during the Early Cretaceous. This result indicates the oldest known evolutionary event of simultaneous hermaphroditism in vertebrates, with the Alepisauroidei being the largest vertebrate clade with this reproductive strategy.

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► The order Aulopiformes (lizardfishes and their allies) arose during the Early Cretaceous and possibly Late Jurassic.
► Major aulopiform lineages originated during the Early Cretaceous, with most extant families appearing by the Late Cretaceous to the Eocene.
► Tubular eyes have arisen independently at different times in three deep-sea pelagic predatory aulopiform lineages.
► Simultaneous hermaphroditism evolved a single time in the stem species of the suborder Alepisauroidei, the clade of deep-sea aulopiforms.
► Simultaneous hermaphroditism most likely arose in the Early Cretaceous indicating this is the oldest simultaneous hermaphroditic strategy among vertebrates.