古生物学：翼竜の起源をたどる

The closest evolutionary relatives of pterosaurs, the first vertebrates to evolve powered flight, may be a group of small, dinosaur-like animals known as lagerpetids, a Nature study reveals. This finding provides a new framework to study their origin, specialized body plan, and flying capabilities.

Tracing the origins of pterosaurs has been difficult, and remains an unsolved question in palaeontology. Pterosaurs have been hypothesized as close relatives of various reptilian groups, including dinosaurs, but no convincing evidence has been advanced to link any non-pterosaur group with pterosaurs exclusively. In this study, Martín Ezcurra and colleagues suggest that lagerpetids, a group of two-legged reptiles that were precursors to dinosaurs, may be a sister group of pterosaurs.

The authors identify similarities in pterosaur and lagerpetid anatomy using micro-computed tomography scans and 3D reconstructions of skeletal remains. Lagerpetids could not fly, but some unique features—such as the shape of the inner ear—that they share with pterosaurs make a compelling case for the relationship. Brain features relating to the enhanced sensory capabilities of pterosaurs are also present in lagerpetids, which indicates that these features evolved before flight.

This evidence illuminates the first steps of the assembly of the unique pterosaur body plan, whose conquest of the air represents one of the most astonishing innovations in vertebrate evolution. Although the exact transition between land-dwelling and flying vertebrates remains unknown, these findings shorten the temporal and anatomical gap between the oldest pterosaurs and their closest relatives.