Body shape diversity in Triassic‒Early Cretaceous neopterygian fishes: sustained holostean disparity and predominantly gradual increases in teleost phenotypic variety

Comprising Holostei and Teleostei, the ~32,000 species of neopterygian fishes are anatomically disparate and represent the dominant group of aquatic vertebrates today. However, the pattern by which teleosts rose to represent almost all of this diversity, while their holostean sister group dwindled to 8 extant species and two broad morphologies, is poorly constrained. A geometric morphometric approach was taken to generate a morphospace from over 400 fossil taxa, representing almost all articulated neopterygian taxa known from the first 150 million years—roughly 60%—of history (Triassic‒Early Cretaceous). Patterns of morphospace occupancy and disparity are examined in order to: assess evidence for a phenotypically 'dominant' holostean phase; evaluate whether expansions in teleost phenotypic variety are predominantly abrupt or gradual, including assessment of whether apomorphy-defined teleosts are as morphologically conservative as typically assumed; compare diversification in crown and s...