Evidence of a specialized feeding niche in a Late Triassic ray-finned fish: evolution of multidenticulate teeth and benthic scraping in †Hemicalypterus

Abstract

Fishes have evolved to exploit multiple ecological niches. Extant fishes in both marine (e.g., rabbitfishes, surgeonfishes) and freshwater systems (e.g., haplochromine cichlids, characiforms) have evolved specialized, scoop-like, multidenticulate teeth for benthic scraping, feeding primarily on algae. Here, I report evidence of the oldest example of specialized multidenticulate dentition in a ray-finned fish, †Hemicalypterus weiri, from the Upper Triassic Chinle Formation of southeastern Utah (∼210-205 Ma), USA. †H. weiri is a lower actinopterygian species that is phylogenetically remote from modern fishes, and has evolved specialized teeth that converge with those of several living teleost fishes (e.g., characiforms, cichlids, acanthurids, siganids), with a likely function of these teeth being to scrape algae off a rock substrate. This finding contradicts previously held notions that fishes with multicuspid, scoop-like dentition were restricted to teleosts, and indicates that ray-finned fishes were diversifying into different trophic niches and exploring different modes of feeding earlier in their history than previously thought, fundamentally altering our perceptions of the ecological roles of fishes during the Mesozoic.

Phanerozoic survivors: Actinopterygian evolution through the Permo‐Triassic and Triassic‐Jurassic mass extinction events

“…). In the Late Triassic, novel feeding modes evolved that were not only related to overall jaw morphology, but also in neopterygian dentition (e.g., Gibson ). Specific features of the dentition were not considered in our data, however the expansion of jaw morphologies seen in our results and novel dentition types found by others highlight that neopterygians were evolving completely new ecotypes in the Middle‐Late Triassic.…”

Tracking dinosaurs in BLM canyon country, Utah

“…The Big Indian Rock beds contain the Last Phytosaur skull (see below) and important tracksites located on Eagle Nest Ridge (see discussion below) to the south. (Schaeffer, 1967;others, 2006a, 2006b;Gibson, 2013aGibson, , 2013bGibson, , 2015, with some work on phytosaurs, especially the Last Phytosaur (Morales and Ash, 1993;Lucas and others, 1997;Martz and others, 2014), and aetosaurs (Martz and others, 2014). Several publications are presently being written to describe many of the new vertebrate specimens both from Lisbon Valley and Indian Creek (see discussion on Indian Creek), as well as the vertebrate trace fossils and localities summarized below (table 1).…”

A giant dapediid from the Late Triassic of Switzerland and insights into neopterygian phylogeny

“…Most Dapedium species have a standard length of around 15–35 cm [18], although dapediids range in size from approximately 8 cm ( Dapedium noricum [12]) to approximately 1 m ( Sargodon tomicus [12]). Only around five of the 30 or so known species of dapediid are present in the Triassic, and are exclusively represented by isolated teeth [19] or flattened [12,14,20] remains. Consequently, their adaptation for durophagy is thought to have facilitated the group's success in the aftermath of the End-Triassic extinction, a time at which many other durophagous taxa went extinct [21,22].…”