A new halecomorph fish from the Middle Triassic of Switzerland and its Systematic implications

Abstract

ABSTRACT The described actinopterygian—from the Middle Triassic of Canton Graubünden, Switzerland—is a small fish with bones and scales covered with a thick layer of ganoine and with a cranium characterized by large nasal bones sutured medially, an orbital region with an uncommon, large postero-dorsal infraorbital 4+5, possibly one small accessory suborbital bone, and an enlarged preopercle with an expanded antero-ventral region that almost contacts the lateral margin of the skull roof throughout the dorsal limb. The new fish shares with halecomorphs the presence of a supra-maxillary bone, and a new halecomorph synapomorphy—the presence of a well-developed dorsal supramaxillary process of the maxilla bearing a posterior notch or articulatory surface for contact with the supramaxilla. The interopercle is small and far away from the posterior part of the lower jaw unlike the condition in halecomorphs and teleosts. †Prosantichthys buergini new genus and new species is proposed as a Halecomorphi incertae sedis, probably close to parasemionotids, but not yet assignable to any of the known halecomorph subgroups.