Two new Actinopterygii (Vertebrata, Osteichthyes) with cosmine from the Bear Gulch Limestone (Heath Fm., Serpukhovian, Mississippian) of Montana USA

Abstract

ABSTRACT. The osteology and histology of two new actinopterygians, Paphosiscus circulocaudus new genus and species, and P. scalmocristus new species, are described from the Upper Mississippian Serpukhovian Bear Gulch Member of the Heath Formation of Montana (USA). These small fish (ca 50–58mm standard length) exhibit head bones and scales with cosmine, the first report of this in any actinopterygian. Other features of Paphosiscus are dorsal, anal and caudal fin margins round posteriorly, dorsal fin long with horizontal dorsal margin and achieving its greatest height immediately before its rounded posterior margin, tall unpaired predorsal ridge scales/fulcra, premaxillae not sutured to other bones, single postrostral bone, one otic canal bone (dermopterotic), dermosphenotic absent as distinct bone, mandibular articulation level with mandibular tooth row, a coronoid process, marginal teeth pleurodont, coronoid teeth with blunt crowns on a single coronoid bone. Species differ in size and features of cranial ...