TEGEOLEPIS: AN UNUSUAL EARLY ACTINOPTERYGIAN FROM THE CLEVELAND SHALE

The diversity of Devonian actinopterygian fishes falls far short of that known from the Mississippian. Devonian actinopterygian evolution tends to be presented as Cheirolepis, the traditional stand-in for acanthodian-like primitive osteichthyan conditions, giving rise to Mimia and Moythomasia, which then yield a radiation of similar forms grouped as ‘palaeoniscids' scattered throughout the remainder of the Paleozoic. In contrast to our rudimentary knowledge of these earliest actinopterygians, far more research attention has focused on Devonian sarcopterygians, and as a result we have a much more detailed picture of diversity at the base of lungfishes, coelacanths and tetrapods. Better knowledge of Tegeolepis clarki (Newberry), an actinopterygian from the Cleveland member of the Upper Devonian Ohio Shale, should help rectify this imbalance of information. Tegeolepis is extraordinary for several reasons: its large size, its peculiar skull shape with long pointed snout, and the incongruently advanced condition of several features in the cranial skeleton. When included in phylogenetic analyses, Tegeolepis has behaved as something of a wild card taxon, with little consistency apparent between alternative hypotheses of sister-group relationships. Our research is building upon the currently available outline description, and we will present new data on the condition of the jaws, dentition, braincase, hyoid arch and paired fins. In several respects, features of Tegeolepis resemble conditions described in recently reported sarcopterygians from the earliest Devonian. Tegeolepis is likely to add significantly to the emerging picture of morphological diversity among early crown-group osteichthyans.