Skeletal remains of Phoebodus politus Newberry 1889 (Chondrichthyes: Elasmobranchii) from a Famennian Konservatlagerstätte in the eastern Anti-Atlas (Morocco) and its ecology

Abstract

The Devonian chondrichthyan Phoebodus (Newberry 1889) has long been known from isolated teeth recovered from a wide variety of fossil localities, ranging from the Middle Devonian to the Upper Missippian (Ginter et al. 2010). Here we provide a preliminary report of the first discovery of substantial, partly articulated skeletal and dental remains of a phoebodont, Phoebodus politus, from Famennian outrops of the eastern Anti-Atlas of Morocco. Initial comparisons support the hypothesized close relationship of pheobodonts with the Upper Mississippian chondrichthyan Thrinacodus gracia (Grogan & Lund 2008, Ginter et al. 2010). Both taxa exhibit an anguiliform body and elongate slender cranium. However, P. politus also exhibits dorsal fins with ctenacanth-like fin spines, echoing informal records of similar fin spine and tooth associations from the Famennian of Alaska (Maisey, in Ginter et al. 2010). This Moroccan material represents an important addition to the limited data set of Devonian chondrichthyans. As such, these data will provide a valuable test of recent phylogenetic hypotheses (Pradel et al. 2011; Coates et al. 2017) and addition to analyses of early gathostome diversity and disparity before and after the end Devonian Hangenberg Event (Friedman & Sallan 2012). Among living elasmobranchs, Chlamydoselachus uniquely displays a body shape, snout form and tooth morphology resembling those of P. politus. Acknowledging that the structure and likely biomechanics of the axial skeletons and jaws of these widey separated genera differ considerably, we nevertheless suggest that Chlamydoselachus (Ebert & Compagno 2009) provides the best available living model for understanding the ecomorphology of this remarkable, late Devonian comparator.