New data on Ossinodus pueri, a stem tetrapod from the Early Carboniferous of Australia

Abstract

ABSTRACT Significant new material of the Early Carboniferous stem tetrapod Ossinodus pueri has been found in the Ducabrook Formation, Queensland, Australia. An articulated partial skull (including skull roof and palate) as well as isolated jugal, surangular, postsplenial, intercentra, and haemal arch elements are described for the first time. New features of the cranial material include a preopercular bone, and an entirely enclosed quadratojugal sensory canal. This canal exits from the accessory paraquadrate foramen on the inner face of the quadratojugal, suggesting that the foramen was not an opening for nerves or blood vessels to enter the skull. It is argued that enclosed sensory canals may be present but undetected in other early tetrapods. A new reconstruction of the skull and the first full body reconstruction of O. pueri show a tetrapod that appears to be quite different from the whatcheeriids, Whatcheeria and Pederpes. Two phylogenetic analyses, one in which the taxon has an intertemporal, and one in which that bone is absent, place Ossinodus differently. In the first, Ossinodus remains in the Whatcheeriidae, while in the second (in which the intertemporal is absent) it is stemward of the Whatcheeriidae, adding credence to previous suggestions that the Whatcheeriidae may be a grade rather than a clade.