An articulated embolomere skeleton (Amphibia: Anthracosauria) from the Lower Pennsylvanian (Bashkirian) of Nova Scotia

Abstract

Recently discovered skeletal material greatly expands our knowledge of the embolomeres from the Early Pennsylvanian locality of Joggins, Nova Scotia. These specimens are probably attributable to Calligenethlon watsoni Steen that has been described previously from this locality, but despite their articulated condition and relative completeness, this assignment is equivocal. Inclusion of the most complete specimen, NSM 994 GF 1.1, in a previous phylogenetic analysis of the Embolomeri results in a sistergroup relationship between NSM 994 GF 1.1 and Anthracosaurus . However, none of the 16 synapomorphies supporting this relationship are unique to these two taxa, but rather all occur in one or more of the other taxa in the analysis. This indicates extensive homoplasy within embolomeres and emphasizes the difficulties inherent in resolving embolomere interrelationships. The dirth of unequivocal synapomorphies is probably also reflects the conservative nature and basal status of embolomeres within the initial Palaeozoic tetrapod radiation.