Spines of the stem chondrichthyanDoliodus latispinosus(Whiteaves) comb. nov. from the Lower Devonian of eastern Canada

Abstract

The higher taxonomic affinities of fin spines from the Lower Devonian (Emsian) Atholville beds, Campbellton Formation, near Campbellton, New Brunswick, Canada, originally identified as Ctenacanthus latispinosus, have been uncertain since they were first described by Whiteaves in the late 19th century. Woodward subsequently referred the species to Climatius, because the isolated Canadian fin spines were similar to those preserved in articulated specimens of Climatius reticulatus from the Lower Old Red Sandstone (Lochkovian) of Scotland. Spines of the same form as the Atholville beds specimens are also found in Emsian mudstones on the Gaspé Peninsula, Québec. One of the fin spine forms appears identical to the pectoral fin spines on an articulated specimen from the Campbellton Formation that has been assigned to the stem chondrichthyan Doliodus problematicus, a taxon erected for isolated diplodont teeth. By comparison with median and paired fin spine morphology on the climatiiform Climatius reticulatus from the Scottish Lower Old Red Sandstone and the spines preserved on the articulated Doliodus, isolated fin spines from Campbellton and several localities on the Gaspé Peninsula are now identified as belonging to Doliodus latispinosus comb. nov. The variety of spine morphotypes recognized—pectoral, prepelvic, prepectoral, and median—support a phylogenetic position within the “acanthodians” rather than “conventionally defined chondrichthyans”.