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”.

Architectural and ultrastructural features of tessellated calcified cartilage in modern and extinct chondrichthyan fishes

“…D. latispinosus (Lower Devonian, Emsian, ca . 393–407 bp ) is an important “transitional fossil,” possessing an acanthodian‐like complement of paired and median spines, as well as a shark‐like cranium, jaws and teeth (Miller et al ., 2003; Maisey et al ., 2009; Maisey et al ., 2014; Burrow et al ., 2017; Maisey et al ., 2017b). Miller et al .…”

A critical appraisal of appendage disparity and homology in fishes

“…latispinosus, which also possesses prepectoral and possibly admedian spines (Burrow et al, 2017;Maisey et al, 2017), and W. priscus (Potvin-Leduc, 2017). latispinosus, which also possesses prepectoral and possibly admedian spines (Burrow et al, 2017;Maisey et al, 2017), and W. priscus (Potvin-Leduc, 2017).…”

“…D. latispinosus, which also possesses prepectoral and possibly admedian spines (Burrow et al, 2017;Maisey et al, 2017), and W. priscus (Potvin-Leduc, 2017). Notably, it has also been suggested based on the results of a phylogenetic analyses on cranial morphological characters that D. latispinosus may occupy a more stemward position in the chondrichthyan phylogeny, prior to the Euchondrocephali-Elasmobranchii split (Maisey, Turner, Naylor, & Miller, 2014;Pradel, Tafforeau, Maisey, & Janvier, 2011).…”

The dentition of Omalodontiformes, the order of unusual Devonian stem-chondrichthyans

“…This was confirmed by Turner (2004) who re-examined Traquair's collection in Edinburgh and provided sketch drawings and photographs of several teeth from that material. She also proposed to place Doliodus problematicus (Woodward, 1892a), because of the form of the base, in the order Omalodontiformes, within the Chondrichthyes, despite the earlier suggestions of its acanthodian affinity (see Burrow et al, 2017;Burrow, 2021). Actually, she had already signalled the basal similarity of Doliodus and Omalodus, in her paper on the material from the Conodont Bed in New York (see above; Turner, 1997).…”

“…In addition to the teeth mentioned above, the Lower Devonian at Campbellton yielded an articulated specimen (NBMG 10127) of a chondrichthyan, the anterior portion of a skeleton, with an almost intact dentition (Maisey et al, 2014), a set of paired ventral spines (pectoral, pre-pectoral and probable pre-pelvic, Maisey et al, 2017;Burrow et al, 2017) and remnants of cartilaginous elements. From the very start after its discovery (Miller et al, 2003) the specimen was referred to as Doliodus problematicus, because of the superficial similarity of the teeth, the structure of tooth whorls, and the locality and horizon in which it was found.…”