Doliodus

The first material that some authors classify as Doliodus was identified by Joseph Whiteaves in 1881, and consists of several isolated fin spines which he identified as a new species in the genus Ctenacanthus, and which he named C. latispinosus. This species had no assigned holotype specimen. In 1889, these spines were suggested to instead belong to the genus Climatius by paleontologist Arthur Smith Woodward, who in 1892 also described a single, fragmentary tooth crown from the same locality (designated NHMUK PVP.6540) This species, which he named Diplodus problematicus, was reclassified as the new genus Doliodus problematicus the following year by paleontologist Ramsay Traquair based on 19 more complete teeth from the same site. A 2003 paper published in Nature by Randall Miller and coauthors described a fossilized cartilaginous fish with a well-preserved dentition, skull, fins, and trunk (designated as NBMG 10127) and tooth anatomy similar to that described by Woodward and Traquair in D. problematicus, and these authors assigned this specimen to that species. of Gaspé, QuebecThe names Doliodus problematicus and Climatius latispinosus were used separately prior to the discovery of the articulated specimen, and in that material's description it was suggested further research was required to determine if the taxa were synonymous. while a 2023 paper by paleontologist Michal Ginter has instead questioned the assignment of any non-tooth material to Doliodus and restricted it to only the D. problematicus teeth. The isolated fin spines described by Whiteaves, the teeth described by Woodward and Traquair, and the more complete skeleton all originate from the Campbellton Formation of Campbellton, New Brunswick. The site is dated to the Emsian stage of the Early Devonian, Additional spines and teeth assigned to the genus has been found in Gaspé, Quebec, in rocks of the York River Formation and Battery Point Formation, which are also dated to the Emsian stage. Michal Ginter includes the Quebecois teeth within the genus. According to Traquair, the genus name is derived from the Greek root δόλιος or dolios, meaning to trick or deceive. The name was given because of how closely the tooth crowns of the genus resemble those of the unrelated Diplodus. == Description ==

Teeth Per Michal Ginter, the genus Doliodus encompasses only isolated teeth and tooth-whorls assigned to D. problematicus. 10127 and showcasing fin spinesLong, curved, dentinous spines protruded from in front of the fins, and four sets of shorter paired spines were present on the underbelly; two sets of prepectoral and prepelvic spines, respectively. The spines had ridges which ran down their length, and the fin spines additionally had rows of denticles. The dorsal fins also likely had spines, but the dorsal fin of NBMG 10127 is poorly preserved. The pectoral spines of this specimen were 5.5 cm long, and the largest isolated spines assigned to D. latispinosus are up to 9 cm long. == Classification ==

When first described material now assigned to Doliodus was classified as genera within the class Chondrichthyes or the then-equivalent Elasmobranchii, namely Ctenacanthus and a xenacanthiform. Since the discovery of the more complete specimen, the genus has been considered a member of the family Omalodontiformes and the family Omalodontidae. It has alternatively been suggested that the genus lacks defining features of the Omalodontiformes, Evolutionary significance Specimen NBMG 10127 is a transitional form between cartilaginous fish and the now-extinct acanthodians. The specimen also represents one of the oldest-known articulated cartilaginous fish alongside the Bolivian Pucapampella, with most older cartilaginous fish remains consisting only of isolated scales and teeth. == Paleoecology ==

'' may have been the apex predator of the Atholville Beds Specific layers of the Campbellton Formation which preserve Doliodus, termed the Atholville Beds, The Battery Point and York River Formation deposits which preserve fish remains were laid down in similar deltaic, lagoonal environments. In life, Doliodus was potentially an active predator, The large eurypterid Pterygotus anglicus is thought to have been the apex predator of the Atholville Beds. == See also ==