The genus was named by
Louis Agassiz in 1843. It was formerly regarded as belonging to the
Climatiformes but recently reassigned to the
Diplacanthiformes, in which it is united with, amongst others,
Rhadinacanthus,
Uraniacanthus, and
Culmacanthus. Diplacanthiforms were widespread during the Middle and early
Late Devonian. They are best represented in the
Middle Devonian, by articulated fossils, fin spines, and abundant scales, the latter particularly from northern Europe. In a latest revision of the genus
Diplacanthus, a large number of species from Europe were synonymized with earlier Scottish species, and these too were redefined.
D. crassisimus was taken to have precedence over
D. striatus as the name of the type specimen.
Diplacanthus longispinus was reassigned to
Rhadinacanthus longispinus, within which were also included
Diplacanthus horridus (Woodward, 1892) and
Diplacanthus ellsi.
Diplacanthus tenuistriatus and
Diplacanthus kleesmentae were however retained. Non-Laurussian species such as
Diplacanthus acus from South Africa were not considered in this review.
Species • †
D. crassisimus Duff, 1842 (
type species) • †
D. gravis? Valiukevičius, 1986 • †
D. kleesmentae? Valiukevičius, 1988 • †
D. poltnigi? Valiukevičius, 2003 • †
D. solidus? Valiukevičius, 1986 • †
D. tenuistriatus Traquair, 1844
Diplacanthus is most commonly associated with deposits traditionally interpreted as fresh water. However, Waterloo Farm is interpreted as
estuarine in origin, as is the Canadian
Miguashaia lagerstätte from which two species of
Diplacanthus have been described. The description of
Angelacanthus acus provided the first record of a diplacanthid from the
Famennian, with diplacanthids having previously been thought to have gone extinct by the end of the
Frasnian. == References ==