Orthacanthus Agassiz, 1843

Johnson, Gary D. & Thayer, David W., 2009, Early Pennsylvanian xenacanth chondrichthyans from the Swisshelm Mountains, Arizona, USA, Acta Palaeontologica Polonica 54 (4), pp. 649-668 : 650

Genus Orthacanthus Agassiz, 1843

Type species: Orthacanthus cylindricus ( Agassiz, 1843) (= O. gibbosus ), Late Carboniferous, Coal Measures, Manchester, England. Spine figured in Agassiz (1843: pl. 45: 7–9), but its whereabouts is unknown ( Hampe 2003: 205).

1843 Diplodus Agassiz, 1843: 204 , pl. 22B: 1.

1883 Didymodus Cope, 1883: 108 .

1885 Diacranodus Garman, 1885: 30 .

1889 Diplodus ; Woodward 1889: 10.

1889 Orthacanthus ; Fritsch 1889: 100–112, pls. 81–90.

1946 Xenacanthus Beyrich, 1848 ; Olson 1946: 286–288, fig. 1.

1952 Xenacanthus ; Hotton 1952: 489–500, pl. 58.

1970 Xenacanthus ; Berman 1970: 19–20.

Diagnosis.—Limited to dentition. Heterodont; teeth with minimum of three cusps, two principal cusps and an intermediate cusp; secondary intermediate cusps sometimes present. Principal cusps labio−lingually compressed, often with edges developed into carinae that are usually serrated; cristae absent; major transverse axes of proximal ends <45° to, and often nearly parallel to, the labial margin of the base between these cusps. Apical button isolated from cusps; central (median) foramen present. Basal tubercle with flat or convex surface. See Hampe (2003: 205).