EUTHACANTHIDAE Berg, 1940

Newman, Michael J., Burrow, Carole J., Den Blaauwen, Jan L. & Davidson, Robert G., 2014, The Early Devonian acanthodian Euthacanthus macnicoli Powrie, 1864 from the Midland Valley of Scotland, Geodiversitas 36 (3), pp. 321-348 : 325

Family EUTHACANTHIDAE Berg, 1940

TYPE AND ONLY GENUS. — Euthacanthus Powrie, 1864 .

DIAGNOSIS. — Acanthodians lacking an oral dentition; ring of five sclerotic bones; closeset branchiostegal plates over part of the branchial region; dermal pectoral girdle comprises a single pair of triangular postbranchial plates, each with one spine, that are not contiguous with the scapulocoracoid; simple scapulocoracoid with a columnar shaft; scapulocoracoid is covered laterally only by normal body scales, not dermal tesserae; anterior dorsal, posterior dorsal, anal, pectoral and pelvic fin spines are robust with thick walls and a wide pulp canal, and longitudinal ornament ridges; four to six pairs of prepelvic spines; polygonal tectal tesserae.

REMARKS

Cladistic analyses (e.g., Hanke & Wilson 2004; Brazeau 2009; Burrow & Turner 2010; Davis et al. 2012; Zhu et al. 2013) have shown that the order Climatiiformes sensu Denison (1979) is paraphyletic, and Euthacanthus does not fall into other recognized orders. Berg (1940) raised the family Euthacanthidae to incorporate Euthacanthus and possibly Brachyacanthus Egerton, 1860 , and Miles (1966) also considered that Euthacanthus and Brachyacanthus were members of the same family as both forms have no teeth and a principle gill cover that did not cover the whole gill chamber. Newman et al. (2011) excluded Brachyacanthus from the Euthacanthidae based on the fin spine ridge ornamentation, and as none of the recent cladistic analyses support a sister relationship between Euthacanthus and Brachyacanthus (or any other genera) we consider the Euthacanthidae to be a monogeneric family.