Uraniacanthus Miles, 1973

Newman, Michael J., Davidson, Robert G., Blaauwen, Jan L. Den & Burrow, Carole J., 2012, The Early Devonian Acanthodian Uraniacanthus curtus (Powrie, 1870) n. comb. from the Midland Valley of Scotland, Geodiversitas 34 (4), pp. 739-759 : 743

Genus Uraniacanthus Miles, 1973

TYPE SPECIES. — Uraniacanthus spinosus Miles, 1973 , original designation, from the Lochkovian of Herefordshire, England.

REVISED DIAGNOSIS. — Diplacanthiform acanthodians with two pairs of prepectoral fin spines; anterior dorsal fin spine with a marked posteriorly-pointing curvature at the tip; postorbital plates with rounded to spiky raised tubercles; broad, spatulate opercular covers ornamented with fine ridges in a loose chevron pattern; smooth gnathal bone with a subtriangular dorsal process, on Meckel’s cartilage; scales, when ornamented, with three to eight grooves extending the whole length of the scale crown.

REMARKS

This diagnosis is mostly based on the diagnosis for Gladiobranchus given by Hanke & Davis (2008). As originally noted by Hanke et al. (2001), Miles (1973: text-fig. 17A, pl. 12, fig. 1) mistakenly identified Uraniacanthus spinosus as an ischnacanthiform based on the association of one of his figured specimens with a dentigerous jaw bone, and misidentification of a postorbital plate as a jaw element ( Hanke & Wilson 2004). Bernacsek & Dineley (1977) erected a new taxon Gladiobranchus probaton for partial specimens lacking the rostrum and jaws from the Lochkovian MOTH locality, Northwest Territories, Canada. They placed both Uraniacanthus and Gladiobranchus in a new family Gladiobranchidae Bernacsek & Dineley, 1977 indicating a close relationship between the two genera. Prepectoral spines have not previously been identified in U. spinosus , but spines anterior to the pectoral fin spine and close to the branchiostegal plates that Miles (1973: pl. 13, figs 1, 2) identified as isp. 1 (intermediate spines) could rather be prepectoral spines: the laterally compressed holotype ( Miles 1973: pl. 11) shows isp. 1 posteriorly positioned, close to the pelvic spines. The only clear differences between specimens assigned to the two genera are the ornamentation of the postorbital plates and the more robust posterior dorsal fin spine of G. probaton . As previously suggested by Hanke & Davis (2008; also Hanke pers. comm. 2009), these differences are too minor to support separate genera. As described below, Euthacanthus curtus and G. probaton show even closer similarity.