Description
Original diagnosis after Bolton, 1896 [22433]: Spine small, not exceeding 19mm. in length, gently arched, sides flat, with seven longitudinal ridges, the convex and concave margins bearing acute spine-like denticles. The denticles of the convex margin few in number and placed at equal distances apart, these pointing a little forwards and upwards, and the angle which they make with the margin being not more than ten degrees. Only three denticles shown, but a fourth probably given off just above the broken upper edge. The first lateral ridge directly prolonged into the lowest denticle of the convex margin, the second ridge giving origin to the second and third denticles, and probably continuing upwards to a fourth (though a slight dislocation of the spine at this point prevents a clear determination). The denticles of the concave margin larger, stronger, and more numerous than those of the convex margin, and directed outwards at an angle fully double that of the latter. A cluster of five spines placed at the base, in fan-fashion, the margin spreading out between them like a web.
Revised diagnosis after Martill, Del Strother & Gallien, 2014 [20257]: Modified dermal spines resembling those of Listracanthus, but with irregular distribution of subsidiary spines on posterior border and not as many, and more widely spaced and of irregular length. Posterior subsidiary spines are hollow almost to their tips.

Remarks
shark-references Species-ID=13932;
type species (Listracanthus spinatus) of Acanthorhachis Martill,Del Strother & Gallien, 2014 [20257] by original designation (Art. 68.2 ICZN);

References