The Echinoid Directory

Aulechinus Bather & Spencer, 1934, p. 558

[=Ectinechinus MacBride & Spencer, 1938, p. 95, type species Ectinechinus lamonti MacBride & Spencer, 1938]

Diagnostic Features	Test subspherical in life; test plating thin and imbricate. Apical disc small (less than 20% test diameter). A single large genital plate and five small ocular plates; small periproctal plates present centrally. Ambulacra more or less straight and narrow; biserial; strongly imbricate. Plating simple with small pore-pair on each plate, the inner pore being sutural. Pore-pairs positioned close to perradius; perradial zone depressed forming groove externally. No tubercles. Adradial margins of ambulacral plates bevelled strongly beneath interambulacral plates. On the inner surface of ambulacral plates there are strongly developed perradially directed flanges that fully enclose the radial water vessel within the ambulacral plates. Interambulacral zones wide; composed of many semi-regularly arranged scale-like plates. Plates imbricate towards the interradius and adapically. Interambulacral plates without granulation or tuberculation. Peristome small, with small plates. Lantern broad and flattened. Hemipyramids with shallow foramen magnum; teeth wide, U-shaped and composed of a double series of alternating wedge-like elements; ?no compasses or rotulae. No spines.
Distribution	Upper Ordovician (Ashgill), Scotland.
Name gender	masculine
Type	Aulechinus grayae Bather & Spencer, 1934, by original designation. Holotype BMNH E31412.
Species Included	A. grayae Bather & Spencer, 1934; Ashgill, Scotland. A. lamonti (MacBride & Spencer, 1938); Ashgill, Scotland.
Classification and/or Status	Stem group Echinoidea; unnamed plesion. Unknown.
Remarks	The distinction of this species from Ectinechinus rests entirely on whether the perradial zone of the ambulacra is depressed or not externally. This may be a taphonomic feature. The difference in pore structure, those of Aulechinus being simple, and those of Ectinechinus double, does not appear to be true. Consequently the two genera are here synonymized. Eothuria, which occurs in the same beds, is easily distinguished by its very different pore morphology, ambulacral plates being pierced by a circular structure with 6-12 small perforations. MacBride, E. W. & Spencer, W. K. 1938. Two new Echinoidea, Aulechinus and Ectinechinus, and an adult plated holothurian, Eothuria, from the Upper Ordovician of Girvan, Scotland. Transactions of the Royal Society, London B229, 91-136, pls 10-17.