Trochaclis regalis Marshall, 1995

Herbert, David G., 2024, The Vetigastropoda (Mollusca) of Walters Shoal, with descriptions of two new genera and thirty new species, European Journal of Taxonomy 923, pp. 1-119 : 50-51

Trochaclis regalis Marshall, 1995

Fig. 22

Trochaclis regalis Marshall, 1995: 97 , figs 11–12, 15.

Type loc.: off Three Kings Islands , northern New Zealand.

Material examined

WALTERS SHOAL – slopes • 2 empty shells; stn DW4881; 33°16′ S, 43°50′ E; depth 377–382 m; 2 May 2017 • 3 empty shells; stn DW4886; 33°17′ S, 43°56′ E; depth 573–582 m; 3 May 2017.

Distribution

Recorded from the vicinity of the Three Kings Islands, off northern New Zealand (310–710 m) and the slopes of Walters Shoal (382–573 m); dredged on sandy substrata; living specimens unknown.

Remarks

When describing Trochaclis regalis, Marshall (1995) noted that it was ‘exceedingly similar’ to T. versiliensis Warén, Carrozza & Rocchini, 1992 from the western Mediterranean and adjacent Atlantic, the only difference being the degree of persistence of the spiral rib on the early teleoconch whorls. Given the absence of shared species in the vetigastropod faunas of the NE Atlantic and New Zealand, Marshall considered the New Zealand material to be specifically distinct and believed that further differences would be found when the soft parts became available for comparison. The material from Walters Shoal is likewise ‘exceedingly similar’ to T. regalis and T. versiliensis . In this instance, however, the vetigastropod faunas of the upper bathyal (archibenthic) zone of the south-western Indian Ocean and the region north of New Zealand not uncommonly contain shared, widely distributed species, including four species discussed herein, Acremodontina carinata , Bichoristes wareni , Bolma recens and Calliotropis eucheloides , as well as Calliotropis acherontis Marshall, 1979 . The five specimens available from Walters Shoal show considerable variability in the strength and persistence of the spiral rib. It is distinct and delineates a shoulder-like angulation on the first teleoconch whorl in all specimens, but extends only to 1.25 whorls in some ( Fig. 22F ), to 1.75 whorls in others and even to the outer lip at 2.25 whorls in one ( Fig. 22C ). Since I can find no diagnostic characters by which to separate the specimens from Walters Shoal from T. regalis , I regard them as conspecific.

Moelleriopsis gritta Hoffman, 2020 from the Azorean region is superficially similar to specimens of the present species in which the spiral rib persists to the aperture, but that species is larger (diameter up to 2.8 mm) and its protoconch bears spiral threads and does not project above the first teleoconch whorl.

Figures

Fig. 22. Trochaclis regalisMarshall, 1995,Walters Shoal, stn DW4881 (MNHN). A–C.Apertural, oblique basal and apical views of specimen with persistent shoulder cord, diameter 1.1 mm. D. Protoconch of A, scale bar=100 μm. E–F. Apertural and apical views of specimen with shoulder cord evanescing after first whorl, diameter 1.1 mm.