Agariste phrygium ( Herbert & Kilburn, 1986 )

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 : 3

Agariste phrygium ( Herbert & Kilburn, 1986)

Fig. 1

Emarginula phrygium Herbert & Kilburn, 1986: 10 , figs 30–34.

Type loc.: off Qora River (32°34.0′ S, 28°49.7′ E), E Cape, South Africa, depth 400– 420 m .

Agariste phrygium – Landau et al. 2003: 24.

Emarginula phrygium – Herbert 2015: 22 . — Muratov & Heyns-Veale 2020: 59 , fig. 8 (of holotype).

Material examined

WALTERS SHOAL – slopes • 1 empty shell; stn DW4887; 33°17′ S, 43°57′ E; depth 599–640 m; 3 May 2017; MNHN .

Distribution

Walters Shoal and the eastern seaboard of South Africa; dredged on coarse sandy substrata at depths of 420–599 m; living specimens unknown.

Remarks

This highly distinctive species was previously known only from the holotype. This second specimen from Walters Shoal is considerably larger than the holotype (base 9.0× 6.1 mm, height 8.3 mm vs base 5.8× 4.7 mm, height 3.7 mm) and proportionately taller, suggesting that height increases more rapidly than length as the shell grows. The shell is also proportionately narrower, but this is almost certainly simply a reflection of the width of the object on which it was living.

Landau et al. (2003) drew attention to the similarity between this species and Emarginula compressa Cantraine, 1835 from the Pleistocene of Italy, type species of Agariste Monterosato, 1892 . They considered the strongly convex base and markedly recurved apex with the protoconch off-set to the right, shared by these species to be distinctive features distinguishing Agariste from Emarginula . Sculpturally, A. phrygium differs from A. compressa in having a relatively coarse sculpture of radial ribs and uneven concentric ridges, whereas A. compressa has a much finer sculpture of close-set radial ribs and irregular concentric growth-lines ( Palazzi & Villari 1996: pl. 2 figs 78–79; Vazzana 1996: pl. 2 fig. 8). Agariste juliencilisi Landau, Marquet & Grigis, 2003 , from the Pliocene of Spain, is sculpturally more similar to A. phrygium , but the shell is more laterally compressed and has a much lower profile.

Figures

Fig. 1. Agariste phrygium (Herbert & Kilburn, 1986), Walters Shoal, stn DW4887, base 9.0× 6.1 mm, height 8.3 mm (MNHN). A–B. Lateral and dorsal views. C–D. Anterior and posterior views. E. Basal view.