Eucalathis ergastica Fischer & OEhlert, 1890

Hansen, Jesper, 2024, Brachiopods of the Norwegian fauna northern North Atlantic and Arctic, with a focus on, Fauna norvegica 43, pp. 12-68 : 36-37

Eucalathis ergastica Fischer & OEhlert, 1890

Figures 23 , 24

Eucalathis ergastica Fischer & OEhlert, 1890, p. 73 .

Description: Shell low to moderately ventribiconvex and slightly longer than wide. Outline subtriangular to subpentagonal and widest close to front. Ventral umbo pointed and with moderately high interarea bisected by elongate subtriangular pedicle opening. Pedicle divided into many rootlets. Anterior commissure rectimarginate. Dorsal valve often with slight sulcus. Ornamentation of 14–27 costellate ribs, as well as abundant and strong lamellar growth breaks. Ribs triangular in cross section. Middle dorsal rib not larger than the others. Shell matrix endopunctate with very tiny punctae. Colour porcelain white to slightly yellowish. Broad hinge teeth not supported by dental plates. Short and anteriorly directed loop. Crural processes not meeting. Dorsal median septum lacking. Maximum shell size 7 mm.

Depth range: 280–2736 m depth (Logan 2007).

Temperature range: 9.5–12˚C (this study).

Substrate: Mud, sand, stones and rock, and often associated with corals ( Fischer & OEhlert 1891; Logan 1983; Anadón 1994; Anadón et al. 2022). Can also be attached to Porifera as in the illustrated examples.

Geography: Celtic Sea, Bay of Biscay, W Spain, Azores, Morocco, the Canary Islands and Western Sahara ( Fischer & OEhlert 1890; Cooper 1981a; Logan et al. 2007).

rootlets. Anterior commissure rectimarginate. Ornamentation of 14–44 costellate ribs, typically strongly beaded by tubercles— especially on ventral valve. Middle dorsal rib stronger or higher than the others and corresponded by an intercosta or two smaller and lower median costellae on ventral valve. Shell matrix endopunctate with very small punctae. Colour greyish to yellowish white. Crenulate valve margin. Strong and very wide hinge teeth not supported by dental plates. Dorsal valve with short but highly raised crura with a short, fragile loop extension usually not preserved. Median septum lacking, but weak median thickening of valve floor often presents in both valves. Shell up to 5 mm long.

Depth range: 549–2995 m depth ( Brunton & Curry 1979; Logan 2007).

Geography: Celtic Sea, Bay of Biscay, Mauritania,? Mediterranean, the Azores, the Mediterranean and south to the Canary Islands ( Brunton & Curry 1979; Logan et al. 2007; Zezina 2014).

Figures

Figure 23. Eucalathis ergastica. a–b: dorsal and ventral views of specimen from batch BMNH PI. ZB 4975, Bay of Biscay, 950–1005 m; c–d: dorsal and ventral views of another specimen from the same batch; e: ventral exterior view of juvenile specimen from the same batch. Scalebar 1mm. Photos: Jesper Hansen.

Figure 24. Distribution of Eucalathis ergastica.