Mendicula aff. ferruginosa Forbes, 1844

Oliver, P. Graham, 2015, Deep-water Thyasiridae (Mollusca: Bivalvia) from the Oman Margin, Arabian Sea, new species and examples of endemism and cosmopolitanism, Zootaxa 3995 (1), pp. 252-263 : 259-261

Mendicula aff. ferruginosa Forbes, 1844

Figs 4 F–G

Material. Five specimens, Off Ras Madrakah, southern Oman, Discovery cruise 211 st. 12719#1, 19°08´N 58°39´E, 3150m, collected P.G. Oliver, 31 October 1994. NMW.Z. 1995.009.19.

Description. To 2 mm in length. Equivalve. Equilateral prosogyrous beaks. Subcircular, posterior margin more narrowly rounded than anterior. Posterior area weakly demarcated by a radial angulation; submarginal sulcus narrow; lunule a slight depression. Hinge with an anterior thickening that in the right valve most developed. Exteriorly with a heavy ferruginous coating.

Remarks. These shells are inseparable from the deep water examples of M. ferruginosa in the Atlantic Ocean ( Figs 4 H–I) and the eastern Pacific Ocean (Coan et al., 2000). They are thinner and less heavily coated than the shelf examples. Very similar taxa are M. memorata from SE Australia, M. sudamericana Zelaya, 2010 from the southern Ocean and Thyasira ockelmanni Keuning & Schander, 2010 from the abyssal Norwegian Sea. Variation seen in M. ferruginosa from the NE Atlantic (see Oliver et al., 2010) makes definitive recognition of these species from shell characters uncertain.

Figures

FIGURE 4. A, Axinulus aff. croulinensis, Oman margin; B, Axinulus croulinensis Jeffreys, Loch Fyne, 40 m, Scotland, National Museum Wales; C, Axinulus undescribed, Gulf of Mexico, National Museum Wales; D, A. brevis Verrill & Bush, Rockall Trough, 1595 m, National Museum Wales; E – F, Mendicula aff. ferruginosa, Oman margin; G – H, Mendicula ferruginosa Forbes, Rockall Trough, 1595 m, National Museum Wales; I, Leptaxinus indusarium Oliver & Levin, holotype, National Museum Wales, NMWZ. 2005.34.1.