Megerlia King, 1850

Bitner, Maria Aleksandra, 2007, Recent brachiopods from the Austral Islands, French Polynesia, South-Central Pacific, Zoosystema 29 (3), pp. 491-502 : 496-498

Genus Megerlia King, 1850

TYPE SPECIES. — Anomia truncata Linnaeus, 1767 , by original designation ( King 1850: 145).

Megerlia truncata ( Linnaeus, 1767) ( Fig. 3I, J )

Anomia truncata Linnaeus, 1767: 1152 , no. 229.

Megerlia truncata – Logan 1979: 68-72, text-fig. 21, pl. 9, figs 1-23. — Bitner 1990: 145-147, text-fig. 10, pl. 2, figs 6-9; pl. 7, figs 3-6; pl. 8, figs 1-7.

Megerlia gigantea – Cooper 1981a: 27, 28, pl. 6, figs 1-26. — d’Hondt 1987: 38, 39.

Megerlia echinata – Laurin 1997: 452, 453, figs 38, 39.

MATERIAL EXAMINED. — Austral Islands. Rurutu, BENTHAUS, stn DW 2009, 1 complete specimen, including soft parts.

DEPTH RANGE. — 320- 450 m.

MEASUREMENTS. — Length 4.5 mm, width 5.7 mm, thickness 1.9 mm.

REMARKS

Although the material consists of only one complete specimen, Megerlia truncata is an easily distinguishable species. The studied specimen has a small shell, wider than long, weakly biconvex; ventral valve convex, dorsal valve is posteriorly convex and anteriorly irregularly concave. The surface of the dorsal valve is very irregular, reflecting the irregularity of the substrate. Except a small fragment, it gives no indication of radial ornamentation ( Fig. 3J ), while the ventral valve bears numerous fine ribs. The foramen is large, and present on the dorsal valve as well.

Re-examination of the material kept in the Muséum national d’Histoire naturelle, Paris, and described as Megerlia gigantea ( Deshayes, 1863) by Cooper (1981a) and d’Hondt (1987) shows that those specimens certainly belong to M. truncata , as pointed by Davidson (1880). Deshayes (1863) created his species based on a single specimen, and attributed it to the genus Morrisia (junior synonym of Platidia ). His specific name gigantea followed from the fact that he believed it to be the largest species of Platidia .

The specimen from the Indian Ocean described by Zezina (1987) as Megerlina gigantea is characterized by the absence of crura, and may belong to Megerlia acrura Hiller, 1986 originally described from off South Africa. The latter species is very similar to M. truncata , differing in the lack of crura ( Hiller 1986).

Figures

FIG. 3. — A-H, Thecidellina maxilla (Hedley, 1899); A, dorsal view of complete specimens attached to each other (MNHN BRA-3051), Ruturu Island,stn DW 2001, 200-550 m; B, C, inner view of ventral valve (B) and tilted (C) to show hemispondylium (MNHN BRA-3052), Ruturu Island, stn DW 2003, 250-330 m; D, E, inner view of dorsal valve (D) and posterior view (E) to show trilobed cardinal process (MNHN BRA-3053), Ruturu Island, stn DW 1998, 250-302 m; F, inner view of dorsal valve (MNHN BRA-3054), Arago Bank, stn DW 1978, 120-180 m; G, H, dorsal and lateral views of complete specimen (MNHN BRA-3055), Ruturu Island, stn DW 2001, 200-550 m; I, J, Megerlia truncata (Linnaeus, 1767), ventral and dorsal views of complete specimen (MNHN BRA-3050), Ruturu Island, stn DW 2009, 320-450 m. All SEM. Scale bars: A-C, F-J, 2 mm; D, E, 1 mm.