Megerlia King, 1850

Bitner, Maria Aleksandra & Logan, Alan, 2016, Recent Brachiopoda from the Mozambique-Madagascar area, western Indian Ocean, Zoosystema 38 (1), pp. 5-41 : 30-32

Genus Megerlia King, 1850

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

Megerlia truncata ( Linnaeus, 1767) ( Fig. 17 G-K; Table 15)

Anomia truncata Linnaeus, 1767: 1152 , 229.

Mühlfeldtia truncata – Fischer & Oehlert 1891: 80, pl. 7, figs 11a-u.

Megerlia truncata – Davidson 1887: 103, pl. 19, figs 11-20. — Brunton et al. 1967: 177, pl. 4, figs 14-25. — Logan 1979: 68, pl. 9, figs 1-23. — Cooper 1981b: 16, pl. 3, figs 5-11.

Megerlia gigantea – Cooper 1981a: 27-28, pl. 6, figs 1-26.

MATERIAL EXAMINED. — North West Madagascar. MIRIKY, stn DW 3228, 1 bivalved specimen. — Stn DW 3232, 2 bivalved specimen. — Stn DW 3239, 1 bivalved specimen. — Stn CP 3240, 1 bivalved specimen. — Stn CP 3247, 1 bivalved specimen. — Stn DW 3289, 1 bivalved specimen. — Stn CP 3293, 1 ventral valve. — Stn DW 3294, 3 bivalved specimens.

South Madagascar. ATIMO VATAE, stn DW 3515, 1 bivalved specimen. — Stn CP 3527, 1 bivalved specimen. — Stn DW 3528, 9 bivalved specimens. — Stn DW 3529, 4 bivalved specimens. — Stn DW 3552, 12 bivalved specimens, 3 ventral valves, 5 dorsal valves. — Stn DW 3553, 2 bivalved specimens, 1 ventral valve. — Stn CP 3613, 2 bivalved specimens. — Stn CP 3615, 1 bivalved specimen, 2 dorsal valves.

DEPTH RANGE. — 184- 442 m.

MEASUREMENTS. — See Table 15.

REMARKS

Three of the four known species of Megerlia that occur globally are found in the Indian Ocean . Megerlia truncata , the type species is widely distributed throughout the oceans of the World ( Cooper 1981b; Logan 2007) but is perhaps most common in the Mediterranean Sea ( Logan 1979). Jackson (1921) also recorded this species from the Persian Gulf. The present study is the first published record of M. truncata from the southern Indian Ocean unless the variety monstruosa (Scacchi, 1838) is accepted as a synonym (see Logan 1979; Bitner 1990; Hiller 1994). Specimens from Madagascar are virtually indistinguishable from typical Mediterranean forms and usually inhabit the same moderate depths down to about 500 m. Cooper (1981b) notes the variability in the external shell of this species, while the progressive changes that take place during the ontogenetic development of the loop of the dorsal valve have been illustrated by Davidson (1887) and Logan (1979), among others. The closely-related M. echinata has been recorded from the coast of South Africa and in the Red Sea ( Cooper 1973a; Logan et al. 2008), while another comparable Megerlia species from the Indian Ocean area is M. acrura Hiller, 1986 from the coast of South Africa (see below). M. gigantea (Deshayes, 1863) , described by Cooper (1981a) from South of Madagascar, is here placed in the synonymy of M. truncata because, in our opinion, there are insufficient reasons to separate them and, in this respect, we therefore follow Davidson (1887) rather than Cooper (1981a).

Figures

FIG. 17. — A-F, Megerlia acrura Hiller, 1986: A, B, ventral and lateral views of complete specimen (MNHN IB-2013-94), North-West Madagascar, off the Bay of Nazendry, MIRIKY, stn DW 3239, 230-288 m; C-F, interior of dorsal valve (MNHN IB-2013-95), oblique and tilted views, and enlargement (F) of posterior part to show details of cardinalia, Mozambique Channel, Inhambane transect, MAINBAZA, stn CC 3159, 148-152 m, SEM; G-K, Megerlia truncata (Linnaeus, 1767): G, H, dorsal views of complete specimens (MNHN IB-2013-96-97), North-West Madagascar, MIRIKY; G, West of Nosy Be, stn DW 3232, 210-310 m; H, in front of the Nazendry Bay, CP 3289, 332-379 m; I, J, Inner view of ventral valve (MNHN IB-2013-98), and enlargement of posterior to show teeth, area and pedicle collar, South Madagascar, South of Faux-Cap ATIMO VATAE, stn DW 3552, 264-280 m, SEM; K, inner view of dorsal valve (MNHN IB-2013-99), stn DW 3552, 264-280 m, SEM. Scale bars: A, B, G, H, 3 mm; C-E, I, K, 2 mm; F, J, 1 mm.