Macandrevia emigi, Bitner & Logan, 2016

Bitner, Maria Aleksandra & Logan, Alan, 2016, Recent Brachiopoda from the Mozambique-Madagascar area, western Indian Ocean, Zoosystema 38 (1), pp. 5-41 : 22

Macandrevia emigi n. sp.

( Fig. 12 ; Table 11)

TYPE MATERIAL. — Mozambique Channel. MAINBAZA, stn CC 3170 , holotype ( MNHN IB-2013-71 ; Fig. 12 J-Q). — Same data, stn CP 3139, three paratypes ( MNHN IB-2013-72 - 74 ; Fig. 12 D-I) .

TYPE LOCALITY. — Mozambique Channel, Maputo transect, MAIN- BAZA, stn CC 3170, 25°58’S, 34°47’E, 949- 952 m.

ETYMOLOGY. — Named in honour of Christian C. Emig (BrachNet, Marseille, France), a prodigious worker in the field of inarticulated brachiopods.

MATERIAL EXAMINED. — Mozambique Channel. MAINBAZA, stn CP 3139, 1 bivalved specimen. — Stn CC 3170, 1 bivalved specimen. South Madagascar. ATIMO VATAE, stn CP 3589, 35 bivalved immature specimens.

DESCRIPTION

Shell of medium size (maximum observed length 12.6 mm), thin, translucent, elongate oval to rounded while young to subpentagonal in adult, ventribiconvex. Shell surface smooth with numerous growth lines. Lateral commissures straight, anterior commissure rectimarginate to incipiently sulcate. Hinge line short, slightly curved. Beak suberect to erect. Foramen large, oval, permesothyrid, deltidial plates rudimentary. Ventral valve interior with small teeth supported by divergent dental plates united by a callus closely applied to the valve floor ( Fig. 12H, N ). Dorsal valve interior with small cardinal process and high inner socket ridges. Inner hinge plates attached directly to the valve floor. Low, short median septum present in early stages of ontogeny ( Fig. 12 D-F), in adults median septum absent ( Fig. 12O, P ). Loop long with narrow descending and ascending branches, transverse band moderately broad with short projections, and short spines anteriorly ( Fig. 12Q ).

REMARKS

The superfamily Zeillerioidea comprises 10 extant species belonging to a single genus, Macandrevia ( Logan 2007) . Species of the genus have previously been recorded virtually from pole to pole and usually from cold deep waters ( Cooper 1975) but not from the Indian Ocean or western and central Pacific. This description of a new species, based mainly on 35 specimens from South Madagascar, is thus the first record of the genus from the Indian Ocean . Most species of Macandrevia are eurybathic, with M. tenera extending down to 4600 m but the depth range of M. emigi n. sp. is much less. The new species is comparable in size to the northern Atlantic species, M. novangliae Cooper, 1977 and M. tenera (Jeffreys, 1876) ( Cooper 1975, 1977, 1981b), other species are much larger. However, the species from the Madagascar region differs from all hitherto described species in its triangular outline.

Figures

FIG. 12. — Macandrevia emigi n. sp.: A-C, dorsal views of complete specimens (MNHN IB-2013-75-76), South Madagascar, South-West Point Barrow, ATIMO VATAE, stn CP 3589, 132-153 m; D-F, inner view of dorsal valve of young individual (MNHN IB-2013-73), and oblique view (E) and enlargement of posterior part (F) to show details of a loop, paratype, stn CP 3589; G, H, inner view of ventral valve (MNHN IB-2013-74) and tilted view to show dental plates (H), paratype, stn CP 3589; I, dorsal view of complete specimen (MNHN IB-2013-72), paratype, Mozambique Channel, Inhambane transect, MAINBAZA, stn CP 3139, 1092- 1195 m; J-Q, complete specimen (MNHN IB-2013-71), holotype, Mozambique Channel, Maputo transect, MAINBAZA, stn CC 3170, 949-952 m: J-L, dorsal, anterior and lateral views, M, N, posterior part of ventral valve interior and tilted view to show distinct dental plates,SEM O-Q, interior view of dorsal valve, oblique view, and enlargement of fringe of spines (Q), SEM. Scale bars: A-E, G, M, O, P, 2 mm; F, H, N, 1 mm; I-L, 5 mm; Q, 500 µm.