Ennucula eltanini Dell 1990

"Ennucula eltanini n.sp. (Figs 6, 7)

MATERIAL EXAMINED: Eltanin Stn 1605; Hero Stn 484.

DISTRIBUTION: The new species is so far known only from Magellan Strait and off western Tierra del Fuego in 307-544 m.

DESCRIPTION: Shell small, beaks prominent, situated about posterior third. Anterodorsal margin, anterior and posterior margins evenly curved, posterodorsal margin flattened, meeting posteroventral margin rather abruptly. Valves of medium inflation. Lunule hardly distinct, escutcheon bounded by sunken margin. Sculpture of rather irregular, widely spaced, coarse growth lines. Exterior covered by a thin, fragile, brownish yellow epidermis. Hinge plate of medium strength with 8-10 anterior and 5-7 posterior teeth, with a relatively small, upright, roundish chondrophore. Interior smooth and polished with faint, radial threads, internal valve margins smooth.

MEASUREMENTS: L 4.1 mm, H 3.2 mm, inflation 1.1 mm.

HOLOTYPE: Hero Stn 484, in collection of National Museum of Natural History, Washington (USNM 860080).

PARATYPES: Eltanin Stn 1605 in collection of National Museum of Natural History, Washington (4, USNM 860081) and of National Museum of New Zealand (one, MF.56625).

REMARKS: Ennucula eltanini n.sp. shares many of the characters of the New Zealand Ennucula strangeiformis (Del], 1956), which Bergmans (1978: 706) pointed out is very similar to the Australian Nucula dilecta Smith, 1891. The lack of marked interior marginal crenulations and of radial shell structural elements generally precludes the inclusion of this group of species in the genus Nucula or even in the subfamily Nuculinae Gray, 1824 (in the sense of Maxwell, 1988), it being rather in the subfamily Nuculominae Maxwell, 1988. Within the latter subfamily, the only known genus with reasonably close affinities would appear to be Ennucula Iredale, 1931. The small, roundish chondrophore present in this group of species contrasts with the more elongate, obliquely set chondrophore usually considered typical of Ennucula. In the meantime, this rather anomalous group is retained in Ennucula, although a new taxon may prove necessary when a thorough critical revision of the Nuculidae is undertaken.

Ennucula eltanini differs from E. strangeiformis (Dell, 1956) (= ?dilecta Smith, 1891) in the markedly narrower shell and evenly curved anterior outline. It is quite distinct from all other known Magellanic members of the family."

(Dell, 1990: 8)