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Comprehensive Description

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Description

"Nucula austrobenthalis n.sp. (Figs 1, 3)

 

MATERIAL EXAMINED: Eltanin Stns 260, 848, 945, 1939, Cruise 17 Stn 14.

 

DISTRIBUTION: Known from a wide range of deep-water basins south of 56°S in 3519-4209 m.

 

DESCRIPTION: Shell relatively large, elongate, beaks strongly incurved, close to posterior margin. Dorsal margin gently sloping, anterior margin broadly rounded, ventral margin evenly curved, posterior squarish, concave below beaks. Valves narrowly inflated. Sculpture of strong, regular, closely spaced commarginal ribs crossed by fine radial striae. Epidermis thin, golden yellow. Escutcheon narrow, elongate, smooth, strongly depressed. Lunule very large, margin clearly marked off, a simple broad radial ridge running through middle of lunule, inner margin strongly depressed. Hinge plate moderately developed, anterior gently curved bearing 19-25 evenly developed teeth, posterior short with 7-11 teeth. Anterior and posterior teeth separated by a moderately large, obliquely set chondrophore. Interior of valve smooth and polished with subsurface, fine radial structural elements showing through, ventral margin finely crenulate.

 

MEASUREMENTS: See Table 1.

 

HOLOTYPE: EItanin Stn 945, in collection of National Museum of Natural History, Washington (USNM 860075).

 

PARATYPES: EItanin Stns 260 (one, USNM 860076), 848 (2, USNM 860076), 1939 (one, 860078) and Cruise 17, Stn 14 (one, USNM 860079) in National Museum of Natural History, and from Stn 945 (one, MF.56626) and Cruise 17, Stn 14 (one, MF.56627) in National Museum of New Zealand.

 

REMARKS: This new species has a superficial resemblance to the type species of Nuculoma Cossmann, 1907, N. castor (Orbigny), which also has strong commarginal ribs and a wide lunule, but which lacks the radial striae and has smooth inner ventral margins. Nucula austrobenthalis has most of the characters of Nucula (s.str.) and seems best placed in this genus. The elongate shape and squarish posterior margin make it distinctive.

 

There are no characters whereby the specimens from each of the Southern deep water basins may be distinguished from one another.

 

Table 1. Measurements of Nucula austrobenthalis"

                                            
 

Locality

 
L (MM)H (mm)Inflation (mm)Ant. teethPost. teeth
holotype17.013.03.92511
Eltanin Stn 26013.09.63.1197
Eltanin Stn 19,1911.09.02.5187
Eltanin Cr.17, Stn 1415.011.84.0238
 

(Dell, 1990: 6-7)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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