Limatula louiseae Clarke, 1974
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publication ID |
https://doi.org/ 10.1080/00222930310001647442 |
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persistent identifier |
https://treatment.plazi.org/id/7A20464E-EC20-FFD2-FE62-6EC0FCDCCFE0 |
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treatment provided by |
Felipe |
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scientific name |
Limatula louiseae Clarke, 1974 |
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Limatula louiseae Clarke, 1974 View in CoL
( figures 10–12 View FIG View FIG View FIG , 45a View FIG )
Type locality. Lynch sta. 9, 51 ‡ 06.6 ’ N, 37 ‡ 47.3 ’ W, 3110 m.
Holotype. NMNSO, No. 66418.
Material examined. Atlantis sta. OO#2, 33 ‡ 07.0 ’ N, 65 ‡ 03.2 ’ W, 4667 m, 1 spec.
Chain sta. 100, 33 ‡ 56.8 ’ N, 65 ‡ 47.0 ’ W, 4743 m, 1 spec.; sta. 313, 51 ‡ 32.2 ’ N, 12 ‡ 35.9 ’ W, 1500 m, 3 spec.; sta. 331, 41 ‡ 13.0 ’ N, 41 ‡ 36.7 ’ W, 4793 m, 3 spec.
Knorr sta. 299, 07 ‡ 55.1 ’ N, 55 ‡ 42.0 ’ W, 1942 m, 1 spec.; sta. 340, 38 ‡ 14.4 ’ N, 70 ‡ 20.3 ’ W, 3264 m, 1 v.
Atlantis II sta. 155, 00 ‡ 03.0 ’ S, 27 ‡ 48.0 ’ W, 3730 m, 2 spec.; sta. 156, 00 ‡ 46.0 ’ S, 29 ‡ 28.0 ’ W, 3459 m, 1 spec. z2 v.
Distribution. Originally described from one specimen found close to the Mid- Atlantic Ridge, west of Newfoundland ( Clarke, 1974), further specimens are here recorded from a similar latitude to that of the original although further east at slope depth. Elsewhere they are recorded from the mid-Atlantic close to the equator, off Surinam, and in the North America Basin. The species, though rare, appears to be widely spread in the North Atlantic and south to the equator from mid slope to abyssal depths (1500–4793 m).
Redescription ( figures 10 View FIG , 11 View FIG , 45a View FIG ). Although beautifully illustrated by Clarke (1974), he only gives a minimal description of the species.
Shell very small (maximum recorded height 2.4 mm), height/length ratio 1:0.56, fragile, very inflated, equivalve, equilateral, transluscent white, ornamented by unevenly spaced concentric ridges, radial ribs absent but often with microscopic diagonal lines on mid anterior and mid posterior parts of shell, internal median radial groove absent, ears small, somewhat rounded and not prominent, usually without auricular sinuses, occasional specimen with slight suggestion of anterior sinus, curvature of anterior and posterior shell margins similar, anterior margin somewhat flatter in mid-section, ventral margin sharply rounded; umbo large and prominent; hinge plate relatively broad, external margin slightly oblique to vertical axis of shell, each side of hinge margin tends to slope ventrally, internally ventral margin of hinge plate curves distally supported at each end by relatively strong, short, ventrally angled buttress ridge; ligament elongate lozenge shape. Prodissoconch I~ ca 200 M m; interdissoconch height varies~0.5–0.85 mm.
Anatomy ( figure 12 View FIG ). Anatomy very similar to that described for L. subovata . Sensory fold of mantle margin particularly broad, each bears five large tentacles, four on the inner part of the ventral margin and one anterior slightly ventral to the mouth, also an anal tentacle and four or five small papillate tentacles antero-ventrally on outer part of the sensory fold; gills small with 12 or 13
plicae in each demibranch; adductor muscle perhaps more posterior in position than in other species and not particularly large, circular in cross-section.
Remarks. Apart from one specimen taken at mid-slope depth, all others are from abyssal depths. The few specimens recorded to date are widely distributed from equatorial to northern temperate latitudes in the Atlantic. The species is characterized by the almost complete lack of radial ribs. A few very short illdefined radial lines may be present at the ventral margin. Very fine, straight,
parallel lines may be present on either side of the central area of the shell and which traverse inwards. The shell is relatively wide ( figure 11 View FIG ).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.