Tellimya pauciradiata, Raines & Huber, 2012

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 57-59

Tellimya pauciradiata sp. nov.

Figures 29 A–E

Type Material. Holotype: LACM 3158, 1 single LV, 7.9 mm. Paratypes 1–10: LACM 3159, 10 single valves, 2 to 8.8 mm from the type locality. Paratypes 11–12: LACM 3160, 2 single RV from Hanga Roa , Easter Island, dredged 70–100 m. Paratypes 13–18: Coll. MHU, 6 single valves from the type locality.

Type Locality. Dredged at 30–50 m in fine sand, off the western coastline near Tahai, Easter Island, 27°07’20” S, 109°26’30” W .

Description. A typical, subelliptical, comparatively large Tellimya species , fragile in structure and sculptured with weak radials. Shell rather small, though large for the genus, at or below 8.8 mm; subelliptical, slightly narrower anteriorly, equivalve, inequilateral with umbones close to the bulging posterior end; thin, translucent; umbones rounded, pointed, and, as in the type species rather orthogyrate. Prodissoconch, P1 small, but typically worn away, ca. 93 µm length by 65 µm height, P2 with faint commarginal lines, ca. 325 µm length by 276 µm height, P2/N boundary weakly defined. Adult valves white internally and externally; weakly inflated, non-gaping. Surface superficially smooth, except for numerous, weak commarginal lines, crossed by about a dozen weakly impressed, spaced radial lines. The radial sculpture is strongest centrally, vanishing anteriorly and posteriorly. Hinge simple; in both valves with a strong anterior tooth, interpreted for both valves as montacutinid lateral, directed ventrally. Behind this front tooth follows a deep resilial recess. Its posterior end is followed by an oblique, characteristic ridge which was erroneously interpreted as an oblique left lateral by Chavan in Moore (1969: N532) for T. ferruginosa .

Corresponding to this ridge, the posterodorsal margin is bulged. Pallial line continuous, muscle scars unequal, the narrowly shaped anterior scar is significantly larger. Ligament internal and subumbonal. Margins smooth, very fragile.

Comparative diagnosis. The EI material matches the genus Tellimya , and the European type species T. ferruginosa is morphologically very close. This placement was proposed by P. Middelfart, (pers. comm., 2010).

There is nothing similar currently known from the Hawaiian or the Marquesas Islands. However, another undescribed Tellimya species , 4.5 mm, somewhat similar to T. benthicola ( Dell, 1956) , was recently studied from Tahiti. From New Zealand three species are placed within the genus Tellimya , T. aupouria ( Ponder, 1968) , T. benthicola ( Dell, 1956) , and T. reinga ( Crozier, 1966) . The first was originally described in the montacutid subgenus Tellimya ( Ponder, 1968: 127) . The other two were originally described in the genera Scintillona Finlay, 1926 , and Thracia G.B. Sowerby I, 1823 , respectively. However, Marshall (2002: 223) demonstrated that morphologically T. benthicola and T. reinga are closest in shape and hinge to Tellimya . Anatomy and mode of life of the last two species are unknown.

Morphologically, anatomically and in commensal mode of life, T. aupouria matches Tellimya well. Compared to this rather close New Zealand congener, the shape of T. pauciradiata is more attenuated, muscle scars are significantly larger, notably the anterior one, and the EI species grows much larger. Both species however, share the typical sublittoral habitat of Tellimya species. As with the other species of Tellimya , T. aupouria is also commensal, here on the echinoid Brissus gigas Fell, 1947 . Unfortunately the mode of life and host of T. pauciradiata is unknown.

Tellimya benthicola is shorter, more tumid in shape, much smaller in size (less than 4 mm) and prefers a bathyal habitat. Tellimya reinga is distinctly shaped and reversed in breath, broader anteriorly than posteriorly. In addition, T. reinga is nearly 12 mm which is among the largest Tellimya and it also prefers bathyal depths. In both species the anterior lateral is weakly expressed.

In shape, including the posterodorsal bulge, and in sculpture T. pauciradiata is virtually identical to the European T. ferruginosa , e.g. from Brittany. Both share the large sizes for this group with nearly 9 mm and 14 mm respectively. Chavan in Moore (1969: E32 2a) illustrated a non-typical, strongly truncate specimen. The typical rusty deposit of T. ferruginosa , however, was not encountered in the EI species. In addition, the valves of the latter are even more fragile with the commarginal lines weakly expressed and the anterior lateral being more pronounced. The three other European Tellimya species , i.e. T. semirubra ( Gaglini, 1992) , T. tenella ( Lovén, 1846) and T. voeringi ( Friele, 1877) are smaller than T. pauciradiata and distinct in their shorter shape.

“ Tellimya ” ephippiolum Melvill & Standen, 1899, from Boydong Cays in northern Australia is removed from Tellimya , but approaches the genus Kelliopsis Verrill & Bush, 1898 .

Due to its morphology, anatomy and the commensal mode of life Tellimya species are well placed in montacutinids.

Remarks. There is nothing similar known from the Hawaiian or Marquesas Islands.

Distribution. Tellimya pauciradiata is known from many locations around Easter Island, from 30–100 m — E1.

Etymology. The name reflects the weakly marked radial sculpture.