Abranda lamprelli, Raines & Huber, 2012

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 78-79

Abranda lamprelli sp. nov.

Figures 40 A–G

Type Material. Holotype: LACM 3173, single RV 5.7 mm. Paratypes 1–9: LACM 3174, 9 single valves up to 7 mm from the type locality. Paratypes 10–14: LACM 3175, 5 single valves up to 5.4 mm from Mataveri, 150 m. Paratypes 15–24: LACM 3176, 10 single valves up to 7.1 mm from Tahai, 50–100 m. Paratypes 25–32: Coll. MHU, 8 single valves from Tahai, 50–100 m.

Type Locality. Dredged at 50–100 m in fine sand, off the western coastline near Tahai, Easter Island, 27°07’20” S, 109°26’30” W .

Description. A small, elongate whitish Abranda species , with a disjunct dentition and an internal ligament portion. Shell small, barely exceeding 7 mm in length, equivalve, elongate-elliptical with a posterior flexure, marked by a weak posterodorsal angle; thin and fragile; whitish with faint radial traces of yellow or orange; no lunule; umbones small, slightly extending the dorsal line, orthogyrate, situated posterior to midline. Prodissoconch pronounced, P1 round, smooth, ca. 88 µm length by 78 µm height, P2 ovate with faint commarginal lines, ca. 155 µm length by 182 µm height. Adult valves weakly inflated. Sculpture of fine commarginal lamellae crossed by microscopic radials; lamellae are easily rubbed off and leave a smooth, glossy surface. Hinge line rather thin, in RV with an anterior and a bifid posterior cardinal, two marked, long laterals extending to dorsal and posterior midline. LV with stronger anterior and a weaker ridge-shaped posterior cardinal, laterals fused to margin and virtually absent. Pallial sinus weakly impressed, in LV broadly rounded, deep and almost reaching anterior scar, halfway confluent with pallial line; in RV shorter, broad, reaching midline, largely confluent. External ligament portion yellowish-brown, moderately extended and narrow; internal portion narrow, obliquely situated behind posterior lateral. Margins rather acute, smooth.

Comparative diagnosis. Closest to the new species is the type species of Abranda , Tellina modestina Tate, 1891 . This assessment was confirmed by A. Langleit, (pers. comm., 2010).

Abranda is an unusual tellinid genus mainly known from Australian waters. It shares an internal ligament portion with semelids, and has a disjunct dentition with weak or absent laterals in the LV. The valves are comparatively small, thin and commarginally sculptured.

Compared to Abranda modestina ( Tate, 1891) , the pallial sinus in A. lamprelli is deeper in the LV, reaching the anterior scar, the two laterals in the RV are wider, more elongate and the shape is even more attenuated. Abranda modestina reaches 14 mm, whereas A. lamprelli is not known above 7 mm. Abranda hypelliptica ( Salisbury, 1934) , from Australia and the closely related A. radiatolineata ( Yokoyama, 1924) , share a similar size, but are shorter and higher in shape and often found in reddish colors. Abranda jeanae ( Healy & Lamprell, 1992) , from Australia is distinct by having a higher shape, stronger sculpture and much larger size.

Remarks. There is nothing similar known from the Hawaiian Islands. The genus Abranda seems to be excluded from the Caribbean Tellina species in biogeography, shell morphology, hinge and size. Instead Abranda approaches the genera of Pinguitellina Iredale, 1925 , or Arcopagia Brown, 1827 , but is here generically separated.

Distribution. Abranda lamprelli is commonly found at many locations around Easter Island, in fine sand, from 50–200 m — E1.

Etymology. The name given to this species is in honor of the late Kevin Lamprell, who provided the senior author with years of advice prior to his passing 2003.