Lasaea eastera Raines &amp; Huber 2012, sp. nov.
Creators: name: Raines, Bret
name: Huber, Markus
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Bivalvia
Galeommatida
Lasaeidae
Lasaea
Lasaea eastera

description: <i>Lasaea eastera</i> sp. nov. Figures 26 A–H <b>Type Material.</b> Holotype: LACM 3150, 1 articulated specimen, 2.9 mm. Paratype: LACM 3151, 1 articulated specimen, 2 mm. <b>Type Locality.</b> Dredged at 30–80 m in fine sand, off the western coastline near Tahai, Easter Island, 27°07’20” S, 109°26’30” W. <b>Description.</b> A small, translucent white <i>Lasaea</i> species, with narrow, subcentral umbones. Shell small, below 3 mm, equivalve, subequilateral, oval with almost straight ventral margin; thin and translucent; uniformly whitishyellow outside, whitish inside; umbones narrow, pointed, subcentral, weakly prosogyrate. Prodissoconch, P1surface somewhat eroded, ovate and pronounced, ca. 75 µm length by 50 µm height, P2 smooth, with nearly obsolete growth striae, ca. 350 µm length by 340 µm height. Adult valves weakly inflated. Sculpture of weak commarginal striae, rather widely and somewhat irregularly spaced, radial elements absent. Hinge line thin, cardinals largely fused to lamellar posterior lateral and to shorter lamellar anterior lateral, laterals separated by a wide depression. Pallial line continuous. Ligament elongate, very thin and very narrow, marginally, embedded posterior to the umbones; resilifer subumbonal. Margins smooth. <b>Comparative diagnosis.</b> <i>Lasaea hawaiensis</i>, originally described from the Hawaiian Islands, was recorded early by Rehder (1980) from <i>EI</i> and is present with numerous specimens. However, these are very uniform in shape, solidity and color, typically with reddish staining in the umbonal area. No other <i>Lasaea</i> species has been described from the Hawaiian Islands. The new species has the same basic hinge configuration, though with a weaker, narrower hinge line and finer dentition. The structure is more fragile and translucent. The color is whitish and absent of any staining. The commarginal lines are wider and somewhat irregular. The umbones of adult <i>L. eastera</i> are most notably more pointed, narrower and stronger, exceeding the dorsal line and nearly centrally located. <i>Lasaea australis</i> (Lamarck, 1818), from South Australia is more solid, with distinct color, stronger sculpture, and rather trigonal in shape with posteriorly placed umbones. It also grows to a much larger size, 6.5 mm. <i>Lasaea colmani</i> Ó Foighil &amp; Thiriot-Quiévreux, 1999, from Sydney is less than half the size, broader with very low broad, posteriorly placed umbones. Numerous species have been described from New Zealand. Thereof, <i>L. hinemoa</i> Finlay, 1928, (syn. <i>L. rossiana</i> Finlay, 1928), is similar in shape and color to <i>L. hawaiensis</i>, and shares similar distinctive markings as <i>L. eastera</i>, notably colors and stronger hinge. <i>Lasaea hinemoa</i> also grows larger (4.6 mm) than the <i>EI</i> species. <i>Lasaea maoria</i> (Powell 1933), shares its fragile structure, small size and white color with that of <i>L. eastera</i>, but the pronounced broader umbones and the lower and broader shape do not match. In addition, the hinge line of <i>L. eastera</i> is narrow and the dentition weak, whereas even the smaller <i>L. maoria</i> has a comparatively more solid and stronger dentition. <i>Lasaea parengaensis</i> Powell, 1935, is very distinct in oblique-trigonal shape. <b>Remarks.</b> While <i>L. hawaiensis</i> is commonly encountered, <i>L. eastera</i> is very uncommon. The deeper habitat of the two <i>EI</i> species is highly unusual compared to the otherwise shallow global <i>Lasaea</i> species. This change in habitat is probably influenced by the active downslope sediment transport noted by DiSalvo <i>et al</i>. (1988: p. 454). <b>Distribution.</b> At present <i>Lasaea eastera</i> is only known from the type locality— <b>E1</b>. <b>Etymology.</b> The name reflects the type locality.
description: Published as part of <i>Raines, Bret &amp; Huber, Markus, 2012, 3217, pp. 1-106 in Zootaxa 3217</i> on pages 51-53
description: {"references": ["Rehder, H. A. (1980) The marine mollusks of Easter Island (Isla de Pascua) and Sala y Gomez. Smithsonian Contributions to Zoology, Number 289, 167 pp.", "Lamarck, J. B. P. A. de (1818) Histoire naturelle des animaux sans vertebres, presentant les caracteres generaux et particuliers de ces animaux, leur distribution, leurs classes, leurs familles, leurs genres, et la citation des principales especes qui s'y rapportent; precedee d'une introduction offrant la determination des caracteres essentiels de l'animal, sa distinction du vegetal et des autres corps naturels, enfin, l'exposition des principes fondamentaux de la zoologie. Deterville &amp; Verdiere, Paris, 5, 612 pp.", "O Foighil, D. &amp; Thiriot-Quievreux, C. (1999) Sympatric Australian Lasaea species. (Mollusca: Bivalvia) differ in their ploidy levels, reproductive modes and developmental modes. Zoological Journal of the Linnean Society, 127 (4), 477 - 494.", "Finlay, H. J. (1928) The recent Mollusca of the Chathman Islands. Transactions and Proceedings of the of the Royal Society of New Zealand, 59, 232 - 286.", "Powell, A. W. B. (1933) The marine Mollusca of the Chatham Islands. Records of the Auckland Institute and Museum, 1 (4), 181 - 208.", "Powell, A. W. B. (1935) Marine Mullusca from the Bounty Islands. Records of the Canterbury Museum, 4, 29 - 39.", "DiSalvo, L. H., Randall, J. E. &amp; Cea, A. (1988) Ecological reconnaissance of Easter Island sublittoral marine environment. National Geographic Research, 4, 451 - 473."]}