Borniola pasca 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
Borniola
Borniola pasca

description: <i>Borniola pasca</i> sp. nov. Figures 28 A–F <b>Type Material.</b> Holotype: LACM 3154, 1 single LV, 3.2 mm. Paratypes 1–3: LACM 3155, 3 single valves up to 2.2 mm from Tahai, 27°07’20” S, 109°26’30” W, 30–80 m. Paratypes 4–10: LACM 3156, 8 single valves up to 3 mm from the type locality. Paratypes 11–13: LACM 3157, 2 articulated specimens and 1 single valve, up to 3.4 mm, Motu Iti, 65 m. Paratypes 14–16: Coll. MHU, 1 articulated specimen and 2 single valves from Motu Iti, 65 m. <b>Type Locality.</b> Dredged at 50–100 m, in sand, La Perouse Bay, Easter Island, 27°04’26” S, 109°16’50” W. <b>Description.</b> A small, opaque white, shape-variable <i>Borniola</i> with a well defined disjunct dentition and the typical radial sculpture. Shell small, below 3.5 mm, variable in shape from rounded ovate to subquadrate, equivalve; no lunule; inequilateral; umbones prominent, pointed, opisthogyrate, posteriorly placed. Prodissoconch, P1 smooth, D-shaped, weakly defined, ca. 175 µm length by 142 µm height, P2 round, commarginally lined, ca. 356 µm length by 306 µm height. Adult valves rather compressed; non-gaping. Sculpture of dense, somewhat irregular, commarginal growth lines, crossed by dense, diverging radial striae. Hinge rather solid, without cardinals. RV with two strong, divergent, elongate laterals separated by a small depression; LV nearly edentate with a weakly expressed extended anterodorsal lamellar ridge parallel to the margin and a shorter, slightly more curbed lamellar ridge, parallel to the posterior margin. Weak hinge plate present. Pallial line continuous. Ligament internal, subumbonal. Margins smooth. <b>Comparative diagnosis.</b> The hinge configuration somewhat approaches the genus <i>Kurtiella</i> Gofas &amp; Salas, 2008. They (2008: 122) interpreted the spread teeth in the RV, but also the marginal ridges in the LV as laterals. As such species of <i>Kurtiella</i> have no cardinal teeth, but two marked laterals in the RV and much weaker dentition in the LV. However, the remote biogeography and distinct shape exclude it from this group. Moreover a weak hinge plate is present in <i>B. pasca</i> and the subumbonal pit in the RV is much less pronounced than in species of <i>Kurtiella</i>. From the Hawaiian Islands nothing similar is known, but numerous <i>Borniola</i> species from New Zealand are comparable (e.g. Powell, 1979: fig. 97). Notably, <i>Borniola powelli</i> Crozier, 1966, shares traits in hinge and shape with <i>B. pasca.</i> The genus <i>Borniola</i> was erected by Iredale (1924: 207) for the Sydney <i>Bornia lepida</i> (Hedley, 1906). Iredale gave no distinguishing remarks other than “very interesting species”. Hedley (1906: 543) illustrated the denticulate <i>B. lepida</i> hinge with two divergent teeth in one valve, but did not comment on the dentition in the other, nor did Chavan <i>in</i> Moore (1969: N523). Though reversing the left and right valves, Laseron (1956: 16) captured the <i>Borniola</i> species well, illustrating the type and other specimens, and noting the other hinge as edentate. As such, the hinge configuration within the genera <i>Kurtiella</i> and <i>Borniola</i> is comparable, although with a weak hinge plate still present in <i>Borniola</i>. In addition the genus <i>Borniola</i> is characterised by its radial sculpture. The shape is compressed, typically subequilateral, but in most species inequilateral. <i>Borniola</i> species are small in size, rarely surpassing 10 mm. <b>Remarks.</b> Due to a simple, non-reflected and non-tentaculate mantle, a single inner demibranch in most species and the hinge morphology of <i>Borniola</i> neatly sits in between <i>Kurtiella</i> and <i>Mysella</i>. Today, <i>Borniola</i> is placed within the montacutinids. Per Bouchet <i>et al</i>. (2010), the family Borniolidae Iredale &amp; McMichael, 1962, is treated as invalid. <b>Distribution.</b> <i>Borniola pasca</i> is rather common from several locations around Easter Island, in fine sand from 30–100 m, also in subtidal caves in Motu Tantarra, <i>EI</i>, 35–40 m — <b>E1</b>. <b>Etymology.</b> The name reflects its rather common occurrence at Isla de Pascua.
description: Published as part of <i>Raines, Bret &amp; Huber, Markus, 2012, 3217, pp. 1-106 in Zootaxa 3217</i> on pages 55-57
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