Elliptiolucina fernandoi, Kiel & Aguilar & Kase, 2020

Kiel, Steffen, Aguilar, Yolanda M. & Kase, Tomoki, 2020, Mollusks from Pliocene and Pleistocene seep deposits in Leyte, Philippines, Acta Palaeontologica Polonica 65 (3), pp. 589-627 : 599-600

Elliptiolucina fernandoi sp. nov.

Fig. 10 .

Zoobank LSID: urn:lsid:zoobank.org:act:6A60B3D8-F57F-498C-9E7D-895ADB4496FC

Etymology: In honour of Allan Gil S. Fernando (Quezon City, Philippines), for his invaluable help in dating the Bata Formation.

Type material: Holotype NMP-2163, an articulated specimen with the hinge of the right valve exposed. Paratype NMNS PM 28119 , a slightly damaged specimen with the anterior adductor muscle scars exposed from the type locality .

Type locality: Liog-Liog Point , Leyte, Philippines .

Type horizon: Upper Pliocene part of the Bata Formation .

Material.— Three specimens from the Pliocene of Liog-Liog Point : type material and NMNS PM 28149 . One specimen from the Pleistocene of Cambantug Point , NMNS PM 28122 and two from the Pleistocene of Buhoc Point , NMNS PM 28123 , 28124 .

Dimensions (in mm).—NMP-2163, L = 68.0, H = 55.1; NMNS PM 28119, L = 67.5, H = 55.1.

Diagnosis.—Average size for genus, outline oval but not very elongate, moderately inflated; hinge plate broad for genus, with distinct short, thick remnant of a cardinal tooth in left valve; no lateral teeth.

Description.—Shell oval in outline, umbones small, pointed, very little elevated above hinge plate, situated just anterior to vertical midline of shell; anterior margin broadly rounded or slightly oblique below vertical midline; posterior margin broadly rounded; anterodorsal margin straight to slightly convex, posterodorsal margin evenly convex or with slight median angulation; ventral margin evenly convex. Inflation moderate, evenly convex; lunule and escutcheon long, narrow, bordered by sharp ridges. Shell surface covered by fine, commarginal growth increments, most distinct in anterodorsal area; very slight, broad radial depressions marking antero- and posterodorsal areas. Hinge plate strong, right valve with triangular cavity underneath umbo, right valve with short, broad, vertical remnant of cardinal tooth; no lateral teeth. Anterior adductor muscle scar diverging from pallial line by ~40°, anterior pedal retractor scar round, distinct from adductor muscle scar.

Remarks.—The three extant species described by Cosel and Bouchet (2008) from deep waters of the Philippines and Indonesia ( Elliptiolucina magnifica , E. labeyriei , and E. virginiae ) differ from E. fernandoi by being more elongate and, except for E. labeyriei , by having a narrower hinge plate. E. williamsae Glover and Taylor, 2016 from 280–679 m depth in the central Philippines is smaller than E. fernandoi (44.1 mm vs. 68.0 mm maximum length) and it possesses a prominent anterior lateral tooth in the right valve that is missing in E. fernandoi . The extant E. ingens Okutani, 2011 from 576–594 m depth on the slope of the East China Sea ( Okutani 2011), growth to bigger size (up to 90.7 mm) and is more inflated than E. fernandoi .

Three fossil species of Elliptiolucina are described to date. The late Oligocene E. washingtonia Kiel, 2013 from western Washington state, USA, is more elongate and has a straighter posterodorsal margin than E. fernandoi . The middle Miocene E. neozelandica Amano, Little, and Campbell, 2018 from the Moonlight North seep deposit in New Zealand ( Amano et al. 2018) is much smaller and has more elevated umbones than E. cambantugensis . The late Miocene Elliptiolucina hetzeli ( Martin, 1933) from asphalt deposit on Buton Island, Indonesia ( Martin 1933; Kiel 2013) is more elongate and has more narrowly rounded anterior and posterior margins compared to E. fernandoi .

Stratigraphic and geographic range.—Late Pliocene to early Pleistocene: Leyte, Philippines.

Figures

Fig. 10. The lucinid bivalve Elliptiolucina fernandoi sp. nov. from the Pliocene Liog-Liog seep deposit in Leyte, Philippines. A. Holotype NMP-2163, articulated specimen; view on left (A1) and right (A2) valves, view on the dorsal side (A3), close-up on hinge of right valve (A4). B. Paratype NMNS PM 28119, slightly damaged, articulated specimen; view on exterior of right valve and hinge of left valve (B1), view on exterior of left valve (B2), close-up on hinge of left valve (B3).