Conchocele visayaensis, 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 : 593

Conchocele visayaensis sp. nov.

Fig. 4 .

Zoobank LSID: urn:lsid:zoobank.org:act:B519A43A-40C5-4D98-9DF6-24314E078AC6

Etymology: In reference to the Visaya Basin, the type region.

Type material: Holotype NMP-2160, an articulated specimen.

Type locality: Cambantug Point , Leyte, Philippines .

Type horizon: Lower Pleistocene part of the Bata Formation .

Material.— The holotype and 11 articulated specimens (in one lot: NMNS PM 28126 ) .

Dimensions (in mm).—NMP-2160, L = 77.6, H = 66.4.

Diagnosis.—Large Conchocele with slightly concave anterior margin; posterodorsal area rather narrow, median ridge indistinct to absent, posterior sulcus curved, producing deep indent in posterior shell margin; ventral margin well rounded, transition to posterior margin indistinct.

Description.—Large, well-inflated shells, W/H ratio of single valve ~0.36, umbones terminal, blunt, prosogyrate; anterior margin long, slightly concave; anterodorsal area broad, heart-shaped, bordered by distinct ridge; posterodorsal area narrow, smooth, bordered by blunt sulcus and ridge that form deep indentation at posterior margin; ventral margin gently convex, ending posteriorly at posterior sulcus; outer surface with fine, irregular growth lines.

Remarks.—For differences to Conchocele majimai see above. Compared to Conchocele visayaensis , Conchocele sp. from Papua New Guinea ( Samadi et al. 2015: fig. 2F) has a curved rather than angular transition from posterodorsal to posterior margin, and the posterior sulcus in a more dorsal position, resulting in a smaller posterodorsal area and in a broader and more curved posteroventral margin. The same applies to extant North Pacific shells typically identified as Conchocele bisecta ( Coan et al. 2000; Kamenev et al. 2001; Kharlamenko et al. 2016). Shells identified as “ Conchocele bisecta Conrad ” dredged from Sagami Bay, Japan, in the collection of the National Museum of Nature and Sciences in Tsukuba (T. Haga coll.) are very similar, if not identical, to Conchocele visayaensis .

Stratigraphic and geographic range.—Early Pleistocene, Leyte, Philippines.

Figures

Fig. 4. The thyasirid bivalve Conchocele visayaensis sp. nov. from the Pleistocene Cambantug Point seep deposit at Leyte, Philippines, holotype NMP- 2160, outer shell surface of right (A1) and left (A2) valves; anterior side (A3), posterodorsal margin (A4).