Bathymodiolus labayugensis, Kiel & Fernando & Magtoto & Kase, 2022

Kiel, Steffen, Fernando, Allan Gil S., Magtoto, Clarence Y. & Kase, Tomoki, 2022, Mollusks from Miocene hydrocarbon-seep deposits in the Ilocos-Central Luzon Basin, Luzon Island, Philippines, Acta Palaeontologica Polonica 67 (4), pp. 917-947 : 922-923

publication ID	https://doi.org/ 10.4202/app.00977.2022
persistent identifier	https://treatment.plazi.org/id/0470A855-EA7D-FF9F-FCD9-FE338A6AF9B6
treatment provided by	Felipe
scientific name	Bathymodiolus labayugensis
status	sp. nov.

Treatment

Bathymodiolus labayugensis View in CoL sp. nov.

Fig. 5 View Fig .

Zoobank LCID: urn:lsid:zoobank.org:act:5E3EB20E-A4A9-4E9F-BF8E-0295FF7A96BB

Etymology: For the Barangay Labayug, where the Northern Cement Corporation Quarry is located.

Type material: Holotype NIGSPAL-005, isolated LV with shell partially broken off. Paratypes: NRM Mo 192523–192532, mostly isolated valves embedded in rock matrix; all from block B in the type locality .

Type locality: The “shale quarry” within the Northern Cement Corporation quarry in Pangasinan province, Luzon, Philippines .

Type horizon: Seep carbonate blocks enclosed in the Amlang Formation (Upper Miocene) .

Material.— 65 specimens from block B (NIGSPAL-005, 006, 007, NRM Mo 192472–192533) , one specimen from block D (NIGSPAL-008), one specimen from block F ( NRM Mo 192541), six fragmentary specimens from block G , five specimens from block I ( NRM Mo 192680–192684). All from the type locality and horizon .

Dimensions ( in mm).— Holotype NIGSPAL-005: L = 57.5, H = 27.0, W (single) = 10.0; paratypes: NRM Mo 1922523: L = 41.6, H = 22.5; NRM Mo 1922524: 44.5, H = 24.2; NRM Mo 192525: 41.5+, H = 25.0; NRM Mo 192526: L = 42.5, H = 28.3; NRM Mo 192527: L = 42.5, H = 25.8; NRM Mo 192528: L = 33.0, H = 22.4; NRM Mo 192529: L = 37.1, H = 21.7; NRM Mo 192530: L = 45.4, H = 22.0; NRM Mo 192531: L = 30.3, H = 13.8, W = 9.5; NRM Mo 192532: L = 24.5, H = 13.0.

Diagnosis.—Shell small for genus, widening posteriorly; umbo in subterminal position; anterior side broad, evenly rounded, dorsal margin long, gently convex, ventral margin concave; maximum inflation at center of shell.

Description.—Elongate, arched modioliform shell of medium size (up to 57.5 mm), height/length ratio about 0.45, width/ height ratio ~0.8. Surface smooth except for fine growth lines. Blunt ridge running from beak toward posteroventral area; area before ridge depressed, area dorsal to ridge broad and flat. Beak low, prosogyrate, in subterminal position. Anterior margin rounded; ventral margin concave; posterodorsal margin long, convex, continuing into subtruncated posterior margin. Internal groove running from umbones to dorsal side of large, D-shaped posterior adductor muscle scar.

Remarks.— Bathymodiolus labayugensis differs from the Miocene Bathymodiolus heretaunga Saether, Little, Campbell, Marshall, Collins, Alfaro, 2010b , from seep deposits in New Zealand by having the umbones in a more anterior position ( Saether et al. 2010b). Two fossil Bathymodiolus species have been reported from the fossil record of Japan, the Oligocene Japanese “ Bathymodiolus ” inouei Amano and Jenkins, 2011 and the Miocene Bathymodiolus akanudaensis ( Kuroda, 1931) ; both have a more angular and more anteriorly situated transition from dorsal to posterior margin compared to B. labayugensis ( Kuroda 1931; Amano et al. 2010; Amano and Jenkins 2011). The Middle to Late Miocene “ Bathymodiolus ” moroniae from the “Calcari a Lucina ” seep deposits in Italy ( Kiel and Taviani 2017) differs from B. labayugensis by having a straight dorsal margin, in contrast to the curved one of B. labayugensis . The same applies to the Oligocene–Miocene Bathymodiolus palmarensis Kiel, Campbell, and Gaillard, 2010 , from the Caribbean region ( Kiel et al. 2010, Kiel and Hansen 2015).

Stratigraphic and geographic range. —Upper Miocene of Luzon, Philippines.