Elliptiolucina sp.

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 : 929-932

Elliptiolucina sp.

Fig. 11 .

Material.— Six specimens from block E ( NRM Mo 192466– 192471) , 2 specimens from block H ( NRM Mo 192411– 192412) , 1 specimen from block I ( NRM Mo 192664). Upper Miocene of the “shale quarry” within the Northern Cement Corporation quarry in Pangasinan province, Luzon, Philippines .

Dimensions (in mm).—NRM Mo 192470: L = 21.0, H = 18.8, W = 9.0; NRM Mo 192469: LV L = 17.2, H = 12.0; NRM Mo

192412: LV L = 15.0, H = 14.4; NRM Mo 192411: RV L = 14.3+, H = 11.7; NRM Mo 192664, L = 21.7+, H = 21.8.

Remarks.—Species of Elliptiolucina typically have lengths between 70.0 and 140.0 mm ( Cosel and Bouchet 2008; Okutani 2011; Kiel 2013; Glover and Taylor 2016; Kiel et al. 2020a). This applies also to the two species of Elliptiolucina reported from Pliocene seep deposits in Leyte, Philippines ( E. ingens Okutani, 2011 , and E. fernandoi Kiel, Aguilar, and Kase, 2020a ), which further differ from the species reported here by having less convex ventral margins ( Kiel et al. 2020a). An exception is the Middle Miocene Elliptiolucina neozelandica Amano, Little, and Campbell, 2018 , which reaches only about 35.0 mm in length, but differs from the species reported here by being more elongated and having a less convex ventral margin ( Amano et al. 2018). We consider the small specimens reported here as juveniles and refrain from assigning them to any described or new species.

Family Vesicomyidae Dall and Simpson, 1901

Genus Pliocardia Woodring, 1925

Type species: Anomalocardia bowdeniana Dall, 1903 , by original designation; Pliocene , Bowden Formation, Jamaica .

Pliocardia ballesterosi sp. nov.

Fig. 12 .

Zoobank LCID: urn:lsid:zoobank.org:act:67677ED9-BF0C-4BD1-B194-A6BFCFC836DF

Etymology: For Alfredo D. Ballesteros, Jr., Sustainable Development and Community Relations Department Head of the Northern Cement Corporation, who aided collecting at the quarry.

Type material: Holotype NIGSPAL-025, isolated RV with preserved shell . Paratypes: NRM Mo 192546–192552, articulated and disarticulated specimens mostly with preserved shell material, from the type locality and horizon .

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.— Nine specimens from block B ( NRM Mo 192613–192618, NIGSPAL-025, 027) , 20 specimens from block F ( NRM Mo 192546–192565). All from the type locality and horizon .

Dimensions (in mm).—NIGSPAL-025: L = 31.0, H = 24.0, W (single) = 11.0; NRM Mo 192552: L = 32.4, H = 24.7, W = 20.0; NRM Mo 192550: L = 29.7, H = 22.3, W = 16.8; NRM Mo 192546: L = 30.0, H = 2.1, W (single) = 8.0; NRM Mo 192551: L = 35.0, H = 25.7, W (single) = 10.0; NRM Mo 192547: L = 30.6, H = 25.2, W (single) = 7.8); NIGSPAL-026: L = 26.1, H = 20.1, W = 16.0.

Diagnosis.—Large, well inflated, oval to subquadrate shell, posterodorsal sulcus poorly developed; blunt, elevated, prosogyrate umbones in very anterior position; lunular incision well-defined; small, shallow pallial sinus.

Description.—Shell large compared to the type species of Pliocardia , but small compared to members of the “ cordata group”, reaching 32.4 mm in length; outline oval to subquadrate, posterior margin subtruncated to acutely rounded, ventral and posterodorsal margin convex, anterior margin narrow, more-or-less acutely rounded; posterior ridge and groove poorly developed on most specimens; lunular incision deep, outline broadly lenticular; escutcheon narrow, poorly defined; no external sculpture except for numerous fine growth increments. Hinge plate moderately broad, rather short, three cardinal teeth in each valve; in RV, cardinal strong, pointing anteroventrally, cardinal 3a short, parallel to shell margin, 3b elongate, bifurcated, raised edges, subparallel to shell margin, posterior edge about three time the length as anterior edge; in LV, cardinal 2a strong, pointing anteriorly, cardinal 2b blunt, broadly trapezoid, with two short raised edges, cardinal 4b moderately long, parallel to shell margin. Anterior adductor muscle scar oval, with narrow connection to small pedal retractor scar; posterior adductor muscle scar round to slightly oval, distinct but not deep; pallial line entire, with shallow pallial sinus.

Remarks.—Most similar to P. ballesterosi in overall shell shape is the extant Pliocardia kuroshimana Okutani, Fujikura, and Kojima, 2000 , which occurs also in a Pleistocene seep deposit in the central Philippines (Kiel et al. 2000). Pliocardia ballesterosi differs from P. kuroshimana mainly by its smaller and less elevated umbones, with P. kuroshimana having the point of maximum inflation in the shell’s center whereas it is displaced toward the anterior in P. ballesterosi , and by having a narrower but longer ligament nymph. Another similar species is “ Pliocardia ” ticaonica Dall, 1908a , extant off Ticao island (central Philippines) and also found in the early Pleistocene Cambantug Point seep deposit in Leyte, Philippines ( Kiel et al. 2020a). Pliocardia ballesterosi differs from “ P.” ticaonica by having distinct lunular incision, which is only very indistinct in “ P.” ticaonica , by its slightly less prosogyrate and prominent umbones, and by having a less distinct posterodorsal ridge than “ P.” ticaonica .

The Early to Middle Miocene Pliocardia kawadai ( Aoki, 1954) from Japan has a deeper posterior groove and associated wider posterodorsal area, and its pallial sinus reaches up to the anterior margin of the posterior adductor muscle scar (see Amano and Kiel 2012: figs. 7 and 12), whereas in Pliocardia ballesterosi the pallial sinus is entirely below the posterior muscle scar, and the pallial line reaches the scar on its ventral side. The Middle Miocene Pliocardia? tanakai Miyajima, Nobuhara, and Koike, 2017 , from Japan differs from P. ballesterosi by its more elongate-oval shell outline, smaller and more pointed umbones. Pliocardia? tanakai is also less inflated and thus has a narrower and more elongate lunular area, and lacks a pallial sinus ( Miyajima et al. 2017).

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

Genus Archivesica Dall, 1908

Type species: Callocardia gigas Dall, 1896 , by original designation; Recent , Gulf of California.

Remarks.— Archivesica is used here in the sense of Amano and Kiel (2010) and Amano et al. (2019a); in molecular studies, this genus is of often referred to as “ gigas /kilmeri complex” or “ gigas group” ( Audzijonyte et al. 2012; Valdés et al. 2013; Johnson et al. 2017).

Archivesica ? sp. 1 Fig. 13 .

Material.— One specimen from block B (NIGSPAL-029), 17 specimens from block C (NIGSPAL-028), 3 specimens from block E ( NRM Mo 192418–192420) , 3 specimens from block I ( NRM Mo 192670–192672). Upper Miocene of the

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

Dimensions (in mm).— NRM Mo 192670: L = 34.5, H = 18.7; NRM Mo 192671: L = 68.3, H = 38.4; NRM Mo 192672: L = 16.5, H = 9.3.

Description.—Elongate, oval shell, umbones positioned at anterior 20% of shell; external surface smooth, internal surface with radial striation; hinge plate short, moderately broad; RV hinge with two radiating, strong cardinal teeth, cardinal 1 pointing downward, cardinal 3b pointing posteriorly; LV hinge with three radiating, strong cardinals, 2a and 2b at almost right angles to each other, 4b short, subparallel to dorsal margin.

Remarks.—These specimens have the general outline of other elongate, fossil Archivesica , and also the hinge dentition resembles that of other Archivesica species. However, they are only hesitantly assigned to Archivesica because the available material does not show the taxonomically important pallial sinus. The internal radial striation seen on some of the specimens is uncommon among vesicomyids, but has for example been documented from the elongate, extant West African vesicomyid Christineconcha regab ( Cosel and Olu, 2009) ( Krylova and Cosel 2011) .

Figures

Fig. 11. The lucinid bivalve Elliptiolucina sp. from Upper Miocene seep deposits of the Amlang Formation in Pangasinan province, Luzon, Philippines. A. NRM Mo 192411, small RV. B. NRM Mo 192412, small LV. C. NRM Mo 192412, small LV, showing aams (C1) and in general view (C2). D. NRM Mo 192470, larger, articulated specimen, view on LV (D1) and in dorsal view (D2). E. NRM Mo 192664, large internal mold of LV. Abbreviation: aams, anterior adductor muscle scar.

Fig. 12. The vesicomyid bivalve Pliocardia ballesterosi sp. nov. from Upper Miocene seep deposits of the Amlang Formation in Pangasinan province, Luzon, Philippines. A. NIGSPAL-025, holotype, an isolated RV with preserved hinge, in apical view showing lunular incision (A1), view on outer shell showing sculpture and outline (A2), and close-up on hinge with cardinal teeth numbers indicated (A3). B. NRM Mo 192552, paratype, articulated specimen with partially removed shell, view on LV showing pallial sinus and pams (B1), in apical view showing strong inflation (B2), close-up on anterior side showing lunular incision (B3). C. NRM Mo 192550, paratype, articulated shell with only moderate inflation, view on RV (C1) and apical view (C2). D. NRM Mo 192549, paratype, outer side of large RV. E. NRM Mo 192546, paratype, hinge of LV with cardinal teeth numbers indicated. F. NRM Mo 192548, paratype, fragment of interior of RV showing anterior muscle scars. G. NRM Mo 192551, paratype, isolated LV showing pallial line. H. NRM Mo 192547, paratype, large, isolated LV showing pallial line.Abbreviations: aprs, anterior pedal retractor scar; pams, posterior adductor muscle scar.

Fig. 13. The vesicomyid bivalve Archivesica? sp. 1 from Upper Miocene seep deposits of the Amlang Formation in Pangasinan province, Luzon, Philippines. A. NRM Mo 192671, views on hinges of RV (A1) and LV (A2), cardinal teeth numbers indicated; and view on outer side of LV showing interior radial striations (A3). B. NRM Mo 192418, small, articulated specimen, in dorsal view showing absence of lunule or lunular incision (B1), and view on RV (B2). C. NRM Mo 192419, very small specimen showing pallial line and posterior adductor muscle scar. D. NRM Mo 192672, small, isolated LV. E. NRM Mo 192670, medium-sized, isolated RV showing internal radial striation.