Meganodontia hoernea ( Des Moulins, 1868 )

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 : 926-929

Meganodontia hoernea ( Des Moulins, 1868)

Fig. 8 .

1868 Lucina hoernea sp. nov.; Des Moulins 1898: 368.

2017 Meganodontia hoernea ( Des Moulins, 1868) ; Kiel and Taviani 2017: 450, figs. 6, 7.

Material.— Three specimens from block A (NIGSPAL-017– 019), 6 specimens from block H ( NRM Mo 192403–192409), one from block I ( NRM Mo 192661). Upper Miocene of the “shale quarry” within the Northern Cement Corporation quarry in Pangasinan province, Luzon, Philippines .

Dimensions (in mm).— NRM Mo 192403: L = 87.0, H = 85.0; NRM Mo 192404: L = 80.0, H = 75.5; NRM Mo 192405: L> 100.0; NIGSPAL-017: L = 105.2, H = 103.0, W = 66.6; NIGSPAL-018: L = 90.4, H = 84.4, W = 49.1; NIGSPAL-019: L = 84.1, W = 46.1.

Two large Neogene lucinids described from Taiwan most likely also belong to Meganodontia . Among them, the Pliocene Loripes goliath Yokoyama, 1928 , differs from the Philippine specimens of Meganodontia hoernea by having stronger, more elevated umbones ( Yokoyama 1928: 86, pl. 9: 8, pl. 10: 1). The same applies to Loripes pregoliath Hu and Tseng in Hu, 1995, from the Miocene Nanchuang Formation in Taiwan, which is also smaller (L = 75.0 mm vs. L> 100.0 mm in the Philippine M. hoernea ) and more inflated than M. hoernea from the Northern Cement Corporation quarry ( Hu 1995: 1995–1996, pl. 349: 10, 13; pl. 350: 4, 6, 7).

Stratigraphic and geographic range. —Middle and Upper Miocene strata of Italy and the Philippines.

Genus Lucinoma Dall, 1901

Type species: Lucina filosa Stimpson, 1851 , by original designation; Recent , North Atlantic Ocean .

Lucinoma saetheri Amano, Little, and Campbell, 2018

Fig. 9 .

Material.— Two specimens from block A (NIGSPAL-020, 021), three specimens from block B ( NRM Mo 192623– 192625) , one specimen from block E ( NRM Mo 192434). Upper Miocene of the “shale quarry” within the Northern Cement Corporation quarry in Pangasinan province, Luzon, Philippines .

Remarks.— Meganodontia hoernea is widespread and frequent in Middle and Late Miocene-aged seep deposits in northern Italy ( Taviani 1994; Kiel and Taviani 2017), and the Late Miocene specimens reported here from the Philippines are virtually identical to well-preserved specimens of M. hoernea illustrated in Kiel and Taviani (2017: fig. 7).

The extant and Pleistocene Meganodontia acetabulum differs from M. hoernea by its more strongly convex posterodorsal margin and narrower posterodorsal area ( Bouchet and Cosel 2004; Kiel and Taviani 2017; Kiel et al. 2020a). An Early Miocene Meganodontia sp. from Cuba ( Kiel and Hansen 2015: fig. 7A–C) is more strongly inflated and has a less distinct posterior sulcus. The medium-sized M. haunuiensis Amano, Little, and Campbell, 2018 , from Early Miocene seep deposits in New Zealand differs mainly by having a shorter anterior adductor muscle scar (see Amano et al. 2018: fig. 3F 2).

Dimensions (in mm).—NIGSPAL-020: L = 44.0, H = 43.5; NIGSPAL-021: L = 52.1, H = 45.1, W = 29.0.

Remarks.—A similar species that should be re-assigned to Lucinoma is Lucina (Myrtea) butonensis Beets (1942 : pl. 30: 143–146); the anterodorsal margin of Lucinoma saetheri is more acutely rounded than in L. butonensis .

Stratigraphic and geographic range. —Lower and Middle Miocene of New Zealand (North Island), Upper Miocene of Luzon, Philippines.

Lucinoma acutilineata ( Conrad, 1849)

Fig. 10 .

1849 Lucina acutilineata sp. nov; Conrad 1849: 725, pl 18: 2.

1962 Lucinoma acutilineatum (Conrad) : Kamada 1962: 95, pl. 9: 10– 16, pl. 10: 1–3.

1963 Lucinoma acutilineata (Conrad) , Moore 1963: 70, pl. 15: 7–10, 12.

Material.— Four specimens from block A (NIGSPAL-022– 024), 1 specimen from block B ( NRM Mo 192584) , 3 specimens from block E ( NRM Mo 192428–192430) , 2 specimens from block I ( NRM Mo 192634, 192635). Upper Miocene of the “shale quarry” within the Northern Cement Corporation quarry in Pangasinan province, Luzon, Philippines .

Dimensions (in mm).—NIGSPAL-023: L = 49.5, H = 49.9, W = 22.1; NIGSPAL-024: L = 36.2, H = 33.3, W = 13.4.

Remarks.—The Miocene specimens of Lucinoma acutilineata from western North America and Japan show a range of outlines from roundish to pentangular shells ( Hirayama 1954; Kamada 1962; Moore 1963). The roundish Philippine specimens documented here are quite similar to the holotype, which was re-illustrated in Moore (1963: pl. 15: 9). Similarly flat Lucinoma species from the Neogene of the Philippines include Lucinoma aff. kastoroae Cosel and Bouchet, 2008 , from the Pliocene Liog-Liog Point seep deposit, Leyte, Philippines and Lucinoma kosatorea Kiel, Aguilar, and Kase, 2020 , from the Pleistocene Cambantug Point seep deposit, Leyte. Both species have a more acutely rounded anterior shell margin than L. acutilineata .

Stratigraphic and geographic range. —Miocene; Philippines, Japan, northwestern North America.

Figures

Fig. 8. The lucinid bivalve Meganodontia hoernea (Des Moulins, 1868) from Upper Miocene seep deposits of theAmlang Formation in Pangasinan province, Luzon, Philippines. A. NRM Mo 192403, isolated LV showing anterior adductor muscle scar (aams). B. NRM Mo 192404, small, articulated specimens in dorsal view.

Fig. 9. The lucinid bivalve Lucinoma saetheri Amano, Little, and Campbell, 2018, from Upper Miocene seep deposits of the Amlang Formation in Pangasinan province, Luzon, Philippines. A. NRM Mo 192623, articulated specimen, view RV (A1), LV (A2) and on dorsal side (A3). B. NRM Mo 192624, damaged, articulated specimen, view on LV showing fine concentric ribbing (B1) and on dorsal side showing inflation and ligament (B2). C. NIGSPAL-020, articulated specimen with well-preserved concentric ribs, view on RV (C1) and on dorsal side (C2). D. NRM Mo 192625, small articulated specimen, view on LV (D1) and on dorsal side (D2).

Fig. 10. The lucinid bivalve Lucinoma acutilineata (Conrad, 1947) from Upper Miocene seep deposits of the Amlang Formation in Pangasinan province, Luzon, Philippines. A. NIGSPAL-023, large articulated specimen, view on RV. B. NIGAPAL-024, medium-sized, articulated specimen, view on RV showing outline and widely spaced commarginal ribs (B1), and dorsal view showing inflation, lunule and escutcheon. C. NRM Mo 192429, articulated specimen with most shell material detached, showing muscle scars and pallial line, view on RV (C1), LV (C2) and on dorsal side (C3). D. NRM Mo 192584, specimen with broken apical portion, view on LV.E. NRM Mo 192430, small specimen, RV mostly an internal mold showing muscle scars and pallial line E1), LV with preserved shell (E2), and view on dorsal side showing ligament (E3). F. NRM Mo 192428, small RV showing external sculpture. G. NRM Mo 192634, small LV showing external sculpture.