Heteroconchia Gray, 1854
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publication ID |
https://doi.org/ 10.4202/app.01061.2023 |
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persistent identifier |
https://treatment.plazi.org/id/04619145-8477-FFCC-FFAA-F803FD4FD1FE |
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treatment provided by |
Felipe |
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scientific name |
Heteroconchia Gray, 1854 |
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Subclass Heteroconchia Gray, 1854
Order Venerida Gray, 1854 View in CoL
Family Vesicomyidae Dall and Simpson, 1901 View in CoL
Subfamily Vesicomyinae Dall and Simpson, 1901 View in CoL
Genus Vesicomya Dall, 1886 View in CoL
Type species: Callocardia atlantica Smith, 1885 , by original designation; Recent , North Atlantic Ocean .
Vesicomya ? sp. 1
Fig. 2A–G View Fig .
Material.—One articulated specimen ( NRM Mo 204811) from the SR2 seep deposit of Peckmann et al. (2002) [= UWBM loc. B6702], in the lower Oligocene part of the Lincoln Creek Formation, western Washington State, USA.
Dimensions (in mm).— NRM Mo 204811: L = 17.0, H = 14.5, W = 12.8.
Description.—Large for genus, well inflated; umbones large, blunt, strongly raised, displaced anteriorly to approximately 30% of total shell length; anterior margin truncate, acutely rounded; ventral margin very slightly convex; posterodorsal margin gently sloping, accompanied by submarginal ridge and weak sulcus to its anterior; lunular incision short, heartshaped; escutcheon short, lanceolate; surface with irregular growth lines. Hinge plate narrow, with teeth oriented subparallel to dorsal margin, as is typical for Vesicomya .
Vesicomya ? sp. 2
Fig. 2H–K View Fig .
Material.—One articulated specimen and two isolated RV ( NRM Mo 204701–03) from the SR4 seep deposit of Peckmann et al. (2002) [= UWBM loc. 17426], in the upper Oligocene part of the Lincoln Creek Formation, western Washington State, USA.
Dimensions (in mm).— NRM Mo 204701: L = 6.5, H = 5.0; NRM Mo 204702: L = 5.6; NRM Mo 204703: L = 4.3.
Description.—Average size for genus, well inflated; umbones subcentral, raised, prosogyrate; posterior margin angular due to weak ridge from umbones to posteroventral corner; surface with irregular growth lines; lunular incision deeply incised, broad, short.
Remarks.— Vesicomya ? sp. 1 and sp. 2 reported here are potentially the oldest fossil records of the Vesicomya (sensu stricto). Unfortunately, in neither of the two species the pallial line or muscle scars are visible, thus some doubt about their assignments to Vesicomya remain (cf., Cosel and Salas 2001; Krylova et al. 2018). The only other fossil species that can confidently be assigned to Vesicomya sensu stricto is Vesicomya margotae Beets, 1953 , from the Upper Miocene of Indonesia (Buton Island, Beets 1953) and the Pliocene of the Philippines (Leyte Island, Kiel et al. 2020a).
A lower Oligocene record of a putative Vesicomya sp. was published by Goedert and Campbell (1995: 26, fig. 3), a single valve approximately 12 mm long with a convexity of 4.8 mm, from the Makah Formation. However, that specimen is more elongate than a typical Vesicomya and the hinge is not observable in the only known specimen. If the Makah Formation fossil is indeed a vesicomyid, it is more likely a juvenile Squiresica or Isorropodon .
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