Glycymeris

Superregnum: Eukaryota
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Spiralia
Cladus: Lophotrochozoa
Phylum: Mollusca
Classis: Bivalvia
Subclassis: Pteriomorphia
Ordo: Arcida
Superfamilia: Limopsoidea

Familia: Glycymerididae
Genus: Glycymeris

Glycymeris, common name the bittersweet clams, is a genus of saltwater clams, marine bivalve molluscs in the family Glycymerididae.

Etymology

The genus name comes from the Ancient Greek word glykymaris (perhaps from Glykys (sweet) and Meris (part)), a word which is only recorded once in Greek literature.
Fossil records

These clams are very common as fossils, from the Cretaceous period in the Valanginian age (between 140.2 ± 3.0 mya and 136.4 ± 2.0 mya). Fossil shells of these molluscs can be found all over the world. Genus Glycymeris includes about 100 extinct species.[1][2]
Fossil valve of Glycymeris inflata from the Pliocene of Italy
Description

The shells are generally biconvex, with equal valves round in outline, and slightly longer than wide. Their size varies from medium to large. The external ligament lacks transverse striations. These clams are a facultatively mobile infaunal suspension feeders.
Habitat

They are widespread on shallow seabeds that consist of heterogeneous-grained sediments.
Species

Species within this genus include:[3]

Glycymeris albolineata (Lischke, 1872) - White-lined bittersweet
Glycymeris amboinensis
Glycymeris americana (DeFrance, 1829) - Giant bittersweet
Glycymeris arcodentiens
Glycymeris aspersa (Adams & Reeve, 1850)
Glycymeris bimaculata (Poli, 1795) - Two-spotted bittersweet
Glycymeris castanea Lamarck
Glycymeris connollyi Tomlin, 1925
Glycymeris dampierensis
Glycymeris decussata (Linnaeus, 1758) - Decussate bittersweet
Glycymeris delessertii (Reeve, 1843)
Glycymeris diomedea
Glycymeris glycymeris (Linnaeus, 1758) - Dog cockle or European bittersweet
Glycymeris formosus
Glycymeris gordoni (Nowell-Usticke, 1959)
Glycymeris kauaia
Glycymeris kona
Glycymeris longior (Broderip & G. B. Sowerby I, 1833)
Glycymeris modesta (Angas, 1879)
Glycymeris molokaia
Glycymeris muskatensis Melvill, 1897 - Muscat bittersweet
Glycymeris nummaria (Linnaeus, 1758)
Glycymeris nux
Glycymeris oculata (Reeve, 1843)
Glycymeris pectinata (Gmelin, 1791) - Comb bittersweet
Glycymeris pectiniformis (Lamarck, 1819)
Glycymeris pectunculus (Linnaeus, 1758)
Glycymeris reevei (Mayer, 1868) - Reeve's bittersweet
Glycymeris radians (Lamarck, 1819) - Rayed bittersweet
Glycymeris rotunda (Dunker, 1882)
Glycymeris septentrionalis (Middendorff, 1849)
Glycymeris sericata (Reeve, 1843)
Glycymeris spectralis Nicol, 1952 - Spectral bittersweet
Glycymeris strigilata Sowerby, 1833
Glycymeris tellinaeformis (Reeve, 1843)
Glycymeris undata (Linnaeus, 1758) - Atlantic bittersweet
Glycymeris yessoensis (Sowerby, 1886)

Gallery

Fossil Glycymeris glycymeris at the Geopaleontologic Museum GAMPS

Glycymeris glycymeris - Meermandel

Glycymeris glycymeris - Galicia (Spain

Glycymeris modesta - Pakiri, New Zealand