| Glycymeris Temporal range: | |
|---|---|
 | |
| Fossil shells of a Glycymeris species from the Upper Pliocene | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Bivalvia |
| Order: | Arcida |
| Family: | Glycymerididae |
| Genus: | Glycymeris da Costa, 1778 |
| Type species | |
| Arca glycymerisLinnaeus, 1758 | |
| Synonyms | |
| |
Glycymeris, common name the bittersweet clams, is a genus of saltwater clams, marine bivalve molluscs in the family Glycymerididae. [1]
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.
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. [2] [3]
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.
The shells of large saltwater bittersweet clams in the genus Glycymeris have a special archaeological significance in the southwestern USA, because the shells were used in trade item production by the Hohokam tribe of Amerindians. In this context the shells are known to archeologists as "Glycymeris shells". [4]
These Glycymeris shells came from a very large (up to 10 cm) and handsome species, Glycymeris gigantea , which is found in what is now western Mexico, from the Pacific coast of Baja California, throughout the Gulf of California, and from there as far south as Acapulco. The Hohokam people primarily used these large shells to make bracelets and rings; the center of the shell was generally removed immediately after the bivalves were collected, and before transport back to the Hohokam villages in the Gila Basin. [5] [6]
There are several scholarly journals which have articles dealing with shell trade in the American Southwest which mention the Glycymeris shell. Finds of Glycymeris have also been made in Europe with finds in Vinča. [7] Glycymeris shells have also been found in the eyes of statuettes found in Ur. [7]
They are widespread on shallow seabeds consisting of heterogeneous-grained sediments.
Species within this genus include: [8]
