Spondylidae
| Thorny oysters Temporal range: Triassic - Recent |
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| A shell of S. regius | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Bivalvia |
| Subclass: | Pteriomorphia |
| Order: | Pectinoida |
| Suborder: | Pectinina |
| Superfamily: | Pectinoidea |
| Family: |
Spondylidae Gray, 1826 |
| Genus: |
Spondylus Linnaeus, 1758 |
| Species | |
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See text
Spondylus is a genus of bivalve molluscs, the only genus in the family Spondylidae. As well as being the systematic or scientific name, Spondylus is the most often used common name for these animals, though they are also known as spondylids, thorny oysters, and spiny oysters (though they are not, in fact, oysters) . The meat of these bivalves is edible.
The many species of Spondylus vary considerably in appearance and range. They are grouped in the same superfamily as the scallops. They are not closely related to true oysters (family Ostreidae); however, they do share some habits such as cementing themselves to rocks rather than attach themselves by a byssus. Their key characteristic is that the two halves of their shells are joined with a ball-and-socket type of hinge rather than with a toothed hinge, as is more common in other bivalves. They also still retain vestigial anterior and posterior auricles ("ears", triangular shell flaps) along the hinge line, a common feature of scallops though not of oysters.
Like all scallops, Spondylus spp. have multiple eyes around the edges of their shells, and have relatively well-developed nervous systems. Their nervous ganglia are concentrated in the visceral region, with recognisable optic lobes connected to the eyes.
Spondylus shells are much sought after by collectors, and a lively commercial market exists for them.
The genus Spondylus originated in the Mesozoic era and it is known in the fossil records from the Triassic to the Quaternary (age range: from 235.0 to 0.0 million years ago). There are about 40 extinct species.
These molluscs can be found in fossil shells all over the world. They are present in cretaceaous rocks in the Fort Worth Formation of Texas and in the Trent River Formation of Vancouver as well as in other parts of North America.
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