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Spondylus is a of bivalve mollusks, the only genus in the family Spondylidae. As well as being the systematic name, Spondylus is the most often used common name for these animals, though they are also known as thorny oysters or spiny oysters.

Thorny oyster from East Timor. The "eyes" on this individual can be seen on the fringe between mantle and shell.

There are many species of Spondylus, and they vary considerably in appearance and range. They are grouped in the same superfamily as the scallops, but like the true oysters (family Ostreidae) they cement themselves to rocks, rather than attaching themselves by a byssus. Their key characteristic is that the two parts of their shells are hinged together with a ball and socket type of hinge, rather than a toothed hinge as is more common in other bivalves.

Spondylus have multiple eyes around the edges of the shell, and they have a relatively well developed nervous system. 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 there is a lively commercial market in them.

History

Moche Spondylus. 200 B.C. Larco Museum Collection Lima , Peru.

Archaeological evidence shows that people in Neolithic Europe were trading the shells of Spondylus gaederopus to make bangles and other ornaments as long as 5,000 years ago (Varna necropolis). The shells were harvested from the Aegean Sea but were transported far into the centre of the continent. In the LBK and Lengyel culture, Spondylus shells from the Aegean Sea were worked into bracelets and belt-buckles.

Spondylus princeps are also found off the coast of Ecuador, and have been important to Andean peoples since pre-Columbian times, serving as offerings to the Pachamama as well as some kind of currency. In fact much like in Europe the Spondylus shells also reached far and wide as pre-Hispanic Ecuadorian peoples traded them with peoples as far north as present-day Mexico and as far south as the central Andes. The Moche people of ancient Peru worshipped animals and the sea and often depicted Spondylus shells in their art. ^[1]

Species

Pacific thorny oyster, Spondylus princeps Broderip, 1833, from the Sea of Cortez, Mexico.

The interior of two fossil valves of Spondylus from the Pliocene of Cyprus.

• Atlantic thorny oyster, Spondylus americanus Hermann, 1781
• Nude thorny oyster, Spondylus anacanthus Mawe, 1823
• European thorny oyster, Spondylus gaederopus Linnaeus, 1758
• Spondylus ictericus Reeve, 1856
• Japanese spiny oyster, Spondylus japonica
• Pacific thorny oyster, Spondylus princeps Broderip, 1833
• Spondylus calcifer Carpenter, 1857
• Regal thorny oyster Spondylus regius
• Spondylus tenellus Reeve, 1856
• Spondylus versicolor
• Wright's thorny oyster, Spondylus wrightianus

• Domain: Eukaryota Whittaker & Margulis,1978 - eukaryotes
  • Kingdom: Animalia Linnaeus, 1758 - animals
    • Subkingdom: Bilateria (Hatschek, 1888) Cavalier-Smith, 1983 - bilaterians
      • Branch: Protostomia Grobben, 1908 - protostomes
        • Infrakingdom: Lophotrochozoa - Lophotrochozoans
          • Superphylum: Eutrochozoa
            • Phylum: Mollusca (Linnaeus, 1758) Cuvier, 1795 - Molluscs
              • Class: Bivalvia Linnaeus, 1758 - Bivalves
                • Subclass: Metabranchia
                  • Superorder: Filibranchia
                    • Order: Pteriomorpha
                      • Superfamily: Pectinoidea
                        • Family: Spondylidae Gray, 1826 - Thorny Oysters
                          • Genus: Spondylus C. Linnaeus, 1758