Pectinidae

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Pectinidae
Temporal range: Triassic to Recent
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Ostreoida
Suborder: Pectinina
Superfamily: Pectinoidea
Family: Pectinidae
Wilkes, 1810
Genera

See text.

The Pectinidae (from Latin pecten meaning comb), common name "scallops", are a family of saltwater bivalve mollusks. They are hermaphrodite, and the male gonads mature first. There are numerous species of various sizes in all of the oceans, and a number species are of commercial importance. Some pectinidae live attached by means of a filament they secrete, others are simply recumbent, but a form of jet-propulsion created by repeatedly clapping their valves closed can propel them swiftly but erratically through the water when they sense the presence of a predator such as a starfish.

Contents

[edit] Shell morphology

In general, shells of Pectinidae consist of two valves, which are circular to broadly ovate with the right valve usually more inflated than the left valve. The valves become narrower and pointed at the umbones which have flattened triangular extensions on both sides, known as auricles or ears. The upper edge of the ears forms a somewhat straight hinge line. The umbones project only slightly above this line. Most Pectinidae have radial ribs and concentric ridges, although a few are smooth. The ctenolium is a key shell feature that separates Pectinidae from all other families.

[edit] Distribution and habitat

Pectinidae inhabit all the oceans of the world, with the largest number of species living in the Indo-Pacific region. Most species of Pectinidae live in relatively shallow watersfrom the low tide line to 100 meters, while others prefer much deeper water. Although some species only live in very narrow environments, most are opportunistic and can live under a wide variety of conditions. Pectinidae can be found living within, uppon, or under either rocks, coral, rubble, sea grass, kelp, sand or mud. Adult specimens are either byssally attached or cemented to a substrate, while others are free swimmers.

[edit] Fossil record

The fossil history of Pectinidae is rich in species and specimens. The earliest known records of true Pectinidae (those with a ctenolium) can be found from the Triassic period over 200 Million years ago.[1] The earliest species were divided into two groups, one with a nearly smooth exterior: Pleuronectis von Schlotheim, 1820, while the other had radial ribs or riblets and auricles: Praechlamys Allasinaz, 1972. [2] Fossil records also indicate that the existence of Pectinidae has been unstable at times; from being the most speciose family of the Mesozoic era, to almost disappearing completely by the end of the Cretaceous period. Fortunately survivors evolved rapidly during the Tertiary period. Nearly 7,000 species and subspecies names have been introduced for both fossil and recent Pectinidae.

[edit] Taxonomy and list of genera

There are more than 30 genera and around 350 species in the family Pectinidae. Raines & Poppe (2006) list nearly 900 species' names, most considered either questionable or non valid. They state that there are over 50 genera and around 250 species and subspecies. While species are generally well circumscribed, their attribution to subfamilies and genera is sometimes equivocal, and there is minimal information about phylogeny and relationships of the species, not least because most work has been based on adult morphology (Barucca et al., 2004).

[edit] Genera

Family Pectinidae

[edit] Gallery

[edit] References

  1. ^ Treatise on Invertebrate Paleontology Geological Society of America, Kansas, Part N, Vol. I (1969) p. N348.
  2. ^ Waller, T. R. (1993): The evolution of "Chlamys" (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific. American Malacological Bulletin 10 (2): 195-249.
  • Barucca, M., Olmo, E., Schiaparelli, S. & Canapa, A. (2004): Molecular phylogeny of the family Pectinidae (Mollusca: Bivalvia)
  • Raines, B. K. & Poppe, G. T. (2006): The Family Pectinidae. In: Poppe, G. T. & Groh, K.: A Conchological Iconography. 402 pp., 320 color plts., ConchBooks, Hackenheim, ISBN 3-925919-78-3.

[edit] External links

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