Rudists

Taxobox
name = Rudists

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image_width = 240px
image_caption = Rudist bivalves from the Cretaceous of the Omani Mountains, United Arab Emirates. Scale bar is 10 mm.
fossil_range = Jurassic to Late Cretaceous
regnum = Animalia
phylum = Mollusca
classis = Bivalvia
subclassis = Heterodonta
ordo = Hippuritoida
ordo_authority =
subdivision_ranks = Families
subdivision =
*Antillocaprinidae
*Caprinidae
*Caprotinidae
*Diceratidae
*Dictyoptychidae
*Hippuritidae
*Ichthyosarcolitidae
*Plagioptychidae
*Polyconitidae
*Radiolitidae
*Requieniidae

Rudists are a group of bizarrely shaped marine heterodont bivalves that arose during the Jurassic, and became so diverse during the Cretaceous that they were major reef-building organisms in the Tethys Ocean. The Jurassic forms were elongate, with both valves being similarly shaped, often pipe or stake-shaped, while the reef-building forms of the Cretaceous had one valve become a flat lid, with the other valve becoming an inverted spike-like cone. They were among the many animal groups that perished during the Cretaceous–Tertiary extinction event .

The rudists are, according to different systematic schemes, placed in the orders Hippuritoida or Rudistes (sometimes Rudista). Their "classic" morphology consisted of a lower, roughly conical valve that was attached to the seafloor or to neighboring rudists, and a smaller upper valve that served as a kind of lid for the organism.

Their classification as true reef-builders is controversial, yet they were one of the most important constituents of reefs during the Cretaceous period. [http://www.palaeos.com/Mesozoic/Cretaceous/Aptian.html] At one point, rudist reefs fringed the North American coast from the Gulf of Mexico to the present-day Maritime Provinces. Because of their high porosity, rudist reefs are highly-favored oil traps.

ee also

*"Inoceramus"

References

* [http://www.paleotax.de/rudists/intro.htm "An Introduction to the Paleontology of Rudist Bivalves." (Accessed 7/2/06)]
* [http://www.palaeos.com/Mesozoic/Cretaceous/Aptian.html Paleos.com: "The Aptian Age" (info on rudists) (Accessed 7/2/06)]