Carapaces
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A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.


Crustaceans

In crustaceans, the carapace functions as a protective cover over the
cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
(i.e., the fused head and thorax, as distinct from the abdomen behind). Where it projects forward beyond the eyes, this projection is called a rostrum. The carapace is calcified to varying degrees in different crustaceans. Zooplankton within the phylum Crustacea also have a carapace. These include Cladocera, ostracods, and isopods, but isopods only have a developed "cephalic shield" carapace covering the head.


Arachnids

In arachnids, the carapace is formed by the fusion of prosomal tergites into a single plate which carries the eyes, ocularium, ozopores (a pair of openings of the scent gland of Opiliones) and diverse phaneres. In a few orders, such as Solifugae and Schizomida, the carapace may be subdivided. In Opiliones, some authors prefer to use the term carapace interchangeably with the term cephalothorax, which is incorrect usage, because carapace refers only to the dorsal part of the exoskeleton of the cephalothorax. Alternative terms for the carapace of arachnids and their relatives, which avoids confusion with crustaceans, are prosomal dorsal shield and
peltidium Peltidium is a prodorsal shield found in animals of the Subphylum Chelicerata, in the Phylum Arthropoda. In some groups (Schizomida, Palpigradi, Solpugida and Opiliones The Opiliones (formerly Phalangida) are an order of arachnids colloquial ...
.


Turtles and tortoises

The carapace is the dorsal (back) convex part of the shell structure of a turtle, consisting primarily of the animal's
rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...
cage, dermal armor, and scutes.


References


External links

* {{Turtle terms Animal anatomy