carapace

carapace , shield, or shell covering, found over all or part of the anterior dorsal portion of an animal. In lobsters, shrimps, crayfish, and crabs, the carapace is the part of the exoskeleton that covers the head and thorax and protects the dorsal and lateral surfaces. In many crustaceans, the term carapace is also used to describe the hard, protective covering of the cephalothorax, as that of the horseshoe crab. The carapace of a turtle's shell is composed of expanded ribs and vertebrae overlain by dermal plates and horny scales.

carapace
1. The dorsal part of the exoskeleton of some crustaceans (e.g. crabs), which spreads like a shield over several segments of the head and thorax.

2. The domed dorsal part of the shell of tortoises and turtles, formed of bony plates fused with the ribs and vertebrae and covered by a horny epidermal layer. The ventral part of the shell (plastron) is similar but flatter.

carapace
1. The domed top of a chelonian shell (Chelonia), composed of two layers:
a. an inner body capsule of interlocking plates (the median neurals associated with the vertebrae; the lateral costals associated with the ribs, and encircled by the marginals); and

b. a covering of horny scutes, forming a similar pattern but not corresponding exactly to the underlying bones.


2. See CEPHALOTHORAX.