Plastron

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The plastron of a common musk turtle.

The plastron is the nearly flat part of the shell structure of a tortoise, what one would call the belly, similar in composition to the carapace; with an external layer of horny material divided into plates called scutes and an underlying layer of interlocking bones.

In certain families there is a hinge between the pectoral and abdominal scutes allowing the turtle to almost completely enclose itself. In certain species the sex of a testudine can be told by whether the plastron is concave, male or convex, female. This is because of the mating position.

Turtle plastrons were used by the ancient Chinese in a type of divination called plastromancy. See also oracle bones.

See also

• "Plastron" is also the name of a half-jacket used in the sport of Fencing.
• "Plastron" is also the name of the bulge on an aircraft, such as the Airbus A340, under the fuselage between the wings that is used to correct airflow around the engine pylons.
• A "plastron" is also a thin permanent layer of air around the body of some aquatic insects, held in place by hydrophobic hairs, and acting as a physical gill.

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