plastron
plastron
1. In Chelonia, the lower part of the shell, which is two-layered, consisting of bony plates corresponding to part of the shoulder girdle and abdominal ribs of primitive reptiles, covered by horny epidermal plates. It is joined to the carapace by a bridge between the legs. In some families it is hinged.
2. In some insects, a physical gill made up of hydrofuge hairs. Insects which use a plastron when diving under water are covered with a thick felt of hairs which are bent over at the tips. The hairs trap a layer of air which is continuous with the tracheal system, and surrounds the animal.
3. In Echinodermata, a flattened area between the mouth and anus, formed by the modification of the posterior interambulacrum. It is densely covered with spines.
1. In Chelonia, the lower part of the shell, which is two-layered, consisting of bony plates corresponding to part of the shoulder girdle and abdominal ribs of primitive reptiles, covered by horny epidermal plates. It is joined to the carapace by a bridge between the legs. In some families it is hinged.
2. In some insects, a physical gill made up of hydrofuge hairs. Insects which use a plastron when diving under water are covered with a thick felt of hairs which are bent over at the tips. The hairs trap a layer of air which is continuous with the tracheal system, and surrounds the animal.
3. In Echinodermata, a flattened area between the mouth and anus, formed by the modification of the posterior interambulacrum. It is densely covered with spines.
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plastron