Exoskeleton and Plastron

Exoskeleton noun - The exterior protective or supporting structure or shell of many animals (especially invertebrates) including bony or horny parts such as nails or scales or hoofs.

Plastron and exoskeleton are semantically related. In some cases you can replace term "Plastron" with "Exoskeleton", this nouns are similar.

Plastron noun - (zoology) the part of a turtle's shell forming its underside.

Exoskeleton and plastron are semantically related. Sometimes you can use "Exoskeleton" instead a noun "Plastron".