ENDOSKELETON
endoskeleton
(noun) the internal skeleton; bony and cartilaginous structure (especially of vertebrates)
Source: WordNet® 3.1
Etymology
Noun
endoskeleton (plural endoskeletons)
(anatomy) The internal skeleton of an animal, which in vertebrates is composed of bone and cartilage.
Source: Wiktionary
En`do*skel"e*ton, n. Etym: [Endo- + skeleton.] (Anat.)
Definition: The bony, cartilaginous, or other internal framework of an
animal, as distinguished from the exoskeleton.
Source: Webster’s Unabridged Dictionary 1913 Edition