[ 'θi:kə(ʊ)dɒnt ]
■ noun Palaeontology a Triassic fossil reptile of a group ancestral to dinosaurs and other archosaurs.
Origin
C19: from mod. L. Thecodontia , from Gk thēkē 'case' + odous , odont- 'tooth' (because the teeth were fixed in sockets in the jaw).