牙形石

Conodont \Co"no*dont\ (k[=o]"n[-o]*d[o^]nt), n. [Gr. kw^nos cone
+ 'odoy`s, 'odo`ntos, tooth.] (Zo["o]l.)
A peculiar toothlike fossil of many forms, found especially
in carboniferous rocks. Such fossils are supposed by some to
be the teeth of marsipobranch fishes, but they are probably
the jaws of annelids.