Answer: conodonts

AnswerCrossword Clue
conodontsA tooth of this animal, often found as a fossil
conodontsCONODONT, a fossil (the preserved remains of a plant or animal)
conodontsAn extinct marine animal of the Cambrian to Triassic periods, having a long wormlike body, numerous small teeth, and a pair of eyes. It is now believed to be the earliest vertebrate