conodonts

For decades, geologists have used strange microscopic, toothlike fossils called conodonts to date Paleozoic marine sediments without having any idea what kind of creature originally possessed these elements. The discovery in the early 1980s of fossils of complete conodont animals (also called Conodontophora, meaning “conodont-bearing”) showed that conodont elements belonged to a small early marine vertebrate. As of 2012, scientists classify conodonts in the phylum Chordata.