Different groups of conodonts shed light on what temperatures were at different depths. (livescience.com)
Another standard biostratigraphic method — linking the timing of different rock layers by the comings and goings of fossilized teeth of tiny eellike creatures called conodonts — also couldn't be used, because the same species didn't live in cool and tropical waters. (sciencemag.org)
Collectively they are known as conodonts for the ring of long, conical teeth in their pharynx. (scientificamerican.com)