conodont
noun
co·no·dont ˈkō-nə-ˌdänt 
ˈkä-
ˈkä- : a Paleozoic toothlike fossil that is probably the remains of an extinct eellike marine animal that may be an invertebrate or primitive vertebrate
also : the animal from which conodonts are derived
Example Sentences
Recent Examples on the Web Surrounding remains—fossils of tiny, extinct marine animals called graptolites and conodonts—served as biomarkers to help confirm when the early scorpions wandered the earth. 
Katie Camero, WSJ, 16 Jan. 2020 The event took its hardest toll on marine organisms such as corals, shelled brachiopods, eel-like creatures called conodonts, and the trilobites. Michael Greshko, National Geographic, 30 Sep. 2019 In several pulses across the Devonian, ocean oxygen levels dropped precipitously, which dealt serious blows to conodonts and ancient shelled relatives of squid and octopuses called goniatites. Michael Greshko, National Geographic, 30 Sep. 2019 One of the most important is the teeth of conodonts—extinct, eel-like creatures—which go back 520 million years. Rachel E. Gross, Smithsonian, 16 Apr. 2018
Katie Camero, WSJ, 16 Jan. 2020 The event took its hardest toll on marine organisms such as corals, shelled brachiopods, eel-like creatures called conodonts, and the trilobites. Michael Greshko, National Geographic, 30 Sep. 2019 In several pulses across the Devonian, ocean oxygen levels dropped precipitously, which dealt serious blows to conodonts and ancient shelled relatives of squid and octopuses called goniatites. Michael Greshko, National Geographic, 30 Sep. 2019 One of the most important is the teeth of conodonts—extinct, eel-like creatures—which go back 520 million years. Rachel E. Gross, Smithsonian, 16 Apr. 2018 Word History
Etymology
International Scientific Vocabulary con- (from Greek kōnos cone) + -odont
First Known Use
1859, in the meaning defined above