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Any of various minute, toothlike or bladelike fossils made of the mineral apatite and dating from the Cambrian to the late Triassic Period. They are virtually the only preserved parts of extinct eellike animals that are now thought to have been primitive vertebrates similar to the modern hagfishes. Conodonts grew in paired assemblages in the head region of the animal and probably formed part of the feeding apparatus. They are the most widespread microfossils of the Paleozoic Era and are very important for determining the age of rock strata.