conodont

Conodonts are an extinct group of early chordates known primarily from small, tooth-like, phosphatic elements that formed the conodont apparatus. The soft-bodied conodont animals were jawless and are generally thought to have had an eel- to lamprey-like appearance. They inhabited marine environments from the Cambrian to the end of the Triassic, and their microscopic elements are among the most common fossils in Paleozoic rocks, valued for biostratigraphy and stratigraphic correlation.

The conodont apparatus consisted of multiple elements of different shapes, including platforms, blades, and denticles. Euconodonts show complex, varied element morphologies, whereas paraconodonts have simpler, cone-shaped elements. Because soft tissues are rarely preserved, reconstructions of the full animal are indirect, but conodonts are broadly regarded as early vertebrates within the jawless (agnathan) lineage.

The fossil record of conodonts is extensive and diverse, aiding the definition of Paleozoic marine stages. They first appeared in the early Cambrian (roughly 520 million years ago) and persisted until the end of the Triassic (about 200 million years ago). The first appearance datum of Hindeodus parvus marks the base of the Triassic, a key boundary in geological time, while conodonts ultimately became extinct by the late Triassic.

In biostratigraphy, conodont elements serve as standard index fossils: they are small, robust, and rapidly evolving, enabling precise dating and correlation of marine sediments worldwide. In addition to stratigraphic applications, conodonts contribute to paleoenvironmental and isotopic studies through geochemical analysis of their apatite remains.