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→Conodonts
==Conodonts==
==Conodonts==
[[file:applied-paleontology_fig17-8.png|thumb|{{figure number|1}}See text for explanation.]]
[[file:applied-paleontology_fig17-8.png|thumb|300px|{{figure number|1}}Typical conodonts.]]
Conodonts are extinct toothlike microfossils composed of calcium phosphate whose biological affinities, while poorly understood, lie with chordates. Conodonts are widely distributed in marine rocks of Cambrian through Triassic age. They are excellent indicators of time and thermal maturity—especially in carbonates, where other methods of evaluating organic thermal maturity are less successful. Conodonts are commonly used as zonal indices for the latest Cambrian through Triassic because they were abundant, evolved rapidly, and were widespread geographically.<ref name=ch17r83>Sweet, W., C., 1988, The Conodonta: morphology, taxonomy, paleoecology, and evolutionary history of a long-extinct animal phylum: Oxford [University Press] Monographs on Geology and Geophysics 10, 212 p.</ref> Although found in most marine rocks, conodonts are most efficiently recovered from the insoluble residues of carbonates dissolved in weak acids or from easily disaggregated shales.
Conodonts are extinct toothlike microfossils composed of calcium phosphate whose biological affinities, while poorly understood, lie with chordates. Conodonts are widely distributed in marine rocks of Cambrian through Triassic age. They are excellent indicators of time and thermal maturity—especially in carbonates, where other methods of evaluating organic thermal maturity are less successful. Conodonts are commonly used as zonal indices for the latest Cambrian through Triassic because they were abundant, evolved rapidly, and were widespread geographically.<ref name=ch17r83>Sweet, W., C., 1988, The Conodonta: morphology, taxonomy, paleoecology, and evolutionary history of a long-extinct animal phylum: Oxford [University Press] Monographs on Geology and Geophysics 10, 212 p.</ref> Although found in most marine rocks, conodonts are most efficiently recovered from the insoluble residues of carbonates dissolved in weak acids or from easily disaggregated shales.