Abstract

Evolution of Triassic platform conodonts proceeded along three morphologically similar but apparently unrelated lineages: a gondolellid stock, members of which possess definite platforms in earliest growth stages; a neospathodid stock, members of which lack platforms in earliest growth stages; and gladigondolellid stock. Continuous stratigraphic sequences from both [western] North America and Europe demonstrate the patterns of evolution in neospathodid stock which produced a succession of species having great biostratigraphic usefulness in Upper Triassic rocks. Because neospathodid species often comprise the majority of specimens in a sample, with all growth stages represented, these elements may have been the only conodonts in the apparatuses of the animals bearing them. Gondolellid elements, however, probably were part of a diversely constituted apparatus.

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