Lower-middle Darriwilian index conodonts from the Precordillera: new taxonomical approaches

Abstract

A taxonomic review study on the apparatuses of the lower-middle Darriwilian index conodonts, based on the collections from the Precordillera and those described and illustrated in worldwide literature, had led to a new interpretation of the Lenodus apparatus composition. This apparatus is composed of pectiniform elements without mirror symmetry (Pa and Pb elements) with pastiniscaphate morphology and sometimes showing a micropattern structure (honeycomb) on the platform surface. The transitional series of S elements present the elements alate Sa, tertiopedate Sb, bipennate Sc, and quadriramate Sd with wartlike extensions on the tip of the cusps, and the M elements have a modified “geniculate” morphology. The analysis of the apparatuses of the Darriwilian index conodonts allows us to interpret that the genus Lenodus includes the following species: Lenodus variabilis, Lenodus crassus, Lenodus pseudoplanus, and Lenodus suecicus. This proposal is supported by the apparatus architecture, the transitional morphological features of the P elements, and the micropattern structure on the P and S elements present in all these species.