Variation on cranidial shape of Parabolinella argentinensis Kobayashi (Trilobita, Olenidae) from the Tremadocian of northwestern Argentina: Taxonomic implications

Abstract

The late Cambrian-Early Ordovician sequences of the Cordillera Oriental in northwestern Argentina are extensive and highly fossiliferous. The olenid trilobite Parabolinella argentinensis Kobayashi sensu Harrington and Leanza, 1957 was reported from a great number of Tremadocian localities and includes a wide range of morphologies. Based on specimens collected from the type locality (Purmamarca, Jujuy) and the quebrada Moya (Huacalera, Jujuy), as well as on material of the Harrington and Leanza collections in the University of Buenos Aires, classic morphometry and geometric morphometry methods were used to evaluate the variability in the cranidium of P. Argentinensis. The results obtained from the two methodologies are similar. Both analyses allowed the review of the diagnosis of P. Argentinensis, and the distinction of two new morphologies: Parabolinella clarisae n. Sp. And Parabolinella pompadouris n. Sp. The results show how morphogeometrics distinguishes more clearly the three morphotypes and provides graphical representations of the differences between those groups and how from the representations plus the correlation between classical variables and principal components, new diagnostic characters that distinguish the three morphospecies, can be identified.