Morphometrics of Leptoplastides marianus (Hoek) (Trilobita, Olenidae) from the Tremadocian of north-western Argentina: taxonomic implications

Morphometrics can be an important tool in systematic studies, providing taxonomists with strong elements of quantification and formal hypothesis testing. Here, these tools are tested for the trilobite Leptoplastides marianus (Hoek) which was originally described on the basis of three deformed specimens from west Tarija, Bolivia. Following the conclusions of Harrington & Leanza, a wide range of morphological variation is accepted for this species, and the name was applied to a large number of specimens from north-western Argentina. Based on specimens collected from the quebrada Moya (Huacalera, Jujuy), as well as on material in the Harrington & Leanza collections in the University of Buenos Aires, traditional morphometric and geometric morphometric methods were used to evaluate the variation of the cranidial shape of L. marianus sensu Harrington & Leanza. The results allow discrimination between two clearly different morphotypes. The name L. marianus should be restricted to the type specimens, given the deformation of these materials. In addition, L. argentinensis and L. granulosus are both valid names for the two morphotypes recognized in the present paper.