Geometric morphometry enables species hypotheses testing and the assignment of historical type specimens in the genus Callirhinus Blanchard (Coleoptera: Scarabaeidae: Anomalini)

Abstract

Abstract Assignation of old type specimens is important for nomenclatural stability, but when it comes to ancient specimens, the use of certain techniques is sometimes not appropriate, due to the condition or age of the specimen. In this study, the supposedly polymorphic and monotypic genus Callirhinus Blanchard was analysed with geometric morphometric techniques and photographs of the pronotum, with the purpose of identifying the locality of the old type specimen (19th century) and to test a priori defined hypothetical species by cumulation of evidence within an integrative taxonomic protocol using geometric morphometry, complemented by morphology and geographical discontinuity. Five morphotypes were defined a priori, and principal component, canonical variates analysis, and distances tests for the assignment of the type specimen based on canonical scores and Procrustes distances between means of groups were carried out. Statistical significance was found in four axes validating the species hypotheses, discovering that the type specimen belongs to the morphotype from Jalisco state. Additionally, a taxonomic treatment, the description of four new species, C. choperi Ramírez-Ponce & Zaragoza sp. nov., C. nandu  Ramírez-Ponce & Zaragoza sp. nov., C. huiinis  Ramírez-Ponce & Zaragoza sp. nov., and C. veeme  Ramírez-Ponce & Zaragoza sp. nov. , keys for the species determination, new distributional records, and a map are provided. The present work demonstrates that Geometric Morphometry is an adequate analytical tool that supports taxonomic identification at low cost and without damaging historical specimens.