Variability and variation in Rhyncholestes raphanurus Osgood (Paucituberculata, Caenolestidae)

GONZÁLEZ, BALTAZAR; BROOK, FEDERICO; MARTIN, GABRIEL M.

Revista Chilena de Historia Natural

BMC

Año: 2020 vol. 93

Background: Caenolestids are a group of poorly known South American marsupials with a restricted distribution inPáramo and Subpáramo environments of the Andes from Colombia and western Venezuela to Bolivia (representedby the genera Caenolestes and Lestoros), and Valdivian rainforest in southern Chile (including a separate populationin Chiloé Island) and Argentina, where a single species lives: the Long-nosed shrew opossum (Rhyncholestesraphanurus). The objectives of this work were to analyze the intraspecific variability of R. raphanurus, which includesan anatomical description of the skull and dentition, describe its geographic variation, test for sexual dimorphism,and assess potential differences between continental and Island populations.Methods: Linear Mossimann-transformed variables were used to assess sexual differences within a large population(La Picada), compare sexes within other continental populations, and in a separate analysis, compare continentalfrom Island samples. A full model Principal Components Analysis was performed to assess differences betweenmales and females of the continental and Island populations. A thorough description of the skull and teeth of thespecies and comparisons with other living Caenolestidae is presented.Results: Rhyncholestes raphanurus presents little geographic variation, even between Island and continentalpopulations. Similarly, we found no significant difference between sexes of this species in cranial and dentalmeasurements. We provide a detailed description of cranial morphology and its variation, and also, the firstdescription of the occipital bones, which haven?t been previously described for any Paucituberculata.Conclusions: Comparative studies of continental and Chiloé Island specimens support the treatment of R.raphanurus as a single valid species, especially since morphologic and morphometric differences fall within theextremes of continental populations. The morphology of R. raphanurus clearly separates this genus from otherextant Caenolestidae, and in a much greater degree than the differences found between Lestoros and Caenolestes.