Journal
JOURNAL OF MAMMALOGY
Volume 102, Issue 1, Pages 155-172Publisher
OXFORD UNIV PRESS INC
DOI: 10.1093/jmammal/gyaa147
Keywords
Colombia; convergence; Ecuador; Neomicroxus; Sigmodontinae; Venezuela; volcanic ash
Categories
Funding
- Fundacion Ecominga
- GIZ international cooperation
- Agencia Nacional de Promocion Cientifica y Tecnologica [2014-1039]
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Neomicroxus is a genus of high-Andean cricetids with unique morphological features and hypsodonty, likely evolved in response to volcanic ash falls during the Neogene. Its isolated phylogenetic position and morphological convergence suggest the need for a new tribe classification within the cricetid family.
While hypsodonty mostly is associated with medium to large body sizes in sigmodontine rodents, high-crowned molars combined with small bodies rarely are recorded. This latter condition is present in Neomicroxus (Sigmodontinae, incertae sedis), a genus of high-Andean cricetids also characterized by a noticeable set of cranial traits, including enlarged turbinals and rostrum, slanting zygomatic plate, and a marked backward displacement of the vertical ramus of the dentary, linked with an enlargement of the basicranial region. These morphological features, combined with the isolated position of this lineage in molecular-based phylogenies, indicate that Neomicroxus should be situated in a new tribe. We name and describe this Paramo novelty monotypic clade here. As a working hypothesis, the hypsodonty displayed by this group is considered an evolutionary response to continued volcanic ash falls that characterized the region during the Neogene. A reappraisal of tribe recognition within the two cricetid largest subfamilies, arvicolines and sigmodontines, is made, coupled with a discussion about the role of morphological convergence in long-nose cricetids.
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