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| (A-E) Oreoryzomys balneator (Thomas, 1900); (F-J) O. hesperus (Anthony, 1924); (K-O) Oreoryzomys jumandi Brito, Vargas, García, Tinoco & Pardiñas, in Brito, Vargas, Tinoco, García, Carrión-Olmedo, Koch, Wistuba, Nivelo-Villavicencio et Pardiñas. 2026. |
Abstract
The until recently monotypic cricetid genus Oreoryzomys inhabits piedmont and cloud forests, primarily in eastern Ecuador and northwestern Peru. Erected following the taxonomic revision of a polytypic Oryzomys complex two decades ago, Oreoryzomys has remained poorly understood, with most references limited to the original descriptions of its type species (O. balneator) and a subspecies (O. b. hesperus). Here, we present an integrative taxonomic revision of the genus, based on new field collections and comprehensive museum-based analyses. Phylogenetic reconstructions from mitochondrial and nuclear gene sequences, combined with morphometric and qualitative morphological data, support the recognition of three species: (1) a redescribed O. balneator from central-eastern Ecuador; (2) O. hesperus, elevated to full species rank based on topotypic material; and (3) a new species from populations of the Quijos River Valley, northeastern Ecuador. This revision triples the known species diversity of Oreoryzomys and highlights the genus as a notable radiation of small-bodied oryzomyines adapted to Andean environments. Our findings emphasize the need for systematic revisions of other poorly known Andean rodents to better reveal the hidden diversity of cricetids and the role of the Andes in shaping Neotropical biodiversity.
Keywords: Andes, Ecuador, New species, Oreoryzomys balneator, Oreoryzomys hesperus, Oryzomyini, Peru
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| External appearance of the three Oreoryzomys species (left panels) and details of their feet and hands (right panels). Top row: (A) live lateral view (O. balneator, MECN 5815); (B–C) plantar and dorsal views of foot; (D–E) palmar and dorsal views of hand (MECN 6140). Middle row: (F) live lateral view (O. a. hesperus, MECN 4789); (G–H) plantar and dorsal views of foot; (I–J) palmar and dorsal views of hand. Bottom row: (K) live lateral view (Oreoryzomys jumandi sp. nov., MECN 8278, holotype); (L–M) plantar and dorsal views of foot; (N–O) palmar and dorsal views of hand. Scale = 10 mm. Photographs (A–J, L–O) by J Brito; (K) by R Wistuba. |
Oreoryzomys jumandi new species. Brito, Vargas, García, Tinoco & Pardiñas
Jumandi Mountain Mouse,
Ratón montano de Jumandi (in Spanish)
Diagnosis: A species of Oreoryzomys distinguished by the following combination of characters: incisive foramina short, not reaching the anterior margin of M1 (Fig. 6F); frontoparietal (coronal) suture distinctly V-shaped (Fig. 6E); stapedial process of the auditory bulla elongate and pointed, projecting beyond the posterior margin of the alisphenoid (Fig. 9F); median lacerate foramen broad and positioned at a distance from the bulla; M3 with the hypoflexus shallow, forming a lake-like structure; and m2 with a long mesolophid fused to the mesostyle (Fig. 11C).
Etymology: Named in honor of Jumandi, a Quijo warrior who led the first indigenous uprising against Spanish conquistadors in the Americas on 29 November 1578 (Santos-Granero, 1992). In recognition of his historical significance, Jumandi was officially declared a National Hero by the Asamblea Nacional del Ecuador in November 2011.
Jorge Brito, Rocío Vargas, Nicolás Tinoco, Rubí García, Julio C. Carrión-Olmedo, Claudia Koch, Ricarda Wistuba, Carlos Nivelo-Villavicencio and Ulyses F.J. Pardiñas. 2026. Mountains of Diversity: A Systematic Revision of the Andean Rodent Genus Oreoryzomys (Cricetidae: Sigmodontinae). PeerJ. 14:e20515. DOI: doi.org/10.7717/peerj.20515 [January 9, 2026]
