[Mammalogy • 2026] Oreoryzomys jumandi, O. balneator, O. hesperus, ... • Mountains of Diversity: A Systematic Revision of the Andean Rodent Genus Oreoryzomys (Rodentia: Cricetidae: Sigmodontinae)

 

(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. 

 DOI: doi.org/10.7717/peerj.20515

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

 

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]

 

[Mammalogy • 2025] Oreoryzomys huancabambensis • Introduction to the Systematics of Oreoryzomys balneator (Rodentia: Cricetidae) with the Description of A New Species from Peruvian montane forests

[B, D] Oreoryzomys huancabambensis sp. nov. Llancachahua-Tarqui, Ruelas, Escobar & Pacheco,  
[A, E] Oreoryzomys balneator  (Thomas, 1900)

in Llancachahua-Tarqui, Ruelas, Escobar et Pacheco Torres, 2025. 

DOI: doi.org/10.15381/rpb.v32i4.31354 

 Researchgate.net/publication/398062542

Abstract

Oreoryzomys is a monotypic genus represented solely by Oreoryzomys balneator and has long been considered enigmatic due to the scarce information available since its description more than a century ago. In this study, we present a systematic revision of O. balneator with an integrative approach, focusing on Peruvian populations. We analyzed 73 specimens using morphological methods, complemented with phylogenetic analyses based on two mitochondrial genes. Our results reveal that the Peruvian populations previously referred as O. balneator represent a new and unnamed species. This species is genetically and morphologically differentiated, and geographically isolated from O. balneator sensu stricto (from Tungurahua Province, the type locality) and from the western Ecuadorian populations of El Oro Province. We formally describe this new species which inhabits montane forests from southeastern Ecuador (Zamora Chinchipe Province) to northeastern Peru (Piura and Cajamarca departments), at elevations between 1520 to 2990 m a.s.l. This work represents the first systematic revision of this genus, providing novel insights into its phylogenetic relationships, distribution, and natural history.

Keywords: Andes, Huancabamba Depression, Oryzomyini, Piura Department, Yungas

External comparisons between Oreoryzomys balneator (AMNH 67569, A, C, E)
and Oreoryzomys huancabambensis sp. nov. (MUSM 10701, B, D, F).

Live specimen of Oreoryzomys huancabambensis sp. nov. (MUSM 55512, holotype) from Habaspite, Carmen de la Frontera, Piura Department. Note the presence of three commensal staphylinid beetles on the head of the specimen.

Photograph taken by Víctor Pacheco.

Oreoryzomys huancabambensis sp. nov.

 A) Panoramic view of the type locality of  Oreoryzomys huancabambensis sp. nov. in Habaspite, Carmen de la Frontera Province, Piura Department, in 2021.
B) Typical habitats within forest patches, and C) low-scale mining activities in the type locality.

Photographs taken by Víctor Pacheco.

 

Daniel Llancachahua-Tarqui, Dennisse Ruelas, Elizabeth Escobar and Víctor Raúl Pacheco Torres. 2025. Introduction to the Systematics of Oreoryzomys balneator (Rodentia; Cricetidae) with the Description of A New Species from Peruvian montane forests. Revista peruana de biología. 32(4): e31354. DOI: doi.org/10.15381/rpb.v32i4.31354 

 Researchgate.net/publication/398062542_Introduction_to_the_Systematics_of_Oreoryzomys_balneator_with_the_description_of_a_new_species_from_Peruvian_montane_forests

[Mammalogy • 2025] Daptomys nunashae • Hidden Diversity in Daptomys (Rodentia: Cricetidae): A New Species from lower montane forests of central Peru

 

Daptomys nunashae

Pacheco, Sánchez-Vendizú, Fajardo, Cossíos & Cadenillas, 2025

DOI: doi.org/10.11646/zootaxa.5696.4.1 

Abstract

Daptomys Anthony, 1929, comprises at least five species, distributed in lower and premontane Neotropical forests from Venezuela to Bolivia, but its real diversity is likely underestimated. During recent expeditions to Tingo María National Park, Huánuco Department, in central Peru, we collected two specimens of Daptomys in premontane forest, that represent a new lineage. Here, we present an integrative approach combining coalescent phylogenetic analyses (based on cytochrome b and three nuclear gene sequences), along with morphological and morphometric data, to support the recognition of the Huánuco specimens as a new species of Daptomys, which we describe in this paper. The new species can be distinguished from other congeners by a unicolored tail ending in a distinct pencil of white hairs, a very small toothrow, anteriorly expanded nasals, a very short incisive foramina, a long palate with a prominent median process, and a large postglenoid foramen. In addition, the species delimitation methods recovered D. musseri as a valid species which is supported also by morphological and morphometric differentiation and distribution pattern.

Mammalia, Daptomys, Tingo María National Park, Peru

Daptomys nunashae

 

Víctor PACHECO, Pamela SÁNCHEZ-VENDIZÚ, Úrsula FAJARDO, Daniel COSSÍOS and Richard CADENILLAS. 2025. Hidden Diversity in Daptomys (Rodentia: Cricetidae): A New Species from lower montane forests of central Peru.  Zootaxa. 5696(4); 451-481. DOI: doi.org/10.11646/zootaxa.5696.4.1 [2025-09-26]

[Mammalogy • 2024] Neodon lhozhagensis • A New Species of Mountain Vole (Rodentia: Cricetidae: Neodon) from south Xizang, China

 

Neodon lhozhagensis Wang & Jiang,

in S.-Y. Wang, Y.-X. Li, Q. Li, Song, H.-J. Wang, He, Onditi, Khanal, X.-Y. Li, Chen et Jiang, 2024.  

Lhozhag mountain vole |  洛扎松田鼠  ||  

DOI: doi.org/10.24272/j.issn.2097-3772.2024.011 

Abstract

A survey of small mammals conducted on the Qinghai-Xizang Plateau in August 2023 yielded a series of specimens of a distinctive and previously unidentified Neodon species from high-altitude shrubland and grassland habitats at elevations of 2800–4000 m in Lhozhag County, Xizang, China. This study employed an integrative approach, combining molecular and morphological evidence to determine the taxonomic placement of the species. Results confirmed that these specimens represent a new species, formally described herein as Neodon lhozhagensis sp. nov. The new species can be distinguished from all other Neodon species based on larger body size, longer tail, five closed triangles in first lower molar, and obvious interorbital crest. Molecular analysis strongly supported Neodon lhozhagensis sp. nov. as a monophyletic clade that diverged from its sister taxon, Neodon tsonaensis, approximately 0.89–1.68 million years ago. Kimura-2-parameter genetic distances of the complete cytochrome b gene between Neodon lhozhagensis sp. nov. and other nominal Neodon species ranged from 9.3% to 12.8%. This discovery underscores the importance of continued efforts to investigate and document the biodiversity of the Himalayan region.

Keywords: Neodon, Small mammals, Taxonomy, Morphology, Molecular systematics

Skull and skin of Neodon lhozhagensis sp. nov. (KIZ042896)
A: Dorsal, ventral and lateral views of skull and mandibles; B: Upper and lower molars; C: Dorsal, ventral, and lateral views of skin. 10 mm (A); 5 mm (B); 50 mm (C).

Photo bySi-Yuan Wang

Neodon lhozhagensis Wang & Jiang, sp. nov.

Suggested common name: Lhozhag mountain vole, 

洛扎松田鼠.

Diagnosis: The M1 of Neodon lhozhagensis sp. nov. possesses five closed triangles anterior to the posterior transverse space, a characteristic shared with N. clarkei, N. bershulaensis, and N. linzhiensis, but distinct from all other known species of the genus. The interorbital crest is prominently developed, differentiating it from N. bershulaensis (Figure 5). Compared to N. clarkei, Neodon lhozhagensis sp. nov. has a longer incisive foramina (5.4±0.3 mm vs. 4.9±0.4 mm) and a wider interorbital breadth (4.2±0.2 mm vs. 4.0±0.1 mm). Additionally, the new species is characterized by a larger body size, including a longer tail and a greater relative tail length (TL=50–65 mm; TL/HB=41.67%–54.17%) compared to N. linzhiensis (TL=27–37 mm; TL/HB=30.00%–35.24%).

Etymology: The specific name lhozhag is derived from Lhozhag County, the type locality of the new species, and –ensis is Latin for “belonging to”.

Distribution: The Lhozhag mountain vole is presently known only from Lhozhag County, south Xizang, China, at elevations of 2800–4000 m a.s.l. It is allopatric with other Neodon species.

Habitat: Bamboo forests, coniferous forests, and shrubs.

 

Si-Yuan Wang, Yi-Xian Li, Quan Li, Wen-Yu Song, Hong-Jiao Wang, Shui-Wang He, Kenneth Otieno Onditi, Laxman Khanal, Xue-You Li, Zhong-Zheng Chen and Xue-Long Jiang. 2024. A New Species of Mountain Vole (Rodentia, Cricetidae, Neodon) from south Xizang, China. Zoological Research: Diversity and Conservation. 1(4); 282-289. DOI: doi.org/10.24272/j.issn.2097-3772.2024.011 

[Mammalogy • 2022] Thomasomys burneoi • A New Species of Andean Mouse of the Genus Thomasomys (Rodentia: Cricetidae: Sigmodontinae) from the eastern Andes of Ecuador

Thomasomys burneoi 

 Lee, Tinoco & Brito, 2022

 

DOI: 10.3897/vz.72.e78219

Abstract

We name and describe a new species of Andean mouse from the eastern slope of the Andes of central Ecuador (Sangay National Park). This rodent is large-bodied (head-body length 167–184 mm) inhabiting the wet montane forest between 3,400–3,900 m in elevation. A molecular phylogeny based on mitochondrial genes resolved the new species as a member of the “aureus” group, closely related to an undescribed species from north Ecuador. This finding increases the diversity of Thomasomys to 48 species, of which 18 species inhabit Ecuador. In addition, the species described herein is the largest species of the genus described in Ecuador.

Key words: Montane forest, Rodentia, Thomasomyini

Dry skin in dorsal, ventral, and lateral views of Thomasomys burneoi, sp. nov. (MECN 5662, holotype). Scale bar = 10 cm.
 Morphology of the dorsal and plantar surface of the right hind foot of: A, C Thomasomys burneoi (MECN 5666, paratype) and Thomasomys pardignasi (MECN 5852, holotype) and B, D Acronyms: I–V = digits, 1–4 = pads, h = hypothenar pad, t = thenar pad. Scales = 10 mm.

Thomasomys burneoi sp. nov. (MECN 5259, paratype), external appearance of an adult female alive in its natural habitat in the Cubillines, Sangay National Park, Ecuador.

Family Cricetidae Fischer, 1817

Subfamily Sigmodontinae Wagner, 1843

Tribe Thomasomyini Steadman & Ray, 1982

Genus Thomasomys Coues, 1884

Thomasomys burneoi sp. nov. 

Burneo’s Olfield Mouse 

Ratón andino de Burneo (in Spanish)

Thomasomys praetor: Lee et al. 2011:9; part no Thomasomys praetor (Thomas, 1900) 

Thomasomys princeps: Lee et al. 2015:10; part no Thomasomys princeps (Thomas, 1895)

Thomasomys aureus: Brito et al. 2019:9; par not Thomasomys aureus Tomes, 1860

Diagnosis: A species of Thomasomys from the aureus group described by the following character combinations: large size (combined head and body length 167–184 mm); postauricular patch present; wide metatarsal patch; hind foot large > 40 mm; M1 with broad and deep anteroflexus; additional anterior edge on procingulum of M1 present; M3 with metaflexus large and mesoloph distinctive; m1 with small and distinctive anterolophid; m1 with ectolophid; m2–m3 with hypoflexid wide; m3 size equals m2.

Thomas E. Lee Jr., Nicolás Tinoco and Jorge Brito. 2022. A New Species of Andean Mouse of the Genus Thomasomys (Cricetidae, Sigmodontinae) from the eastern Andes of Ecuador. Vertebrate Zoology. 72: 219-233. DOI: 10.3897/vz.72.e78219

 

[Mammalogy • 2021] Thomasomys pardignasi • Discovery of the First Amazonian Thomasomys (Rodentia: Cricetidae: Sigmodontinae): A New Species from the remote Cordilleras del Cóndor and Kutukú in Ecuador

Thomasomys pardignasi

Brito, Vaca-Puente, Koch & Tinoco, 2021

DOI: 10.1093/jmammal/gyaa183

 facebook.com/JorgeBritoMolina

Abstract

A new species of the cricetid rodent genus Thomasomys is described from the montane forests of the Cordilleras del Cóndor and Kutukú, southeastern Ecuador, at elevations between 1,770 and 2,215 m. The species has a large body size (head and body length 137–147 mm) in comparison with other species in the genus, and also is distinguished from its congeners by presenting a tail longer than the head–body length, presence of genal vibrissae 1 and 2, wide presphenoid, first and second lower molars with ectolophid, and third lower molar slightly shorter than the second. A molecular phylogeny based on mitochondrial genes resolved the new species a member of the “aureus” group, most closely related to Thomasomys aureus sensu stricto (genetic distance 8.57%) and as well as an additional undescribed species from southeastern Ecuador. This finding increases the diversity of Thomasomys to 46 species, of which 17 species are present in Ecuador. In addition, the species described herein is the first Thomasomys from the Amazonian basin, a genus that up to now was thought to be restricted to Andean ranges.

montane forest, Rodentia, Thomasomyini, Thomasomys aureus

Thomasomys pardignasi sp. nov. (MECN 5852, holotype)
 external appearance of the adult female alive in its natural habitat in the Cordillera de Kutukú, Ecuador 

Family Cricetidae Fischer, 1817

Subfamily Sigmodontinae Wagner, 1843

Tribe Thomasomyini Steadman and Ray, 1982

Genus Thomasomys Coues, 1884

Thomasomys pardignasi sp. nov.

Pardiñas’ Andean Mouse

Ratón andino de Pardiñas (in Spanish)

Diagnosis: A species of Thomasomys that can be recognized by the following combination of characters: head and body length of 137–145 mm; tail longer than the head and body length, measuring 210–226 mm; tail with 12 rows of scales per cm on the axis; genal vibrissae 1 and 2 present; wide presphenoid; upper maxillary row 6.4–6.6 mm; M1 with shallow anteroflexus; M3 with reduced paracone; m1–m2 with ectolophids and without ectostylids; m3 slightly shorter than m2.

Etymology: This species is named in honor of Ulyses F. J. Pardiñas (Argentina, b. 18 May 1969), a prominent paleontologist who has dedicated his academic life to the study of sigmodontine rodents. The epithet of the species is formed from the surname “Pardiñas,” taken as a noun in the genitive case (replacing “ñ” with “gn” as per article 27 of ICZN), with the Latin Suffix “i” (ICZN 31.1.2).

  

 

Jorge Brito, Sarah Vaca-Puente, Claudia Koch and Nicolás Tinoco. 2021. Discovery of the First Amazonian Thomasomys (Rodentia, Cricetidae, Sigmodontinae): A New Species from the remote Cordilleras del Cóndor and Kutukú in Ecuador. Journal of Mammalogy. gyaa183. DOI: 10.1093/jmammal/gyaa183

 facebook.com/JorgeBritoMolina/posts/10224816746075561

Describimos una nueva especie de roedor cricétido del género Thomasomys proveniente de los bosques montanos de las Cordilleras del Cóndor y Kutukú, sureste de Ecuador, a una altura comprendida entre 1,770–2,215 m. Se trata de una especie de tamaño corporal grande (longitud cabeza-cuerpo 137–147 mm) con respecto a las demás especies del género, que se distingue de sus congéneres por presentar una cola más larga que la longitud cabeza-cuerpo, presencia de vibrisas genales 1 y 2, presfenoide ancho, primer y segundo molar inferiores con ectolófido y tercer molar inferior ligeramente más corto que el segundo. Una filogenia molecular derivada a partir de los genes mitocondriales muestra que la nueva especie forma parte del grupo “aureus,” cercanamente relacionada con Thomasomys aureus sensu stricto (distancia genética de 8.57%) y con otra especie de Thomasomys aún no descrita del sudeste ecuatoriano. Este hallazgo aumenta la riqueza de Thomasomys a 46 especies, de las cuales 17 están presentes en Ecuador. Adicionalmente, la especie descrita aquí es el primer Thomasomys de la cuenca amazónica, un género que hasta ahora había estado restringido a ambientes andinos.

bosque montano, Rodentia, Thomasomyini, Thomasomys aureus

  

[Mammalogy • 2023] Oecomys jamari • Unveiling Hidden Diversity of Oecomys (Rodentia: Cricetidae: Sigmodontinae) from Brazilian Central Amazonia: Description of A New Species and New Lineages

 

 Oecomys jamari (UFROM619), an adult female. 

Saldanha, Semedo, Mendonça, Lima-Silva, Messias, Sampaio, Brandão & Rossi, 2023

DOI: 14772000.2023.2259037 

Photo by R.F.B. Mendonça.

Abstract

The arboreal rice rat of the genus Oecomys Thomas, 1906 is one of the most speciose genera of the subfamily Sigmodontinae, with 19 species currently recognized and occurring from eastern Panama to northern Argentina, Paraguay, and in northern, central and eastern Brazil. Herein we describe a new species using an integrative approach based on molecular, morphological, and morphometric data. We used in our assessment recently collected specimens from the states of Pará and Rondônia, one of the most deforested regions in Brazil. We examined 51 specimens of Oecomys from museum collections including name-bearing types from most of the distributional range of the genus. We also sequenced 32 specimens of Oecomys, and for the molecular analyses, we used the mitochondrial marker Cytochrome b and the nuclear marker intron 7 of β-fibrinogen. Our mitochondrial marker results recovered a strongly supported clade composed of two divergent clades (3.78%), one including lineages of O. bicolor and O. cleberi, and the other clade representing the new species. The topology of concatenated mitochondrial and nuclear data also recovered Oecomys sp. nov. as a sister lineage of the O. bicolor and O. cleberi clade. Also, both markers recovered new lineages from the O. bicolor and O. cleberi species group. The new species can be discriminated from other Oecomys species by pelage colour and craniodental characters, such as absent or small mastoid fenestra, and the presence of alisphenoid strut, small subsquamosal fenestra, presence of sphenopalatine vacuities, and presence of accessory loph of M1 and M2 paracones. The new species occurs exclusively in the Rondônia centre of endemism, delimited by the rivers Amazon to the north, Tapajós to the east, and Madeira to the west. The description of this new Oecomys increases the diversity, and also contributes to elevate Amazonian Sigmodontinae species richness and endemism in this still poorly known biome.

 

Key words: Amazonian forest, integrative taxonomy, Jamari National Forest, Oryzomyini, Rondônia centre of endemism, Sigmodontinae 

  The paratype of Oecomys jamari sp. nov. (UFROM619), an adult female in life.

Photo by R.F.B. Mendonça.

Oecomys jamari sp. nov.

Jamari arboreal rice rat

 

Juliane Saldanha, Thiago Borges Fernandes Semedo, Ravena Fernanda Braga de Mendonça, Luan Gabriel Lima-Silva, Mariluce Rezende Messias, Iracilda Sampaio, Marcus Vinicius Brandão and Rogério Vieira Rossi. 2023. Unveiling Hidden Diversity of Oecomys (Rodentia: Cricetidae) from Brazilian Central Amazonia: Description of A New Species and New Lineages.  Systematics and Biodiversity. 21(1); 2259037. DOI: 14772000.2023.2259037 

[Mammalogy • 2023] Neacomys marci • A New Species of the Spiny Mouse Genus Neacomys (Rodentia: Cricetidae: Sigmodontinae) from northwestern Ecuador

 

Neacomys marci  Brito & Tinoco, 

in Tinoco, Koch, Colmenares-Pinzón, Castellanos & Brito, 2023.

DOI: 10.3897/zookeys.1175.106113

 

Abstract

Neacomys is a genus of small spiny or bristly sigmodontine rodents that are common components of mammalian faunas in multiple biomes on Central and South America. Recent studies on this group have demonstrated that there is cryptic diversity yet to be discovered within currently recognized species that have not received comprehensive revisions, as well as in areas that have been overlooked. Here we ratify this assertion by describing a new species previously misidentified as the Narrow-footed Spiny Mouse (Neacomys tenuipes) from the Chocó biogeographic region in northwestern Ecuador, Neacomys marci Brito & Tinoco, sp. nov. Distinctiveness of this entity is supported by the combination of the following morphological characters: small size (head-body length 65–85 mm); long tail (69–126% longer than head-body length); pale buff-colored but gray-based belly fur; white throat; hypothenar pad usually absent; long nasals; and a condylar process higher than the coronoid process. Likewise genetic distance analyses and phylogenetic reconstructions based on cytochrome-b (Cytb) sequence data indicate a clear divergence from typical populations of N. tenuipes, and a sister relationship between them. The results presented here increase the diversity of Neacomys to 24 species, placing it among the most diverse genera within the sigmodontine rodents.

Key words: Chocó biogeographic, Neacomys tenuipes, premontane forest

Live specimen of Neacomys marci sp. nov. in its natural habitat (MECN 6230, Estación Fisher, Ecuador). Please note the color of a living animal.

 

Ventral views of the skin of A Neacomys marci sp. nov. (MECN 6232, holotype; Estación Fisher, Ecuador), and B Neacomys tenuipes (UIS-MHN-M 1723; Finca La Bufalera, Colombia).

Note the white-furred throat in N. marci sp. nov. (arrowed).

Family Cricetidae Fisher, 1867

Subfamily Sigmodontinae Wagner, 1843

Tribe Oryzomyini Vorontsov, 1959

Genus Neacomys Thomas, 1959

 

 Neacomys marci Brito & Tinoco, sp. nov.

 Marc’s White-throated Spiny Mouse, 

Ratón espinoso de Marc

Neacomys tenuipes: Brito et al. 2021a; Curay et al. 2022 (non Neacomys tenuipes Thomas, 1900).

Diagnosis: A species of Neacomys with the following combination of characters: small size (head-body length 65–85 mm), long tail (69–126% longer than head and body length), belly fur pale buff but with gray based hairs, white throat, long nasals (which extend well beyond the plane of the lacrimal), condylar process higher than coronoid process, M1 anterocone divided, M1 with broad protoflexus; m1–m3 with wide hypoflexids.

Etymology: Named in honor of Marc Hoogeslag of Amsterdam, the Netherlands. He was co-founder and leader of the innovative Land Acquisition Fund of the International Union for the Conservation of Nature - Netherlands, which helps local groups throughout the world to establish new ecological reserves and conserve endangered species. Fundacion EcoMinga’s Reserva Manduriacu, the habitat of this new species, is one of the many reserves which have benefited from Marc’s program. The species epithet is formed from the surname “Marc” taken as a noun in the genitive case, adding the Latin suffix “i” (ICZN 31.1.2).

Nicolás Tinoco, Claudia Koch, Javier E. Colmenares-Pinzón, Francisco X. Castellanos and Jorge Brito. 2023. New Species of the Spiny Mouse Genus Neacomys (Cricetidae, Sigmodontinae) from northwestern Ecuador. ZooKeys. 1175: 187-221. DOI: 10.3897/zookeys.1175.106113

[Mammalogy • 2022] Chilomys carapazi, C. georgeledecii, etc. • Unlocking Andean sigmodontine Diversity: Five New Species of Chilomys (Rodentia: Cricetidae) from the Montane Forests of Ecuador

Chilomys georgeledecii Brito, Tinoco, García, Koch & Pardiñas
Chilomys carapazi  Brito & Pardiñas

in Brito​, Tinoco, Pinto, ... et Pardiñas, 2022. 

DOI: 10.7717/peerj.13211

Abstract 

The Andean cloud forests of Ecuador are home to several endemic mammals. Members of the Thomasomyini rodents are well represented in the Andes, with Thomasomys being the largest genus (47 species) of the subfamily Sigmodontinae. Within this tribe, however, there are genera that have escaped a taxonomic revision, and Chilomys Thomas, 1897, constitutes a paradigmatic example of these “forgotten” Andean cricetids. Described more than a century ago, current knowledge of this externally unmistakable montane rodent is very limited, and doubts persist as to whether or not it is monotypic. After several years of field efforts in Ecuador, a considerable quantity of specimens of Chilomys were collected from various localities representing both Andean chains. Based on an extensive genetic survey of the obtained material, we can demonstrate that what is currently treated as C. instans in Ecuador is a complex comprising at least five new species which are described in this paper. In addition, based on these noteworthy new evidence, we amend the generic diagnosis in detail, adding several key craniodental traits such as incisor procumbency and microdonty. These results indicate that Chilomys probably has a hidden additional diversity in large parts of the Colombian and Peruvian territories, inviting a necessary revision of the entire genus.

External aspect of Chilomys carapazi sp. nov., in its natural habitat. 

(painted by Glenda Pozo).

Family Cricetidae Fischer, 1817

Subfamily Sigmodontinae Wagner, 1843

Tribe Thomasomyini Steadman and Ray, 1982

Genus Chilomys Thomas, 1897

Chilomys carapazi sp. nov. Brito and Pardiñas

Carapaz’s Forest Mouse, 

Ratón del bosque de Carapaz (in Spanish)

 

Etymology: Named in honor of Richard Carapaz Montenegro, an Ecuadorian professional cyclist born in the Provincia de Carchi. The species epithet is formed from the surname “Carapaz,” taken as a noun in the genitive case, adding the Latin suffix “i” (ICZN 31.1.2).

Diagnosis: A species of Chilomys which can be identified by the following combination of characters: Head and body length ~95 mm; dorsal surface of foot covered with round scales and without interspaces; long nasal (~8.5 mm); long diastema (~8.2 mm); M2 with broad hypoflexus (similar in width to mesoflexus); m1 without anteromedian flexid.

Natural history: The type locality is located in the headwaters of the Gualpi River in the lower montane ecosystem (Cerón et al., 1999). The local expression of the montane cloud forest is characterized by a tree canopy that reaches 30 m high. The understory is luxurious and mostly composed of species belonging to Araceae, Melastomataceae, Cyclanthaceae, Bromeliaceae, and ferns. From the same pit falls where Chilomys carapazi sp. nov., was obtained, we also collected the sigmodontines C. georgeledecii, Pattonimus ecominga, Melanomys caliginosus, Microryzomys minutus, Nephelomys cf. pectoralis, and Thomasomys bombycinus, the heteromyid Heteromys australis, the marsupials Caenolestes convelatus, Mamosops caucae, and the soricid Cryptotis equatoris.

 External aspect of Chilomys georgeledecii sp. nov. (MECN 6024, holotype),
an adult male from Reserva Drácula, Carchi, Ecuador.

 Photograph by J. Brito.

Chilomys georgeledecii sp. nov. Brito, Tinoco, García, Koch and Pardiñas

Ledeci Forest Mouse, 

Ratón del bosque de Ledeci (in Spanish)

 

Etymology: Named in honor of Czech and US international conservationist George Campos Ledeci, who has worked to promote more environmentally friendly infrastructure development projects in Ecuador and other countries. The species epithet is formed from the surname “Ledeci,” taken as a noun in the genitive case, adding the Latin suffix “i” (ICZN 31.1.2).

Diagnosis: A species of Chilomys which can be identified by the following combination of characters: Head and body length ~83–90 mm; tail longer than head and body length combined (~144.4–177.7%); dorsal surface of foot with round scales and large interspaces; zygomatic plate slightly tilted backwards; M2 with narrow hypoflexus (distinctly narrower than mesoflexus); m1 with anteromedian flexus.

Natural history: Reserva Drácula belongs to the subtropical and lower montane ecosystem (Cerón et al., 1999). The local expression of the cloud montane forest is characterized by a tree canopy that reaches 30 m high. The understory is luxurious and mostly composed of species belonging to Araceae, Melastomataceae, Cyclanthaceae, Bromeliaceae, and ferns. Stomachs from six specimens were dissected to inspect content (Supplemental S4). Sampled C. georgeledecii sp. nov., were insectivorous, preying primarily on fly larva. Identifiable prey items were 50% Diptera, 28.5% Coleoptera, 7.1% Hymenoptera, 7.1% Blattodea, and 7.1% Annelida. From the same pit falls where C. georgeledecii sp. nov., was obtained, we also collected the sigmodontines Chilomys carapazi sp. nov., Pattonimus ecominga, Melanomys caliginosus, Microryzomys minutus, Nephelomys cf. pectoralis, Oecomys sp., Rhipidomys latimanus, Tanyuromys thomasleei, Sigmodontomys alfari, and Thomasomys bombycinus, the heteromyid Heteromys australis, the marsupials Caenolestes convelatus, Mamosops caucae, and Marmosa isthmica, and the soricid Cryptotis equatoris.

Chilomys neisi sp. nov. Brito, Tinoco, García, Koch, and Pardiñas

Neisi Forest Mouse, 

Ratón del bosque de Neisi (in Spanish)

 

Etymology: Named in honor of Neisi Dajomes Barrera, an Ecuadorian athlete weightlifting athlete born in the Provincia de Pastaza; Ecuadorian female Olympic gold medalist. The species epithet is formed from the name “Neisi” taken as a noun in apposition.

Diagnosis: A species of Chilomys which can be identified by the following combination of characters: long nasal (~8.4–8.8 mm); zygomatic plate straight; M1 without anteromedian flexus; M1–M2 with indistinct mesoloph; M2 with narrowed hypoflexus (similar in width to mesoflexus); m1 without anteromedian flexus; hemal arches absent.

Natural history: The zoogeographic area where Chilomys neisi sp. nov., occurs is Temperate (Albuja et al., 2012). The ecosystem corresponds to the montane forest (Ministerio del Ambiente del Ecuador, 2013), which is characterized by trees with abundant orchids, ferns, and bromeliads. Chilomys neisi sp. nov., was collected in mature forest where the undergrowth is visually dominated by herbaceous families such as Poaceae (Chusquea sp.), Araceae, and Melastomataceae. On the steep slopes, the palm (Ceroxylon sp.) predominates. Stomach content from one specimen revealed Coleoptera (one larva), and Chrysomelidae (one adult). Chilomys neisi sp. nov., was collected in sympatry with the didelphids Marmosops caucae Caenolestes caniventer and C. condorensis, and the rodents Akodon mollis, Nephelomys albigularis, Microryzomys minutus, Oreoryzomys balneator, and Thomasomys taczanowskii.

External aspect of Chilomys percequilloi sp. nov. (MECN 5854, holotype),
an adult male from Cordillera de Kutukú, Morona Santiago, Ecuador.

Photograph by J. Brito.

Chilomys percequilloi sp. nov. Brito, Tinoco, García and Pardiñas

Percequillo Forest Mouse, 

Ratón del bosque de Percequillo (in Spanish)

Etymology: This species is named in honor of Alexandre Reis Percequillo (nickname PC), Brazilian contemporary biologist devoted to the study of Neotropical mammal fauna and a specialist in oryzomyine rodents. The species epithet is formed from the surname “Percequillo,” taken as a noun in the genitive case, with the Latin suffix “i” (ICZN 31.1.2).

Diagnosis: A species of Chilomys identified by the following combination of characters: tail with 18–20 rows of scales per centimeter on axis; zygomatic plate sloping backwards; M1–M2 with mesoloph; M2 with broader hypoflexus (similar in width to mesoflexus); m1 with anteromedian flexus; hemal arches present.

Natural history: The zoogeographic area where C. percequilloi sp. nov., occurs is Eastern Sub-Tropical, Temperate and Altoandino (Albuja et al., 2012). The ecosystem corresponds to the montane forest (Ministerio del Ambiente del Ecuador, 2013), which is characterized by trees with abundant orchids, ferns, and bromeliads. Chilomys percequilloi sp. nov., was collected in mature forest where the undergrowth is visually dominated by herbaceous families such as Poaceae (Chusquea sp.), Araceae, and Melastomataceae. On the steep slopes, the royal palm (Dictyocaryum lamarckianum) predominates. Stomach contents of three specimens were analysed. Identifiable prey items were 25% Lepidoptera, 25% Blattodea, 25% Diptera, and 25% Acari (Supplemental S4). Chilomys percequilloi sp. nov., was collected in sympatry with the didelphids Marmosa germana, Marmosops caucae and Monodelphis adusta, and the rodents Akodon aerosus, A. mollis, Nephelomys auriventer, N. nimbosus, Oreoryzomys balneator, Rhipidomys albujai, Thomasomys pardignasi, T. cinnameus, T. erro, and T. salazari.

Chilomys weksleri sp. nov. Brito, García, Pinto and Pardiñas

Weksler Forest Mouse, 

Ratón del bosque de Weksler (in Spanish)

Etymology: This species is named in honor of Marcelo Weksler, Brazilian contemporary biologist devoted to the study of living and fossil Neotropical cricetids. The species epithet is formed from the surname “Weksler,” taken as a noun in the genitive case, with the Latin suffix “i” (ICZN 31.1.2).

Diagnosis: A species of Chilomys which can be identified by the following combination of characters: Head and body length ~74–85 mm; tail longer than head and body length combined (~143–153%); dorsal surface of foot with round scales and small interspaces; zygomatic plate leaning forward; M2 with broader hypoflexus (similar in width to mesoflexus); m1 with anteromedian flexus.

Natural history: The zoogeographic area where Chilomys weksleri sp. nov., occurs is Temperate (Albuja et al., 2012). The ecosystem corresponds to the montane forest (Ministerio del Ambiente del Ecuador, 2013), which is characterized by trees with abundant orchids, ferns, and bromeliads. Chilomys weksleri sp. nov., was collected in mature forest where the undergrowth is visually dominated by herbaceous families such as Poaceae (Chusquea sp.), Araceae, and Melastomataceae. The species was collected in sympatry with the didelphids Marmosops caucae, Caenolestes caniventer and C. fuliginosus, and the rodents Akodon mollis, Nephelomys moerex, Microryzomys minutus, Thomasomys aureus, T. baeops, and T. silvestris.

Family Cricetidae Fischer, 1817

Subfamily Sigmodontinae Wagner, 1843

Tribe Thomasomyini Steadman and Ray, 1982

Genus Chilomys Thomas, 1897

Type species (by monotypy).—Oryzomys instans Thomas, 1895.

Etymology.—None originally, but Néstor Cazzaniga (in litteris) suggested that Thomas (1897) employed the Greek noun τιλός (chilos), meaning “grass” to distinguish Chilomys from Oryzomys, whose generic epithet is composed of ὄρσζα (oryza), meaning “rice.”

Geographic distribution.—Known from Andean montane forests and Páramo-forest ecotone from northwestern Venezuela in the north to northern Perú in the south, generally ranging between 1,000 and 4,050 m above sea level.

Chronological distribution.—Recent; no fossils are known.

Contents.—The type species (C. instans) and, in order of nomination, C. fumeus Osgood, 1912, C. carapazi sp. nov. Brito & Pardiñas, C. georgeledecii sp. nov. Brito, Tinoco, García, Koch & Pardiñas, C. neisi sp. nov. Brito, Tinoco, García, Koch, & Pardiñas, C. percequilloi sp. nov. Brito, Tinoco, García & Pardiñas, and C. weksleri sp. nov. Brito, García, Pinto & Pardiñas (this paper).

Conclusions: 

After more than a century of stasis in alpha taxonomy an integrative approach supported by extensive field sampling reveals that the poorly-known Andean thomasomyine Chilomys instans constitutes a complex of species. Five new species are described here, from Ecuadorian populations inhabiting montane forests on both sides of the Andes. Preliminarily, the newly revealed diversity can be attributed to allopatric speciation associated with the effect of Quaternary glacial-interglacial cycles on vegetation belts. Chilomys emerges as a morphologically distinctive Andean thomasomyine that exhibits unique specializations related to the procumbency of the incisors and probably associated to an invertebrate feeding strategy.

  

Jorge Brito​, Nicolás Tinoco, C. Miguel Pinto, Rubí García, Claudia Koch, Vincent Fernandez, Santiago Burneo and Ulyses F. J. Pardiñas. 2022. Unlocking Andean sigmodontine Diversity: Five New Species of Chilomys (Rodentia: Cricetidae) from the Montane Forests of Ecuador.  PeerJ. 10:e13211. DOI: 10.7717/peerj.13211

[Mammalogy • 2022] Mindomys kutuku • A New Species of Mindomys (Rodentia, Cricetidae: Sigmodontinae) from Cordillera de Kutukú (Ecuador), with Remarks on External Traits as Indicators of Arboreality in Sigmodontine Rodents

 Mindomys kutuku  

Brito, Koch, Tinoco & Pardiñas, 2022

 Kutukú Rat | Rata de Kutukú  ||  DOI: 10.3897/evolsyst.6.76879

 painted by Glenda Pozo 

Abstract

The diversity of the oryzomyine rat Mindomys (Cricetidae, Sigmodontinae, Oryzomyini), is doubled here with the description of a new species from the remote Cordillera de Kutukú (Ecuador). The novel form can be easily differentiated from Mindomys hammondi –type species of the genus– by a large set of anatomical traits including, among others, larger jugals, parietal “wings” extending to zygomatic roots, larger otic capsules, well-exposed petrosals, narrow zygomatic plates almost without upper free borders, foramen magnum caudally oriented, larger molars, and accessory root of first upper molar present. Until now, the records of Mindomys were restricted to western Andean foothills. The material from Kutukú highlights an Amazonian species and reinforces the valuable biological significance of isolated mountain ranges in eastern Ecuador. Since Mindomys shows some external traits classically related to arboreal life, here we present a brief reappraisal of this poorly explored topic. A partially neglected anatomical system in sigmodontine studies, the fore feet, encloses crucial information reflecting arboreality.

Key Words: Arboreal cricetids, Ecuador, fore feet, Kutukú mountain range, Oryzomyini, Sigmodontinae

Family Cricetidae Fischer, 1817

Subfamily Sigmodontinae Wagner, 1843

Tribe Oryzomyini Vorontsov, 1959

Genus Mindomys Weksler, Percequillo & Voss, 2006

Mindomys kutuku sp. nov. (MECN 5809, holotype; Cordillera de Kutukú, Ecuador):
external aspect based on museum skin in dorsal (a), ventral (b), and lateral (c) view.

Scale bar: 50 mm.

Three-dimensional reconstruction of the skull of Mindomys kutuku sp. nov. based on micro-CT data of the holotype (MECN 5809; Cordillera de Kutukú, Ecuador):
cranium in dorsal, ventral, and lateral view, and left hemimandible in labial view.

Scale bar: 10 mm.

 Mindomys kutuku sp. nov.

 Kutukú Rat, Rata de Kutukú

Diagnosis: A species of Mindomys smaller than M. hammondi, with opisthodont upper incisors; zygomatic notch very shallow; zygomatic plate moderately narrow and almost without upper free border; zygomatic plate frontally directed; posterior margin of the zygomatic plate anterior to M1; interorbital constriction moderately posterior and narrow; molars of absolute larger size comparatively to the skull, large jugal fully separating maxillary and squamosal portions of the zygomatic arch; hamular process of pterygoid large; alisphenoid strut present; parietal lateral “wing” reaching the zygomatic root; otic capsule medium in size; undefined hamular process of the squamosal; paraoccipital process small; well-exposed petrosal; caudally directed foramen magnum; minute Hill foramen; long incisive foramen; inferior ridge of the masseteric crest not concealing the lower margin of the dentary; lateral view of m3 not hidden by the ascending ramus; angular process of the dentary shorter than condyle; M1 broad, with anterior stylar shelf, anteroposteriorly compressed procingulum and defined anterolingual conule; M1 paracone and metacone transversally compressed; M1 accessory root present; M2 mesofosette rounded; M3 posterior lobe transversally compressed with closed metaflexus.

External aspect of Mindomys kutuku sp. nov., in its natural habitat

 (painted by Glenda Pozo).

Distribution and remarks: Known only from the type locality (Fig. 5). The zoogeographic terrain in which M. kutuku was collected belongs to the eastern subtropics (Albuja et al. 2012). The holotype was collected in evergreen montane forest of the Cordilleras Cóndor-Kutukú (Ministerio del Ambiente del Ecuador 2013), which is characterized by trees with abundant orchids, ferns and bromeliads. The height of the emerging vegetation reaches up to 25 m. M. kutuku was collected within a mature forest near a stream (Fig. 10). The surrounding undergrowth has a visual domain of herbaceous families such as Araceae and Melastomataceae. On the slopes, the royal palm (Dictyocaryum lamarckianun) predominates. The new species was collected in sympatry with the didelphids Marmosops caucae and Monodelphis adusta and the sigmodontine rodents Akodon aerosus, Chilomys sp., Hyaleamys yunganus, Nephelomys auriventer, Microryzomys minutus, Oecomys superans, Oreoryzomys balneator and Rhipidomys albujai.

General landscape of the Cordillera de Kutukú (Ecuador), aerial survey in east-west orientation (a, b), photographs taken on August 26, 2017; field expedition in evergreen montane forest (c, d), and stream near the trapping site (d), photographs taken on September 8, 2017.

Etymology: The specific epithet is a noun in apposition after the type locality, Kutukú.

 Jorge Brito, Claudia Koch, Nicolás Tinoco and Ulyses F. J. Pardiñas. 2022. A New Species of Mindomys (Rodentia, Cricetidae) with Remarks on External Traits as Indicators of Arboreality in Sigmodontine Rodents. Evolutionary Systematics 6(1): 35-55. DOI: 10.3897/evolsyst.6.76879