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As presently defined, the tapeworm genus Andrya Railliet, 1895 (Cyclophyllidea: Anoplocephalidae sensu stricto) includes the type species A. rhopalocephala (Riehm, 1881) in hares of the genus Lepus Linnaeus (Leporidae) in western Eurasia and four species in cricetid (Neotominae, Sigmodontinae) and octodontid rodents in North and South America. The host range of Andrya is puzzling, be-cause it is the only genus of anoplocephalid (s. s.) cestodes parasitising both rodents and lagomorphs. The present morphological analy-sis shows that the American species of Andrya share multiple consistent features, in which they differ from those of A. rhopalocephala and the morphologically related Neandrya cuniculi (Blanchard, 1891). The main differences concern the position of the uterus with re-spect to the longitudinal osmoregulatory canals and testes. Consequently, a new genus Andryoides gen. n. is proposed for the American species, resulting in the following combinations: Andryoides neotomae (Voge, 1946) comb. n. (type species), Andryoides octodonensis (Babero et Cattan, 1975) comb. n., Andryoides vesicula (Haverkost et Gardner, 2010) comb. n. and Andryoides boliviensis (Haverkost et Gardner, 2010) comb. n. However, A. boliviensis is regarded here as a junior synonym of A. vesicula (new synonymy). The present study also defines the morphological key features for all the valid genera of cestodes of the family Anoplocephalidae (s. s.), and dis-cusses the phylogenetic affinities and historical biogeography of Andryoides and other endemic American anoplocephalid cestodes.

El género Spalacopus incluye una sola especie, S. cyanus, endémica de la región central del Chile, siendo una de las especies mejor adaptada a la vida subterránea de la familia Octodontidae. Miembro del linaje que consiste en Octodontomys como hermano de Octodon y el clado representado por Spalacopus y Aconaemys. Si bien la morfología externa y cráneo-dentarias en S. cyanus han sido bien estudiadas, su morfología postcraneal es pobremente conocida. Por las peculiaridades de su estilo de vida y locomoción entre los miembros de la familia, es interesante caracterizar detalles de la morfología del esqueleto postcraneal de esta especie e inferir sus aspectos funcionales de la morfología. Se revisaron 29 ejemplares con material de postcráneo disponibles en dos colecciones sistemáticas: Museo de La Plata (MLP), La Plata, Buenos Aires, Argentina y Colección de Mamíferos del Instituto de Ciencias Ambientales y Evolutivas (UACH), Universidad Austral de Chile, Valdivia, Chile. Para la descripción detallada de la morfología de los elementos óseos se dividió al esqueleto en las siguientes regiones: esqueleto axial, cintura escapular y miembros anteriores, y cintura pélvica y miembros posteriores. Las estructuras incluidas en el esqueleto axial fueron descriptas principalmente en sentido cráneo-caudal y en los miembros en sentido próximo-distal. La observación de las estructuras se realizó con las lupas estereoscópicas Leica Wild M3Z y Nikon SMZ 745T, incluyendo fotografías para ilustrar las descripciones. En la morfología postcraneal de S. cyanus se observan características que se consideran altamente conservadas entre los miembros de la familia Octodontidae, pero algunos caracteres son exclusivos de la especie. El esqueleto axial está compuesto por siete vértebras cervicales, 12 ó 13 torácicas, seis o siete lumbares, cuatro sacras, entre 16 y 18 caudales, 12 ó 13 pares de costillas y un esternón compuesto por cinco esternebras. Los elementos óseos de las cinturas pectoral y pélvica como de los miembros anterior y posterior se describen en detalle, excepto los carpos y tarsos debido al mal estado de preservación o ausencia de los mismos. El patrón morfológico que presenta el postcráneo de S. cyanus se ajusta a un plan anatómico típico de especies terrestres y en algunos elementos óseos (húmero y ulna principalmente) se observan características típicamente asociadas con la habilidad excavadora. Los datos generados permitirán a futuro una mejor interpretación de los atributos postcraneales funcionalmente relacionados con los diferentes estilos de vida, evaluar sus estrategias locomotoras, así como también comprender la evolución de estos rasgos en un contexto filogenético. The genus Spalacopus includes only one species, S. cyanus, endemic to central Chile and one of the species best adapted to a subterranean lifetyle in the family Octodontidae. It is a member of the lineage consisting in Octodontomys as a sister clade containing Octodon and of a clade represented by Spalacopus and Aconaemys. Although the external and cranio-dental morphology have been well studied, little is known of the postcranial morphology of S. cyanus. Because of the peculiarities of its lifestyle and locomotion among the members of the family, it is interesting to characterize details of the morphology of the postcranial skeleton of this species and to infer their functional aspects of the morphology. Twenty-nine specimens with postcranial material stored in two collections were studied: Museo de La Plata (MLP), La Plata, Buenos Aires, Argentina and Colección de Mamíferos del Instituto de Ciencias Ambientales y Evolutivas (UACH), Universidad Austral de Chile, Valdivia, Chile. To describe in detail the morphology of the bone elements, the skeleton was divided in the following regions: axial skeleton, scapular girdle and forelimb, and pelvis girdle and hindlimb. The structures included in the axial skeleton were mainly described in cranial-caudal orientation and the limbs in proximal-distal orientation. All structures were observed with stereoscopic microscopes Leica Wild M3Z and Nikon SMZ 745T including pictures to illustrate the descriptions. Highly conservative characteristics among members of the family Octodontidae were observed in the postcranial morphology of S. cyanus, although some characters are exclusive to this species. The axial skeleton has seven cervical vertebrae, 12 or 13 thoracic, six or seven lumbar, four sacral, 16 to 18 caudal vertebrae, 12 or 13 ribs and a sternum with five sternebrae. The elements of the scapular and pelvic girdles as well as forelimbs and hindlimbs are described in detail, except the carpus and tarsus due to their poor state of conservation, or because they not available. The morphological pattern observed in the postcranial skeleton of S. cyanus conforms to a typical anatomical plan for terrestrial species, and some bones (mainly humerus and ulna) present characteristics associated with digging. The information obtained provided will allow a better interpretation of the postcranial attributes, functionally related with different lifestyle, in a future, as well as the evolution of the traits in a phylogenetic context. Fil: Pérez, María Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Conservación de los Murciélagos de Argentina; Argentina Fil: Díaz, María Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Conservación de los Murciélagos de Argentina; Argentina. Fundación Miguel Lillo; Argentina

Viscacha rats (genus Tympanoctomys Yepes, 1942) are ecologically, physiologically, and behaviorally unusual octodontid rodents endemic to the Monte and Patagonian desert biomes of Argentina. The geographic ranges of the different species of Tympanoctomys have been described in general terms but have not been associated with spatial and climate data. Within species, populations are patchily distributed and genetically distinct. We investigated the predicted distribution of Tympanoctomys and the influence of climate fluctuations on their geographic range in historical, current, and future, scenarios. Our objectives were to characterize the environmental niche of the genus, propose a paleoclimatic context for the oldest fossils, characterize the environmental niches for T. barrerae and T. kirchnerorum, and forecast potential future distributions for these taxa. Ecological niche models were constructed using occurrence records from 1941 to the present wherein we identified several precipitation and temperature variables as important predictors of the geographic distributions of the genus, and the species T. barrerae and T. kirchnerorum. Based on our models’ results, we hypothesize that the distribution of Tympanoctomys has contracted from historical to modern times. At the species level, T. kirchnerorum likely experienced the most dramatic change, suffering a large contraction of its historical distribution resulting in its limited present distribution. Given these findings, projected future climate fluctuations and global warming are expected to affect the distributions and persistence of these species.

Hearing in subterranean rodents exhibits numerous peculiarities, including low sensitivity and restriction to a narrow range of comparatively low frequencies. Past studies provided two conflicting hypotheses explaining how these derived traits evolved: structural degeneration and adaptive specialization. To further elucidate this issue, we recorded auditory brainstem responses from three species of social subterranean rodents that differ in the degree of specialization to the underground habitat: the naked mole-rat (Heterocephalus glaber) and the Mashona mole-rat (Fukomys darlingi), which represent the ancient lineage of African mole-rats (Bathyergidae), and the coruro (Spalacopus cyanus), a South American rodent (Octodontidae) that adopted a subterranean lifestyle in more recent geological time. Additionally, we measured call amplitudes of social vocalizations to study auditory vocal coupling. We found elevated auditory thresholds and severe hearing range restrictions in the African mole-rats, with hearing in naked mole-rats tending to be more sensitive than in Mashona mole-rats, in which hearing notably deteriorated with increasing age. In contrast, hearing in coruros was similar to that of epigeic rodents, with its range extending into ultrasonic frequencies. However, as in the mole-rats, the coruros’ region of best hearing was located at low frequencies close to 1 kHz. We argue that the auditory sensitivity of African mole-rats, although remarkably poor, has been underestimated by recent studies, whereas data on coruros conform to previous results. Considering the available evidence, we propose to be open to both degenerative and adaptive interpretations of hearing physiology in subterranean mammals, as each may provide convincing explanations for specific auditory traits observed.

Here, a detailed description of the forelimbs and hindlimbs of all living species of the genus Tympanoctomys are presented. These rodents, highly adapted to desert environments, are semi-fossorial with capacity to move on the surface as well as to build burrows. The shape, structure, and size of the limbs are described. Contrary to what was expected for scratch digging semi-fossorial species, Tympanoctomys have slender humerus, radius and ulna; with narrow epicondyles of the humerus and short olecranon of the ulna with poorly developed processes. Following our descriptions, no intrageneric morphological variation regarding to the configuration of the limbs was detected, probably due to phylogenetic proximity, and not related to specific variations in response to different use of substrates or habits. The obtained results constitute a source of previously unpublished information as well as an important base for future analysis in different studies, such as morphometric, morpho-functional, or phylogenetic researches. Fil: Pérez, María Julieta. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina Fil: Barquez, Ruben Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina Fil: Díaz, María Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina

A new argasid (Argasidae) tick is herein described based on morphology and molecular data obtained from larvae parasitizing Octodon degus and from ticks collected inside burrows in northern Chile. Unfed laboratory-reared larvae were mounted in slides for morphometrical and morphological analyses. Larvae of Ornithodoros octodontus n. sp. share morphological traits with Ornithodoros quilinensis and Ornithodoros xerophylus, two species associated with rodents in the Argentinean Chaco. However, a longer hypostome with two rows of 21 and 22 denticles each one, and conspicuous leaf-shaped anal plates separate O. octodontus. While nymphal stages of O. octodontus lack cheeks and possess a micromammillated dorsal integument, adults have cheeks and exhibit markedly irregular mammillae along their dorsal surface. Phylogenetic analyses of neotropical Argasidae based on mitochondrial 16S rDNA sequences point that O. octodontus forms a monophyletic group with O. xerophylus and an unidentified Ornithodoros sp. from Bolivia, all of them associated with burrow-dweller rodents. Ornithodoros aragaoi and Ornithodoros davisi, two rare species collected once only in the Peruvian Andean Plateau during 1955 are morphologically closely related with adults and nymphs of O. octodontus. Biological observations of O. octodontus revealed autogenic females. For the moment, subgeneric classification of this new species depends on further biological studies. The fauna of ticks occurring in Chile is now represented by 22 species, 11 belonging to the Argasidae family.

Caviomorph rodents represent a major adaptive radiation of Neotropical mammals. They occupy a variety of ecological niches, which is also reflected in their wide array of locomotor behaviors. It is expected that this radiation would be mirrored by an equivalent disparity of tarsal-metatarsal morphology. Here, the tarsal-metatarsal complex of Erethizontidae, Cuniculidae, Dasyproctidae, Caviidae, Chinchillidae, Octodontidae, Ctenomyidae, and Echimyidae was examined, in order to evaluate its anatomical variation and functional-adaptive relevance in relation to locomotor behaviors. A qualitative study in functional morphology and a geometric morphometric analysis were performed. We recognized two distinct tarsal-metatarsal patterns that represent the extremes of anatomical variation in the foot. The first, typically present in arboreal species, is characterized by features that facilitate movements at different levels of the tarsal-metatarsal complex. The second pattern, typically present in cursorial caviomorphs, has a set of features that act to stabilize the joints, improve the interlocking of the tarsal bones, and restrict movements to the parasagittal plane. The morphological disparity recognized in this study seems to result from specific locomotor adaptations to climb, dig, run, jump and swim, as well as phylogenetic effects within and among the groups studies.

The Andean degu, Octodontomys gliroides Gervais & d'Orbigny, 1844, has a broad distribution inhabiting pre-Andean pre-Puna and Puna environments of tropical South America. In order to understand the phylogeographic patterns of Octodontomys gliroides, we sequenced 579 bp of the mitochondrial DNA control region from 100 individuals collected from 20 populations across its entire distributional range. The phylogenetic and parsimony network, in conjunction with analysis of molecular variance (AMOVA), revealed a structured pattern of geographic differentiation of O. gliroides, with the occurrence of two well-defined evolutionary lineages: lineage A, restricted to Bolivia and Chile, and lineage B, restricted mainly to Argentina. Analysis of population structure inferred three genetic clusters along the distribution of O. gliroides that mostly agree with the four major barriers inferred by BARRIER analysis (e.g. rivers, salt flats, deserts, and mountain systems). In addition to the significant differentiation found among all levels studied, a positive correlation was identified between genetic and geographic distance, similar to as expected under the isolation-by-distance model. The most recent common ancestor of O. gliroides was estimated as c. 5.99 Mya, and the divergence between lineages A and B is estimated to have occurred by the Middle Pleistocene, about 0.69 Mya. The mismatch distributions and neutrality tests suggested a signal of population range expansion for both lineages coincident with major climatic changes that occurred during the wet–dry events of the Pleistocene in the Andean Puna region. Bayesian skyline plots (BSPs) for lineage A suggest a long history of constant population size followed by a period of slight to moderate demographic expansion at c. 0.04 Mya, whereas lineage B remained unclear after BSP analysis, probably because of the limited sample size.

The convergent evolution of subterranean rodents is an excellent model to study how natural selection operates and the genetic bases of these adaptations, but the study on the different taxa has been very uneven and still insufficient. In the octodontoid caviomorph rodent superfamily there are two independent lineages where they have recently evolved into totally underground lifestyles: the genera Ctenomys (tuco-tucos) and Spalacopus (coruro). The underground habitat is characterized by an hypoxic and hypercapnic atmosphere, thus gas exchange is one of the most important challenges for these animals. The invasion of the underground niche could have modified the selective regimes of proteins involved in the respiration and transport of O2 of these rodents, positively selecting mutations of higher affinity for O2. Here we examine the sequence variation in the beta globin gene in these two lineages, within a robust phylogenetic context. Using different approaches (classical and Bayesian maximum likelihood (PAML/Datamonkey) and alternatives methods (TreeSAAP)) we found at least three sites with evidence of positive selection in underground lineages, especially the basal branch that leads to the Octodontidae family and the branch that leads to the coruro, suggesting some adaptive changes to the underground life. We also found a convergence with another underground rodent, which cannot be identified by the above methods.

Octodontomys Palmer, 1903 Octodon: P. Gervais and d’Orbigny, 1844:22. Part (description of gliroides); not Octodon Bennett, 1832. Neoctodon Thomas, 1902:114. Type species Neoctodon simonsi Thomas (= Octodon gliroides P. Gervais and d’Orbigny) by original designation; preoccupied by Neoctodon Bedel, 1892 (Insecta: Coleoptera). Octodontomys Palmer, 1903:873. Replacement name for Neoctodon Thomas. CONTEXT AND CONTENT. Order Rodentia, suborder Hystricomorpha, infraorder Hystricognathi, family Octodontidae. This species was originally placed within the genus Octodon but later raised to generic status by Thomas (1902) as Neoctodon. The name Neoctodon Thomas was preoccupied by Neoctodon Bedel, 1892, a genus of beetle, Palmer (1903) assigned Octodontomys as a substitute name. Octodontomys is monotypic., Published as part of Pérez, M. Julieta & Díaz, M. Mónica, 2018, Octodontomys gliroides (Rodentia: Octodontidae), pp. 74-83 in Mammalian Species 50 (963) on page 74, DOI: 10.1093/mspecies/sey010, http://zenodo.org/record/4573547, {"references":["PALMER, T. S. 1903. Some new generic names of mammals. Science, n. s. 17: 873.","BENNETT, E. T. 1832. Characters of a new genus of rodent Mammalia, presented by Mr. Cuming. Proceedings of the Committee of Science and Correspondence of the Zoological Society of London, Part 2: 46 - 48.","THOMAS, O. 1902. On two new genera and rodents from the highlands of Bolivia. Proceedings of the Zoological Society of London 1: 114 - 117.","BEDEL, L. 1892. Revision des Scarabaeus palearctiques. L'Abeille; journal d'entomologie 27: 281 - 288."]}

Octodontomys gliroides (P. Gervais and d’Orbigny, 1844) Mountain Degu Octodon gliroides P. Gervais and d’Orbigny, 1844:22. Type locality “des Andes boliviennes, à Lapaz;” La Paz, Bolivia. Neoctodon simonsi Thomas, 1902:115. Type locality “Mountainous region south and south- east of the Titicaca- Poopo basin. Potosí, 4400 metres,” Bolivia. Octodontomys gliroides: Thomas, 1913:143. First use of current name combination. CONTEXT AND CONTENT. Context as for genus. Octodontomys gliroides is monotypic (Verzi et al. 2015a). Mountain Degu Octodon gliroides P. Gervais and d’Orbigny, 1844:22. Type locality “des Andes boliviennes, à Lapaz;” La Paz, Bolivia. Neoctodon simonsi Thomas, 1902:115. Type locality “Mountainous region south and south- east of the Titicaca- Poopo basin. Potosí, 4400 metres,” Bolivia. Octodontomys gliroides: Thomas, 1913:143. First use of current name combination. CONTEXT AND CONTENT. Context as for genus. Octodontomys gliroides is monotypic (Verzi et al. 2015a). DIAGNOSIS Octodontomys gliroides (Fig. 1) resembles other members of the family Octodontidae, being most similar to the mountain viscacha rat Octomys mimax and species of the genus Tympanoctomys; however, O. gliroides has upper and lower molariforms with an asymmetrical occlusal pattern (Octomys and Tympanoctomys have a figure-8 occlusal pattern—Reig and Quintana 1991; Hutterer 1994; Kramarz 2005). Other distinctive features of the teeth and skull of O. gliroides (Fig. 2) include: the alveolar portion of the 1st molariform tooth (DP4) is slightly inclined anteriorly, medial to the incisor; as a result, an anterior extension of the maxillaries into the posterior margins of the incisive foramina, where DP4 is inserted, is scarcely developed to nearly absent (Verzi 2001; Verzi et al. 2015a). The molariform teeth have folds (flexi or flexids) that are shallow or absent; the maxillary cheek teeth have the anterior lobe protruding as in Octodon, but without a penetrating lingual fold (hypoflexus— Verzi and Carrín Iglesias 1999; Verzi 2001; Verzi et al. 2015a). The auditory bullae are of medium size (14.6 ± 0.7 mm) and slightly inflated compared with other desert-adapted octodontids such as Octomys (15.8 ± 0.3 mm) and Tympanoctomys (17.2 ± 0.9 mm—Mares et al. 2000). GENERAL CHARACTERS Octodontomys gliroides is a medium- to large-sized octodontid, with a body mass ranging from 100–200 g; total length, 200–380 mm; length of tail, 100–190 mm; length of hind foot, 33–40 mm; length of ear, 24–35 mm (Díaz 1999; Mares et al. 2000; Díaz and Barquez 2002; Verzi et al. 2015a). It is a semisubterranean genus of the family Octodontidae and, like Octodon and Tympanoctomys, has large eyes, ears, and hind feet (Lacey and Ebensperger 2007). The pelage is relatively long and silky; dorsal coloration is grayish drab streaked with black; tail has a reddish buffy brush; the venter has white hairs with gray bases, except on the chin and throat where they are pure white, which contrasts sharply with the dorsum (Thomas 1902; Ipinza et al. 1971; Mares et al. 2000; Verzi et al. 2015a). The ears are large, finely covered by short grayish hairs, with white tufts on the anterior ends (Ipinza et al. 1971; Díaz and Barquez 2002). Feet are hairy with the claw covered by hair, the plantar surfaces bear fine granulations (Thomas 1902; Contreras et al. 1987; Díaz and Barquez 2002), and plantar pads are prominent (Ipinza et al. 1971). The tail is nearly 80% of the head and body length; it is bicolored, with an elongated, brown or ochraceous brush extending from the tip. Juveniles are darker with a grayer venter and have an essentially unicolored tail that terminates in a short, black or dark drab brush (Díaz and Barquez 2002; Verzi et al. 2015a). The rostrum is relatively long and narrow; postorbital processes are absent or reduced; interorbital region is relatively broad and divergent with breadth slightly less than the breadth of the rostrum (9.23 mm versus 7.41 mm); lacrimal is large and triangular; palate is short, and the mesopterygoid fossa has an inverted “V” shape, not extending beyond M1; pterygoids leaning on the bullae (Díaz 1999; Mares et al. 2000). Incisive foramina are large with the posterior most ends behind the premaxillary-maxillary suture; the lateral edges of the posterior bor- der of the incisive foramina are not raised (Mares et al. 2000). The lateral flange of the canal for the infraorbital nerve is well developed and has the dorsal end free, not joined to the maxillary (Glanz and Anderson 1990; Verzi et al. 2015a). Masseteric crest and the tubercle for the insertion of the M. masseter medialis pars infraorbitalis are discontinuous (Verzi et al. 1999, 2001; Kramarz 2005). The zygomatic arches are little expanded, with a low and slightly deep jugal fossa for the posterior masseter muscle; shape of suture of jugal and zygomatic process of squamosal squared or rounded (Mares et al. 2000; Verzi et al. 2015a). The lateral supraoccipital processes show greatest development, with the long process extending to the squamosal process and then turning conspicuously downward (Glanz and Anderson 1990). Woods (1984:424, 428) mentioned a “slight lateral supraoccipital process” in both Ctenomyidae and Octodontidae, but Glanz and Anderson (1990) considered this description slightly misleading because the supraoccipital process is well developed in O. gliroides. The paraoccipital processes are small, thick, and incompletely joined to the bullae, with each root directed medially due to the development of the mastoid bullae (Mares et al. 2000; Verzi et al. 2015a). The mandible is slender, low, and moderately hystricognathous; the coronoid process is small; the condylar process is broad and slightly behind the angular process, the latter being short, slender, and slightly flattened; the lunar notch is shallow (Díaz 1999; Mares et al. 2000; Verzi et al. 2015a); the masseteric crest is not prominent (Verzi 2002). Mean cranial measurements (mm, ± SD, sample size in parentheses—Mares et al. 2000, specimens from Argentina and Bolivia) were: greatest length of skull, 45.3 ± 1.3 (25); basal length, 39.6 ± 1.3 (22); zygomatic breadth, 23.3 ± 0.7 (26); mastoid breadth, 22.1 ± 0.7 (21); least interorbital breadth, 9.4 ± 0.4 (29); length of nasals, 16.6 ± 0.9 (26); breadth of rostrum, 8.2 ± 0.3 (26); length of diastema, 11.5 ± 0.5 (28); length of maxillary toothrow, 8.1 ± 0.6 (28); length of bulla, 14.6 ± 0.7 (23); width of bulla, 11.3 ± 0.3 (23); width of zygomatic plate, 1.9 ± 0.2 (26); length of mandibular toothrow, 8.5 ± 0.6 (27); length of mandible, 27.5 ± 0.9 (28). Mean cranial measurements (mm, ± SD, sample size in parentheses—Díaz 1999, specimens from Argentina) were: condyle incisive length, 42.2 ± 1.2 (11); occipitonasal length, 43.8 ± 1.5 (10); braincase breadth, 17.9 ± 0.5 (11); zygomatic breadth, 23.0 ± 0.8 (10); mastoid breadth, 14.2 ± 2.1 (9); least interorbital breadth, 9.3 ± 0.4 (11); length of rostrum, 17.9 ± 0.7 (9); breadth of rostrum, 7.8 ± 0.5 (10); length of nasals, 15.9 ± 0.9 (4); length of diastema, 11.5 ± 0.4 (11); length of maxillary toothrow, 8.7 ± 0.5 (11); greatest alveolar length of M1, 2.7 ± 0.2 (10); alveolar width of M1, 2.08 ± 0.11 (6; please note this was original reported incorrectly as 4 ± 5.7 (10)); greatest length of incisive foramina, 4.07 ± 0.7 (10); palate length, 16.8 ± 0.7 (11); maxima distance between the external border of M3, 7.5 ± 0.5 (11); length of bulla, 14.0 ± 0.9 (10); length of mandibular toothrow, 9.2 ± 0.5 (11); length of mandible, 25.8 ± 1.2 (11). These 2 cited publications differ in mastoid breadth; it is possible that Mares et al. (2000) included part of the bulla in their measurement. The upper incisors are orthodont or slightly proodont, orange, narrow, and short; the lower incisors are orange, high, narrow, with a suboval section, straight lingual enamel edge, and curved labial edge; on the labial side, the enamel extends beyond one-half of the tooth face (Verzi et al. 1999; Verzi 2002). Like all octodontids, O. gliroides is characterized by ever-growing (hypsodont) molar teeth. In the upper molariforms, the folds (flexi) are absent in the adult and the posterior lobe is not extended labially. The molariforms are asymmetrical with no reentrant folds (Hutterer 1994), except in juveniles, which have flexids and fossettids (Verzi 1994; Verzi et al. 2016). Lower molariform teeth have an asymmetrical occlusal pattern, nearly figure-8 shaped, with slightly oblique and rounded lobes and shallow traces of folds; deciduous dp4 with mesoflexid reduced or absent and hypoflexid barely visible (Verzi 1994; Verzi et al. 2015a); the mesoflexid of m1 and m2 remains open in advanced stages of wear (Kramarz 2005); with mesoflexid less evident than hypoflexid (Verzi 1994); last upper and lower molars (M3/m3) reduced in size (Verzi 2002; Verzi et al. 2015a). O. gliroides has oblique, posterolabial-anterolingual, unilateral chewing (anterolingual jaw displacement and alternate occlusion); according to phylogenetic analyses, this is primitive for octodontids (Verzi 2001; Olivares et al. 2004). The masticatory direction (in molariform teeth, defined as asymmetry in dentine wear relative to the sagittal plane) is 58° in Octodontomys (Vassallo and Verzi 2001). Hutterer (1994) considered the occlusal pattern of Octodontomys to be plesiomorphic, because it matches with the molars of the Oligocene Platypittamys, a putative octodontid. The similarities in the cranial morphology of O. gliroides and the basal octodontoid rodent Prospaniomys make O. gliroides an optimal species for reconstructing masticatory muscle origins and insertions of this extinct species (Álvarez and Arnal 2015). The data matrix of Olivares et al. (2012) and Verzi et al. (2016) should be consulted for additional cranial and dental characters for O. gliroides. Álvarez et al. (2011) and Álvarez et al. (2015) examined 2- and 3-dimensional craniomandibular geometric morphometric characters in an evolutionary context. DISTRIBUTION Octodontomys gliroides has a disjunct distribution (Fig. 3) in the Andean and Sub-Andean areas of southwestern Bolivia (from La Paz Department to Tarija Department), northern Chile (Arica- Parinacota and Tarapacá regions), and northwestern Argentina (several localities in Salta and Jujuy provinces, one in La Rioja Province, being highly probably in Catamarca Province—Cabrera 1961; Mann Fischer 1978; Pine et al. 1979; Contreras et al. 1987; Mares et al. 2000; Muñoz-Pedreros 2000; Díaz and Barquez 2002; Díaz and Verzi 2006; Díaz and Barquez 2007; Verzi et al. 2015a; Rivera et al. 2016). In Argentina, this species occupies the High Andes, Monte Desert of Mountains and Isolated Valleys, and Puna ecoregions (Díaz and Verzi 2006). Ojeda et al. (2011) mentioned that O. gliroides is restricted to northern Monte of Mountains and Isolated Valleys. It is found on both sides of the Andes, a distribution marked by an east to west gradient of decreasing rainfall that results in east and west (from theAndes) populations with contrasting differences in the abundance and patchiness of vegetation cover (Rivera et al. 2014, 2016). This species has an elevation range from about 1,200 m at Villa Union in La Rioja Province, Argentina to about 4,400 m in Potosí, Bolivia. Verzi et al. (2015a) indicated that the lowest altitude for the distribution of this species is 200– 300 m. However, this information is incorrect because the data taken from Diaz and Ojeda (1999) correspond to measurements of precipitation (200–300 mm), and this information was misinterpreted by editors during the final process of editing the book Mammals of South America (Patton et al. 2015). FOSSIL RECORD Although Octodontomys gliroides has no fossil record, it is the most primitive extant octodontid. Its cranial and dental anatomy resemble some species from the Miocene and Pliocene of Argentina (Verzi and Carrín Iglesias 1999; Verzi et al. 1999; Verzi 2002; Verzi et al. 2014), suggesting that it may be an early octodontid offshoot (Verzi et al. 2015b). Gallardo and Kirsch (2001) mentioned that Verzi (1994) considered hypsodonty in Ctenomys and Octodontomys to be indicative of common ancestry and re-erected the subfamily Ctenomyinae to include these 2 genera; however, their interpretation of Verzi’s conclusion was erroneous because Verzi stated “hypsodonty has originated independently several times in rodents” (see Verzi 1994:92) and thus does not support the idea of common ancestry. Opazo (2005) estimated the divergence of Octodontomys from its sister clade (Octodon + Spalacopus + Aconaemys) at 6.07 ± 1.34 million years ago, near the end of the Miocene. This value agrees with the results of both Gallardo and Kirsch (2001), who used DNA hybridization data, and Verzi et al. (2016), using morphological and molecular data, to obtain an estimated divergence of 5–7 million years ago; but it is older than the estimate of Honeycutt et al. (2003; 2.9–4.1 million years ago) based on molecular data (nucleotide sequence data from nuclear receptor and mitochondrial genes nucleotide sequence). The morphology of the lower incisor is shared with the extinct octodontid Neophanomys, but whether this character state is primitive or derived is difficult to determine (Verzi et al. 1999). Octodontomys has been recorded in the archaeological site Inca Cueva 5 site, Jujuy Province, Argentina (2,120 ± 120 to 780 ± 100 years before present) based on 3 left mandibular rami; the area corresponds to the oriental border of the Puna steppe (Teta and Ortiz 2002). Octodontomys gliroides produces middens (amalgamations of plant remains, bones, insects, feathers, and rodent feces, glued together within a crystallized matrix of rodent urine), which have proven to be important sources of paleontological evidence (Betancourt and Saavedra 2002; Latorre et al. 2005). In the Atacama (Chile), middens have been recorded from possibly the Quaternary for O. gliroides as well as other families of rodents (e.g., Chinchillidae, Abrocomidae, and Muridae—Latorre et al. 2005). Arnal and Vucetich (2015a, 2015b) used extant species of the family Octodontidae, including O. gliroides, to revise the taxonomy of the fossil rodent Acaremys (Hystricognathi, Octodontoidea, Acaremyidae) and to analyze phylogenetic relationships of the Pan-Octodontoidea group. FORM AND FUNCTION Dental formula for Octodontomys gliroides is i 1/1, c 0/0, p 1/1, m 3/3, total 20. Buccal surfaces of the upper teeth are progressively rotated more distally from the distal to the mesial ends of the arches, with DP4 being nearly transverse to the line of the arch (Miles and Grigson 1990). O. gliroides has simplified teeth without reentrant angles or cement (Glanz and Anderson 1990). In hypsodont rodents, the enamel of the molariforms typically has a different structure on the side of first contact (leading edge) and the opposite face (trailing edge); O. gliroides is more primitive compared to Ctenomys in this regard, with Hunter– Schreger bands limited to some areas. In a study of ultrastructure of the incisor enamel and delineated morphofunctional traits among octodontoid genera with disparate digging adaptations, O. gliroides had an enamel thickness more than double that of the other taxa studied (e.g., Ctenomys, Octodon, Dactylomys — Vieytes et al. 2007). The relative thickness of external index showed the lowest values in the fossorial O. gliroides and the arboreal Bolivian bamboo rat Dactylomys boliviensis than the other species studied, and this has been interpreted by Vieytes et al. (2007) as indicative of low wear resistance. The middle ear of O. gliroides has 3 cavities: bulla, anterior, and posterior recesses. The bulla is divided into 8–10 large pneumatized air cells, and the cochlea protrudes into the tympanic cavity medially (Heller et al. 1976). In the normal ear, these structures have fairly uniform radiolucency without evidence of thickening of the septae of the bulla or areas of bony sclerosis (Heller et al. 1976). In extant species of fossorial rodents, the degree of reduction in size of the eye indicates the adaptation level to the subterranean lifestyle (Pearson 1984). The size of the orbital cavity provides information about the size of the eye and can be estimated using the zygomatic index (see Verzi 2002:316). The comparative analysis of Verzi (2008) showed that echyimid rodents have relatively larger orbits than octodontids (for O. gliroides, mean index value of 1.22, range 1.13–1.38). The eyes of O. gliroides are much larger than those of Octodon, matching the inferred crepuscular or nocturnal habits of this species (Rowlands 1974, not seen cited in Wilson and Kleiman 1974) compared to the apparently diurnal habits of Octodon (Wilson and Kleiman 1974). Vasallo and Mora (2007) included O. gliroides in an allometric analysis of the effect of size on skull attributes (development of the mandibular angle and masseteric crest, and the robustness of incisors) in ctenomyid and octodontid rodents. They concluded that in Octodontomys, as in other octodontids and in ctenomyids, mandibular width and cross-sectional shape of the incisors show a significant and positive association with basicranium length. They also noted that O. gliroides clearly differs from Ctenomys by the intensification of the hystricognath condition (lateral expansion of the mandibular angle and masseteric crest) in Ctenomys. The glans penis of Octodontomys has 2 long spines on each side of the intromittent sac (2-2 pattern), although some specimens show a 2-3 pattern (Spotorno 1979; Contreras et al. 1993); these spines are the longest among octodontids (average length 5.6 mm—Contreras et al. 1993). These features indicate that O. gliroides is more closely related to generalist and subterranean species than to Octomys or Tympanoctomys, as the 1-1 pattern is interpreted to be ancestral and the 2-2 pattern derived in extant octodontid rodents (Contreras et al. 1993). O. gliroides shows the longest baculum among octodontids, which gradually tapers from the base to the tip (Contreras et al. 1993). 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The genus Octodontomys contains only a single species, Octodontomys gliroides (P. Gervais and d'Orbigny, 1844), the mountain degu, found in Andean and Sub-Andean regions of 3 countries, Argentina, Bolivia, and Chile, from elevations of about 1,200'4,400 m. This fossorial octodontid is typical of dry areas, inhabits rocky zones, and is active during the day and the first few hours of night. It is not of special conservation status, being common throughout its distribution, and is considered a species of "Least Concern." Fil: Pérez, María Julieta. Universidad Nacional de Tucumán/facultad de Ciencias Naturales E Instituto Miguel Lillo/instituto de Ecología Regional; Argentina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Díaz, María Mónica. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina

The genome of the red vizcacha rat (Rodentia, Octodontidae, Tympanoctomys barrerae) is the largest of all mammals, and about double the size of their close relative, the mountain vizcacha rat Octomys mimax, even though the lineages that gave rise to these species diverged from each other only about five million years ago. The mechanism for this rapid genome expansion is controversial, and hypothesized to be a consequence of whole genome duplication or accumulation of repetitive elements. To test these alternative but nonexclusive hypotheses, we gathered and evaluated evidence from whole transcriptome and whole genome sequences of T. barrerae and O. mimax. We recovered support for genome expansion due to accumulation of a diverse assemblage of repetitive elements, which represent about one half and one fifth of the genomes of T. barrarae and O. mimax, respectively, but we found no strong signal of whole genome duplication. In both species, repetitive sequences were rare in transcribed regions as compared to the rest of the genome, and mostly had no close match to annotated repetitive sequences from other rodents. These findings raise new questions about the genomic dynamics of these repetitive elements, their connection to widespread chromosomal fissions that occurred in the T. barrerae ancestor, and their fitness effects ? including during the evolution of hypersaline dietary tolerance in T. barrerae. Fil: Evans, Ben J.. Mc Master University; Canadá Fil: Upham, Nathan S.. Mc Master University; Canadá. Field Museum of Natural History; Estados Unidos. University of Yale; Estados Unidos Fil: Golding, G. Brian. Mc Master University; Canadá Fil: Ojeda, Ricardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Ojeda, Agustina Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina

Tuco-tucos (Ctenomys) and related coruros (Spalacopus) are South American subterranean rodents. An energetically demanding lifestyle within the hypoxic/hypercapnic underground atmosphere may change the selective regime on genes involved in O2 transport in blood. In addition, some species of tuco-tucos may be found at high altitude, thus facing additional reductions in changes O2 availabily. We examined sequence variation in the alpha globin subunit gene of hemoglobine in these lineages, within a robust phylogenetic context. Using different approaches (classical and Bayesian maximum likelihood (PAML/Datamonkey) and alternatives methods (TreeSAAP)) we found at least 2 sites with evidence of positive selection in the basal branch of Octodontidae, but not in tuco-tucos. These results suggest some adaptive changes associated to fossoriality, but not strictly to life underground.

2. Kirchners’ Viscacha Rat Tympanoctomys kirchnerorum French: Octodon des Kirchner / German: KirchnerViscacharatte / Spanish: Rata vizcacha de Patagonia Taxonomy. Tympanoctomys kirchnerorum Teta et al, 2014, “ Argentina, Province of Chubut, department of Gastre, 18 km NNE by road of Los Adobes, conjunction between Ruta Provincial 58 and Zanjon El Colorado (43°13'51.6", 68°38'49.1", 517m).” This species is monotypic. Distribution. S Argentina, known distribution limited to the type locality and surrounding areas in Chubut Province. Descriptive notes. Head-body 111-136 mm, tail 111-120 mm, ear 14-15 mm, hindfoot 29-35 mm; weight 50-80 g. Kirchners’ Viscacha Rat is slightly smaller than the Red Viscacha Rat (T. barrerae). Its skull is more bowed in dorsal profile than the Red Viscacha Rat. Color of Kirchners’ Viscacha Rat is pale brown dorsally and whitish to white ventrally. Tail is relatively long (43-50% of head-body length), with a medium terminal brush. Short, thick, and whitish hairs cover forefeet and hindfeet. Oral bristle bundles are well developed. Kirchners’ Viscacha Rat has 2n = 102, similar to that of Red Viscacha Rat. Karyotype has 32 pairs of metacentric to submetecentric chromosomes and 18 pairs of subtelocentric chromosomes. Sex chromosomes could not be discriminated but probably resembled those of the Red Viscacha Rat. Sperm morphology of Kirchners’ Viscacha Rat is smaller in size but similar in shape to that of the Red Viscacha Rat. Habitat. Sandy terrain in a general badland landscape within the Chuquiraga avellanedae (Asteraceae) steppe of the Patagonian Ecoregion at an elevation of 500 m. Burrows of Kirchners’ Viscacha Rat have typical semicircular entrances c.10 cm high, are well curved above and flat below, and are usually placed under Atriplex (Amaranthaceae) bushes. Plant cover near burrows is sparse, consisting mostly of low shrubs, such as Atriplex, C. avellanedae, Prosopis sp. and Prosopidastrum sp. (both Fabaceae), and Schinus johnstonii (Anacardiaceae). Food and Feeding. There is no specific information for this species, but Kirchners’ Viscacha Rat probably feeds mainly on halophytic vegetation (e.g. Atriplex). Breeding. There is no information available for this species. Activity patterns. There is no specific information available for this species, but Kirchners’ Viscacha Rat is apparently nocturnal. Movements, Home range and Social organization. There is no specific information available for this species, but Kirchners’ Viscacha Rat is probably solitary. Status and Conservation. As a newly described species, Kirchners’ Viscacha Rat has not been assessed on The IUCN Red List. No information is available aboutits conservation status, but its very limited distribution (restricted to the type locality) together with its recent extirpation (Late Holocene) from the Chubut River Valley and potential impact of mining in central Patagonia suggest that Kirchners’ Viscacha Rat has a high risk of extinction in the short term. Bibliography. Gallardo et al. (2009), Leon et al. (1998), Ojeda et al. (2007), Pardinas et al. (2012), Sauthier et al. (2009), Teta et al. (2014).

9. Coastal Degu Octodon lunatus French: Octodon a dents de lune / German: Kistendegu / Spanish: Degu de costa Other common names: Moon-toothed Degu Taxonomy. Octodon lunatus Osgood, 1943, “Olmue, Province of Valparaiso, Chile.” M. Tamayo and D. Frassinetti in 1980 included O. lunatus in O. bridgesii. The two are very similar and hard to distinguish, but O. lunatus has a karyotype distinct from O. bridgesii. Monotypic. Distribution. Chile’s Coastal Mountain Range W of the Central Valley, from Bosque Fray Jorge National Park (Coquimbo Region) to Quilpué (Valparaiso Region). Descriptive notes. Head—body 167-221 mm, tail length 152-161 mm; weight averaging 233 g. Proportions and color of the Coastal Degu are similar to Bridges’s Degu (O. bridgesii). Tail of the Coastal Degu is straight and shorter than head-body length (45% ofits total length), with a terminal brush. Ears are large. Pelage is dense and is a uniform ocher-brown, with white spots under axillary and inguinal parts. Chromosome complement is 2n = 78, FN = 114. Habitat. Rocky areas with dense scrublands and small forests along the coast from sea level to 1200 m. Food and Feeding. The Coastal Degu is mainly herbivorous and eats leaves, seeds, grass, and small amount of insects. In Tiltil (Santiago Metropolitan Region), diet is 75% plant tissue, 23% seeds, and 2% insects. Breeding. There is no information available for this species. Activity patterns. Apparently the Coastal Degu has variable activity patterns. Some authors reported crepuscular-nocturnalactivity, while others studies suggested diurnal activity. Movements, Home range and Social organization. There is no information available for this species. Status and Conservation. Classified as Near Threatened on The IUCN Red List. The Coastal Degu was classified as Vulnerable in 2008. Major threat is loss of habitat from agricultural expansion and livestock grazing. Bibliography. Iriarte (2008), Lessa et al. (2010), Munoz-Pedreros (2000), Munoz-Pedreros & Yanez (2009), Osgood (1943), Spotorno et al. (1995), Tamayo & Frassinetti (1980), Woods & Kilpatrick (2005)., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on pages 540-541, DOI: 10.5281/zenodo.6615351

3. Golden Viscacha Rat Pipanacoctomys aureus French: Octodon doré / German: Goldene Viscacharatte / Spanish: Rata vizcacha dorada Taxonomy. Pipanacoctomys aureus Mares et al., 2000, “28 km S, 9-3 km W Andalgala; Departamento Poman, Catamarca Province, Argentina, 27° 50’ 03” 8° 66’ 15” 59” W; elevation 680 m,” Salar de Pipanaco, Saujil Department. R. M. Barquez and colleagues in 2002 treated it as Tympanoctomys based on morphological characteristics, howeverit lacks of a formal description. C. A. Woods and C. W. Kilpatrick in 2005 and M. H. Gallardo and colleagues in 2007 have continued to recognize Pipanacoctomys as a valid genus. This last revision has been followed here. Morphological data suggest a sister taxon relationship with Salinoctomys and very close relationship with Tympanoctomys. Monotypic. Distribution. NW Argentina, known only from the type locality in the Salar de Pipanaco, S Catamarca Province. Descriptive notes. Head—body 166-178 mm,tail 127-145 mm, ear 19-22 mm, hindfoot 32-40 mm. The Golden Viscacha Rat is medium-sized to large-sized. It has large and inflated auditory bullae. Dorsal pelage is golden blond, and venteris white to pale cream. Tail is long (76-85% ofits head-body length), with well-developed terminal rufous brush. Whitish hairs cover forefeet and hindfeet. Buccal bristles are present but not as developed as in the Red Viscacha Rat (7. barrerae). The Golden Viscacha Rat has a karyotype of 2n = 92, with 44-45 pairs of biarmed chromosomes and a biarmed X-chromosome and uniarmed Y-chromosome. Habitat. Edge ofsalt pans associated with peri-saline shrublands of Heterostachys sp., Atriplex lampa, and Suaeda divaricata (all Amaranthaceae). The Golden Viscacha Rat lives in a restricted, narrow band of halophytic plants that lays between bare salt flats and more typical Monte Desert habitats of Prosopis (Fabaceae), Larrea (Zygophyllaceae), and other shrubs of the Monte. Complex burrow systems are shallow and have several openings. Food and Feeding. The Golden Viscacha Rat is herbivorous and specializes on halophytic plants. It forages on Heterostachysritteriana, which has compressed leaves that form small, salt-filled balls. High salt content of these leaves cannot be reduced via mechanical means (as can leaves of Atriplex) and buccal brushes of Pipanacoctomys seem to be less well developed than those of Tympanoctomys. Breeding. Birth of a Golden Viscacha Rat was observed in October. Newborn was well haired, and eyes and ears were open within a few hours after birth. Activity patterns. There is no specific information for this species, but the Golden Viscacha Rat is considered to be nocturnal. Movements, Home range and Social organization. The Golden Viscacha Ratis ground dwelling, and apparently more than one individual can inhabit a single mound—different from the Red Viscacha Rat. Status and Conservation. Classified as Critically Endangered on The IUCN Red List. Extent of occurrence of the Golden Viscacha Rat is less than 100 km?, and its area of occupancy is less than 10 km®. All individuals occurin a single location, and extent and quality of habitat continues to decline there. Major threat to the Golden Viscacha Rat is loss of habitat to expanding olive plantations. Bibliography. Barquez et al. (2002), Gallardo et al. (2007), Mares, Braun et al. (2000), Mares, Morello & Goldstein (1985), Ojeda & Bidau (2013g), Woods & Kilpatrick (2005).

12. Chilean Rock Rat Aconaemys fuscus French: Tunduco du Chili / German: Stidamerikanische Felsenratte / Spanish: Tunduco de Chile Other common names: Great Rock Rat Taxonomy. Schizodon fuscus Waterhouse, 1842, “from Chile.” Modified by G. R. Waterhouse in 1848 to the Valle de las Cuevas near the Volcano of Peteroa, Argentina. G. R. Waterhouse in 1842 described A. fuscus based on two specimens collected by T. Bridges but never designated a type specimen, which was formally designed by O. Thomas in 1927. O. P. Pearson in 1984 summarized taxonomic history of A. fuscus. Monotypic. Distribution. Andean areas of C Chile, between Curic6 (Maule Region) and Temuco (Araucania Region) and CW Argentina (Mendoza Province), between 33° S and 41°S. Descriptive notes. Head-body 150-170 mm,tail 55-78 mm, ear 8-12 mm; weight 80-230 g. The Chilean Rock Ratis small-sized to medium-sized. Tail is relatively short (31% of its total length), without a terminal tuff, unlike other species of octodontids. Ears are small. Forelegs are strong, with long claws. Pelage is dark brown dorsally, and venteris lighter brownish yellow. Hands and feet are grayish. Karyotype is 2n = 56, FN = 108. Habitat. Rocky outcrops in highland forests of Araucaria araucana (Araucariaceae) to above Andean tree and shrub lines and flat, sandy areas covered with xerophytic shrubs and grasses such as Poa lanuginosus (Poaceae), Acacia caven (Fabaceae), Ephedra (Ephedraceae), Rosa, and Rubus (both Rosaceae), at elevations of 1000-4000 m. Food and Feeding. The Chilean Rock Rat is herbivorous and eats mainly grasses, seeds, bulbs, and roots. It also feeds on pine nuts and roots of A. aracucana and subterranean bulbs of Amarylidaceae and Alstromeriaceae. It can accumulate and store food in chambers in their burrows. Breeding. Newborn young and pregnant female Chilean Rock Rats have been recorded in spring (October-November). Activity patterns. The Chilean Rock Rat is mainly nocturnal, although daytime activity has also been reported. They only leave their burrows during the day, searching for food or to take short excursions. They have high frequency vocalizations., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 541, DOI: 10.5281/zenodo.6615351

7. Bridges’s Degu Octodon bridgesii French: Octodon de Bridges / German: Walddegu / Spanish: Degu de Bridges Other common names: Bridges's Octodon Taxonomy. Octodon bridgesii Waterhouse, 1845, “Chile.” Restricted by O. Thomas in 1927 to “Rio Teno, Colchagua,” O’Higgins, Chile. This species is monotypic. Distribution. Chile’s Coastal Mountain Range in Cauquenes (Maule Region), Tomé (Bio Bio Region), and Nahuelbuta National Park (L.a Araucania Region) W of the Central Valley, and through the Chilean Andes from Banos de Cauquenes (O’Higgins Region) to Banos del Rio Blanco (La Araucania Region) and adjacent Argentina (Lanin National Park, Neuquén Province). Latitudinal range 34-40° S. Descriptive notes Head-body 150-200 mm, tail length 102-167 mm; weight averaging 92 g. Bridges’s Degu is medium-sized. Ears are large. Tail is short (44-46% ofits total length) and straight, with a terminal brush of black hairs. Pelage is soft and is ocherbrown, with white spots underaxillary and inguinal parts. Karyotype is 2n = 58, FN = 116. Habitat. Rocky and dense scrublands in Chile and dense forests, especially of Nothofagus (Nothofagaceae), in Argentina, at elevations from sea level to 1200 m. Bridges’s Degu prefers low densities oftrees, bare ground, and dead branches. It is scansorial but can climb and build nests in vegetation. In Chile, habitats are dominated by Baccharis sp. and Podanthus mitiqui (both Asteraceae); Aristotelia chilensis (Elaeocarpaceae); Eupatorium salvia (Asteraceae); Lithraea caustic and Schinus latifolius (both Anacardiaceae); Adesmia arborea (Fabaceae); and Beilschmiedia miersii (Lauraceae). Food and Feeding. Bridges’s Degu is herbivorous and eats leaves, seeds, and grasses. The most important item on the diet is Pinus radiata (Pinaceae). Breeding. Reproductive activity of Bridges’s Degu occurs in April-December. Litter sizes are 2-3 young. Activity patterns. Bridges’s Degu is nocturnal. It can climb with help from its straight tail that rests on the ground. It is rarely seen, but its presence can be detected by its noisy alarm calls. Movements, Home range and Social organization. Average home range of the Bridges’s Degu is estimated to be 1242 m*. Status and Conservation. Classified as Vulnerable on The IUCN Red List. Major threat to Bridges’s Degu is deforestation from forestry and agricultural activities. It disappeared from the Andean range in central Chile due to habitat clearing for horticultural development, and it was extirpated in the coastal range by local intensification of agriculture in areas previously unused by local farmers. Bibliography. Gallardo (1992), Gallardo et al. (2007), Iriarte (2008), Munoz & Murua (1987), Munoz-Pedreros (2000), Mufoz-Pedreros & Yanez (2009), Ojeda & Bidau (2013c), Pearson (1995), Podesta et al. (2000), Redford & Eisenberg (1992), Saavedra (2003), Simonetti (1989a, 1994), Simonetti & Saavedra (1998), Thomas (1927a), Verzi & Alcover (1990), Waterhouse (1845)., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 540, DOI: 10.5281/zenodo.6615351

4. Chalchalero Viscacha Rat Salinoctomys loschalchalerosorum French: Octodon des Chalchaleros / German: Chalchaleros-Viscacharatte / Spanish: Rata vizcacha de Los Chalchaleros Taxonomy. Salinoctomys loschalchalerosorum Mareset al., 2000, “26 km SW Quimilo, Departamento Chamical, La Rioja Province, Argentina, (30° 02’ 43.4” S, 65° 31’ 13.4” W; elevation 581 m. ” R. M. Barquez and colleagues in 2002 treated it as Tympanoctomys based on morphological characteristics, howeverit lacks of a formal description. C. A. Woods and C. W. Kilpatrick in 2005 and M. H. Gallardo and colleagues in 2007 have continued to recognize Salinoctomys as a valid genus. This last revision has been followed here. Morphological analyses suggest that Salinoctomys, which is not represented in any molecular analysis, is member of the desert-adapted clade (Octomys [Tympanoctomys + Pipanacoctomys]), with a sister relationship with Pipanacoctomys. Monotypic. Distribution. W Argentina, known only from the type locality in NE La Rioja Province. Descriptive notes. Head-body 144-156 mm, tail 111-119 mm, ear 17 mm, hindfoot 28-30 mm. The Chalchalero Viscacha Rat is medium-sized. It has large and inflated auditory bullae. Pelage is brownish black dorsally and white ventrally. Tail is long (more than 75% of head-body length) with black tuft. Whitish to pale brownish hairs cover forefeet and hindfeet. Buccal bristles are present, but they are not well developed. Karyotype is unknown. Habitat. Peri-saline shrublands associated with the Salinas Grandes salt flat at elevations of 500-600 m. The Chalchalero Viscacha Ratlives in a burrow system restricted to a narrow band of halophytic plants thatlies between bare salt flat and dense thornscrub of cacti, trees, and shrubs, typical of the Gran Chaco. Food and Feeding. The Chalchalero Viscacha Rat specializes on halophytic vegetation and seems to forage mainly on Heterostachys ritteriana (Amaranthaceae)—often most abundant in the immediate vicinity of its burrow system. It has been found in food stores in burrows. Breeding. A pregnant Chalchalero Viscacha Rat with two embryos was collected in July. Activity patterns. There is no information available for this species. Movements, Home range and Social organization. There is no information available for this species. Status and Conservation. Classified as Critically Endangered on The IUCN Red List. Extent of occurrence of the Chalchalero Viscacha Rat is less than 100 km?, and its area of occupancy is less than 10 km? All known individuals are in a single location, and extent and quality of its habitat continues to decline. Bibliography. Barquez et al. (2002), Gallardo et al. (2007), Mares et al. (2000), Ojeda & Bidau (2013h), Woods & Kilpatrick (2005).

2. Kirchners’ Viscacha Rat Tympanoctomys kirchnerorum French: Octodon des Kirchner / German: KirchnerViscacharatte / Spanish: Rata vizcacha de Patagonia Taxonomy. Tympanoctomys kirchnerorum Teta et al, 2014, “ Argentina, Province of Chubut, department of Gastre, 18 km NNE by road of Los Adobes, conjunction between Ruta Provincial 58 and Zanjon El Colorado (43°13'51.6", 68°38'49.1", 517m).” This species is monotypic. Distribution. S Argentina, known distribution limited to the type locality and surrounding areas in Chubut Province. Descriptive notes. Head-body 111-136 mm, tail 111-120 mm, ear 14-15 mm, hindfoot 29-35 mm; weight 50-80 g. Kirchners’ Viscacha Rat is slightly smaller than the Red Viscacha Rat (T. barrerae). Its skull is more bowed in dorsal profile than the Red Viscacha Rat. Color of Kirchners’ Viscacha Rat is pale brown dorsally and whitish to white ventrally. Tail is relatively long (43-50% of head-body length), with a medium terminal brush. Short, thick, and whitish hairs cover forefeet and hindfeet. Oral bristle bundles are well developed. Kirchners’ Viscacha Rat has 2n = 102, similar to that of Red Viscacha Rat. Karyotype has 32 pairs of metacentric to submetecentric chromosomes and 18 pairs of subtelocentric chromosomes. Sex chromosomes could not be discriminated but probably resembled those of the Red Viscacha Rat. Sperm morphology of Kirchners’ Viscacha Rat is smaller in size but similar in shape to that of the Red Viscacha Rat. Habitat. Sandy terrain in a general badland landscape within the Chuquiraga avellanedae (Asteraceae) steppe of the Patagonian Ecoregion at an elevation of 500 m. Burrows of Kirchners’ Viscacha Rat have typical semicircular entrances c.10 cm high, are well curved above and flat below, and are usually placed under Atriplex (Amaranthaceae) bushes. Plant cover near burrows is sparse, consisting mostly of low shrubs, such as Atriplex, C. avellanedae, Prosopis sp. and Prosopidastrum sp. (both Fabaceae), and Schinus johnstonii (Anacardiaceae). Food and Feeding. There is no specific information for this species, but Kirchners’ Viscacha Rat probably feeds mainly on halophytic vegetation (e.g. Atriplex). Breeding. There is no information available for this species. Activity patterns. There is no specific information available for this species, but Kirchners’ Viscacha Rat is apparently nocturnal. Movements, Home range and Social organization. There is no specific information available for this species, but Kirchners’ Viscacha Rat is probably solitary. Status and Conservation. As a newly described species, Kirchners’ Viscacha Rat has not been assessed on The IUCN Red List. No information is available aboutits conservation status, but its very limited distribution (restricted to the type locality) together with its recent extirpation (Late Holocene) from the Chubut River Valley and potential impact of mining in central Patagonia suggest that Kirchners’ Viscacha Rat has a high risk of extinction in the short term. Bibliography. Gallardo et al. (2009), Leon et al. (1998), Ojeda et al. (2007), Pardinas et al. (2012), Sauthier et al. (2009), Teta et al. (2014)., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 538, DOI: 10.5281/zenodo.6615351

4. Chalchalero Viscacha Rat Salinoctomys loschalchalerosorum French: Octodon des Chalchaleros / German: Chalchaleros-Viscacharatte / Spanish: Rata vizcacha de Los Chalchaleros Taxonomy. Salinoctomys loschalchalerosorum Mareset al., 2000, “26 km SW Quimilo, Departamento Chamical, La Rioja Province, Argentina, (30° 02’ 43.4” S, 65° 31’ 13.4” W; elevation 581 m. ” R. M. Barquez and colleagues in 2002 treated it as Tympanoctomys based on morphological characteristics, howeverit lacks of a formal description. C. A. Woods and C. W. Kilpatrick in 2005 and M. H. Gallardo and colleagues in 2007 have continued to recognize Salinoctomys as a valid genus. This last revision has been followed here. Morphological analyses suggest that Salinoctomys, which is not represented in any molecular analysis, is member of the desert-adapted clade (Octomys [Tympanoctomys + Pipanacoctomys]), with a sister relationship with Pipanacoctomys. Monotypic. Distribution. W Argentina, known only from the type locality in NE La Rioja Province. Descriptive notes. Head-body 144-156 mm, tail 111-119 mm, ear 17 mm, hindfoot 28-30 mm. The Chalchalero Viscacha Rat is medium-sized. It has large and inflated auditory bullae. Pelage is brownish black dorsally and white ventrally. Tail is long (more than 75% of head-body length) with black tuft. Whitish to pale brownish hairs cover forefeet and hindfeet. Buccal bristles are present, but they are not well developed. Karyotype is unknown. Habitat. Peri-saline shrublands associated with the Salinas Grandes salt flat at elevations of 500-600 m. The Chalchalero Viscacha Ratlives in a burrow system restricted to a narrow band of halophytic plants thatlies between bare salt flat and dense thornscrub of cacti, trees, and shrubs, typical of the Gran Chaco. Food and Feeding. The Chalchalero Viscacha Rat specializes on halophytic vegetation and seems to forage mainly on Heterostachys ritteriana (Amaranthaceae)—often most abundant in the immediate vicinity of its burrow system. It has been found in food stores in burrows. Breeding. A pregnant Chalchalero Viscacha Rat with two embryos was collected in July. Activity patterns. There is no information available for this species. Movements, Home range and Social organization. There is no information available for this species. Status and Conservation. Classified as Critically Endangered on The IUCN Red List. Extent of occurrence of the Chalchalero Viscacha Rat is less than 100 km?, and its area of occupancy is less than 10 km? All known individuals are in a single location, and extent and quality of its habitat continues to decline. Bibliography. Barquez et al. (2002), Gallardo et al. (2007), Mares et al. (2000), Ojeda & Bidau (2013h), Woods & Kilpatrick (2005)., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 539, DOI: 10.5281/zenodo.6615351

6. Mountain Degu Octodontomys gliroides French: Octodon a longue queue / German: Pinselschwanzratte / Spanish: Degu del Monte Other common names: Chozchori, Long-tailed Octodon Taxonomy. Octodon gliroides P. Gervais & d’Orbigny, 1844, “des Andes boliviennes, a Lapaz,” La Paz, Bolivia. Phylogenetic position of Octodontomys remains uncertain. Most molecular studies support a sister relationship with the Chilean clade (Octodon [Aconaemys + Spalacopus]), while others place it basal to the desert-adapted Argentinean clade (Octomys [Tympanoctomys + Pipanacoctomys]). Monotypic. Distribution. Andean and sub-Andean zones of SW Bolivia, N Chile, and NW Argentina. Descriptive notes. Head-body 161-182 mm, tail 100-190 mm; weight 100-200 g. The Mountain Degu is mediumsized to large-sized. Skull is nearly similar to that of species of Octomys. Rostrum is relatively long and narrow. Tympanic bullae are large and well developed, like other desert-adapted octodontids. Pelage is long and silky. Dorsal fur is grayish brown, and venteris white, with gray bases to hairs. Chin and throat are pure white. Ears are large and covered with short grayish hairs. Tail is long (c.80% of head-body length) and bicolored, with well-developed, brown-ocher brush extending from tip. Chromosome complement is 2n = 38, FN = 64. Habitat. Open, xeric, and rocky areas of the Puna, dominated by columniform cacti (Browningia, Cereus, Trichocereus, and Opuntia, Cactaceae), shrubs, and herbaceous plants, at elevations of 2000-5000 m. The Mountain Degu is a scansorial species, but it can make superficial burrows in patches of columnar and ground-level cacti or shrubs, where they feed on vegetation, hide from predators, and rear offspring. Tail is used for substrate support when climbing. Food and Feeding. The Mountain Degu is herbivorous and eats on cacti and pods and seeds of acacia (Acacia, Fabaceae). Individuals feed on acacia sheaths in winter and cactus fruits in summer; they also eat leaves and bark of resinous shrubs and can use cactus tissues to satisfy water requirements. Breeding. Gestation of the Mountain Degu is 100-109 days, with litter sizes of 1-3 offspring. Precocial young are born completely furred and with open eyes. Juveniles in various stages of development have been found in November, and pregnant females and young in January and May. Activity patterns. The Mountain Degu is nocturnal. Its activity is highest after sunset and decreases after sunrise. Movements, Home range and Social organization. The Mountain Degu is social and communicates with gurgles, twitters, and squeaks in low, mid-, and high frequencies. A recent study of two populations of Mountain Degus identified social groups of 2-3 or 2—4 individuals. Mountain Degus from the same social group always used one burrow system for resting and hiding. Males have larger home ranges than females. Status and Conservation. Classified as Least Concern on The IUCN Red List. The Mountain Degu has no apparent conservation threats, and it can live in areas of high human densities. It has a wide distribution and presumably a large overall population. Bibliography. Contreras, Torres-Mura, Spotorno & Walker (1994), Contreras, Torres-Mura & Yanez (1987), Diaz, G.B. & Ojeda (2000), Diaz, M.M. (1999), Gallardo (1992), Gallardo & Kirsch (2001), George & Weir (1972b), Honeycutt et al. (2003), Iriarte (2008), Mann (1978), Munoz-Pedreros (2000), Opazo (2005), Pine et al. (1979), Reig (1986), Rivera (2013), Rivera et al. (2014), Rowe etal. (2010), Tirira, Boada, Weksler et al. (2008a), Upham & Patterson (2012), Weir (1974)., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on pages 539-540, DOI: 10.5281/zenodo.6615351

1. Red Viscacha Rat Tympanoctomys barrerae French: Octodon de Barrera / German: Rote Viscacharatte / Spanish: Rata vizcacha colorada Other common names: Plains Viscacha Rat, Red Viscacha-rat Taxonomy. Octomys barrerae Lawrence, 1941, “La Paz, Mendoza Province, Argentina.” This species is monotypic. Distribution. Patchily in arid regions of W & C Argentina, known only from 13 localities in San Juan, Mendoza, La Pampa, and Neuquén provinces (between 29° S and 38° 8S). Descriptive notes. Head-body 125-160 mm, tail 93-147 mm, ear 13-19 mm, hindfoot 30-36 mm; weight 52-104 g. Males tend to be larger than females. The Red Viscacha Rat has a relatively large head; cranial width is greater than cranial length due to extremely developed auditory bullae that are more than 45% of greatest length of skull. Dorsal pelage is reddish brown; ventral pelage is white. Tail is long (82% ofits head-body length) and terminates in a black brush. Whitish hairs cover forefeet and hindfeet. It has a specialized oral bundle of rigid hairs behind upper incisors. Kidneys are specialized with an elongated renal papilla able to concentrate urine at a maximum of 7080 mOsm/liter, similar to other desert rodents that forage on halophytic vegetation. The Red Viscacha Rat has a 2n = 102, FN = 200 karyotype, the largest in both diploid and fundamental number among mammals. Karyotype is composed of completely biarmed chromosomes that include 36 pairs of metacentric to submetacentric chromosomes, 14 pairs of subtelocentric autosomes, and a XY sex chromosome system. Sperm morphology is peculiar with a paddle-like sperm head, and sperm lengths are the largest reported for rodents. The Red Viscacha Rat was proposed to be the first tetraploid mammal known, but other studies presented evidence that its genomeis diploid rather than polyploid. Habitat. Salt basins and sand dunes in the lowland habitats of Monte and Patagonian deserts at elevations of 300-1400 m. The Red Viscacha Rat lives in complex burrow systems built in soft soil associated with sand dunes and salty environments. Each burrow system has several entry holes that connect with internal tunnels and galleries. Orientation of holes changes seasonally; in winter, holes are mostly oriented toward sunlight, and galleries are constructed so that they receive direct sunlight in winter and indirect sunlight in summer. Food and Feeding. The Red Viscacha Rat has a strictly and highly specialized herbivorous diet and feeds mainly on halophytic vegetation (e.g. Atriplex, Allenrolfea, Heterostachys, and Suaeda, all Amaranthaceae). Low proportions of species of true grasses (Poaceae) are detected in diets and are eaten in lower proportions than available. The Red Viscacha Rat scrapes surfaces of Atriplex leaves with lower incisors and oral bundle of rigid hairs behind upper incisors before consumption, which helps remove and discard salt excess on leaves and reduces salt ingestion. Breeding. On average, captive female Red Viscacha Rats have four litters per year. Neonates have closed eyes and weigh 4 g at birth. At five days of age, they weighed 8 g and opened their eyes after six days. Juveniles start to consume plants at c.10 days old, although weaning is not complete. Juveniles scrape Atriplex leaves as their mothers do. Activity patterns. The Red Viscacha Rat is normally considered to be nocturnal, but it is sometimes active during the day. Movements, Home range and Social organization. The Red Viscacha Rat is a grounddwelling solitary species and occurs at low densities. One individual lives in each burrow system. Anecdotal reports indicate that a male and a female occupy the same burrow system, probably during mating; in another case, two males were trapped in the same burrow. Isolated, patchy populations of Red Viscacha Rats are, in some cases, separated by hundreds of kilometers. Status and Conservation. Classified as Near Threatened on The IUCN Red List. Several attributes of the Red Viscacha Rat (e.g. patchy distribution, habitat and trophic specialization, and low densities) increase its vulnerability. Change from Vulnerable to Near Threatened since the last assessment reflected a better understanding of its biology within its distribution. In particular, occurrence and area of occupancy (new population records) were extended. Recent studies have detected genetic distinctiveness in some populations that could have important implications for conservation and management of the Red Viscacha Rat. Bibliography. Berman (2003), Diaz & Ojeda (1999), Diaz et al. (2000), Gallardo, Bickham et al. (1999), Gallardo, Gonzalez & Cebrian (2006), Gallardo, Kausel et al. (2004), Gallardo, Sauthier et al. (2009), Giannoni et al. (2000), Grzimek (2004), Lawrence (1941), Mares, Braun & Channell (1997), Mares, Ojeda et al. (1997), Ojeda, A.A. (2010), Ojeda, A.A. et al. (2007), Ojeda, R.A. & Bidau (2013j), Ojeda, R.A. & Diaz (1997), Ojeda, R.A., Gonnet et al. (1996), Ojeda, R.A., Roig et al. (1989), Reca et al. (1996), Sauthier et al. (2009), Svartman et al. (2005), Torres et al. (2003), Torres-Mura et al. (1989), Verzi et al. (2002), Woods & Kilpatrick (2005), Yepes (1942)., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 538, DOI: 10.5281/zenodo.6615351

11. Porter’s Rock Rat Aconaemys porter French: Tunduco de Porter / German: PorterFelsenratte / Spanish: Tunduco de Porter Taxonomy. Aconaemys porteri Thomas, 1917, “Osorno, S. Chile,” slopes of Volcan Osorno, Los Lagos Region. O. P. Pearson in 1984 synonymized A. porteri with A. fuscus, but M. H. Gallardo and D. Reise in 1992 confirmed that the two were morphologically and chromosomally distinct species. Based on molecular data, A. porteri is clearly distinct from the other two species of Aconaemys and has a basal phylogenetic position to the sister pair of A. fuscus and A. sagei. Monotypic. Distribution. Andes of Argentina and Chile, in Chile it occurs from Villarica to Puyehue volcanoes (Los Lagos Region) and in Argentina it extends from Lanin to Nahuel Huapi national parks (Neuquén Province). Descriptive notes. Head-body 148-192 mm, tail 68-85 mm, ear 20-22 mm, hindfoot 30-37 mm; weight 105-160 g. Ears are small. Forelegs have long claws. Pelage is dark brown dorsally and bright rufous on ventral parts. Main feature of dentition is long and wide incisors. Karyotype is 2n = 58, FN= 112. Habitat. Mountain plains with gentle slopes, occurring in dense bamboo and southern beech forests (Nothofagus dombeyi, Nothofagaceae) at elevations of 900-2000 m. Food and Feeding. Porter’s Rock Rat is herbivorous and feed on leaves, sprouts,little branches of bamboo, and pine nuts of araucarias. Breeding. There is no specific information for this species, but an anecdotal report indicated that one female Porter’s Rock Rat had three embryos at the end of October. Activity patterns. Porter’s Rock Rat is mainly nocturnal, but it can be active during the day. During winter,it is active under snow. Movements, Home range and Social organization. Porter’s Rock Ratis colonial and fossorial. It builds networks of interconnected superficial tunnels, with entrances 1 m from each other. It lives in small groups of up to seven individuals in communal burrow systems. In some burrows, thin bamboo stems and aggregations offeces are found. Porter’s Rock Rat makes a very strong group squeak. Status and Conservation. Classified as Data Deficient on The IUCN Red List. There is an absence of information about recent extent of occurrence, conservation threats, and ecological requirements. Porter’s Rock Rat is considered rare in the Los Lagos Region of Chile. Bibliography. Chapman (2008), Gallardo & Reise (1992), Honeycutt et al. (2003), Ipinza et al. (1971), Iriarte (2008), Munoz-Pedreros (2000), Opazo (2005), Pearson (1983, 1984), Thomas (1917a), Woods & Kilpatrick (2005)., Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Octodontidae, pp. 536-541 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 541, DOI: 10.5281/zenodo.6615351