ANNOTATED KEYS FOR IDENTIFYING SMALL MAMMALS LIVING IN OR NEAR NAHUEL HUAPI NATIONAL PARK OR LANIN NATIONAL PARK, SOUTHERN ARGENTINA

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1 Mastozoología Neotropical; 2(2): ISSN SAREM, 1995 ANNOTATED KEYS FOR IDENTIFYING SMALL MAMMALS LIVING IN OR NEAR NAHUEL HUAPI NATIONAL PARK OR LANIN NATIONAL PARK, SOUTHERN ARGENTINA Oliver P. Pearson Museum of Vertebrate Zoology, University of California. Berkeley, California, U.S.A ABSTRACT: The mammalian fauna of northwestern Patagonia, Argentina (at about 40 SL) is composed of a rich mixture of species that range in a wide variety of habitats and elevations, from lowland steppe and thorn scrub to highland desert. The natural history of the small mammal fauna of this region has been poorly known. In an effort to fulfill this gap I have assembled a series of keys for the proper identification of this peculiar fauna. These annotated keys provide a better chance for the correct determination of 37 species of volant and nonvolant small mammals, and general comments on their taxonomy, habits and distribution. Photographs of skull, mandibles and molar teeth are illustrated for most of the species. RESUMEN: Claves comentadas para la identificación de los pequeños mamíferos de los Parques nacionales Nahuel Huapi o Lanin, del sur de Argentina. La fauna de mamíferos del noroeste de Patagonia (a los 40 2 lat sur) esta compuesta por una rica mezcla de especies distribuidas en una gran variedad de hábitats y alturas, desde la estepa y matorral arbustivo al desierto de altura. La historia natural de los micromamíferos de esta región es poco conocida. En un esfuerzo por llenar este vacio he elaborado una serie de claves para ayudar a la identificación de esta fauna peculiar. Estas claves comentadas proveen una mejor oportunidad para la correcta determinación de 37 especies de mamíferos voladores y no voladores, incluyéndose comentarios generales sobre taxonomía, hábitos y distribución. La mayoría de las especies son ilustradas con fotos de craneo, mandíbula y molariformes. Key words: Patagonia, Argentina, small mammals, Nahuel Huapi, Lanin. The honre of this fauna in northwestern Patagonia at about 40 S Latitude is a region where cool moist mountain forests of Southern Beech trees (Nothofagus) meet the semiarid, windswept Patagonian steppe. The fauna itself is a mixture of species found only in this isolated strip of forest shared by Chile and Argentina (Figure 1), species found only or primarily in the steppe, and species that range widely in thorn scrub, desert, and highaltitude habitats. Some of these widely-dispersed species are found as far north as the mountains of Peru. In spite of the cold, snowy winters and per- sistent high winds, this small-mammal fauna is unusually abundant and diverse. The average 24-hour trap success in all habitats during an 8- year period was 19 percent. A line of traps set within the transition zone between forest and steppe, locally called the pre-cordillera, will frequently have 50 percent success, with eight to ten species representad. A single family of owls may capture 15 species of small mammals within a period of a few months, and the captures will be much more evenly distributed among the available species of mammals than in the Northern Hemisphere where a few species of mice tend to dominate the diet of the predators. Recibido 20 Mayo Aceptado 12 Setiembre 1995.

2 100 Oliver P. Pearson General accounts of the taxonomy, distribution, or biology of many of the animals covered in this report may be found in the following publications, listed chronologically: Allen, 1905; Cabrera and Yepes, 1940; Osgood, 1943; Cabrera, 1957, 1961; Hershkovitz, 1962; Greer, 1965; Reise, 1973; Mann, 1978; Tamayo and Frassinetti, 1980; Olrog, 1980; Honacki et al., 1982; Pearson and Pearson, 1982; Christie, 1984a, 1984b; Patterson et al., 1989, 1990; Nowak, 1991; Redford and Eisenberg, 1992; Wilson and Reeder,1993; Braun, 1993; S teppan, 1993, 1995; Massoia and Chebez, 1993; Ubeda et al., 1994; Grigera et al., 1994; Monjeau et al., 1994; Kelt, The animals represented in this report are: Page MARSUPIALS 16 Dromiciops australis 16 Lestodelphys halli 16 Rhynocholestes raphanurus 17 Thylamys pusilla 17 Fig. 1: Map showing the location of: 1) Nahuel Huapi National Park, 2) Lanin National Park, 3) Huechulafquen lake, 4) Lacar lake, 5) Nahuel Huapi lake. The mammal fauna of this region has been poorly known. Little has been published on the natural history of many of the species, and the taxonomy of most of the genera and species has been so little studied that frequently it is impossible to put a meaningful scientific or common name on a specimen, even if one has been successful in "identifying" it. In an effort to increase the rate of growth of our knowledge of this fauna, I have assembled the following keys so that interested students will have a better chance than at present of identifying properly some of these interesting animals. BATS 17 Histiotus macrotus I 7 Histiotus montanus 17 Lasiurus blossevillii 18 Lasiurus cinereus* 18 Lasiurus ega* 18 Myotis chiloensis 18 Tadarida brasiliensis 18 CRICETINE RODENTS 19 Abrothrix longipilis 19 Abrothrix olivaceous 19 Abrothrix sanborni* 19 Abrothrix xanthorhinus 19 Akodon iniscatus 20 Calomys musculinus 20 Chelemys macronyx 21 Eligmodontia morgani 21 Euneomys chinchilloides 22 Euneomys mordax* 22 Geoxus valdivianus 22 Irenomys tarsalis 23 Loxodontomys micropus 23 Notiomys edwardsii 23 Oligoryzomys longicaudatus 24 Phyllotis xanthopygus 24

3 KEY TO SMALL MAMMALS 101 Reithrodon auritus 24 MURID RODENTS 25 Mus domesticus 25 Rattus norvegicus 25 HYSTRICOGNATH RODENTS 26 Aconaemys porteri 26 Aconaemys sagei 26 Ctenomys haigii 26 Ctenomys maulinus 27 Ctenomys sociabilis 27 Galea musteloides 28 Lagidium boxi 28 Microcavia australis 28 Myocastor coypus 29 Octodon bridgesii 29 HARES 30 Lepus capensis 30 * Not in the present account. A key to the bats of the region is presented (Appendix, Table 5), as well as three separate keys to the terrestrial small mammals based on External Characters (Appendix, Table 6), Crania (Appendix, Table 7), and Mandibles (Appendix, Table 8). The key to crania and the key to mandibles were prepared to facilitate identification of small-mammal remains recovered from owl pellets. I have tried to use cranial features that survive the digestive process, and so some of the measurements are not the same ones used customarily in taxonomic studies. It has not always been possible to separate species using a single character, and uncertainty may be encountered, especially between the various species of Abrothrix and Akodon. Reference to the individual species accounts may clarify some of the uncertainty. Fine calipers are necessary to use the skull key and the mandible key, but after a little experience with the key, the user learns to estimate whether a feature is "larger than" some critical measurement. Some form of magnification is helpful. Molar toothrows were measured at the level of the alveolus so that even if teeth are missing an approximation can be made by measuring the distance between the empty sockets. Skulls and mandibles of bats are not keyed or illustrated because they are seldom found in pellets. In many of the individual species accounts that follow, the length of the head plus body and the length of the tau are given without further notation. Major dichotomies in the keys are the presence or absence of a large gap between the incisor and the posterior teeth (to separate marsupials from rodents), presence or absence of longitudinal grooves on the front surface of the upper incisors, and size or ratios of various parts of the body, skull, or mandible. Figure 2 illustrates some of the features and measurements used in the keys, and photographs of skulls, mandibles, and molar teeth are found in Appendix, Figures Tables 3 and 4 summarize some of the cranial and mandibular differences. The geographic ranges of most of the species can be found, on a coarse scale, in Redford and Eisenberg (1992) and, on a fine scale, in Christie (1984a). A useful feature of the cranium, not utilized in the keys because it is difficult to quantify, is the inflation or lack of inflation of the frontal region aboye the anterior root of the zygomatic arch. In all species of Abrothrix, Akodon, Chelemys, Geoxus, and Notiomys this region is rounded, swollen. I have considered the region of this study to be made up of eight kinds of habitat, each chosen for features thought to be of importance to the small mammals. The eight habitats are: Forest (bosque). Stands of one or more of the three species of Nothofagus or of Austrocedrus, dense enough so that the lower trunks are free of branches; understory can be open or dense, with or without bamboo. Shrub (matorral). Bushes more than 1 m tall, even small trees. Especially important in various places are Colletia, Berberis, Fabiana, Discaria, Chacaya, bushy Nothofagus antarctica, and bamboo. Includes bamboo thickets if they were not included in Forest because of the presence of large trees.

4 102 Oliver P. Pearson INCISIVE FORAMINA DIASTEMA PALATE POST PALATAL PITS MESO PTERYGOID FOSSA PARAPTERYGOID FOSSA BULLAR TUSES WIDTH OF R OSTRUM INFRAORBITAL FORAMEN FRONTAL REGION INTERORBITAL BREADTH ZYGOMATIC PLATE CORONOID PROCESS M2 CONDYLOID PROCESS LENGTH OF CONDYLOID PROCESS CAPSULAR PROJECTION LENGTH OF MANDIBLE A NGULAR PROCESS DEPTH OF MAN DIBLE LENGTH OF TOOTHROW PROODONT ORTHODONT Fig. 2: Features and measurements of skulls and mandibles used in the keys.

5 KEY TO SMALL MAMMALS 103 Table 1: Relative abundance of various species as measured by trap success (%) in each of the eight habitats. For example, 9.6% of the traps set in Forest caught Abrothrix longipilis, but only 1.4% caught Abrothrix olivaceus. Overall trap success was 17.8% in Forest, 26.5% in Shrub habitat, but only 5.8% in Turf. Trap success was about 5 times greater in autumn than in spring. The aboye percentages have not been corrected for this seasonal effect. Some habitats may have been trapped more intensively at one season than at the other. FOREST SHRUB STEPPE BUNCH GRASS WEEDS TURF ROCKS BARE Abrothrix longi Abrothrix oliv Abrothrix xantho Auliscomys Chelemys Dromiciops Eligmodontia Euneomys chinch Geoxus Irenomys Loxodontomys Oligoryzomys Phyllotis Rattus Reithrodon Table 2: The probability of capture of each of various species of small mammals in each of the eight habitats. For example, 18% of the Abrothrix longipilis were trapped in forest but only 5% in Bunchgrass, whereas no Abrothrix xanthorhinus were caught in Forest and 44% of them in Bunchgrass. Shrub habitat supported the most species, Turf supported the fewest. FOREST SHRUB STEPPE BUNCH GRASS WEEDS TURF ROCKS BARE Abrothrix longi Abrothrix oliv Abrothrix xantho Chelemys Dromiciops Eligmodontia Euneomys chinch. O o Geoxus lrenomys Loxodontomys Oligoryzomys Phyllotis Rattus Reithrodon

6 104 Oliver P. Pearson Table 3:Characters of crania of rats and mice (Cricetidae and muridae) A" <,'. 0 1/4, 1,.1/4'.0 se.',. cso.<4s. op O0' (P. 2> o.1.. p' z,' <1;k9,s, j. 1 4«C1 g' l "*0" 11" 4>"? ' ', q:'\ e, S '1' -..,, o «,s9. s.15).9 z,1' (1\,4' ' :.4' J?.1, ',5,,,' 41 `t'. s'''' 4, 'QP A? ", $\ 4,\ ev / c5' / s.01 s.s'',b5.1' o. '', $'' 1 i;<,9 oos c s c.p.,,.. c., c3,.`w $5 4'5 115,,c', 5' 40 $\''..0`5' c." +.4N''' Abrothrix longi. 4.0 no yes yes or = no > short no no < 4-3,3,3 Abrothrix oliv. 3.6 no yes yes or = no > short no no < 4-3,3,3-2 Abrothrix xantho. 3.3 no yes yes or = no > short no no < 4,3,3 Akodon iniscatus 4.0 no yes yes or = small = med. no' yes «Calomys musc. 3.6 no no = yes <or = med. no yes < 4,3,3 Chelemys macro. 5.7 no yes no or = no > short no no < 4-3,3,2 Eligmodontia 3.7 no no yes yes < med no no < 4,3,3-2 Euneomys chinch. 5.8 yes no yes fossa < med yes yes < 3,3,2 Euneomys mordax 6.4 yes no yes fossa < long yes no < 3,3,2 Geoxus valdiv. 3.4 no yes yes or = no > none no no < 4,3,3 Irenomys tars. 5.4 yes no no or = yes = med. sl. no = 3,3-2,3-2 Loxodontomys 5.9 no no no or = yes < or = long yes no sl < 4-3,3,3 Mus domesticus 3.3 no no yes tiny < short no no «3,3,2 Notiomys edward. 3.4 no sl. yes small > none no no «Oligoryzomys 3.8 no no yes yes = long no sl. < 3,3,3 Phyllotis xantho. 5.4 no no yes yes = or > med. no no < 4,3,3-2 Rattus norveg. 7.2 no no yes no > short no no < 5,4-3,3 Reithrodon aur. 6.6 yes no no fossa < long yes no < 5-4,3,4-3 Table 4: Characters of mandibles of rats and mice (cricetidae and muridae) c%) / CY,- _k ' o f 0/ Y ':.).2'":1. IS", (5)., 3. /.c. b'' cl, "1/'S 4. e, 1:.,,t CA',,e,,i? ".12' It c9 é \ ' ' \-k"'' / ' \`e5 'le c.,1'. ci 12, Sg t 1.' ós'c' i. CN' '' ólt,.< Al\ ' '),<I,. \- ''. "I' +$\ -* \ 5" 1, (S D''. $\*.r ''' e (9 Abrothrix longipilis 4.0 slight long small no < 3-2,3-2,2 Abrothrix olivaceus 3.6 no long small no < 2,3,2 Abrothrix xanthorhinus 3.3 no med-long small no < 3-2,3,2 Akodon iniscatus 4.1 no long med-large yes < 3,2,2 Calomys musculinus 3.3 no med-long small no < 4,3,3 Chelemys macronyx 5.8 yes long med. yes «3,2,2 Eligmodontia morgani 3.7 no short small-med no < 4,3,2 Euneomys chinchilloides 5.9 yes short large yes < or = 2,2,2 Euneomys mordax 6.8 yes short large? < or = 2,2,2 Geoxus valdivianus 3.2 no short small yes < 2,2,2 Irenomys tarsalis 5.3 no short small yes = 2,2,2 Loxodontomys micropus 6.0 yes short large no < or = 4-3,3-2,2 Mus domesticus 2.7 no short small no «2,2,2 Notiomys edwardsi 3.4 no long small no «Oligoryzomys longi. 3.8 yes med large yes sl.< 2,2,2 Phyllotis xanthopygus 5.4 no short small no < 4,3,2 Rattus norvegicus 7.2 no med-long small-med yes < 4,3,3est Reithrodon auritus 6.6 yes short med. no < 4,3,3-2

7 KEY TO SMALL MAMMALS 105 Steppe (estepa arbustiva). Scattered low bushes, usually less than one meter tal', and usually mixed with bunchgrass; considerable bare ground. Important bushes in this region ate Mulinum, Baccharis, Senecio, Berberis, and Acaena. Bunchgrass (coironal). Relatively pure stands of one or more species of bunchgrass. Weeds (hierbas densas). Dense weeds such as dandelion, thistle, and grasses, usually growing in moist places and protected from heavy grazing; must be dense enough to provide excellent cover for mice close to the ground. Turf (pastizal cespitoso). Closely cropped turf of non-bunch grasses and herbs such as white clover (Trifolium repens) and filaree (Erodium cicutarium), usually bordering moist places. Rocks (pedriscal). Cliffs or tumbled boulders and rocks, the rocks large enough to provide refugia for mice. Bare (peladar). More than half the ground not vegetated, the substrate fine scree or rock; rocky refugia scarce or absent. The bare areas are relatively large, not stippled with bushes as in steppe habitat. This habitat is usually found on windswept hilltops. Each trap fine was classified as belonging to one of these habitats. All of the captures on 274 lines from 1977 to 1985 were then summed (20,000 trap nights) and various characteristics of the fauna and its use of the environment were calculated. The "richness" or "productivity" of the different habitats for small mammals is reflected by the percent trap success for all species combined in each of the eight habitats: Forest Shrub Steppe Bunchgrass Weeds Turf Rocks Bare The relative abundance of each species in each habitat is reflected in the trap success for each species in each habitat (Table 1). An idea of how the world looks to each species of small mammal can be learned from Table 2, where each number represents trap success for each species in each of the habitats, adjusted so that the trap successes for each species (rows) add up to 100 percent. For example, 15% of the Oligoryzomys were caught in Forest, 42% in Shrub, etc. An additional dimension, time, has been added to our understanding of this fauna by the discovery of a cave full of bones brought in by owls and by early man. This deposit was nearly two meters deep; the oldest layer was almost 10,000 years old. Identification of thousands of crania and mandibles revealed that the composition of the small-mammal fauna changed very little, with one exception: the mouse Euneomys chinchilloides was the most abundant species throughout the long history but is now relatively scarce. See Pearson and Pearson (1982), Pearson (1987), and Crivelli et al. (1993). Nearby caves also contain accumulations of rodent feces and urine that are several thousand years old (Pearson and Christie, 1993). Identification of contained plant fragments should provide an interesting vegetational history. MARSUPIALS Dromiciops australis Monito de Monte Identification. A mouse-sized marsupial with prehensile tail equal to or longer than head and body (100 x 105 mm), color pattern strikingly cream and brown splotched, ears furred and equal to or shorter than hind feet, many small sharp teeth without the gap between incisors and molars seen in rodents. The upper incisors are all in an even row without a gap between the first one and the succeeding ones. The lower canine is no higher than the adjacent incisors and premolars (see Figs 3, 18). Similar species. Another small marsupial, Lestodelphys, lives in the steppe to the east of the forest, but both species are caught by owls near Bariloche. Lestodelphys is larger with tail shorter than head and body (135 x 90 mm), ears

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9 KEY TO SMALL MAMMALS 107 Similar species. Compare Lestodelphys and Dromiciops. The body fur of Dromiciops grows farther out onto the base of the tail than in Thylamys. The lower canine of Thylamys is larger than the incisors and premolars, and the hind feet are shorter than the ears. The articular condyles on the mandible are less than 2.7 mm across. Taxonomy. The subspecies may be T. pusilla bruchi. Many publications use the narre Marmosa elegans or Marmosa pusilla. See Creighton (1985), and Gardner and Creighton (1989). Distribution. In semi-arid habitats in Argentina and ranges from Chile north to Bolivia; reaches its southern limit at the Río Collon Cura in the region covered by this report. Habits. Nocturnal, insectivorous, climbs in bushes. The tail may become swollen with stored fat. See Mares et al. (1989). BATS Histiotus macrotus. Murciélago Orejón Identification. A large bat with enormous ears, similar to Histiotus montanus but larger (70 x 57 mm) with longer ears (more than 32 mm). Distribution. The only specimens are from 20 km east of Bariloche, but since it ranges north in the Andes to Peru it probably lives also in Nahuel Huapi Park and Lanín Park. Habits. The individuals near Bariloche were living in the attic of a ranch house together with H. montanus. See Mann (1978), Mares et al. (1989), Pearson and Pearson (1989), Bárquez et al. (1993). Histiotus montanus. Murciélago Orejudo Identification. A moderate-sized bat (66 x 50 mm) with large ears (27 mm), naked tail membrane, and the tail completely enclosed in the membrane (not extending beyond the membrane as in Tadarida). The ears are shorter and narrower than those of H. macrotus. Similar species. H. macrotus has even larger ears (see aboye). Distribution. In steppe and in forest habitats from Santa Cruz north to central Argentina and into Chile. Habits. A nocturnal hunter of insects. Lives in attics of houses, hollow trees, and presumably other warm dark refuges. Not known to hibernate or migrate. See Greer (1965), Mann (1978), Pearson and Pearson (1989), Bárquez et al. (1993). Lasiurus blossevillii. Murciélago Colorado Identification. A striking reddish bat (53 x 55 mm, forearm 40 mm) with relatively short ears (13 mm). Upper surface of the tail membrane is covered with long fur that extends considerably beyond the posterior margin of the membrane. Similar species. Lasiurus ega and L. cinereus, like blossevillii, are relatively shorteared with considerable fur on the dorsal surface of the tail membrane, but they are larger (>65 x >48 mm, forearm >43 mm), their tail membranes not as thickly furred, and they lack the striking reddish coloration of borealis. I have no record of either ega or cinereus in Nahuel Haupi Park or in Lanín Park, but they may occur that far south; they hang in trees and are migratory. The red bat of western North America, Central America, and South America has recently been considered to be a species, blossevillii, distinct from borealis (Baker et al.,1988). Distribution. Throughout most of South America. Habits. Hangs in trees during the daytime and hunts flying insects at night, or even in the late afternoon. Migrates to the north in the autumn and retums in the spring. See Greer (1965), Mann (1978), Mares et al. (1989), Bárquez et al. (1993).

10 108 Oliver P. Pearson Myotis chiloensis. Murciélago Chileno Identification. A very small, dark bat (52 x 38 mm) with small ears (less than 17 mm), the tail membrane almost naked and reaching from the atildes to the tip of the tail. Similar species. See the key to bats. Taxonomy. Myotis aelleni (Baud, 1979) was described from El Hoyo de Epuyen, not far south of Nahuel Huapi Park. I cannot distinguish topotypes of this taxon from specimens of Myotis from other places in Patagonia and have considered them all to belong to the species chiloensis. Distribution. Widespread throughout Patagonia from Tierra del Fuego to considerably north of Lanín Park, in steppe or in forest if there are caves, hollow trees, or dark quiet attics. Sometimes found under the bark of trees. Habits. A nocturnal hunter of flying insects, it sleeps during the day in dark places, frequently in large groups. May hibernate in winter, but hibernating colonies have not been found. Not known to migrate. See Greer (1965), Mann (1978), Pearson and Pearson (1989), Bárquez et al. (1993). Tadarida brasiliensis. Murciélago Cola de Ratón Identification. A small, dark grey bat (67 x 38 mm) with the terminal half of the tail extending beyond the tail membrane. Similar species. None of the other Patagonian bats have a mouse-like tail extending beyond the taja membrane. Distribution. Lives throughout much of Argentina south to Bariloche; in Patagonia found in steppe and in forest habitats. Habits. A nocturnal feeder on flying insects. It lives in dark refuges and crevices, usually in houses. In some places large groups gather in caves, but no such assemblages have been discovered in the region covered in this report. It is not known if they are migratory in this region. See Greer (1965), Mann (1978), Mares et al. (1989), Wilkins (1989), Bárquez et al. (1993). CRICETINE RODENTS Abrothrix longipilis. Ratón de Pelos Largos Identification. A medium-sized dark mouse (105 x 80 mm) with silvery fur on the belly and usually a rich brown or chestnut color along the middle of the back; tail relatively stout. The mandible is unusually long and slender, the zygomatic plate usually slanting, the third upper molar with a central ring visible on the occlusal surface (see Fig. 5, 14, 18). Similar species. See Abrothrix olivaceus. Abrothrix xanthorhinus and Akodon iniscatus are smaller, thinner-tailed, and lack the silvery belly, the rich chestnut back, and the relatively narrow, slanting zygomatic plate. A similar form, quite black on the back and belly, is common in forests just over the frontier in Chile: Abrothrix sanborni. It may be only a subspecies of longipilis (Gallardo et al., 1988). A single specimen of it has been taken in Argentina in the Province of Neuquén at Lago Quillén. Taxonomy. This form was previously known as Akodon longipilis. Several subspecies have been described from Argentina: moerens, nubila, suffusa, francei, and hirtus. For relationships of Abrothrix, see Reig (1987), Gallardo et al. (1988), Spotorno et al. (1990), Spotorno (1992), Smith and Patton (1993). Distribution. This species is the most widely dispersed of any small mammal in the region, from dense moist forest to marshes and to a considerable distance (more than 30 km) out into the steppe provided that there is a modest amount of cover and moisture. Habits. Nocturnal and diumal, terrestrial, eats fungi, seeds, invertebrates; the most abundant mouse in many habitats. See Glanz (1984), Meserve et al. (1988), Patterson et al. (1989, 1990), Pearson (1992, 1983), Kelt (1994), Kelt et al. (1994).

11 KEY TO SMALL MAMMALS 109 Abrothrix olivaceus. Ratoncito Oliváceo Identification. This is a medium-sized (95 x 74 mm) dark brown mouse with dark grey belly and relatively small ears. The mandible is not so slender as in longipilis, and the zygomatic plate not slanting, the third upper molar without a central ring on its occlusal surface, and the first upper molar without a notch on its anterior face (see Fig. 5, 14, 18). Similar species. A. longipilis, which lives in the same habitats, has a silvery grey belly, larger hind feet (usually longer than 24 mm), fatter tail, and usually a chestnut brown dorsal color. A. xanthorhinus and Akodon iniscatus, which usually live in drier more open habitats, are smaller and have shorter tails. Abrothrix xanthorhinus also has a yellowish-brown nose, feet, and tail. Juvenile Auliscomys are difficult to distinguish by external appearance but can be separated by their longer molar toothrow (more than 4 mm) Taxonomy. I consider Akodon mansoensis De S antis and Justo to be a synonym of Abrothrix olivaceus. See Gallardo et al. (1988), Spotorno et al. (1990), Smith and Patton (1993) for relationships of A. olivaceus. Distribution. Lives in moist habitats such as meadows and dense Nothofagus forests in northwestern Chubut, western Río Negro, western Neuquén, and in Chile where it extends into semi-arid scrub habitats. In Argentina it is not found out in the steppe, where A. xanthorhinus replaces it. Habits. A nocturnal and diurnal terrestrial mouse that requires considerable vegetative cover; eats seeds, fruits, vegetation, and invertebrates. See Pearson (1983), Murúa and Gonzáles (1986), Murúa et al. (1987), Gonzáles et al. (1988), Meserve et al. (1988), Patterson et al. (1989,1990), Kelt (1994), Kelt et al. (1994). Abrothrix xanthorhinus. Ratón de Hocico Bayo Identification. A small grey mouse with tail much shorter than head and body (88 x 54 mm) and with a yellow-brown color on the sides of the nose, on the upper surface of the hind feet, and on the under surface of the tail; belly greyish-white. The last upper molar has an enamel ring in the center of the occlusal surface, rarely a notch on the anterior face of the first upper molar (Figs. 6, 16, 18). Similar species. A. xanthorhinus is smaller than A. olivaceus and A. longipilis. Interorbital width of xanthorhinus is less than 4.3 mm, of longipilis more than 4.5 mm. A. xanthorhinus is about the same body size as Notiomys edwardsii but lacks the conspicuous fringe of hairs on the margins of the hind feet of edwardsii and has, unlike edwardsii, easily visible ear pinnae. It is difficult to distinguish from Akodon insicatus, which lives in similar habitat. A. iniscatus displays little orange-brown color on the nose, feet, and tail, but the belly fur may be yellowish. A. iniscatus frequently has a white spot on the chin, and the ears are shorter than those of xanthorhinus (11-14 mm vs mm). The dorsal profile of the skull of iniscatus is bowed, convex; the incisive foramina in the palate are narrow and pointed at the posterior end; the zygomatic plate is usually wider than in xanthorhinus, and the anterior surface of the first upper molar usually has a notch (although young xanthorhinus occasionally show a notch). See also Patterson et al., Taxonomy. Some authors consider xanthorhinus and olivaceus to be the same species (Yáñez et al., 1979). In the region treated in this report, xanthorhinus is a steppe form and olivaceus a forest form; intergrades are found at the steppe/forest interface. See Allen (1905), Apfelbaum and Reig (1989), Spotorno (1992), Spotorno et al. (1990), and Gallardo et al. (1988) for relationships of A. xanthorhinus. Distribution. A. xanthorhinus is a mouse of semi-arid steppe and bunchgrass habitats. It ranges from the pre-cordillera to the Atlantic coast, and south to Tierra del Fuego, where it is said to enter moister, more densely vegetated habitats. Habits. Nocturnal and diurnal, eats seeds, green vegetation, and insects. See Heinemann et al. (1995), Kelt (1994), Mann (1978).

12 110 Oliver P. Pearson Akodon iniscatus. Ratoncito Patagónico Identification. A small mouse (150 x 60 mm) with hispid fur, almost no brown or orange color on the tail, feet, and nose, ears 13 mm or less, the skull with the inflated orbital region of Akodons, wide zygomatic plate (about 2.7 mm), a notch on the anterior face of the first upper and first lower cheekteeth, and no enamel ring in the center of the surface of the last upper molar. Frequently has a white chin (Fig. 6). Similar species. Abrothrix xanthorhinus has larger ears (more than 13 mm), brown or orange color on tail, feet, and nose, narrower zygomatic plate (about 2.0 mm), no notch on the anterior face of the first upper cheektooth, a shorter coronoid process on the mandible, and an enamel ring in the center of the last upper molar. Abrothrix olivaceus has a narrower zygomatic plate and longer ears. Taxonomy. This animal is clearly a close relative of Akodon nucus, which, because of its small ears and notched first molar, I consider to be a subspecies of A. iniscatus. Pending a revision of the genus Akodon, I refer to it as Akodon iniscatus nucus. See Barros et al. (1990). Distribution. Found in semi-arid steppe habitat north of the Río Collon Cura, where it is sympatric with Abrothrix xanthorhinus. Akodon i. iniscatus is sympatric with Abrothrix xanthorhinus farther south in Patagonia. Habits. No information. Calomys musculinus. Laucha Bimaculada Identification. A small mouse (70 x 70 mm) with tail about equal to or slightly shorter than the head and body; hind foot small (less than 19 mm); usually a bright tawny line separating the belly and sides. The interorbital region of the skull is flat, sharp-edged, the frontal region not inflated. Similar species. Eligmodontia has longer, silkier fur and much longer feet (more than 21 mm) Abrothrix xanthorhinus usually has a rusty color on feet, tail, and nose and its hind feet are heavier and longer (19 mm or more). Small individuals of Abrothrix olivaceus have larger hind feet (more than 20 mm) Mus has shorter fur, belly fur not as pale, no bright lateral line; the coronoid and condyloid processes of the mandible of Mus are very short. Taxonomy. This species is distinct from the shorter-tailed C. laucha of the pampas (its tail less than 45% of its total length). Distribution. C. musculinus is abundant farther north and northeast in Argentina, but I have found it only in semi-arid habitat north of the Río Collon Cura in Neuquén Province. Massoia and Fornes (1966) reported a specimen from much farther south at Esquel, Chubut Province. Habits. A nocturnal, seed-eating mouse of open habitats. See Crespo et al. (1970), Kravetz et al. (1981), Mills et al. (1992a, 1992b), Dellafiore and Polop (1994). Chelemys macronyx. Ratón Topo Grande Identification. A large, fluffy-furred, shorttailed mouse (130 x 62 mm) with long claws (more than 4 mm) on the front toes; dark grey color, small ears. The coronoid process of the mandible is unusually long, the condyloid process is bent slightly inward, the zygomatic plate is broad and slants somewhat, and the frontal region of the skull is inflated as in the various species of Abrothrix and Akodon (Figs. 7, 14, 16, 18). Similar species. The long front claws separate it from other large, short-tailed mice. Ctenomys has long claws but lacks appreciable ear pinnae. Aconaemys has much broader incisors and four cheekteeth instead of three. The skull of Loxodontomys has a more-vertical zygomatic plate, narrow interorbital region, and a shorter coronoid process. Taxonomy. In some publications this animal is referred to as Notiomys macronyx. Mann (1978) and Tamayo and Frassinetti (1980) listed it as a subspecies of Ch. megalonyx. The type locality of macronyx is not the muchcited Fort San Rafael but undoubtedly is far to the west of that town, high in the mountains near Volcan Peteroa (Pearson and Lagiglia, 1992). Additional collecting and

13 KEY TO SMALL MAMMALS 111 study are necessary to clarify the taxonomy of this genus. The type specimen of Chelemys angustus Thomas is a young-adult Abrothrix longipilis (Pearson, 1983, 1984). Distribution. From the Province of Santa Cruz to the Province of Mendoza, in moist or mesic habitats, usually with rich humus such as in lenga forests (Nothofagus pumilio), but also at high altitude aboye the forests. It ranges out into the steppe at least as far as Pilcaniyeu. Surprisingly, it was not captured during extensive trapping at La Picada in Chile in what would seem to be suitable habitat (Patterson et al., 1989, 1990). Habits. Lives mostly but not entirely underground; nocturnal and diurnal. Eats fungi, seeds, lily stems and rhizomes, and invertebrates. See Mann (1978), Pearson (1983, 1984), Kelt (1994). Eligmodontia morgani. Laucha Sedosa Identification. A small mouse (82 x 82 mm) with silky fur, pure white belly, white patches of fur behind the ears, and a furry cushion on the soles of the large hind feet near the base of the toes. It frequently has golden brown fur along the sides, separated sharply from the white fur of the belly. The interorbital region is relatively broad, flat, sharp-edged; the interpterygoid fossa is quite narrow; the ventral margin of the mandible turras abruptly inward to form a right-angled shelf rather than a slanting shelf as in most other mice; the capsular projection is not prominent. Females are larger than males (Figs. 8, 15, 17, 18). Similar species. Calomys has much smaller hind feet (shorter than 20 mm). Abrothrix xanthorhinus has neither pure white underparts nor a cushion on the soles of the hind feet. Notiomys edwardsi has similar coloration but much shorter tail. Oligoryzomys has a much longer tail, post-palatal pits, and a broader mandible with prominent capsular projection. E. typus from eastern Patagonia has a longer tail and different karyotype. Taxonomy. Specimens from western Neuquén and western Río Negro are short- tailed, and those that have been tested have 32 chromosomes as in E. morgani (Kelt et al., 1991). It is not known whether the range of this form meets or overlaps with that of the 42-chromosome E. typus farther to the east. See also Ortells et al. (1989). Distribution. Found only in the steppe and precordillera where there is bare ground, from western Santa Cruz Province and nearby Chile to western Neuquén Province. It is never found in forest, although a small population west of Bariloche inhabits an island of steppe surrounded by forest. Habits. A nocturnal desert mouse that eats seeds and insects. See Mares (1977), Pearson et al. (1987), Kelt (1994). Euneomys chinchilloides. Rata Sedosa Identification. A long-furred, short-tailed mouse (125 x 65 mm) with grooved incisors, white nose and upper lips, the soles of the hind feet not furry. The anterior element of the first lower cheektooth is a complete island, the second upper and lower cheekteeth are S-shaped, the condyloid process of the lower jaw is bent inward as in Auliscomys and has a prominent capsular projection. The first lower cheektooth has only two roots, one behind the other; the second and third lower molars are of the same size. Similar species. Reithrodon also has grooved incisors, but its tail is longer (more than 70 mm), its hind feet are much larger (more than 30 mm) with the first and fifth toes much reduced; its zygomatic plate is deeply concave, and its condyloid process has a deep furrow on the inner surface. Auliscomys lacks grooves on the upper incisors, has a longer tail (more than 75 mm), the front element of the first lower cheektooth is connected to the succeeding element, and the last lower cheektooth is smaller than the middle lower cheektooth. Chelemys has long claws on the front feet, simpler teeth, and a long coronoid process. A larger species of Euneomys lives in deepsoil habitats farther to the north. The type locality is not Fort San Rafael (Pearson and Lagiglia, 1992). Specimens of it are available

14 112 Oliver P. Pearson from the Santiago region of Chile, the Province of Malleco in Chile, and from near Copahue in Neuquén Province, Argentina. These have been identified as E. mordax. Skulls, presumably of this form have been found in sub-fossil cave deposits in Parque Nahuel Huapi (Pearson and Christie, 1991), and I have seen what appear to be its runways and fecal pellets in appropriate habitat at high altitude at Laguna Toncek in Nahuel Huapi Park.E. mordax is larger than chin-chilloides, the upper toothrow 6.2 mm or longer, and the grooves on the anterior face of the upper incisors are centrally positioned in mordax but lateral in chinchilloides. The two species are sympatric at some places. See also Reise and Gallardo (1990). Taxonomy. Existing specimens of Euneomys from Nahuel Huapi and Lanín Parks are indistinguishable from E. chinchilloides, and E. petersoni is indistinguishable from chinchilloides (Pearson and Christie, 1991). Distribution. Lives in bare, windswept, rocky scree habitat from Santiago south to Tierra del Fuego. Found as high as 2300 m on Cerro Catedral at Bariloche. Habits. Nocturnal, eats green vegetation. See Greer (1965), Mann (1978), Pearson (1987), Pearson and Christie (1991), Kelt (1994). Geoxus valdivianus. Ratón Topo Chico Identification. A small, short-tailed species of burrowing mouse (100 x 44 mm) with short, dark fur somewhat like velvet, pointed nose, and long claws on the front feet. The molars are very small, the zygomatic plate slants distinctly backward, and the lower jaw is very slender (Figs. 9, 15, 17, 18). Similar species. Chelemys is larger, the Akodons amd Abrothrixes all have longer tails and lack the long claws on the front feet. Taxonomy. In some publications it is referred to as Notiomys valdivianus, N. fossor, or Geoxus fossor. See Pearson (1984). Distribution. In humid habitats such as forest and marsh from Santa Cruz to Neuquén and into Chile. Ranges out into the precordil- lera about to the limit of the cypress trees. Habits. Subterranean much of the time but also runs alongside fallen logs and excavates small surface pits in search of earthworms, larvae, and occasionally fungi and vegetation; diurnal and nocturnal. See Greer (1965), Mann (1978), Pearson (1983, 1984), Meserve et al. (1988), Patterson et al. (1989, 1990), Kelt (1994). Irenomys tarsalis. Laucha Arbórea Identification. A fairly large mouse with tail much longer than head and body (110 x 150 mm) and with longitudinal grooves on the anterior surface of the upper incisors. Molar surfaces are very deeply dissected, giving a prismatic appearance, the condyloid process is not bent inward (Figs. 9, 15, 17, 18). Similar species. Oligoryzomys is of similar color and has a long tail, but lacks grooves on its upper incisors; the eyes of Irenomys are larger and are surrounded by dark fur, the tail is thicker and strikingly bicolor, and the body fur looks softer. Phyllotis has larger ears, proportionately shorter tail, lacks grooves on the upper incisors, and the molars are not as highly dissected. Distribution. In forests of Nothofagus and bamboo in Chubut, Río Negro, and Neuquén, and into Chile; occasionally among willows and cypress trees in semiarid areas east of the main forests. Habits. Nocturnal, a good climber, eats seeds, fruits, and green vegetation. See Greer (1965), Pearson (1983), Meserve et al. (1988), Patterson et al. (1990, 1989), Kelt (1994, 1993). Loxodontomys micropus. Pericote Patagónico Identification. A big, fluffy mouse with tail shorter than head and body (130 x 100 mm), ears large (21 mm), front claws not enlarged, soles of hind feet naked; upper incisors not grooved, the zygomatic plate vertical, the ascending ramus of the mandible is bent inward, and the third lower molar is smaller than the second. Some difficulty of identification may

15 KEY TO SMALL MAMMALS 113 be encountered because the population indudes very young individuals of only 12 g (head and body 80 mm) as well as adults up to 100 g (head and body 150 mm) (Figs. 3, 14, 16, 18). Similar species. Phyllotis xanthopygus has bigger ears (more than 23 mm), and its mandibular condyloid process is not bent inward. Reithrodon has grooved incisors and furry soles on the hind feet. Chelemys has a shorter tail and long claws on the front toes. Abrothrix longipilis and A. olivaceus are smaller, have smaller ears (less than 18 mm), smaller feet (less than 27 mm), and an inflated frontal region of the skull. Euneomys chinchilloides is paler, shorter-tailed, and has grooved incisors. E. mordaz has grooved incisors. Taxonomy. In some publications this animal is referred to as Phyllotis micropus, Auliscomys micropus, or Euneomys micropus. Its chromosomes indícate close relationship to species of Auliscomys. The true Euneomys has grooved incisors. See Braun (1993), Steppan (1993, 1995). Distribution. From Santa Cruz to Neuquén in forests, marshes, or mesic brushy habitats; not in desert habitats but found as much as 50 km out into the steppe (Comallo) if there is sufficient vegetative cover. Habits. Nocturnal, inhabits humid or mesic habitats where there is considerable ground vegetation. Eats seeds, green vegetation, fruits, flowers, and fungi. A Microtine analog. See Mann (1978), Pearson (1983), Meserve et al. (1988), Patterson et al. (1989, 1990), Kelt (1994). Notiomys edwardsii Identification. A small short-tailed mouse (88 x 42 mm) with long claws (about 5.3 mm). Ear pinnae almost invisible, reddish brown color on the sides of the nose, whitish belly, and with a conspicuous finge of hairs on the margins of the hind feet. The fur is silky. The skull is short and wide, the zygomatic plate is slanted, short, and leans widely to the side, forming a very open infraorbital foramen; the frontal region is inflated, the molars small and simple. The coronoid process of the mandible is long (Fig. 10). Similar species. Abrothrix xanthorhinus has similar color on the nose but also has ear pinnae and lacks the fringe of hairs on the hind feet and lacks the long claws on the front feet of Notiomys. Eligmodontia and Calomys have easily-visible ear pinnae, longer tails, and narrower infraorbital foramina. Geoxus, like Notiomys, has a short tail and long claws but the fur of the back, sides, and belly is always dark, and the fringe of hairs on the hind feet is lacking. The skull of Geoxus is long and slender. The lower incisors of Geoxus are much more proodont, and the coronoid process much smaller than in Notiomys. The zygomatic plate of Geoxus is more slender but leans far to the side as in Notiomys. Taxonomy. Mitochondrial DNA sequences show that Notiomys is related to Chelemys and Geoxus (Smith and Patton, 1993). Distribution. Known only from a few specimens from Santa Cruz Province and from steppe habitat east of Nahuel Huapi Park. Habits. Lives a somewhat fossorial existence among desert shrubs and bunchgrasses; eats insects. Oligoryzomys longicaudatus. Lauchita de Cola Larga Identification. A small mouse with tail longer than head and body (95 x 120 mm), hind feet relatively large (more than 25 mm), ears small (less than 19 mm), anterior surface of the upper incisors not grooved. Skull with narrow interorbital region, frontal region not inflated, a vertical zygomatic plate, and a pair of foramina at the posterior border of the palate. The mandible is broad, and its capsular projection protrudes conspicuously (see Figs. 11, 15, 17, 18). Similar species. Irenomys is usually larger and has grooved incisors. Eligmodontia, Mus, and Calomys have shorter tails and lack the pair of foramina at the posterior edge of the palate. The Akodons and Abrothrixes have shorter tails and their skulls have inflated frontal regions. Taxonomy. This forro in the past has beca referred to as Oligoryzomys longicaudatus, but

16 114 Oliver P. Pearson is now thought to be a seaparate genus (Carleton and Musser, 1989; Smith and Patton, 1993). A separate species, ma-gellanicus is found farther south in Patagonia (Gallardo and Palma, 1990). Distribution. Throughout the region in brushy places and at the edge of forests; not abundant within dense forests. Habits. Nocturnal, climbs easily, frequently associated with bushes such as rosa mosqueta and blackberry. Eats seeds and fruits. See Contreras (1972), Pearson (1983), Murúa et al. (1987, 1986), Meserve et al. (1988), Patterson et al. (1990, 1989), Redford and Eisenberg (1992), Kelt (1994), Kelt et al. (1994). Phyllotis xanthopygus. Pericote, Lauchón Orejudo Identification. A large mouse (130 x 115 mm) with enormous ears (26 mm or more), fluffy fur, tail slightly shorter than head and body, upper incisors not grooved (Figs. 11, 15, 17, 18). Similar species. Auliscomys micropus has similar body size but shorter tail, smaller ears, and the condyloid process of the Auliscomys mandible is bent inward. Reithrodon has similar large body size but its tail is much shorter than head and body, its hind feet have furry soles, and its upper incisors are grooved. Taxonomy. Formerly known as Phyllotis darwini xanthopygus. See Pearson (1958), Walker et al. (1984), Braun (1993), Steppan (1993). Distribution. In open rocky habitat from the Provine of Santa Cruz north along the Andes to Peru; not in forest or grassland. Habits. A nocturnal mouse of cliffs and boulders; eats seeds, green vegetation and insects. See Mann (1978), Kelt (1994). Reithrodon auritus. Rata Conejo Identification. A large, soft-furred mouse with enormous eyes, relatively short tail (130 x 85 mm), long rather furry ears, and a tuft of pale fur at the base of each ear. The soles of the hind feet are furry, and the first and fifth toes are very short, not reaching beyond the base of the middle three toes. The upper incisors are grooved. The very concave front edge of the zygomatic plate is distinctive, and so is the presence of a long open furrow on the inside surface of the condyloid process of the mandible. Males and females are of the same size (Figs. 7, 15, 17, 18). Similar species. Euneomys has grooved upper incisors as in Reithrodon but lacks the patch of pale fur at the base of each ear, lacks fur on the soles of the hind feet, and at least one of the marginal toes on the hind feet of Euneomys reaches beyond the base of the three middle toes. Compare also Phyllotis and Auliscomys. Taxonomy. I follow Ortells et al. (1988) in using the species name auritus. A revision is needed to decide how many species should be recognized and what are their geographic distributions. Distribution. In steppe and pampa from Santa Cruz to Jujuy, never in forest. Habits. Lives in extensive tunnel systems in green grassy turf habitat; emerges at night to graze on green vegetation. See Pearson (1988), Kelt (1994). MURID RODENTS Mus domesticus. Laucha Europea Identification. A small mouse (head and body less than 95 mm, hind foot less than 20 mm) with tail about as long as head and body. The fur is short, the belly not white. The mandible has a very small coronoid process and a short condyloid process. Similar species. See Calomys. A tail longer than 65 mm separates it from Abrothrix xanthorhinus; the small skull and short rostrum separate it from most akodons and abrothrixes. The hind feet are much shorter than those of Eligmodontia. Taxonomy. Formerly known as Mus musculus.

17 KEY TO SMALL MAMMALS 115 Distribution. A Eurasian invader, found in this region only in or near human habitations. Habits. This is the familiar "house mouse" that occupies homes, farm buildings, and warehouses. Rattus norvegicus. Rata de Agua Identification. A large rat (180 x 170 mm) with a conspicuously scaley tail that is almost as long as the head and body. The body fur is coarse, the ears are leafy, almost naked, and only about half as long as the hind feet. The interorbital region of the skull is narrow, sharpedged, usually with raised ridges; the zygomatic plate is very broad and vertical or even leaning forward at the top. The mandible is very broad with a large coronoid process. Similar species. Phyllotis is large and longtailed like Rattus but has soft fur, a tail with only inconspicuous scales, and smaller feet (less than 32 mm). The ears of Phyllotis are large, almost as long as the hind feet. Auliscomys has a shorter tail. The palate of Rattus extends far behind the last molar; in Auliscomys it ends at the posterior edge of the last molars. Rattus rattus, the black rat or roof rat, is very similar but has a tail longer than its head and body; it is found in the warmer parts of Argentina, but we have no records of it from the region under discussion. The coipu (Myocastor) is much larger, has webbed feet, and four molars. Distribution. In all parts of Argentina, usually near human habitations but, especially in forested parts of Patagonia, able to survive far from man. It was introduced to South America from Europe. Habits. Nocturnal, omnivorous, lives in houses, barns, or in burrows in the ground, especially near poultry, pigs, horses, or slaughter houses where it lives on spilled grain and garbage. Swims well and frequently lives near water. HYSTRICOGNATH RODENTS Aconaemys porteri. Rata de los Pinares Identification. A large, short-tailed rodent (180 x 80 mm) with long claws on the front feet (up to 7 mm), fluffy fur (about 13.5 mm long), wide incisors (more than 4 mm across both incisors at the tip), conspicuous (20 mm) although not large ear pinnae, and combs of stiff bristles at the tips of the hind toes. Upper and lower molars (about 9.5 mm) are double (occlusal surface composed of two ellipses), there is no deep furrow along the jaw outside the lower molars, and the coronoid process is large and vertical. The karyotype is 2n=58, FN=112 (Fig. 12). Similar species. Ctenomys has only rudimentary ear pinnae and much simpler molar tooth pattern. Chelemys is smaller (head and body 130 mm) with much narrower incisors and only three cheekteeth. Aconaemys sagei is darker, smaller, has shorter tail, shorter fur (about 9 mm long), narrower incisors (less than 4.0 mm across both upper incisors at the tip), and shorter front claws (about 5 mm). Octodon bridgesii in Argentina has a longer tail (more than 90 mm), and the front claws of Octodon are not enlarged, the incisors are narrower, and the cheekteeth simpler. Rattus has a much longer tail, no combs of bristles on the hind toes, the front claws are not enlarged, and it has only three cheekteeth on each side. Taxonomy. Aconaemys porteri has been considered to be a subspecies of A. fuscus, but Gallardo (1992) and Gallardo and Reise (1992) note that the karyotype of A. fuscus is 2n=56, FN=108 and of A. sagei 2n=54, FN=104. They believe that they are three distinct species. The southern species, porteri in Parque Nacional Nahuel Huapi and the northern one, sagei, in Parque Nacional Lanín. Additional collecting should be done to determine the ranges of the different populations. Distribution. Scattered populations in dense bamboo and Nothofagus forest in the mountains near the border between Argentina and Chile at about 40 S Latitude.

18 116 Oliver P. Pearson Habits. Lives in small groups in burrow systems; makes tunnels like tuco-tucos, but in forest habitat. Diurna' and nocturnal, eats the leaves, twigs, and shoots of bamboo and probably other vegetation. Produces very highpitched squeaks. See Greer (1965), Mann (1978), Pearson (1983, 1984). Aconaemys sagei. Rata de los Pinares Identification. Similar to A. fuscus but smaller (150 x 65 mm), hind foot less than 30 mm long, width across both upper incisors at the tip less than 4.1 mm. The fur is darker, shorter; the last upper and lower molars have only one island instead of two as in A. fuscus and porteri. The karyotype is 2n=54, FN=104 (see Fig. 12). Similar species. See Aconaemys porteri. Taxonomy. This species was not recognized until recently because of confusion in the identification and site of capture of the type of A. fuscus. See Gallardo (1992), Gallardo and Reise (1992), Pearson and Lagiglia (1992), Pearson (1984). Distribution. In Argentina known only from near Lago Quillén and Lago Hui Hui in Lanín Park where it lives in open, bunchgrass habitat and in second-growth forest of Nothofagus and bamboo. It may be more widespread in Chile, but see Contreras et al. (1987). Habits. Lives in burrows but also travels on the surface in runways through dense grass. Active in daytime. Eats green vegetation. See Pearson (1984). Ctenomys Tucotuco Patagónico Identification. A large, short-tailed burrowing rodent (160 x 68 mm) with long powerful claws on the front toes, almost no external ears, the edges of the hind feet fringed with long stiff hairs. Upper and lower incisors are broad (about 5 mm across the tip of both incisors), not grooved; molar toothrows about 8.5 mm long, the first three molars are single, simple, rounded crescents and the fourth a small peg. All other large rodents, except the other species of Ctenomys, have distinct ear pinnae. The mandible has no deep channel outside the molar teeth. The karyotype is 2n=50, FN=66 (Gallardo, 1991). (See Figs. 13, 14, 16, 18). Similar species. See Chelemys, Ctenomys maulinus, and Ct. sociabilis. Octodon and Aconaemys are equally large but have easily visible ear pinnae (ear flaps) and lack the conspicuous fringe of hairs around the margin of the hind feet. Octodon has much narrower incisors and its last upper molar is not greatly reduced in size. Aconaemys has more complex molars. Guinea pigs (cuises, Microcavia and Galea) have no tail, delicate incisors (less than 3.3 mm across the tip), and deep channels along the mandible outside the molar toothrows. Taxonomy. In some reports C. haigii has been considered to be a subspecies of mendocinus, but the karyotype of mendocinus is 2n=48, FN=76 (Massarini et al., 1991). Clarification of the taxonomy of the dozens of kinds of tucotucos in Argentina awaits a thorough study (Reig et al., 1990). I consider most of the populations of this taxon in Nahuel Huapi and Lanín Parks to be closely related to haigii, but this is not at all certain (Gallardo, 1991; Massarini et al., 1991; Sage et al.,1986). Two other species of Ctenomys border the range of haigii in this region (see next two species). Also see Pearson (1984), and Pearson and Christie (1985). Distribution. Tucotucos of this species are widely distributed in open habitats in the Provinces of Chubut, Río Negro, and Neuquén, usually in light, sandy soil, never in dense forest. Habits. Restricted almost entirely to its underground burrows where it is active day or night; makes a characteristic call sounding like "tuc-a-tuc". Eats vegetation. See Reig et al. (1990). Ctenomys maulinus. Tucotuco de Maule Identification. Similar to Ctenomys haigii (see aboye) but larger. Similar species. Ct. maulinus is larger than Ct. haigii (head and body longer than 195 mm,

19 KEY TO SMALL MAMMALS 117 hind foot longer than 36.5 mm), body paler, usually with less black color on the face; the upper incisors more proodont, the auditory bullae less inflated. Compare also with Ct. sociabilis. Taxonomy. Skins and skulls of Argentine specimens are indistinguishable from topotypes of Ct. maulinus maulinus from Chile (Pearson, 1984), but the species limits of maulinus are uncertain (Gallardo, 1991; Gallardo and Kohler, 1992; ). See also Pearson and Christie (1985). Distribution. Known in Argentina from near Lagos Hui Hui, Huechulaufquen, and Rucachoroi (1235 m elevation) in Parque Lanín, and from the mountains aboye San Martín de los Andes. It is abundant on the west slope of the Andes in Chile. Its range may meet that of Ct. haigii, which is primarily a species of the steppe. Habits. Restricted almost entirely to its underground burrows where it is active day or night. Eats vegetation. See Greer (1965), Gallardo and Kohler (1984), Gallardo and Anrique (1991). Ctenomys sociabilis. Tucotuco Colonial Identification. Similar to Ct. haigii and maulinus. There is a pale patch in sociabilis between each eye and the nostrils, a reddish brown patch lateral to the nostrils, black moustaches on the upper lips below the nostrils, and white hairs around the mouth. The body is large (200 X 75 mm), the upper incisors proodont and quite broad (more than 5.5 mm across both incisors at the tip). The auditory bullae are much less inflated (less than 6.3 mm across) than those of haigii and slightly more slender than those of maulinus. The upper incisors of sociabilis are distinctly wider than the lower incisors. The karyotype is 2n=56, FN=72 (Gallardo, 1991). Similar species. See the preceding two species. Taxonomy. Morphology, chromosomes, tissue enzymes, vocalizations, and behavior all indicate that this is a distinct species (Sage et al., 1986; Pearson and Christie, 1987; Gallardo, 1991). Distribution. Found only in a few colonies in open habitat in the region between Río Traful and Lago Nahuel Huapi west of the Río Limay. No other tucotucos occupy that area, but haigii lives only a few hundred meters away across the Río Limay. Habits. Lives in colonies, active day and night, eats grasses and other vegetation, has a bird-like vocalization. See Pearson and Christie (1985). Galea musteloides. Cuis de Dientes Amarillos Identification. A rat-sized rodent with no tail, hind feet with only three toes, the upper and lower incisors slender, their front surfaces yellow or orange. The molar toothrow is about 13 mm long, each of the four molars made up of two deeply incised tear drops; the mandible has only a small coronoid process and almost no condyloid process; a deep channel runs along the outside of the molar toothrow. Similar species. Another guinea pig, Microcavia, is quite similar but its upper incisors are white, and its condyloid processes or ascending rami, while not large, are of appreciable size. See Contreras (1964). Distribution. Ranges up the Andes into Bolivia and Peru. I have not captured it in the region of this study, but specimens were taken many years ago in steppe habitat at Collon Cura (Neuquén) and Pilcaniyeu (Río Negro). Microcavia lived at these two places also. Habits. A diurnal, herbivorous equivalent of the North American ground squirrels. See Rood (1972). Lagidium boxi. Chinchillón, Ardilla de las Rocas, Vizcacha Identification. A rabbit-sized rodent (400 x 290 mm) with a long tail that is heavily furred for its entire length and with a crest of long, stiff hairs. The incisors are relatively narrow (less than 8 mm across both incisors at the tip), the molar toothrow is about 19 mm long, and each tooth is made up of three simple laminae. The mandible has no coronoid process, a distinct condyloid process, and no deep

20 118 Oliver P. Pearson groove along the mandible outside the molar toothrow. Similar species. No other species of this size has a long crested tail. Skulls of hares (Lepus) also have narrow incisors, but Lepus also has a second pair of incisors immediately behind the upper pair, and has also five cheekteeth on each side of the upper and lower jaws. Skulls of guinea pigs are much smaller with shorter toothrows and with a deep furrow along the mandible outside of the molar toothrow. Taxonomy. I have followed Hayman in Ellerman (1940) in assigning this vizcacha to the short-eared species boxi rather than to viscaccia. He listed two subspecies of boxi: sarae from Pino Hachado in Neuquén and boxi from Pilcaneu in Río Negro. A short-eared form, sumuncurensis from far to the east (Crespo, 1963), may belong to the boxi group also. Distribution. Wherever there are cliffs or slopes covered with large boulders, either in the sierra or out in the steppe. Habits. Diurnal, colonial, grazes on various green plants and lichens. See Pearson (1949, 1948), Mann (1978). Microcavia australis. Cuis Chico de la Patagonia Identification. A rat-sized rodent with no tail; hind feet with only three toes; upper incisors very slender (less than 2.5 mm across the tip), their front surfaces white. Molar toothrow about 10 to 11 mm long, each of the four teeth composed of two deeply incised teardrops; the mandible has a deep channel along the jaw outside the molars. Similar species. Galea is a guinea pig of similar size, but it has yellow or orange upper incisors that are broader and less proodont than those of Microcavia. The claws on the hind toes of Galea are smaller than those of Microcavia, which is a good digger. The mandible of Microcavia has a better developed condyloid process than Galea. To distinguish them in the field: Microcavia gives an alarm call, frequently stands upright in an attention posture, and has a more conspicuous white ring around the eye. Taxonomy. Some publications use the names Caviella, Cavia, or Kerodon. Distribution. In semi-arid steppe habitats through much of Argentina; see Galea. Habits. Diumal, herbivorous, analogous to North American ground squirrels. See Rood (1972), Mann (1978), Contreras and Roig (1978). Myocastor coypus. Coipu, Nutria Identification. A large rodent (even juveniles may be larger than 500 x 200 mm) with moderately hairy tail, large webbed hind feet, and broad orange incisors (more than 10 mm across both incisors at the tip). The molar toothrow is 25 mm or more long, and each molar has a complex surface pattern. Similar species. Tucotucos (Ctenomys) are smaller, shorter-tailed, have no ear pinnae, and have very simple teeth. Vizcachas (Lagidium) have long hairy tails, narrower incisors (less than 8 mm), and simpler molar teeth, each one composed of three laminae. Norway rats (Rattus) are smaller with much narrower incisors and hind feet not webbed. Distribution. In or near water throughout much of Patagonia and Chile. Habits. An aquatic rodent living in marshes, ponds, and streams, analogous to Northern Hemisphere muskrats. Diurnal and nocturnal, eats green vegetation. See Greer (1965), Mann (1978), Woods et al. (1992). Octodon bridgesii. Degu de Bridges Identification. A large, dark, heavy-bodied rat with moderately short tail (180 x 118 mm); ears moderately long, front claws not enlarged (about 4 mm long), hind toes provided with conspicuous, stiff bristles. The upper incisors are narrow (about 3.3 mm across both teeth at the tip), the molars (10.5 mm) are almost as simple as in Ctenomys, but the last molar is not much reduced in size; the mandible has a large coronoid process, lacks a deep furrow

21 KEY TO SMALL MAMMALS 119 along the jaw outside the molars, and rather narrow incisors (Fig. 13). Similar species. Tucotucos have almost no ear pinnae, a much shorter tau', and a very reduced last molar. Both species of Aconaemys have shorter tails (less than 90 mm), enlarged front claws (about 5 to 7 mm), broader incisors, and more complex teeth (each molar consisting of two ellipses). The Norway rat (Rattus) has a longer tail with coarse scales, lacks conspicuous bristles on the hind toes, and has only three cheekteeth. Auliscomys is smaller, lacks bristles on the hind toes, and has only three cheekteeth. Reithrodon is smaller, paler, has notably soft fur, lacks the bristles, has grooved incisors and only three cheekteeth. Taxonomy. Three species of Octodon are known from Chile. I have compared Argentine specimens with specimens of O. degus and lunatus from Chile, and it is clearly distinct from them. Tails of the Argentine form lack a terminal tuft, underparts are without white patches, and molars have deep entrant angles. It seems to be more closely related to O. bridgesi. Michael Christie kindly compared a specimen of the Argentine form with specimens of bridgesi in the British Museum and noted distinct differences, but it is not yet clear whether the Argentine forms merits description as a new species. Verzi and Alcover (1990) listed Argentine specimens as O. bridgesi. See also Gallardo (1992). Distribution. The only adequate Argentine specimens are from Lanín Park: from semiopen forest near the east end of Lago Currhue Chico, 600 m elevation, and from an area of jumbled lava blocks at the upper edge of the forest (1140 m) aboye Laguna Verde. Some skulls recovered from owl pellets at Estancia Haichol in west-central Neuquén (Massoia, 1979) may belong to this species. Habits. Those living in the lava field were cutting twigs of shrubs. Captives ate grass, clover, apple, bread. See Muñoz and Munia (1987), Verzi and Alcover (1990). HARES Lepus capensis. Liebre Identification. A large hare (500 x 100 mm) with long ears and soft, fluffy black-and-white tail. The upper incisors are narrow (6 mm across the tip of both) and grooved, with a second pair of peg-like incisors immediately behind the front incisors; there are five cheekteeth plus a small peg-like last molar in each upper jaw (the series about 16 mm long), and five cheekteeth in each lower jaw. The bones on the sides of the rostrum are highly eroded, and the palate is very short. The mandible is very flat with no conspicuous bulges or shelves. Similar species. Lagidium (long tail, incisors not grooved) and Myocastor (long tail, very broad ungrooved incisors). Both of there have only four cheekteeth on each side in the upper and in the lower jaws. The European rabbit (Oryctolagus cuniculus) is of similar appearance but is smaller (400 x 50 mm) and has smaller hind feet (less than 110 mm) Oryctolagus is colonial and lives in conspicuous burrows. It is spreading southward into the Provine of Neuquén but is not yet known to have reached Lanín Park. Taxonomy. Referred to in some publications as Lepus europaeus. Distribution. Throughout most of Argentina. In the region covered by this report it is abundant in almost all habitats except dense forest. It was introduced into Argentina from Europe a century ago (Grigera and Rapoport, 1983). Habits. Crepuscular and nocturna!, it grazes on many kinds of vegetation and can destroy young trees and garden plants. Does not dig burrows. See Brandani et al. (1977).

22 120 Oliver P. Pearson LITERATURE CITED ALLEN, J.A Report of the Princeton University Expeditions to Patagonia, Vol. 3, Zoology, Part 1. Mammalia of southern Patagonia. 210 pp., 29 Plates. Princeton, New Jersey. APFELBAUM, L.I., and O.A. REIG Allozyme genetic distances and evolutionary relationships in species of akodontine rodents (Cricetidae: Sigmodontinae). Biological Joumal Linnaean Society, 38: BAKER, R.J., J.C. PATTON, H.H. GENO- WAYS, and J.W. BICKHAM Genic studies of Lasiurus (Chiroptera: Vespertilionidae). Occasional Papers Museum Texas Tech. University, No. 117, 15 pp. BARQUEZ, R.M., N.P. GIANNINI, and M.A. MARES Guide to the bats of Argentina. Oklahoma Museum of Natural History, Norman. 119 pp. BARROS, M.A., R.C. LIASCOVICH, L. GONZALES, M.S. LIZZARALDE, and O.A. REIG Banding pattern comparisons between Akodon iniscatus, and Akodon puer (Rodentia, Cricetidae). Zeitschrift fiir Saügetierkunde, 55: BAUD, F.J Myotis aelleni, nov. spec., chauve-souris nouvelle d'argentine (Chiroptera: Vespertilioniade). Rev. Suisse Zool., 86: BRANDANI, A.A., J.N. AMAYA, and M.G. ALSINA Ecología de la liebre (Lepus europaeus P.). I. Estimadores de la edad y estructura de una población del área de San Carlos de Bariloche, Argentina. Physis, Sec. C, 36: BRAUN, J. K Systematic relationships of the Tribe Phyllotini (Muridae: Sigmodontinae) of South America. Oklahoma Museum of Natural History, Special Publication, 50 pp. BUBLITZ, J Untersuchungen zur Systematik der Regenten Caenolestidae Trouessart, Bonner Zool. Monographien, No. 23, 96 pp. CABRERA, A Catálogo de los mamíferos de América del Sur. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Ciencias Zoológicas 4(1): (marsupials, bats). CABRERA, A Catálogo de los mamíferos de América del Sur. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Ciencias Zoológicas 4(2):xxii + pp (rabbits, rodents). CABRERA, A., and J. YEPES Mamíferos Sudamericanos. Historia Natural Ediar, Cia. Argentina de Editores, Buenos Aires, 370 pp. CARLETON, M.D., and G.G. MUSSER Systematic studies of oryzomyine rodents (Muridae, Sigmodontinae): a synopsis of Microryzomys. Bulletin American Museum of Natural History, 191:1-83. CHEHEBAR, C., and E. RAMILO [1992]. Fauna del Parque Nacional Nahuel Huapi. Administración de Parques Nacionales, Buenos Aires, 40 pp. CHRISTIE, M.I. 1984a. Informe preliminar del relevamiento de fauna de Parques Nacionales Lanín y Nahuel Huapi. Vol. 3, Mamíferos. 71 pp. Plan Inventario APN-INVAP S.E., Administración de Parques Nacionales. CHRISTIE, M.I. 1984b. Inventario de la fauna de vertebrados del Parque Nacional Nahuel Huapi. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Zoología, 13: CONTRERAS, J.R Datos acerca de la variación intrapoblacional de la morfología de los molares de entidades de los géneros Galea y Microcavia (Rodentia, Caviidae). Ameghiniana, 3: CONTRERAS, J.R El home range en una población de Oryzomys longicau-

23 KEY TO SMALL MAMMALS 121 datus philippi (Landbeck) (Rodentia, Cricetidae). Physis, 31: CONTRERAS, J.R., and V.G. ROIG Observaciones sobre la organización social, la ecología y la estructura de los habitáculos de Microcavia australis australis en Ñacuñán, Provincia de Mendoza. Ecosur, 5: CONTRERAS, L.C., J.C. TORRES-MURA, and J.L. YAÑEZ Biogeography of Octodontid rodents: an eco-evolutionary hypothesis. Pp In: Studies in Neotropical Mammalogy (B.D. Patterson and R.M. Timm, eds). Fieldiana, Zool, N.S., No. 39, 506 pp. CREIGHTON, G.K Phylogenetic inference, biogeographical interpretations, and the patterns of speciation in Marmosa (Marsupialia: Didelphidae). Acta Zool. Fennica, 170: CRESPO, J.A Dispersión del chinchillón, Lagidium viscacia (Molina) en el noreste de Patagonia y descripción de una nueva subespecie (Mammalia; Rodentia). Neotropica, 9: CRESPO, J.A., M.S. SABATTINI, M.J. PIANTANIDA, and G. de VILLAFAÑE Estudios ecológicos sobre roedores silvestres. Observaciones sobre densidad, reproducción y estructura de comunidades de roedores silvestres en el sur de Córdoba. Secretaría de Estado de Salud Publica, Buenos Aires. 45 pp. CRIVELLI M., E.A., D.E. CURZIO, and M.J. SILVEIRA La estratigrafía de la Cueva Traful I (Provincia del Neuquén). Praehistoria, 1: Buenos Aires. DELLAFIORE, C.M., and J.J. POLOP Feeding habits of Calomys musculinus in the crop fields and its borders. Mastozoología Neotropical, 1: ELLERMAN, J.R The families and genera of living rodents. Vol pp. British Museum of Natural History, London. GALLARDO, M.H Karyotypic evolution in Ctenomys (Rodentia, Ctenomyidae). Journal of Mammalogy, 72: GALLARDO, M.H Karyotypic evolution in Octodontid rodents based on C- band analysis. Journal of Mammalogy, 73: GALLARDO, M.H., G. AGUILAR, and O. GOICOECHEA Systematics of sympatric cricetid Akodon (Abrothrix) rodents and their taxonomic implications. Medio Ambiente (Valdivia), 9: GALLARDO, M.H., and J.A. ANRIQUE Population parameters and burrow systems in Ctenomys maulinus brunneus (Rodentia, Ctenomyidae). Medio Ambiente (Valdivia), 11, No.2: GALLARDO, M.H., and N. KOHLER Genetic divergence in Ctenomys (Rodentia, Ctenomyidae) from the Andes of Chile. Journal of Mammalogy, 73: GALLARDO, M.H., and N. KOHLER Demographic changes and genetic losses in populations of a subterranean rodent (Ctenomys maulinus bruneus) affected by a natural catastrophe. Zeitschrift für Saügetierkunde, 59: GALLARDO, M., and E. PALMA Systematics of Oryzomys longicaudatus (Rodentia: Muridae) in Chile. Journal of Mammalogy, 71: GALLARDO, M.H., and D. REISE Systematics of Aconaemys (Rodentia, Octodontidae). Journal of Mammalogy, 73: GARDNER, A.L Order Microbiotheria. P. 27. In: Mammalian Species of the World: A taxonomic and geographic reference, 2nd edition (D.E. Wilson and D.M. Reeder, eds.). Smithsonian Institution Press, 1206 pp. GARDNER, A.L., and G.K. CREIGHTON A new generic name for Tate's

24 122 Oliver P. Pearson (1933) Microtarsus group os South American mouse opossums (Marsupialia: Didelphidae). Proceedings Biological Society Washington, 102:3-7. GLANZ, W.E Ecological relationships of two species of Akodon in central Chile. Journal of Mammalogy, 65: GONZALES, L.A., R. MURUA, P. ME- SERVE, and Y.C. JOFRE Consecuencias demográficas de la manipulación experimental en la composición de edades de Akodon olivaceus (Rodentia, Cricetidae). Boletín Sociedad Biología Concepcion, Chile, 59: GREER, J.K [1966]. Mammals of Malleco Province Chile. Publications of the Museum, Michigan State Univ., Biol. Ser., 3: GRIGERA, D.E., and E.H. RAPOPORT Status and distribution of the European hare in South America. Journal of Mammalogy, 64: GRIGERA, D., C.A. UBEDA, and S. CALI Caracterización ecológica de la asamblea de tetrápodos del Parque y Reserva Nacional Nahuel Huapi, Argentina. Revista Chilena de Historia Natural, 67: HEINEMANN, K.M., N. GUTHMANN, M. LOZADA, and J.A. MONJEAU Area de actividad de Abrothrix xanthorhinus (Muridae, Sigmodontinae) e implicancias para su estrategia reproductiva. Mastozoología Neotropical, 2: HERSHKOVITZ, P Evolution of Neotropical Cricetine rodents (Muridae) with special reference to the Phyllotine group. Fieldiana: Zoology, 46: HONACKI, J.H., K.E. KINMAN, and J.W. KOEPPL Mammal species of the world. ix pp. Allen Press and Association of Systematics Collections, Lawrence, Kansas. KELT, D Irenomys tarsalis. Mammahan Species No. 447, pp American Society of Mammalogists. KELT, D The natural history of small mammals from Aisen Region, southem Chile. Revista Chilena de Historia Natural, 67: KELT, D.A., and D.R. MARTINEZ Notes on distribution and ecology of two marsupials endemic to the Valdivian forests of southern South America. Journal of Mammalogy, 70: KELT, D.A., P.L. MESERVE, and B.K. LANG Quantitative habitat associations of small mammals in a temperate rainforest in southern Chile: empirical pattems and the importance of ecological scale. Journal of Mammalogy, 75: KELT, D.A., R.E. PALMA, M.H. GA- LLARDO, and J.A. COOK Chromosomal multiformity in Eligmodontia (Muridae, Sigmodontinae), and verification of the status of E. morgani. Zeitschrift fr Saügetierkunde, 56: KRAVETZ, F.O., M. BUSCH, R.E. PERCICH, M.C. MANJON, and P.N. MARCONI Ecología de Calomys laucha (Rodentia, Cricetidae) en el departamento de Río Cuarto (Córdoba). II. Criterios para la determinación de edades y crecimiento. Ecología, 6: MANN F., G Los pequeños mamíferos de Chile. Gayana No. 40, Zoología, 342 pp. MARES, M.A Water economy and salt balance in a South American desea rodent, Eligmodontia typus. Comparative Biochemistry and Physiology, 56A: MARES, M.A., R.A. OJEDA, and R.M. BARQUEZ Guide to the mammals of Salta Province, Argentina. University of Oklahoma Press, xv pp.

25 KEY TO SMALL MAMMALS 123 MARSHALL, L.G Lestodelphys halli. Mammalian Species No. 81, 3 pp., American Society of Mammalogists. MARSHALL, L.G Dromiciops australis. Mammalian Species, No. 99, 5 pp., American Society of Mammalogists. MASSARINI, A.I., M.A. BARROS, V.G. ROIG, and O.A. REIG Banded karyotypes of Ctenomys mendocinus (Rodentia: Octodontidae) from Mendoza, Argentina. Joumal of Mammalogy, 72: MASSOIA, E El género Octodon en la Argentina. Neotropica, 25:36. MASSOIA, E., and J.C. CHEBEZ Mamíferos silvestres del archipiélago fueguino. L.O.L.A., Buenos Aires, 261 pp. MASSOIA, E., and A. FORNES Nuevos datos sobre la distribución geográfica y ecológica del género Calomys (Waterhouse) (Rodentia- Cricetidae). Idia, No. 227:7-9. MESERVE, B.K. LANG, and B.D. PATTERSON Trophic relationships of small mammals in Chilean temperate rainforest. Journal of Mammalogy, 69: MILLS, J.N., B.A. ELLIS, K.T. MCKEE, J.I. MAIZTEGUI, and J.E. CHILDS. 1992a. Reproductive characteristics of rodent assemblages in cultivated regions of central Argentina. Journal of Mammalogy, 73: MILLS, J.N., B.A. ELLIS, J.E. CHILDS, J.I. MAIZTEGUI, and A. CASTRO-VAZ- QUEZ. 1992b. Seasonal changes in mass and reproductive condition of the corra mouse (Calomys musculinus) on the Argentine pampa. Journal of Mammalogy, 73: MONJEAU, J.A., N. BONINO, and S. SABA Annotated checklist of the living land mammals in Patagonia, Argentina. Mastozoología Neotropical, 1: MUÑOZ P., and R. MURUA Biología de Octodon bridgesi bridgesi (Rodentia, Octodontidae) en la Zona Costera de Chile Central. Boletín Sociedad Biológica Concepción, 58: MURUA, R., and L.A. GONZALES Regulation of numbers in two Neotropical rodent species in southern Chile. Revista Chilena Historia Natural, 59: MURUA, R., L.A. GONZALES, and P.L. MESERVE Population ecology of Oryzomys longicaudatus philippii (Rodentia: Cricetidae) in southern Chile. Journal of Animal Ecology, 55: MURUA, R.M., P.L. MESERVE, L.A. GONZALES, and C. JOFRE The small mammal community of a Chilean temperate raen forest: lack of evidence of competition between dominant species. Journal of Mammalogy, 68: NOWAK, R.M Walker' s Mammals of the World. 5th ed., 2 vols, 1629 pp. John Hopkins Univ. Press. OLROG, C.C., and M.M. LUCERO [1981]. Guía de los mamíferos argentinos. Fundación Miguel Lillo, Tucumán, 151 pp. ORTELLS, M.O., O.A. REIG, N. BRUM- ZORILLA, and O.A. SCAGLIA Cytogenetics and karyosystematics of phyllotine rodents (Cricetidae, Sigmodontinae). I. Chromosome multiformity and gonosomal-autosomal translocation in Reithrodon. Genetica, 77: ORTELLS, M.O., O.A. REIG, R.L. WAIN- BERG, G.E. HURTADO DE CATALFO, and T.M.L. GENTILE DE FRONZA Cytogenetics and karyosystematics of phyllotine rodents (Cricetidae: Sigmodontinae). II. Chromosome multiformity and autosomal polymorphism in Eligmodontia. Zeitschrift für Saügetierkunde, 54:

26 124 Oliver P. Pearson OSGOOD, W.H The mammals of Chile. Field Museum of Natural History, Zoological Series, 30:268 pp. PA11ERSON, B.D., and M.H. GALLARDO Rhyncholestes raphanurus. Mammalian Species, No. 286, 5 pp. Amer. Soc. Mammalogists. PATTERSON, B.D., M.H. GALLARDO, and K.E. FREAS Systematics of mice of the subgenus Akodon (Rodentia: Cricetidae) in southern South America, with the description of a new species. Fieldiana: Zoology, new series, No. 23, 16 pp. PATTERSON, B.D., P.L. MESERVE, and B.K. LANG Distribution and abundance of small mammals along an elevational transect in temperate rain forests of Chile. Journal of Mammalogy, 70: PATTERSON, B.D., P.L. MESERVE, and B.K. LANG Quantitative habitat associations of small mammals along an elevational transect in temperate rainforests of Chile. Journal of Mammalogy, 71: PEARSON, O.P Life history of mountain vizcachas in Peru. Journal of Mammalogy, 29: PEARSON, O.P Reproduction of a South American rodent, the mountain vizcacha. American Journal of Anatomy, 84: PEARSON, O.P A taxonomic revision of the rodent genus Phyllotis. University of California Publications in Zoology, 56: PEARSON, O.P Characteristics of a mammalian fauna from forests in Patagonia, southern Argentina. Journal of Mammalogy, 64: PEARSON, O.P Taxonomy and natural history of some fossorial rodents of Patagonia, southern Argentina. Journal of Zoology, London 202: PEARSON, O.P Mice and the postglacial history of the Traful Valley of Argentina. Journal of Mammalogy, 68: PEARSON, O.P Biology and feeding dynamics of a South American herbivorous rodent, Reithrodon. Studies on Neotropical Fauna and Environment, 23: PEARSON, O.P Reproduction in a South American mouse, Abrothrix longipilis. Anatomical Record, 234: PEARSON, O.P., and M.I. CHRISTIE Los tuco-tucos (género Ctenomys) de los Parques Nacionales Lanín y Nahuel Huapi, Argentina. Historia Natural, 5: PEARSON, O.P., and M.I. CHRISTIE Sympatric species of Euneomys (Rodentia, Cricetidae). Studies on Neotropical Fauna and Environment, 26: PEARSON, O.P., and M.I. CHRISTIE Rodent guano (amberat) from caves in Argentina. Studies on Neotropical Fauna and Environment, 28: PEARSON, O.P., and H.A. LAGIGLIA "Fuerte de San Rafael": una localidad tipo ilusoria. Revista del Museo de Historia Natural de San Rafael (Mendoza), 12: PEARSON, O.P., S. MARTIN, and J. BELLATI Demography and reproduction of the silky desert mouse (Eligmodontia) in Argentina. Pp In: Studies in Neotropical Mammalogy: Essays in honor of Philip Hershkovitz (B.D. Patterson and R.M. Timm, eds.). Fieldiana: Zoology, n.s., No. 39. PEARSON, O.P., and A.K. PEARSON Ecology and biogeography of the southern rainforests of Argentina. Pp In: Mammalian biology in South América (M.A. Mares and H.H. Geno-

27 KEY TO SMALL MAMMALS 125 ways, eds.). Special Publications Series, Pymatuning Laboratory of Ecology, University of Pittsburgh. PEARSON, O.P., and A.K. PEARSON Reproduction of bats in southern Argentina. Pp In: Advances in Neotropical Mammalogy, (K.H. Redford and J.F. Eisenberg, eds.). Sandhill Crane Press, Gainesville, Florida. REDFORD, K.H., and J.F. EISENBERG Mammals of the Neotropics. Vol. 2, the southern cone. Univ. Chicago Press, 430 pp. REIG, O.A An assessment of the systematics and evolution of the Akodontini, with the description of a new fossil species of Akodon (Cricetidae: Sigmodontinae). Pp In: Studies in Neotropical mammalogy (B.D. Patterson and R.M. Timm, eds.). Fieldiana, Zool., New Ser., No. 39. REIG, O.A., C. BUSCH, M.O. ORTELLS, and J.R. CONTRERAS An overview of evolution, systematics, population biology, cytogenetics, molecular biology and speciation in Ctenomys. Pp In: Evolution of subterranean mammals at the organismal and molecular levels (E. Nevo and O.A. Reig, eds.). Wiley-Liss, New York. REISE, D Clave para la determinación de los cráneos de marsupiales y roedores chilenos. Gayana, No. 27, 20 pp. REISE, D., and M.H. GALLARDO A taxonomic study of the South American genus Euneomys (Cricetidae, Rodentia). Revista Chilena Historia Natural, 63: ROOD, J.O Ecological and behavioural comparisons of three genera of Argentine cavies. Animal Behaviour Monographs, 5:1-83. SAGE, R.D., J.R. CONTRERAS, V.G. ROIG, and J.L. PATTON Genetic variation in the South American burrowing rodents of the genus Ctenomys (Roden- tia: Cteno-myidae). Zeitschrift für Saügetierkunde, 51: SMITH, M.F., and J.L. PATTON The diversification of South American murid rodents: evidence from mitochondrial DNA sequence data for the akodontine tribe. Biological Journal of the Linnean Society, 50: SPOTORNO, Parallel evolution and ontogeny of simple penis among New World cricetid rodents. Journal of Mammalogy, 73: SPOTORNO, A.E., C.A. ZULETA, and A. CORTES Evolutionary systematics and heterochrony in Abrothrix species (Rodentia, Cricetidae). Evolución Biológica 4: STEPPAN, S.J Phylogenetic relationships among the Phyllotini (Rodentia: Sigmodontinae) using morphological characters. Journal of Mammalian Evolution, 1: STEPPAN, S.J Revision of the tribe Phyllotini (Rodentia; Sigmodontinae), with a phylogenetic hypothesis for the Sigmodontinae. Fieldiana, Zoology, New Series, No. 80, vi pp. Field Museum of Natural History. TAMAYO H., M., and D. FRASSINETTI C Catálogos de los mamíferos fósiles y vivientes de Chile. Boletín Museo Nacional Historia Natural, Chile, 37: UBEDA, C.A., D.E. GRIGERA, and A.R. RECA Conservación de la fauna de tetrápodos. II. Estado de conservación de los mamíferos del Parque y Reserva Nacional Nahuel Huapi. Mastozoología Neotropical, 1: VERZI, D.H., and A. ALCOVER Octodon bridgesi Waterhouse, 1844 (Rodentia: Octodontidae) in the Argentinian living mammalian fauna. Mammalia, 54: WALKER, L.I., A.E. SPOTORNO, and J. ARRAU Cytogenetic and repro-

28 126 Oliver P. Pearson ductive studies of two nominal subspecies of Phyllotis darwini and their experimental hybrids. Journal of Mammalogy, 65: WILKINS, K.T Tadarida brasiliensis. Mammalian Species, No. 331, 10 pp. American Society of Mammalogists. WILSON, D.E., and D.M. REEDER (eds.) Mammal species of the world: a taxonomic and geographic reference. Smithsonian Institution, Washington, 2nd ed., 1206 pp. WOODS, C.A., L. CONTRERAS, G. WILLNER-CHAPMAN, and H.P. WHIDDEN Myocastor coypus. Mammalian Species, No. 398, 8 pp., American Society of Mammalogists. YAÑEZ, J., J. VALENCIA, and F. JAKSIC Morfometría y sistemática del subgénero Akodon (Rodentia) en Chile. Archivos Biología Medicina Experimental, 12:

29 KEY TO SMALL MAMMALS 127 APPENDIX Table 5: Key to the bats in or near Nahuel Huapi Park and Lanin Park. A. Tail extends mouse-like far beyond the posterior edge of the tail membrane... Tadarida brasiliensis AA. Tail almost entirely enclosed within the tail membrane. B. Ears more than 23 mm long (extend far beyond the tip of the nose when folded forward. C. Ears less than 32 mm long... Histiotus montanus CC. Ears more than 32 mm long... Histiotus macrotus BB. Ears less than 23 mm long (do not extend far beyond the tip of the nose when folded forward). D. Tail membrane without fur on the upper surface... Myotis chiloensis DD. Tail membrane with much fur on the upper surface. E. Forearm (elbow to wrist) more than 43 mm long; fur on tail membrane does not extend appreciably beyond the posterior margin F. Color of fur yellowish... Lasiurus ega* FF. Color of fur frosted grey or reddish... Lasiurus cinereus* EE. Forearm less than 43 mm long; fur on tail membrane is long, dense, and extends far beyond the posterior border of the membrane, color reddish... Lasiurus blossevillii * No specimens recorded from within these parks. Table 6: Key to small mammals other than bats, based on externa! characters. A. Jaws filled with an almost-continuous row of small pointed teeth (Marsupials) B. Fur on back and belly uniformly very dark brown... Rhyncholestes BB. Fur grey, belly pale C. All five incisors on each side in contact with each other... Dromiciops CC. A small gap betwen the first incisor and the next four D. Claws on toes of front feet project far beyond the toes... Lestodelphys DD. Claws on front feet do not project beyond the toes... Thylamys AA. Jaws with rodent dentition: a pair of incisors at the front, behind them a long gap with no teeth, then the molars E. Front surface of each upper incisor with a longitudinal groove (use lens) F. Tail longer than 115 mm... Irenomys FF. Tail shorter than 115 mm G. The first and fifth toes on the hind foot very short, barely reaching to the base of the middle three toes... Reithrodon GG. Either the first or the fifth toe of the hind foot moderately long,reaching to about the middle of the adjacent toe... Euneomys EE. Front surface of upper incisors not grooved H. Tail shorter than.52 times length of head and body I. No tail J. Front surface of upper incisors yellow Golea JJ. Front surface of upper incisors white Microcavia II. Short tail K. Hind foot longer than 30 mm L. Almost no external ear pinnae M Black moustaches on upper lips, bordered by rufous patches aboye and white below Ctenomys sociabilis MM Upper lips more uniformly colored, no moustaches N Head and body longer than 195 mm; hind foot longer than 36.5 mm... Ctenomys maulinus NN. Head and body shorter than 195 nun; hind foot shorter than 36.5 mm... Ctenomys haigii LL. Obvious external ear pinnae Aconaemys porteri KK. Hind foot shorter than 30 mm O. Head and body longer than 115 mm (continue)

30 128 Oliver P. Pearson Table 6: Key to small mammals other than bats, based on externa! cbaracters. (continued) P. Hind feet with conspicuous curved bristles covering the claws and extending beyond the claws; both margins of the hind feet do not have a fringe of hairs... Aconaemys sagei PP. Hind feet with only soft hairs at the base of the claws, and these are shorter than the claws; both margins of the hind feet are equipped with fringes of hairs... Chelemys 00. Head and body shorter than 115 mm Q. Shaggy fringe of hairs around one margin of each hind foot; ear pinnae not easily visible... Notiomys QQ. No clear fringe of hairs around the hind feet; ears small but the pinnae easily visible... Geoxus HH. Tail longer than.52 times length of head and body R. Ear large, 25 mm or longer, and hind foot minus ear less than Phyllotis RR. Ears 25 mm or less, or hind foot minus ear more than 1.2 S. A furry pad on the sole of each hind foot... Eligmodontia SS. Soles of hind feet without a hairy pad T. Tail longer than head and body U. Hind foot longer than 31 mm... Rattus UU. Hind foot shorter than 31 mm V. Tail shorter than 100 mm... Mus VV. Tail longer than 100 mm... Oligoryzomys TT. Tail shorter than head and body W. Hind foot times head and body more than 3200 X. Hind foot longer than 32 mm Y. Tail thinly furred, the rings of scales conspicuous... Rattus YY. Tail well-furred, the rings of scales inconspicuous... Octodon XX. Hind foot shorter than 32 mm... Loxodontomys WW. Hind foot times head and body less than 3200 Z. Hind foot times tail less than 1300 a. Hind feet and tail with brownish wash, ears 13.5 mm or longer... Abrothrix xantho. aa. Hind feet and tail whitish or greyish; ears 13.5 mm or less... Akodon iniscatus ZZ. Hind foot times tail more than 1300 b. Belly fur silvery, sides grey or blackish, and back washed with red-brown; tail thick... Abrothrix longipilis bb. Belly white, grey, or brownish; sides and back almost unifonnly colored; tail thin c. Tail much darker aboye than below, the separation sharp d. Ear longer than 14 mm... Abrothrix olivaceus dd. Ear shorter than 14 mm... Akodon iniscatus cc. Tail only slightly darker aboye than below, the separation not sharp e. Inner surface of ears furry... Calomys ee. Inner surface of ears naked or only faintly fuzzy... Mus Table 7: Key to small mammal other than bats, based on crania. A. Jaws almost completely filled with small sharp teeth, no gaps larger that 1.5 mm (Marsupials) B. Rostrum strikingly long and narrow... Rhyncholestes BB. Rostrum not strikingly long and narrow C. The 5 upper incisors on each side are flattened like human incisors and all in contact with each other; lower canine not appreciably longer than the adjacent teeth... Dromiciops CC. The 5 upper incisors on each side are tiny and scarcely flattened, with a distinct gap between the first incisor and the other 4; lower canine much longer than the adjacent teeth (continue)

31 KEY TO SMALL MAMMALS 129 Table 7: Key to small mammal other than bats, based on crania. (continued) D. The second tooth behind the upper canine is almost as large as the third, viewed from the side... Thylamys DD. The third tooth behind the upper canine is much larger than the second, viewed from the side... Lestodelphys AA. Jaws contain a pair of conspicuous incisors in front and then, separated from the incisors by a long gap, a series of closely packed molar teeth (Rodents and Hares) E. Front surface of the upper incisors with a longitudinal groove F. Incisor with a tiny peg-like tooth close behind it... Lepus FF. No peg-like tooth close behind the incisor G. Anterior border of zygomatic plate deeply concave... Reithrodon GG. Anterior border of zygomatic plate straight H. Palate with deep excavations between the molar toothrows; molar pattern S-shaped and somewhat rounded... Euneomys HH. Palate without deep excavations; molar pattem sharp-angled and prismatic... Irenomys EE. Front surface of upper incisors smooth, no groove I. Greatest length of the skull longer than 70 mm J. Toothrow longer than 25 mm; incisive foramina only about half as long as the diastema... Myocastor JJ. Toothrow less than 25 mm; incisive foramina more than half as long as the diastema... Lagidium II. Greatest length of skull less than 70 mm K. Four molariform teeth on each side, and the infraorbital foramen large and gaping. If the number of teeth is not easily counted, they will be seen to consist of 4, 7, or 8 islands with relatively flat surfaces, never with cusps L. The molar toothrows converge sharply and almost touch in front M. Front surface of incisors is yellow... Galea MM. Front surface of incisors is white... Microcavia LL. The molar toothrows converge only slightly, not nearly touching in front N. Pattern of the molar toothrow is 4 simple islands, the last molar very small 0. Molar toothrow shorter than 9.5 mm; incisors barely visible when viewed from aboye (orthodont); upper diastema divided by length of bulla less than 0.80 (i.e. short nose and large bullae) Ctenomys haigii 00. Molar toothrow longer than 9.5 mm; incisors easily visible from aboye (proodont); upper diastema divided by length of bulla is less than 0.80 P. Width of auditory bullae <6.3 mm Ctenomys sociabilis PP. Width of auditory bullae >6.3 mm Ctenomys maulinus NN. Pattern of molar toothrow is 7 or 8 islands Q. Inner entrant angles of first 3 molariform teeth are much deeper than the outer entrant angles, dividing each tooth asymmetrically into two dissimilar islands... Octodon QQ. Inner and outer entrant angles of the first 3 molariform teeth are equally deep, dividing each tooth symmetrically into two similar islands R. Molar toothrow shorter than 9.0 mm; width across both upper incisors at the tip <4.2 mm Aconaemys sagei RR. Molar toothrow longer than 9.0 mm; width across both upper incisors at the tip >4.2 mm... Aconaemys porteri KK. Four molariform teeth on each side and the infraorbital foramen relatively narrow (except in Notiomys) S. Molar toothrow longer than 4.6 mm T. Interorbital region rounded, inflated, zygomatic plate slanted Chelemys TT. Interorbital region flat, not inflated, zygomatic plate not slanted U. Molar toothrow longer than 6.5 mm; interorbital edges very sharp, usually ridged... Rattus UU. Molar toothrow <6.5 mm; interorbital edges square but not very sharp, not ridged (continue)

32 130 Oliver P. Pearson Table 7: Key to small mammal other than bats, based on erania. (continued) V. Palate long, its posterior margin posterior to the last molars; condyloid process of mandible not bent distinctly inward... Phyllotis VV. Palate short, its posterior margin about even with the last molars; condyloid process of mandible bent inward... Loxodontomys SS. Molar toothrow <4.6 mm W. Interorbital and frontal region flat, not inflated X. Interorbital region very narrow, its length less than the length of the molar to throw; bullar tubeslong; the interpterygoid fossa about the same width as the parapterygoid fossae... Oligoryzomys XX. Interorbital region equal to or wider than the length of the molar toothrow; bullar tubes relatively short; the interpterygoid fossa distinctly narrower than the parapterygoid fossae Y. The first upper molar longer than the fist and second combined... Mus YY. The first upper molar equal to or shorter than the second and third combined Z. Palate extends considerably behind the plane of the last molar... Eligmodontia ZZ. Palate does not extend appreciably behind the plane of the last molar... Calomys WW. Interorbital and frontal region rounded, inflated a. Incisive foramina not reaching back to the plane of the first molars... Notiomys aa. Incisive foramina reaching back to or beyond the plane of the first molars b. Zygomatic plate distinctly slanted backwards... Geoxus bb. Zygomatic plate vertical or almost so c. Dorsal profile of skull bowed, rostrum short with the nasals not flared upward; zygomatic plate short and broad; incisive foramina narrowed posteriorly or pointed and reach to the middle of the first molar; anterior surface of the first molar frequently notched... Akodon iniscatus cc. Dorsal profile of skull flat, the rostrum frequently long with uptumed nasals; zygomatic plate narrow; incisive foramina rounded posteriorly and reaching only to the front of the first molar; anterior surface of the first molar rarely notched d. Upper toothrow >3.8 mm; diastema >6 mm... Abrothrix longipilis dd. Upper toothrow <3.8 mm; diastema <6 mm e. Premaxilla-frontal length >16 mm and toothrow >3.4 mm; product of both is >55... Abrothrix olivaceus ee. Premaxilla-frontal length <17 mm and toothrow < 3.5 mm; product of both is <55... Abrothrix xanthorhinus Table 8: Key to small mammals other than bats, based on mandibles. A. Jaw filled with tiny sharp teeth, no gaps longer than about 1 mm (Marsupials) B. One lower incisor enormous and projects horizontally... Rhyncholestes BB. The lower incisors small and projecting upward from the mandible C. Lower canine not appreciably longer than the adjacent teeth... Dromiciops CC. Lower canine much longer than the adjacent teeth D. Jawbone stout and conspicuously curved along the bottom margin; second toothe behind the canine much smaller than the third; articular condyle >2.5 mm across... Lestodelphys DD. Jawbone slender, slightly curved along the bottom; second tooth behind the canine about the same size as the third; articular condyle <2.5 mm across... Thylamys AA. A single incisor in front is separated from the molar by a gap of several mm (Rodents and Hares) E. Molar toothrow longer than 4.6 mm F. A conspicuous shelf or trough runs along the outer face of the mandible alongside the molars G. Front surface of incisors yellow... Golea GG. Front surface of incisors white Microcavia FF. No shelf or trough runs along the outer face of the mandible H. Four or more molariform teeth on each side (continue)

33 KEY TO SMALL MAMMALS 131 Table 8: Key to small mammals other than bats, based on mandibles. (continued) I. Four extremely simple molariform teeth, their surfaces flat crescents, the last one tiny J. Length of toothrow X diastema <75... Ctenomys haigii JJ. Length of toothrow X diastema >75 K. Coronoid process short, <3 mm... Ctenomys sociabilis KK. Coronoid process longer, >3 mm... Ctenomys maulinus Four or more molariform teeth, all of complex shape L. Mandible a flat blade without conspicuous lateral structures; 5 molars Lepus LL. Mandible thick, with lateral expansions; 4 molars M. The first three molariform teeth cut diagonally by the inner and outer entrant angles... Octodon MM. The first three molariform teeth cut straight across by the inner and outer entrant angles N. Molar toothrow longer than 9.0 mm... Aconaemys porteri NN. Molar toothrow shorter than 9.0 mm... Aconaemys sagei HH. Three molariform teeth on each side 0. Inner surface of the condyloid process with a broad, scooped-out furrow; molar roots 4,3, and 2 or 3 = total 9 or 10, at least 4 of them very small Reithrodon 00. Inner surface of condyloid process plain P. Condyloid process bent abruptly toward the midline Q. Coronoid process long, more than 40% of condyloid process; coronoid process projects beyond the angular process (see Fig. 2 for method of measurement); M 3 much smaller than M 2 ; molar roots 3,2,2 = total 7, the 3 roots of M, in line, the middle one small... Chelemys QQ. Coronoid process short, <40% of condyloid process; coronoid process does not project beyond the angular process; M 3 only slightly smaller than M 2 ; molar roots not as aboye R. The anterior cusp on M 1 is a completely isolated island, usually with a notch on the anterior surface; M 2 and M 3 are both S-shaped or Z-shaped and about the same size; each tooth has 2 roots = total 6 roots, all of them large... Euneomys RR. 3The anterior cusp on M i is attached to the next cusp and is without an anterior notch; M 2 in all except old individuals E-shaped, about the same size as M 3, molar roots 3, 2 or 3, 2 = total 7 or 8, at least one of them small Loxodontomys PP. Condyloid process not bent sharply toward the midline S. Molar toothrow longer than 6.5 mm... Ranas SS. Molar toothrow shorter than 6.5 mm T. Molar surfaces angular, prismatic, the inner and outer angles opposite each other and almost meeting in the midline; M 3 complex in shape and as large as M 2 ; molar roots 2,2,2 = total 6... Irenomys TT. Molar surfaces less prismatic, more rounded, the folds opposite but not as deep as aboye; the shape of M 3 not complex and its surface clearly smaller than that of M 2 Phyllotis EE. Molar toothrow shorter than 4.6 mm U. Coronoid process relatively short V. Mandible long and very slender; length of mandible length of toothrow >3.4; molar roots 2,2,2 = total 6Geoxus VV. Mandible not long and slender; length of mandible length of toothrow <3.4 W. Capsular projection prominente M 3 almost as large as M 2 ; ramus >2.9 mm dee (see Fig. 3); molar roots 2,2,2 = total 6... Oligoryzomys WW. Capsular projection not protninent; M 3 distinctly smaller than M 2 ; ramus <2.9 mm deep; molar roots >2,2,2 (continue)

34 132 Oliver P. Pearson Table 8: Key to small mammals other than bats, based on mandibles. (continued) X. Ventral border of the angular process turned abruptly mediad to form a deep shelf; M 3 somewhat smaller than M 2 ; molar roots 4,3,2 = total 9... Eligmodontia XX. Ventral border of the angular process turned mediad only gently to form a narrow, sloping shelf Y. Toothrow <3.1 mm; M 3 much smaller than M 2 ; molar roots 2,2,2 = total 6... Mus YY. Toothrow >3.1 mm; M 3 somewhat smaller than M 2 ; molar roots 4,3,3, = total Calomys UU. Coronoid process relatively long Z. Length of toothrow X length of mandible >33 a. Molar toothrow >3.8 mm; molar roots 3 or 2, 3 or 2, 2 = total Abrothrix longipilis aa. Molar toothrow <3.8 mm b. M 3 as wide or wider than it is long; length of mandible X length of toothrow <38; molar roots 4,3,3, = total Calomys bb. M 3 longer than it is wide; length of mandible X length of molar toothrow >38; molar roots 2,3,2 = total 7... Abrothrix olivaceus ZZ. Length of toothrow X length of mandible <33 c. M 3 much smaller than M... Notiomys CC. M 3 slightly smaller than M 2 d. Notch on anterior surface of M i of most young or young-adults; molar roots 3,2,2 = total 7... Akodon insicatus dd. No notch on anterior surface of M I ; molar roots 3 or 2,3,2 = total Abrothrix xantho.

35 KEY TO SMALL MAMMALS 133 DROMICIOPS AUSTRALIS LESTODELPHYS HALLI Fig. 3: Dorsal, ventral and lateral photographs of skulls of Dromiciops australis and Lestodelphys halli.

36 I 34 Oliver P. Pearson THYLAMYS PUSILLA RHYNCHOLESTES RAPHANURUS Fig. 4: Dorsal, ventral and lateral photographs of skulls of Thylamys pusilla and Rhyncholestes raphanurus.

37 KEY TO SMALL MAMMALS 135 CMS. ' I CMS. ABROTHRIX OLIVACEOUS ABROTHRIX LONGIPILIS Fig. 5: Dorsal, ventral and lateral photographs of skulls of Abrothrix olivaceous and Abrothrix longipilis.

38 136 Oliver P. Pearson ala ' I CMS. AKODON INISCATUS ABROTHRIX XANTHORHINUS Fig. 6: Dorsal, ventral and lateral photographs of skulls of Akodon iniscatus and Abrothrix xanthorhinus.

39 KEY TO SMALL MAMMALS 'OMS. REITHRODON AURITUS CHELEMYS MACRONYX Fig. 7: Dorsal, ventral and lateral photographs of skulls of Reithrodon auritus and Chelemys macronyx.

40 138 Oliver P. Pearson ' I OMS. EUNEOMYS CHINCHILLOIDES ELIGMODONTIA MORGANI Fig. 8: Dorsal, ventral and lateral photographs of skulls of Euneomys chinchilloides and Eligmodontia morgani.

41 KEY TO SMALL MAMMALS 139 Mr61174PRIZICSOISMFAII 11:~5121~40~2 IRENOMYS TARSALIS GEOXUS VALDIVIANUS Fig. 9: Dorsal, ventral and lateral photographs of skulls of Itenoniy.s jarsalis and Geoxus raldirianus.

42 1 40 Oliver P. Pearson 1 1 i i I 1 OMS. LOXODONTOMYS MICROPUS NOTIOMYS EDWARDSII Fig. 10: Dorsal, ventral and lateral photographs of skulls of Loxodontomys micropus and Notiomys edwardsü.

43 KEY TO SMALL MAMMALS 1 41 I I 1 1 I " " C M S. I I CMS. PHYLLOTIS XANTHOPYGUS OLIGORYZOMYS LONGICAUDATUS Fig. 11: Dorsal, ventral and lateral photographs of skulls of Phyllotis xanthopygus and Oligoryzomys longicaudatus.

44 142 Oliver P. Pearson " ' I OMS ' I 1 1 I ACONAEMYS SAGEI ACONAEMYS PORTERI Fig. 12: Dorsal, ventral and lateral photographs of skulls of Aconaemys sagei and Aconaemys porteri.

45 KEY TO SMALL MAMMALS CMS CMS. OCTODON BRIDGESII CTENOMYS HAIGII Fig. 13: Dorsal, ventral and lateral photographs of skulls of Octodon bridgesii and Ctenomys haigii.

46 144 Oliver P. Pearson z ABRO. LONGI. ABRO. OLIV. ABRO. XANTHO. LOXODONTOMYS CHELEMYS CTENOMYS HAIGII Fig. 14: Photographs of upper right molars.

47 KEY TO SMALL MAMMALS 145 ELIGMODONTIA GEOXUS IRENOMYS - OLIGORYZOMYS PHYLLOTIS REITHRODON Fig. 15: Photographs of upper right molars.

48 146 Oliver P. Pearson ABRO. LONGI. ABRO. OLIV. ABRO. XANTHO. 2 LOXODONTOMYS CHELEMYS CTENOMYS HAIGII Fig. 16: Photographs of lower right molars.

49 KEY TO SMALL MAMMALS 147 ELIGMODONTIA GEOXUS IRENOMYS OLIGORYZOMYS PHYLLOTIS REITHRODON Fig. 17: Photographs of lower right molars.

50 148 Oliver P. Pearson REITHRODON ABRO. XANTHO. LOXODONTOMYS IRENOMYS ELIGMODONTIA PHYLLOTIS DROMICIOPS CHELEMYS LESTODELPHYS O CM. Fig. 18: Photographs of mandibles of some of the small mammals from Nahuel Nuapi and Lanín National Parks.