The genus Abrocoma (family Abrocomidae) is distributed from southern Peru and northern Chile to Bolivia and then southward to the west-central region of Mendoza Province, Argentina. The systematics of the genus is poorly known. Ten taxa were originally described but later synonymized into 2 species. Five taxa were included in Abrocoma cinerea and 5 in A. bennetti. A 3rd species, A. boliviensis, was described in 1990, and a new genus and species, Cuscomys ashaninka, were described in 1999. We reevaluate the systematics of the A. cinerea species complex, with emphasis on Argentine specimens, using cranial, dental, and external morphology. A new species of Abrocoma from Mendoza Province, Argentina, is described. Karyotypic information is presented. Behavior, habitat, and natural history are also discussed.
The family Abrocomidae (Rodentia: Hystricognathi), chinchilla rats, contains but 2 genera, Abrocoma, with 3 currently recognized species (Woods 1993), and the recently described Cuscomys, which contains 1 extant species (Emmons 1999). The family, which is endemic to South America, has had a long and varied systematic history. Its members have been recognized as a subfamily (Abrocominae) of the Echimyidae (Ellerman 1940) or of the Octodontidae (Landry 1957). The distinctiveness of the genus has also been recognized at the family level (Cabrera 1961; Patterson and Wood 1982; Woods 1993). Although the higher level relationships of this group are of considerable interest (e.g., Carleton 1984; Miller and Gidley 1918; Reig 1986), they will not be dealt with in this work.
The 4 extant species, Abrocoma bennetti, A. boliviensis, A. cinerea, and Cuscomys ashaninka, are distributed in west-central South America from southern Peru southward to central Argentina. A. bennetti, restricted to the western Andean slopes in Chile, appears to prefer Mediterranean scrub habitat at elevations ranging from sea level to 2,000 m (Mann 1978). Four names have been synonymized under A. bennetti: cuvieri (Waterhouse 1837), helvina (Wagner 1842), laniger (Prell 1934), and murrayi (Wolffsohn 1916). Ellerman (1940) placed these taxa in a single species, A. bennetti and recognized 2 subspecies, A. b. bennetti (including bennetti, cuvieri, helvina, and laniger) and A. b. murrayi. Most investigators (Cabrera 1961; Honacki et al. 1982; Woods 1984, 1993) have followed this arrangement. To date, there is only 1 published report on the chromosomes of Abrocoma: the diploid number for Chilean A. bennetti is 64 and the fundamental number is 114 (Contreras et al. 1990).
Glanz and Anderson (1990) described a new species, A. boliviensis, based on 2 specimens that had been collected in 1926 and 1955 but that had never been identified to species. This taxon is currently known only from the type locality in western Santa Cruz Department, Bolivia.
In 1999, a new genus and species, C. ashaninka, were described based on a single specimen from the Departamento Cusco in Peru (Emmons 1999). Abrocoma oblativus, which is possibly extinct, was also placed in this new genus.
The taxa included in A. cinerea are quite different from A. bennetti, A. boliviensis, and Cuscomys in both external and cranial morphologies. Originally described by Thomas (1919, 1920a, 1920b, 1921a) as distinct species, these taxa (budini, cinerea, famatina, schistacea, and vaccarum) were placed in synonymy with A. cinerea by Ellerman (1940). Unlike his treatment of the bennetti group, however, Ellerman (1940) recognized the distinctiveness of each taxon, but as subspecies rather than as species. This systematic arrangement persists today.
The 1st specimens of Abrocoma (A. bennetti) were collected by Charles Darwin during the voyage of the Beagle, and all but 1 species name (laniger) in the bennetti complex had been assigned by the time the 1st specimen in the currently recognized cinerea group was collected and described (Thomas 1919).
Since Ellerman's (1940) revision of the genus, no systematic review of the taxa comprising the cinerea group has been conducted. Although Glanz and Anderson (1990) described a new species (A. boliviensis) and evaluated the relationship of Abrocoma to other hystricognath rodents, their primary emphasis was not a systematic revision of the genus. Our interest in this group began after we collected a single specimen in west-central Mendoza Province, Argentina, in 1995. The lack of correspondence between the measurements and morphology of this specimen and those published in the literature led us to reexamine the original taxonomic descriptions and type specimens. As we did this, we realized that specimens recognized as A. cinerea had an extremely wide range of variation in morphology, behavior, distribution, habitat, and natural history (Braun and Mares 1996) that invited further inquiry. Herein we review the systematics of the taxa included in the A. cinerea group, evaluate their taxonomic status, and describe a new species of Abrocoma from Mendoza Province, Argentina.
Materials and Methods
One hundred specimens of Abrocoma, including the new specimen from west-central Mendoza Province, were examined; this total represents most available material. All specimens examined are listed in Results and Appendix I with localities and catalog numbers. However, most specimens are represented by a skin only, with no or minimal locality data and no measurements. A few specimens of A. schistacea were excluded from statistical analyses because they were judged to be subadults (based on size and craniodental morphology). Sample sizes were not sufficiently large to evaluate variation due to age or sex. Specimens from the following institutions are reported: British Museum (Natural History), London (BMNH); Universidad Nacional de Tucumán, Colección de Mamíferos Lillo (CML); Instituto Argentino de Investigaciónes de las Zonas Aridas, Mendoza, Argentina (IADIZA-CM); Museo Argentino de Ciencias Naturales “Bernardino Rivadavia,” Buenos Aires (MACN); University of California, Berkeley, Museum of Vertebrate Zoology (MVZ); and United States National Museum of Natural History (USNM).
External, cranial, dental, and mandibular measurements were recorded from specimens examined. External measurements (in millimeters) recorded from specimen labels were total length, length of head and body (total length less tail length), length of tail (length of caudal vertebrae), length of hind foot (length of pes from heel to tip of longest claw), and length of ear (length of pinna from notch).
Cranial, dental, and mandibular measurements were taken with dial calipers and were recorded to the nearest 0.1 mm. These included length of skull (least distance between posterior border of supraoccipitals and tip of nasals), condylobasal length (least distance between posterior margin of occipital condyles and anteriormost projection of the premaxillae), zygomatic breadth (greatest distance across zygomatic arches, perpendicular to longitudinal axis of cranium), breadth of braincase (greatest distance across braincase, typically on squamosals), palatilar length (distance between anteriormost point on the posterior margin of palate and posterior margins of incisive alveoli), length of diastema (distance between posterolateral margin of incisive alveolus and anteromedial margin of alveolus of M1), length of toothrow (distance between anterior margin of alveolus of M1 and posterior margin of alveolus of M3), length of nasals (greatest length of nasal bones from posteriormost projection of frontal suture to tip), interorbital breadth (least distance across frontal bones), width of bullae (width of bullae perpendicular to long axis of skull), length of mandible (distance between the median margin of alveolus of i1 and mandibular condyle), and length of mandibular toothrow (distance between from anterior margin of alveolus of m1 and posterior margin of alveolus of m3).
Chromosomes of the new specimen from west-central Mendoza Province were examined because only those of A. bennetti have been described to date. Cell preparations were made from bone marrow of the femur using the technique described by Baker et al. (1982). Slides of the cell suspensions were prepared in the field and later stained with Giemsa stain. Cell suspensions were preserved in liquid nitrogen and are stored in the frozen tissues division of the Texas Cooperative Wildlife Collection (TCWC), Texas A&M University, College Station, Texas. Determinations of diploid number were based on examination of 10 metaphase spreads for the specimen.
Means, standard deviations, and ranges were calculated for adults in each taxon using StatView 5.0 software (SAS Institute Inc. 1998). Unpaired comparisons of the means (t-test) and variances (F-test) for each character for each species were performed. Values were considered statistically significant at P < 0.05. The new specimen of Abrocoma from west-central Mendoza Province was not included in the tests because n = 1. Phenetic relationships of the taxa were examined using principal components analyses from the software program Numerical Taxonomy and Multivariate Analysis System (NTSYSpc; Rohlf 1998). Measurements for individuals (n = 36) were used instead of means. Analyses were performed using combined external and cranial data as well as using cranial data only. Results were similar; combined results are presented.
The results of the unpaired comparisons of the means (t-test) and variances (F-test) of the variables for each character for each taxon are presented in Table 1. Results for each taxon are discussed in the account for that taxon.
A principal components analysis of correlations among variables showed that most variables had high positive loadings on principal component I, indicating that this component is related to size (Table 2). Component II separates Operational Taxonomic Units (OTUs) on the basis of total length, length of tail, length of hind foot, and interorbital breadth (loadings > 0.50). Component III separates OTUs on the basis of breadth of braincase and width of bullae (loadings > 0.50). The 6 taxa show some grouping and some, although not complete, separation from individuals of the other taxa as shown in the bivariate plot of components I and II (Fig. 1A) and components II and III (Fig. 1B).
Based on our analyses and examination of specimens, we recommend that the 5 taxa that were originally described by Thomas (1919, 1920a, 1920b, 1921a) as species of Abrocoma and later synonymized under A. cinerea by Ellerman (1940) be reinstated at the species level. As Thomas (1921a:217) noted “All these Argentine species of Abrocoma are nearly allied and very similar to each other, but the characters used, slight as they are, seem to be locally constant, while the respective mountain habitats are well separated and often completely isolated.” Because the new specimen of Abrocoma from west-central Mendoza Province does not pertain to any known species of Abrocoma, we describe it as a new species. The description and amended diagnoses of the species follow.
Diagnosis and description
The following characters were considered diagnostic or descriptive of the genus by Glanz and Anderson (1990) and Emmons (1999): size is smaller than in other hystricomorph rodents; length and width of feet are reduced; toes and claws are shortened; 2nd digit on hind feet is specialized with a wide, distally rounded, ventrally hollowed claw, with a slight groove lateral to claw, and with well-developed stiff hairs above claw; hair-comb is present but less developed on digits 3 and 4; palmar surfaces of feet and bottom of toes are naked and covered with small, distinct tubercles; a larger terminal pad is present beneath each claw; ears are relatively large and rounded; zygomatic arch is delicate; anterior ascending process of maxilla is reduced to a slender strut; jugal component of dorsal zygomatic bridge is reduced, and jugal is well separated from lacrimal; jugal does not project posteriorly beyond the general curvature of the zygomatic arch; flange is absent and groove is reduced in medioventral border of infraorbital canal; rostrum is narrow (nasals, premaxillaries, maxillaries); nasals are not inflated anteriorly and are tapering to joined posterior tips; frontals of interorbital region widen posteriorly; bullae are enlarged; basioccipital is narrow; mastoids are positioned dorsally between parietal, squamosal, and occipital bones; mastoids are large and slightly inflated; lateral process of supraoccipital is reduced; incisive foramina are narrow; a single medial foramen tends to form in palate; posterior border of palate is deeply concave without medial ridge; paraoccipital process is short and fused to bullae; temporal foramen is absent or minute; upper cheek teeth are simplified; upper toothrows are more or less parallel; upper and lower incisors are narrow and shortened; lower cheek teeth have 1 labial and 2 deep lingual folds; anterior portion of dentaries is narrow; foramen leading to base of incisor capsule is positioned in trough ventrolateral to posterior molar; angular process is narrow, elongate, and medially inflected; semilunar notch is wide; condyloid process is slender; sigmoid notch is relatively short; coronoid process is reduced; lower jaw lacks ridge or groove on lateral surface.
Abrocoma cinerea Thomas, 1919
184.108.40.206 BMNH; skin and skull; adult male; obtained by E. Budin, field number 540, on 22 March 1919.
Cerro Casabindo, 4,800 m (=15,600 feet), Jujuy Province, Argentina.
Named for its gray coloration (Braun and Mares 1995).
Amended diagnosis and description
Dorsal coloration is light grayish, slightly paler than Pale Neutral Gray, and sides are lighter in color. Hairs of venter are gray basally with whitish tips, which give appearance of venter being white. Sternal gland is covered with white hairs; because of overall coloration of venter the white patch does not appear very distinct. Hairs surrounding perianal region are white to the base. Forefeet and hind feet are covered with whitish hairs. Tail is Pale Neutral Gray above and white, or nearly so, below (description modified from Thomas 1919).
Tubercles of hind feet of A. cinerea from Bolivia (MACN), Chorrillos, Salta Province, Argentina (MACN 30.115, 30.117, 30.118, 30.119), and San Antonio de los Cobres, Salta Province, Argentina (MACN 30.61, 30.62, 30.63) have toe pads that are little developed.
Size is medium (Table 1); total length < 286 mm, length of head and body < 196 mm, length of tail < 96 mm, and length of hind foot < 27.1 mm. Length of tail is significantly less than for all other species, and total length and hind foot length are significantly less than for A. budini, A. famatina, and A. schistacea. The mean ratios of length of tail to total length and length of tail to length of head and body are the least of any for the species in the group, <26% and <35%, respectively.
External measurements reported by Pearson (1951) and Anderson (1997) for A. cinerea in Peru and Bolivia, respectively, are somewhat similar to those reported herein. However, Pearson (1951) found greater measurements for length of hind foot (all specimens; 26, 27, 28.5 mm) and length of tail (one specimen; 74 mm). Anderson (1997) reported ranges but not means; although maximum values for total length (294 mm), length of head and body (204 mm), length of tail (97 mm), and length hind foot (27 mm) are slightly larger than the maximum values we report, the minimum values (except for length of hind foot, 20 mm) are within the ranges reported herein (Anderson 1997).
One pair of nipples is axillary and 1 pair is placed lateral on the abdomen (Pearson 1951).
Interorbital breadth is significantly greater than that of other species in the group. A. cinerea is significantly smaller than A. budini in length of skull, condylobasal length, length of diastema, length of nasals, and length of mandible. A. cinerea is significantly larger than A. famatina in condylobasal length, length of diastema, length of maxillary toothrow, and bullar width.
Nasals are broad at midlength and taper gradually posteriorly. Zygomata are not slanted outward but are oriented more or less vertically. Anterior ascending maxillary portions of zygomata are thick. Zygomatic arches are moderately expanded. Frontals are not constricted. Mastoid islands are medium in size. Posterior border of the palate is a sharp point. Mesopterygoid fossae are wide. Paraoccipital processes are narrow and not flattened. Bullae are inflated.
Incisors are broad, large, and opisthodont. Hypoflexi are slightly narrower than in the other species. Length of maxillary toothrow medium in relation to the condylobasal length (X̄ = 0.221) and length of skull (X̄ = 0.218) is about equal to that of A. schistacea, larger than for A. budini, A. famatina, and A. vaccarum, and much smaller than for Abrocoma, new species.
The penial morphology was described for 3 specimens from Sama, Tarija, Bolivia (Contreras et al. 1993). All 3 individuals exhibited 1 spike on each side of the intromittent sac. Mean length of spike was 6.1 mm (range 5.7–6.4 mm), mean length of baculum was 9.4 mm (range 8.3–10.3 mm), and mean maximum width of baculum was 2.5 mm (range 2.2–2.6 mm).
Thomas (1920b:419, footnote) noted that the measurement reported for length of hind foot for the type specimen (27.5 mm), which was recorded by E. Budin, may be in error. He measured the dry length as 24.6 mm and suggested that the length would not have been more than 25 mm when fresh. Because Thomas (1920b) did not have confidence in this measurement, we did not include it in the numerical analyses.
Budin captured the type specimen “among the rocks on the Volcano of Casabindo” (Thomas 1919:133); the specimens from Sierra de Zenta were found to live “among the rocky volcanic mountains” (Thomas 1921b:616). Anderson (1997) noted that, in Bolivia, it is widely distributed on the altiplano, where it often inhabits stone walls. In southern Peru, Pearson (1951) collected this species in one locality on the altiplano. Animals lived in burrows that had been dug at the edge of a shale outcropping or at the base of bushes. Several animals were found in the same area. In northern Chile, Mann (1978) found A. cinerea inhabited areas with large rocks and carpets of llareta (Laretia).
Pearson (1951) and Mann (1978) noted that this species appears to live in colonies. Mann (1978) also noted that this species has a long, convoluted cecum and a thick intestine with tight flexures that indicate a diet high in cellulose. In Chile, this species possibly feeds on Senecio and Parastrephia (Mann 1978), whereas in Peru, Pearson (1951) suggested that it was foraging on Lepidophyllum or Senecio or both.
In April (Chile), a lactating female with 2 young only several days old was captured (Mann 1978). In August (Bolivia), a lactating female was collected, as were 3 young animals; in November, 1 female had 3 embryos (Anderson 1997). In Peru, Pearson collected a female with a closed vagina and no embryos in mid-October. In early December, a lactating female with an open vagina and no embryos was collected, as was a nonlactating female with an open vagina and 2 embryos. Two young (total length 170 and 182 mm) were also captured.
The MACN specimens from La Paz, Bolivia, which Anderson (1997) listed as unexamined Abrocoma, were determined by J. K. Braun to be specimens of Chinchillula.
Specimens examined (38)
Argentina: Catamarca Province: Pasto alto, 4,000 m, 1 (BMNH 220.127.116.11). Jujuy Province: Cerro Casabindo, 4,800 m, 1 (BMNH 18.104.22.168 type); Sierra de Zenta, 4,500 m, 2 (BMNH 22.214.171.124, 126.96.36.199); locality unknown, 3 (MACN 26.104, 31.190, 31.197). Salta Province: Chorrillos, 4,500–5,000 m, 1 (MACN 30.118); Chorrillos, 5,000 m, 3 (MACN 30.115, 30.117, 30.119); Chorrillos, P. de los Andes, 5,000 m, 2 (CML 280, 89); Los Andes, 5 (MACN 26.101–26.104, 27.48); San Antonio de los Cobres, 4 (CML 90, MACN 26.191–26.193); San Antonio de los Cobres, 3,700 m, 4 (MACN 30.61–30.63, 30.116). Tucumán Province: Concepcíon, 1 (CML 91). BOLIVIA: La Paz: Copacabama, 3 (MACN 41.23, 41.24, 41.25); locality unknown, 8 (MACN 41.166–41.171, 41.173, 41.174).
Argentina: Salta Province: Chorrillos, Los Andes (USNM 35239; Glanz and Anderson 1990). Bolivia: La Paz: La Paz, Tembladerani (Anderson 1997); 8.5 km W of San Andrés de Machaca (Anderson 1997). Oruro: Huancaroma, near Eucaliptus (Anderson 1997). Potosi: Khastor (Anderson 1997). Tarija: Sama (Anderson 1997; Contreras et al. 1993). Department unknown: perhaps Bolivia (Anderson 1997). Chile: Antofagasta Province: San Pedro (MVZ 116805; Glanz and Anderson 1990); Toconce, 60 km ENE of Calama, 4,320 m (MVZ 116801–116804; Glanz and Anderson 1990). Santiago Province: 10 km W of Tiltil, 1,000 m (MVZ 150117; Glanz and Anderson 1990). Peru: Department of Puno: Caccachara (MVZ 116005; Glanz and Anderson 1990). Department of Tacna: 2 km N of Nevado Livine 4,170 m (MVZ 116006; Glanz and Anderson 1990); Challapalca (MVZ 141626; Glanz and Anderson 1990).
Abrocoma uspallata, new species
6367 IADIZA-CM; skin and skeleton; adult male; obtained by J. K. Braun, field number Arg 3990, on 29 March 1995.
Argentina: Mendoza Province: Quebrada de la Vena, ca. 7 km SSE of the village of Uspallata, 32°39.405′S, 69°20.970′W, 1,880 ± 150 m.
The species name refers to the Valle de Uspallata in Mendoza Province, an unusually arid area whose striking beauty was noted long ago by Darwin (1962). The small valley of the type locality (Quebrada de la Vena) opens into the Valle de Uspallata. The use of a geographic locality for the species name also recognizes the fact that Thomas named several forms for mountain ranges on which they were found, and the genus Abrocoma may be found to contain additional new species as unexplored mountain ranges are examined by mammalogists in the future.
Known only from the type locality in the Sierra de Uspallata (Fig. 2).
A species of Abrocoma distinguished from all others in the cinerea group by the following combination of characters: dorsal coloration grayish brown; venter strongly washed with white; tail grayish above, immaculate white below; hind feet large relative to body size; ears large relative to body size; interorbital breadth narrow; zygomatic arches moderately expanded; mastoid islands large; nasals narrow; bullae large, the width 29% of condylobasal length and length of skull; mesopterygoid fossa narrow; paraoccipital processes broad, flattened, and completely adpressed to the bullae; posterior border of palate rounded; incisors small and narrow; length of maxillary toothrow large, 24% of condylobasal length and length of skull; braincase wide.
Length of head and body is 176 mm (Table 1). Head is large. Fur is soft and fine; underfur is dense. Dorsal coloration is grayish brown and includes a mix of Hair Brown, Mouse Gray, and Light Grayish Olive. There are lighter tones at the tips of some hairs (Tiluel Buff) and a washing with Fuscous Black on others. Base of the dorsal hairs is Slate Gray. Soft spines near middle of rump are Fuscous Black, whereas soft spines on the lateral portions of the rump are Tiluel Buff. Hairs of the venter are Slate Gray basally with creamish tips (between Pale Pinkish Buff and White), giving the appearance of a lightly colored venter. Sternal gland is covered with hairs that are white to the base. Hairs that are white to the base surround the perianal region. These two areas do not appear distinctive because of the overall coloration of the venter. Length of tail (108 mm) is >0.5 × length of head and body. Tail is well haired, the same as dorsal color above, and immaculate white below. Ears are relatively large (28 mm) and rounded. Length of hind feet is 31 mm. Forefeet and hind feet are covered with white hairs. Toes are short. Claws are weak and small. Forefoot has 4 digits, hind foot has 5. Hallux of the hind foot is reduced and 4th digit is shortened. The 2nd and 3rd digits of hind foot appear to be syndactylous. Stiff bristles of hair are present above claws of digits of hind foot, except the hallux. Claw of the 1st digit of hind foot is wide and is hollow ventrally. Palmar surfaces of the feet, including the bottoms of digits, are unhaired and covered with well-developed tubercles; a larger terminal pad is present beneath each claw.
Overall characters of the cranium are like those described for the genus. Rostrum (nasals, premaxillae, and maxillae) is elongate and narrow; nasals are evenly narrow for most of their length (Fig. 3). Braincase is rounded and ridges are absent. Frontals are constricted. Mastoid islands are large and located dorsally on the cranium between parietals, squamosals, and occipitals. Lateral processes of supraoccipitals are narrow and elongated.
Long, narrow, incisive foramina extend from anteriormost part of the maxillae; a narrow anterior section is separated from the wider, longer, posterior portion by an attachment of palatal process of premaxillae. Palate is short and narrow, extending posteriorally to about the posterior margins of M2. Posterior border of palate is rounded. Posterior palatal foramina are present as 2 small, separate entities. Pterygoids are delicate and adjacent foramina are large. Mesopterygoid fossa is narrow.
Bullae are inflated, covering the middle lacerate foramina. Bullae are large, relative to condylobasal length (0.286) and length of skull (0.292). Stapedial processes of bullae are complete, dividing the middle lacerate foramina into smaller (lateral) and larger (medial) foramina. Paraoccipital processes are broad, flattened, and fused to bullae.
Zygomatic arches are moderately expanded but do not extend beyond the greatest width of the skull. Zygomata are delicate; anterior ascending processes of the maxillae are reduced to slender struts; jugal parts of dorsal zygomatic bridges are reduced to ventral bases of bridges and, thus, jugals are well separated from lacrimals; there are no posterior projections of the jugals beyond the general curvature at back of the arches.
Lacrimal canals are open on rostrum near dorsal roots of zygomata. Ventral grooves in medioventral borders of infraorbital canals are absent. Anterior and posterior openings of alisphenoid canals are large.
Anterior portions of dentaries are narrowed. Inflected angles of mandible are well developed. Coronoid processes are reduced. Angular processes are elongate, slender, and delicate and are nearly parallel. Semilunar notches are widened. Rami lack ridges or grooves on their lateral surfaces.
Incisors are small, narrow, and short, opisthodont, and orangish in color. Upper toothrows are only slightly convergent anteriorly and could be considered more or less parallel. Cheek teeth are hypselodont (evergrowing). Occlusal surface of cheekteeth wears flat. Lophs of cheek teeth are transverse in orientation. Cusps of upper molars are opposite and compressed anteroposteriorly. Upper cheek teeth have a simplified occlusal pattern that is figure 8–shaped, each tooth deeply bisected by a hypoflexus and a metaflexus. The hypoflexus, larger than the metaflexus, extends about two-thirds the width of the tooth and is somewhat broad. A narrow bridge unites protocone and paracone to hypocone and metacone. The major cusps are not equal in size or shape. For M1 and M2, width across protocone and paracone is greater than distance across hypocone and metacone. Molariform teeth do not appear unusually broad. The M3 has a backwardly projecting heel (posteroloph) and a well-defined posteroflexus. Lower cheek teeth have a distinctly different and complex pattern from that of the upper cheek teeth; 1 labial and 2 deep lingual flexi are present, and spaces formed by these flexi are sharply angular. Length of maxillary toothrow is large relative to condylobasal length (0.238) and length of skull (0.243).
Abrocoma uspallata can be distinguished from all taxa considered by its grayer dorsal and whiter ventral coloration (except A. cinerea), longer tail (except A. budini, shorter, and A. famatina, about equal), larger hind foot, larger ears, narrower nasals, moderately expanded zygomatic arches (except A. cinerea), larger mastoid islands (except A. budini), narrower mesopterygoid foramen (except A. vaccarum), relatively larger bullae, wide and flattened paraoccipital processes, smaller incisors (except A. famatina), and relatively longer toothrow.
From A. budini, A. uspallata can be distinguished by nasal shape and size and shape of the molariform teeth. From A. cinerea and A. budini, A. uspallata can be distinguished by a palate with rounded rather than pointed posterior border. From A. cinerea, A. uspallata can be distinguished by the orientation of the zygomata and narrower interorbital region. Compared with A. schistacea and A. vaccarum, A. uspallata has less broad molars, more opisthodont incisors (A. schistacea), and darker-colored incisors (A. vaccarum).
Diploid number is 66; fundamental number could not be determined, although the majority of the chromosomes appeared to be metacentric or submetacentric.
Abrocoma uspallata has two sets of “vomerinelike” false teeth (Braun and Mares 1996). Pairs of fleshy papillae under the diastema were also reported for C. ashaninka (Emmons 1999). Whether these morphological oddities characterize the species or are present in other members of the family is unknown, as they cannot be observed on animals that have had the skull cleaned.
Specimens examined (1)
Argentina: Mendoza Province: Quebrada de la Vena, ca. 7 km SSE of the village of Uspallata, 32°39.405′S, 69°20.970′W, 1,880 ± 150 m, 1 (IADIZA-CM 6367 type).
Abrocoma budini Thomas, 1920
188.8.131.52 BMNH; skin and skull; adult male; obtained by E. Budin, field number 817, on 15 November 1919.
Otro Cerro, 3,000 m, Catamarca Province, Argentina.
Named for E. Budin, who collected the type specimen.
Known only from the type locality, but probably restricted to Sierra de Ambato, a mountain range in southeastern Catamarca Province, Argentina, and northeastern La Rioja Province, Argentina (Cabrera 1961; Fig. 2).
Amended diagnosis and description
Dorsum is uniformly brownish gray (near Ridgway's Drab), back slightly darker than the sides. Venter is grayish drab, hairs dark grayish or slate for about three-fourths of their length and tips pale drab. Hairs of sternal gland are white to the base, forming a white patch that contrasts with the surrounding coloration of venter. Chin is grayish white. Underside of neck is a stronger drab than other areas of venter. Hairs surrounding perianal region have buffy or whitish tips. Forefeet and hind feet are covered with whitish hairs. Tail is dark drab to grayish above and grayish white or whitish below. Of the species in the group, A. budini is the darkest both dorsally and ventrally. Like A. famatina, this species has a drab throat patch (description modified from Thomas 1920a).
Size is large; total length > 320 mm, length of head and body > 197 mm, length of tail > 130 mm, and length of hind foot > 29.5 mm (Table 1). Mean measurements for total length, length of head and body (except for A. vaccarum), length of tail, and length of hind foot are significantly greater (P < 0.05) than for all other species. Ratios of length of tail to total length and length of tail to length of head and body are greater than 40% and 66%, respectively. All other species, except A. famatina, have ratios that are smaller. When variances for length of ear are compared, A. budini is statistically different from A. cinerea, A. famatina, and A. schistacea.
Abrocoma budini is significantly larger than other species in the group for the following cranial characters (means or variances; Table 1): length of skull, condylobasal length, length of diastema, length of nasals (except A. schistacea), and length of mandible (except A. schistacea). It has significantly longer toothrows (maxillary and mandibular) and palate and wider zygomatic arches than A. famatina, but a significantly narrower interorbital breadth than A. cinerea.
Nasals are evenly narrow for about half to two-thirds their length and then become markedly convergent, ending in a point. Dorsal edge of zygoma is slanted outwards, so that medial edge is easily visible in dorsal view and anterior ascending maxillary portion of zygoma is thin. Zygomatic arches are expanded. Frontals are noticeably constricted. Posterior border of the palate is pointed. Mesopterygoid fossae are wide. Mastoid islands are large. Bullae are slightly inflated.
Incisors are broad, large, and opisthodont. Hypoflexus and metaflexus of upper molars are about equal in size and positioned more or less horizontally. Major cusps of upper molars are more rounded and less anteroposteriorly compressed. Major cusps are about equal in size and shape. Width across the protocone and paracone of M1 and M2 is about the same as distance across hypocone and metacone. Length of maxillary toothrow is small in relation to condylobasal length (X̄ = 0.212) and length of skull (X̄ = 0.203), similar to that of A. famatina and A. vaccarum, smaller than for A. cinerea and A. schistacea, and much smaller than that of A. uspallata.
Thomas (1920a:476) said of this species, “Caught among rocks, in the clefts of which it lives.”
Specimens examined (4)
Argentina: Catamarca Province: Otro Cerro, 3,000 m, 4 (BMNH 184.108.40.206 type, 220.127.116.11, 18.104.22.168, 22.214.171.124).
Argentina: Catamarca Province: Cerro Ambato (USNM 23641; Glanz and Anderson 1990).
Abrocoma famatina Thomas, 1920
126.96.36.199 BMNH; skin and skull; adult male; obtained by E. Budin, field number 960, on 19 March 1920.
La Invernada, Cadena Famatina, 3,800 m, La Rioja Province, Argentina.
Named for the Famatina mountain range.
Known from the Sierra de Famatina (Fig. 2). Cabrera (1961) suggested that this species might also occur in eastern portions of San Juan Province, and we assume he was referring to the Sierra del Valle Fertil or the Sierra Pie de Palo or both. However, these mountain ranges (Famatina, Valle Fertil, and Pie de Palo) are separated from each other by broad expanses of plains. To date no specimens of any Abrocoma are known from the latter areas.
Amended diagnosis and description
Dorsal coloration is grayish, with some brownish tints along midline and rump. Hairs of venter are gray basally with whitish or pale drabby tips; those of throat are a darker drab. Hairs of sternal gland are white to the base, forming a distinct white patch on the venter. Hairs of perianal region are whitish. Forefeet and hind feet are covered with white or whitish hairs. Tail is like dorsum above and whitish below. A. cinerea is generally lighter (grayer) in dorsal coloration, A. vaccarum is similar, and A. budini and A. schistacea are darker. Drab-colored throat patches are absent in all of the other species except A. budini (description modified from Thomas 1920b).
Size is medium; total length ranges from 277 to 299 mm, length of head and body ranges from 164 to 182 mm, length of tail from 108 to 117 mm, and length of hind foot from 28 to 29.5 mm (Table 1). The measurements (as seen in means or variances) for all external characters are significantly smaller (P < 0.05), compared with A. budini; total length, length of tail, and length of hind foot are significantly larger (P < 0.05), compared with A. cinerea. A. famatina has a significantly longer tail (P < 0.05) than A. vaccarum and longer hind feet than A. schistacea. Ratios of length of tail to total length (>38%) and length of tail to length of head and body (>61%) are similar to those given for A. budini, although A. budini is considerably larger in size. Thomas (1920b) stated that ears were smaller compared with other species that had been described at the time (in the cinerea group, A. budini and A. cinerea), but we found only the difference from A. budini to be significant (Table 1).
Abrocoma famatina is significantly smaller than A. budini for all cranial characters (Table 1) except breadth of braincase, interorbital breadth, and width of bullae. Compared with A. cinerea, it has a significantly smaller condylobasal length, diastema length, maxillary toothrow length, interorbital breadth, and bullae width. This species is also significantly smaller than A. schistacea for condylobasal length, length of nasals, maxillary toothrow length, and length of mandibular toothrow.
Nasals are slightly wider at midlength and taper posteriorly. Dorsal edges of zygoma are slanted outwards, so that the medial edges are easily visible in dorsal view, and anterior ascending maxillary portions of the zygoma are thin. Zygomatic arches are expanded. Frontals are noticeably constricted. Mastoid islands are medium in size. Mesopterygoid fossae are wide. Posterior border of palate is rounded. Bullae are inflated.
Incisors are narrow, small, and opisthodont to orthodont. Length of maxillary toothrow medium in relation to condylobasal length (X̄ = 0.215) and length of skull (X̄ = 0.203) are about equal to that of A. budini, A. famatina, and A. vaccarum, smaller than for A. cinerea and A. schistacea, and much smaller than for A. uspallata.
This species “lives under rocks and in their clefts and fissures” (Thomas 1920b:419).
Specimens examined (6)
Argentina: La Rioja Province: Famatina, 1 (MACN 27.55); La Invernada, Cadena Famatina, 3,800 m, 5 (BMNH 188.8.131.52 type, 184.108.40.206, 220.127.116.11, 18.104.22.168, 22.214.171.124).
Abrocoma schistacea Thomas, 1921
126.96.36.199 BMNH; skin and skull; adult female; obtained by E. Budin, field number 1296, on 29 January 1921.
Los Sombreros, Sierra Tontal, 2,700 m, San Juan Province, Argentina.
We are unclear as to the etymology of the specific epithet. However, schistos (Greek) means split or divided.
Known only from the Sierra del Tontal (Fig. 2). Thomas (1921a) and Cabrera (1961) restricted the distribution of this species to southern San Juan Province, including localities of Pedernal and Sierra Tontal.
Amended diagnosis and description
Dorsal coloration grayish drab, slightly darker along the midline. Hairs of venter are grayish basally for most of their length with tips whitish; venter similar to but paler than the dorsum. Sternal gland, which is covered by hairs white to their bases, is apparent as a distinct patch on venter. Whitish hairs surround perianal region. Dorsal surface of tail is like the midline of the dorsum; tail below is whitish yellow. Forefeet and hind feet are covered with whitish hairs. All other species except A. budini are lighter in dorsal and ventral coloration. This species lacks the drab throat patch that is present in A. budini and A. famatina (description modified from Thomas 1921a).
Size is medium to large; total length ranges from 257 to 312 mm, length of head and body ranges from 160 to 196 mm, length of tail from 96 to 120 mm, and length of hind foot from 24.9 to 30.0 mm (Table 1). Compared with A. budini, all external characters are significantly smaller (P < 0.05). Compared with A. cinerea, measurements for total length, length of tail, and length of hind foot are significantly greater (P < 0.05). A. famatina has a larger hind foot. Mean ratios of length of tail to total length (37%) and length of tail to length of head and body (59%) are similar to those for A. vaccarum and A. uspallata.
Abrocoma schistacea is significantly smaller than A. cinerea for interorbital breadth. Condylobasal length, length of nasals, length of maxillary toothrow, and length of mandibular toothrow are significantly larger than for A. famatina. A. budini is larger in length of skull, condylobasal length, and length of diastema, but smaller in length of maxillary toothrow.
Nasals are slightly wider at midlength and taper posteriorly. Dorsal edge of zygoma is slanted outwards, so that medial edge is easily visible in dorsal view, and anterior ascending maxillary portion of the zygoma is thin. Zygomatic arches are expanded. Frontals are noticeably constricted. Mastoid islands are of medium size. Posterior border of palate is rounded. Mesopterygoid fossae are wide. Bullae are slightly inflated.
Incisors are broad, large, and more orthodont than observed in other species in the group. Molariform teeth appear broad. Hypoflexus appears to have a slightly narrower breadth than in other species. Length of maxillary toothrow is medium in relation to the condylobasal length (X̄ = 0.229) and length of skull (X̄ = 0.211) is about equal to that of A. cinerea, larger than for A. budini, A. famatina, and A. vaccarum, and much smaller than for A. uspallata.
Specimens examined (16)
Argentina: San Juan Province: Los Sombreros, Sierra Tontal, 2,700 m, 8 (BMNH 188.8.131.52 type, 66.1933, 184.108.40.206, 220.127.116.11, 18.104.22.168, 22.214.171.124, 126.96.36.199, no number); Pedernal, 1,200 m, 4 (BMNH 188.8.131.52, 184.108.40.206, 220.127.116.11, 18.104.22.168); Sierra Tontal, 4 (BMNH 22.214.171.124, 126.96.36.199, 188.8.131.52, 184.108.40.206).
Argentina: Los Sombreros, Sierra Tontal (USNM 46157; Glanz and Anderson 1990).
Abrocoma vaccarum Thomas, 1921
220.127.116.11 BMNH; skin and skull; adult female; obtained by E. Budin, field number 1364, on 12 March 1921.
Punta de Vacas, 3,000 m, Mendoza Province, Argentina.
Named for type locality. From the Latin vacca, cows, + arum, genitive plural.
Known only from type locality (Fig. 2). Thomas (1921a) gave distribution as encompassing northwestern Mendoza Province, Argentina, although the only known specimens were from the type locality. Cabrera (1961) extended the distribution to include southwestern San Juan Province, although no specimens of this species are known from San Juan Province.
Amended diagnosis and description
Dorsal coloration, including tail above, grayish with some brownish tints, especially along midline and rump. Hairs of venter are gray basally for most of their length, with tips whitish. Sternal gland is covered with hairs that are white to the base; because overall appearance of venter is grayish white, this patch is distinct. Forefeet and hind feet are covered with whitish hairs. Perianal region is surrounded by whitish hairs. Dorsal coloration of tail like that of dorsum; tail is white below. Other species, except A. cinerea, are darker in dorsal coloration and present appearance of a less whitish venter. A. budini and A. famatina also exhibit drab-colored throat patches (Table 1; description modified from Thomas 1921a).
Size is medium; total length ranges from 259 to 285 mm, length of head and body ranges from 165 to 191 mm, length of tail is 94 mm, length of hind foot ranges from 27.3 to 28.0 mm, and length of ear ranges from 25.0 to 27.0 mm (Table 1). Measurements for total length, length of tail, and length of the hind foot are significantly smaller (P < 0.05) than for A. budini; length of tail is significantly larger and smaller (P < 0.05), compared with A. cinerea and A. famatina, respectively. Although Thomas (1921a) found length of the ear to be larger than that for other species in the group, we found no statistical differences; however, we do note that mean and the range are among the highest values for animals examined. Mean ratios of length of tail to total length (35%), and length of tail to length of head and body (53%) are similar to those for A. schistacea and A. uspallata.
Abrocoma vaccarum is significantly smaller than A. budini for the following characters (Table 1): length of skull, condylobasal length, length of diastema, length of nasals, and length of mandible. It is smaller than A. cinerea in interorbital breadth.
Nasals are slightly wider at midlength and taper posteriorly. Dorsal edge of zygoma is slanted outwards, so that the medial edge is easily visible in dorsal view, and the anterior ascending maxillary portion of zygoma is thin. Zygomatic arches are expanded. The frontals are noticeably constricted. Mastoid islands are medium in size. Posterior border of palate is rounded. Mesopterygoid fossae are narrow. Bullae are slightly inflated.
Incisors are broad, large, opisthodont to orthodont, and white to a very pale orange. The molariform teeth appear slightly broader compared with those of the other species, except A. schistacea. Length of maxillary toothrow medium in relation to the condylobasal length (X̄ = 0.211) and length of skull (X̄ = 0.197) is about equal to that of A. budini and A. famatina, smaller than for A. cinerea and A. schistacea, and much smaller than for A. uspallata.
Specimens examined (2)
Argentina: Mendoza Province: Punta de Vacas, 3,000 m, 2 (BMNH 18.104.22.168, 22.214.171.124 type).
South America's extraordinary mammalian fauna includes a number of complex taxa that over the years have had their taxonomy uncritically simplified by being lumped into broadly inclusive species. Such was the case, for example, with Eligmodontia, which was suggested to be a single species (Hershkovitz 1962) based on study of a few specimens, but that contains at least three (e.g., Hillyard et al. 1997; Sikes et al. 1997) and possibly many more. Similarly, the genus Akodon has had numerous named species placed in synonymy; for example, Cabrera (1961) recognized only 38 species. However, recent research, as reflected by the most recent listing of mammalian species (Musser and Carleton 1993; 45 species recognized) suggests that this genus is quite complex, being more like Thomas's many species, rather than Cabrera's fewer species. As taxonomic information accrues on South America's mammals, and as more specimens are collected, and their morphology, cytogenetics, and molecular biology are examined, the number of valid species is continuing to increase. Thus, we are not surprised to find that Abrocoma is also proving to be a complex genus containing a number of species.
Given the age (Glanz and Anderson 1990) and distribution of the genus, it might be expected that numerous species would exist. First, the abrocomids are an old group, with fossils known as early as the Huayquerian in the Argentine provinces of Mendoza and Catamarca (6 million years of age, about equal to the late Miocene of North America; Marshall and Patterson 1981; Spencer 1987). Thus, they were present just after the major Andean uplift of the Mio-Pliocene (Mares 1985) took place. The Andes are characterized by numerous geological components that form isolated mountain ranges (e.g., Sierra de Famatina, Sierras Pampeanas, and Sierra de Ambato), enclosed valleys, and significant habitat islands ranging from salt flats to rocky cliffs. The A. cinerea complex is generally highly specialized for life in rocky cliff faces, and the species show many adaptations for a saxicolous existence (Braun and Mares 1996; Mares 1997), including specializations of the feet. Curiously, A. cinerea may not be as closely allied to rock habitats as the other species in the group, being perhaps what could be characterized as an altiplano specialist that includes rocks within its preferred microhabitat (Fig. 2). The rock fissures that are inhabited by A. uspallata are largely inaccessible to other mammals, and their crystalline fecal and urine piles (middens) suggest great age and fidelity to particular crevices. This would indicate that they are quite restricted as to habitat and unlikely to be found in areas lacking rocks. We have observed that the rock faces that are inhabitable by the species are themselves of limited extent; so we expect that the animals would be quite localized in valleys that are isolated from the main cordillera.
In our earlier paper (Braun and Mares 1996), we assumed that the specimen we collected in Mendoza was A. vaccarum, because the type locality for A. vaccarum is about 50 km distant, although it is at a much higher elevation (about 1,900 m for A. uspallata versus about 3,000 m for A. vaccarum). When we visited the type locality of A. vaccarum, it was clear that the habitats of the 2 localities were very different. A. vaccarum occurs in the short grass and low shrub vegetation of the puna-like high Andean habitat of Mendoza Province, quite different from the Monte Desert habitat (Precordillera) of A. uspallata, with such characteristic desert shrubs as creosote bush (Larrea divaricata, L. cuneifolia, and L. nitida), palo verde (Cercidium microphyllum), and various cacti. Indeed, A. uspallata appears to be a specialist on creosote bush (one of the few such specialists known), suggesting a long association with this Monte Desert plant that is noted for its hundreds of toxic compounds (Mabry et al. 1977).
The fact that the various members of the cinerea complex (excluding A. cinerea) appear to be limited to isolated patches of rocky habitat along the Precordillera and Sierra Pampeanas chains would indicate a classic allopatric pattern of speciation. The saxicolous specializations, as well as possible dietary specializations, suggest that the species are likely quite localized, with dispersal events being uncommon. This would lead to rapid isolation of populations that were able to colonize habitats during periods of climatic change, when ranges might have been more extensive. However, even during periods of increased or decreased aridity, the animals require rocks for successful persistence in a region. Given specialization for rock habitat of the isolated mountains, although the putative ancestor or ancestors may have been less dependent on rock substrate, and in this regard more similar to A. cinerea, a series of species would be expected to have developed along the Andes wherever suitable rocky areas happened to be colonized by the animals.
We have recognized Thomas's original species as being valid and have named a new species from an unusually isolated arid valley. This recommendation, based on character evaluation and geographic separation, is also consistent with a general pattern observed for other taxa from the same or similar localities. We fully expect that additional fieldwork in this largely unstudied area will yield additional species in this genus. Abrocoma appears to be an ideal taxon to examine adaptation, speciation, and differentiation. Using molecular techniques, it should be possible to discern phylogenetic relationships of the taxa and the timing of the pattern of colonization and speciation and to relate this to orographic and climatological events in the Andean Cordillera, Precordillera, and Sierra Pampeanas. We also expect that the most basal species will be one that is less dependent on rock substrate. However, the ecology of the animals remains unstudied.
El género Abrocoma (familia Abrocomidae) se distribuye desde el sur de Perú y norte de Chile hasta Bolivia, y hacia el sur alcanza la región centro-oeste de la provincia de Mendoza, Argentina. La sistemática del género es probremente conocida. Originalmente, se describieron diez taxa pero posteriormente fueron sinonimizadas en dos especies, cinco taxa fueron incluidas en A. cinerea y cinco en A. bennetti. Una tercer especie, A. boliviensis, fue descripta en 1990, y un nuevo género y especie, Cuscomys ashaninka, fueron descriptos en 1999. Se reevalua la sistemática del complejo de especies dentro de Abrocoma cinerea, con énfasis en especímenes de Argentina, usando morfología externa, craneana y dentaria. Se describe una nueva especie procedente de la provincia de Mendoza, Argentina. Se presentan cariotipos y se discute sobre aspectos tales como comportamiento, hábitat e historia natural.
We thank S. Adams for his help in the field during 1995 and J. Suarez for providing us with locality information of Abrocoma in Mendoza Province. Fieldwork was supported by grants from the National Science Foundation (BSR-8906665) and the National Geographic Society (4820-92) to M. A. Mares and a grant from the University of Oklahoma Research Council to J. K. Braun and M. A. Mares. A Fulbright Research Fellowship to J. K. Braun facilitated the examination of specimens in Argentina. We acknowledge the Argentine Fulbright office gratefully for their support. Various aspects of this research and computational facilities were provided by the Sam Noble Oklahoma Museum of Natural History. We acknowledge R. M. Barquez, P. Capllonch, R. A. Ojeda, and S. Ojeda for their help and hospitality. The Instituto para la Administración de Areas Naturales Protedigas “Dr. Claes Ch. Olrog,” the Instituto Miguel Lillo, the Universidad Nacional de Tucumán, and the Instituto Argentino de Zonas Aridas (IADIZA) provided research facilities. Curators at several museums graciously allowed us to examine specimens in their care: P. Jenkins (BMNH), R. M. Barquez (CML), R. A. Ojeda (IADIZA-CM), and M. Piantanida (MACN). Comments by M. D. Carleton greatly improved the manuscript.
Specimens examined but not identified
A list of specimens that were examined but that could not be identified with confidence due to lack of data, or questionable data, for locality, external measurements, or craniodental measurements follows.
Argentina: La Rioja? (MACN 49.247, 49.248); La Rioja (MACN 24.5); San Juan (MACN 39.758, 39.759); San Juan Province: San Guillermo, 1 (MACN 18828). Locality unknown (MACN 26.117, 41.292–41.317).