ARTICLE IN PRESS

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Original investigation New data of the long-clawed mouse Pearsonomys annectens (Cricetidae, Sigmodontinae) and additional comments on the distinctiveness of Pearsonomys

By G. D’Elı´a, Agustina A. Ojeda, F. Mondaca and M.H. Gallardo Seccio´n Evolucio´n, Facultad de Ciencias, Montevideo, Uruguay; Grupo de Investigacio´n en Biodiversidad, Instituto Argentino de Investigaciones de Zonas A´ridas, Mendoza, Argentina; and Instituto de Ecologı´ay Evolucio´n, Universidad Austral de Chile, Valdivia, Chile

Receipt of Ms. 28.12.2004 Acceptance of Ms. 26.8.2005

Abstract The monotypic genus Pearsonomys is one of the least studied sigmodontine genera, so far known only from its holotype. We record four new localities from the Regio´n de Los Lagos (southern Chile) for P. annectens expanding its known distribution by approximately 217 km. Next, we present a phylogenetic analysis based on nuclear DNA sequences aimed to test the phylogenetic position of Pearsonomys. Results of this analysis corroborate that Pearsonomys belongs to the abrotrichine radiation being sister of Geoxus. Subsequently, we provide descriptions of P. annectens molars (tetralophodont pattern with reduced mesoloph/id), penis (complex type), stomach (unilocular- hemiglandular), and karyotype (2n=56; FN=62). The discussion of these new data is framed according the results of the phylogenetic analysis. r 2005 Deutsche Gesellschaft fu¨r Sa¨ugetierkunde. Published by Elsevier GmbH. All rights reserved.

Key words: Pearsonomys, rodentia, Chile, valdivian forest

Introduction The sigmodontine genus Pearsonomys, Patter- nature of the holotype, an old adult son 1992 belongs to a recently recognized male with advanced tooth wear, few radiation of mostly central and southern details were provided about its dental mor- Andean genera of the New World endemic phology. Similarly, the karyotype of P. subfamily Sigmodontinae, for which the annectens is so far unknown. Remarkably, informal name of ‘‘Anden clade’’ or abjro- other than the original description, only one trichines was coined (Smith and Patton 1999; additional study has analyzed samples of see also D’Elia 2003). Pearsonomys; this was a study based on Currently Pearsonomys encompass only one cytochrome b gene sequences aimed to assess species, P. annectens, Patterson 1992, which sigmodontine phylogenetic relationships was described on the basis of one specimen (Smith and Patton 1999). Consequently, of from the area of Mehuı´ n in the southern all abrotrichine genera, Pearsonomys is by far Chilean province of Valdivia. Due to the the least known; indeed, it is one of the least

1616-5047/$ - see front matter r 2005 Deutsche Gesellschaft fu¨r Sa¨ugetierkunde. Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.mambio.2005.08.004 Mamm. biol. ] (]]]]) ] ]]]–]]] ARTICLE IN PRESS

2 G. D’Elı´aetal. studied genera of the entire sigmodontine Applied Biosystems). Sequencing reactions were radiation. run in an ABI 377 automated sequencer. In all With the goal of partially filling the gap on cases, both heavy and light DNA strands were our knowledge about the long-clawed mouse sequenced. Sequences of both strands were recon- ciled using Sequencer Navigator version 1.0.1 P. annectens, the aim of this study was to (Applied Biosystems). All sequences were deposited present new recording localities for this in GENBANK (Table 1). Sequence alignment was species, provide a description of its dentition, carried out with the program Clustal X (Thompson penis, stomach, and karyotype, as well as et al. 1997), by using the default values for all present a phylogenetic analysis based on alignment parameters. Aligned sequences were nuclear DNA sequences aimed to test the subjected to maximum parsimony analysis (MP; phylogenetic position of this taxon. Farris 1982; Kluge and Farris 1969). Characters were treated as unordered and equally weighted. PAUP* 4 (Swofford 2000) was used to perform 200 replicates of heuristic searches with random addi- Material and methods tion of sequences and tree bisection-reconnection branch swapping. Two measures of topology All voucher specimens, tissue samples, and cell support were carried out. First, 1000 parsimony suspensions are housed at the mammal collection jackknife replications (JK; Farris et al. 1996) with of the Instituto de Ecologı´ a y Evolucio´ ndela three addition sequence replicates each, the dele- Universidad Austral de Chile, Valdivia, Chile tion of one-third of the character data, and (IEEUACH). Measurements, sex, and locality data MAXTREE set to 5000 were performed. Branches were recorded from specimen tags. Geographic with less than 50% of support were allowed to distances were estimated, on the basis of the collapse. Second, Bremer support values (BS; latitude and longitude data recorded in specimen Bremer 1994) were computed for each node in tags. PAUPÃ using command files written in TreeRot version 2 (Sorenson 1999).

Phylogenetic analysis We have included representatives of all sigmodon- Karyotypic analysis tine tribes as well as several sigmodontine genera Four specimens (IEEUACH 1064, 1745, 3851, whose phylogenetic relationships are not clear (see 7057) of P. annectens were karyotyped using D’Elı´ a 2003). Considering previous findings that standard chromosome techniques. Mitotic meta- place Pearsonomys within the abrotrichine group phases from direct bone-marrow were obtained (Smith and Patton 1999), taxonomic coverage is following a colchicine-hypotonic technique (Verma particularly broad with regards to abrotrichine and Babu 1995). Bone marrow was incubated in taxa, for which, when possible, more than one 0.1 ml (0.05%) colchicine plus 9.9 ml KCl (0.075 M) individual per species was included. We have for 40 min at 371C and subsequently fixed in 3:1 included outgroups (Nixon and Carpenter 1993) methanol: glacial acetic acid. Non-differential that are representative of each of the other primary chromosome staining was performed in phos- clades that, together with the subfamily Sigmo- phate-buffered Giemsa (pH=6.8). Ten metha- dontinae comprise the family Cricetidae (Steppan phases spreads were counted for each specimen. et al. 2004). A fragment of 1186 bp of the first exon Fundamental Numbers (FN) refers only to auto- of the nuclear gene Interphotoreceptor Retinoid somes (Patton 1967). Binding Protein (hereafter IRBP) was used as evidence for the phylogenetic analysis. For some specimens a shorter fragment was used. Specimens Morphology included in the phylogenetic analysis, and source and length of their sequences are listed in Table 1. Dental description followed Reig (1977) and was IRBP sequences acquired here were amplified and based on three specimens (IEEUACH 1063, 1745, sequenced in one or two fragments using the 3851) from Fundo San Martin, Valdivia Province primers A1–F1 and E1–D reported by Jansa and (see below). Penis description followed Hopper and Voss (2000) and following a protocol presented by Musser (1964) and was based on excised phalli these authors. Negative controls were included in from four formalin-preserved specimens all experiments. Amplification products were se- (IEEUACH 5427, 5461, 5463 5464). A ventral cut quenced in both directions with the amplification exposed the urethral processes and the anterior primers and dye-labeled nucleotides (Big Dye, mounds of the baculum; a second cut exposed the ARTICLE IN PRESS

New data of Pearsonomys annectens (Sigmodontinae) 3

Table 1. Species included in the phylogenetic analysis (1–32: ingroup; 33–39: outgroup). GENBANK accession numbers are provided for all sequences; for those shorter than 1186 bp their length is indicated between parentheses. For the sequences acquired in this study catalog numbers and the localities of the corresponding specimens are provided. An * indicates sequences whose first 747 bp (approximately) were acquired in D’Elı´a (2003) and completed here. An # indicates sequences completely acquired here. Voucher specimens for the individuals whose sequences were partially or completely acquired in this study are catalogued in the following collections: Argentina, Coleccio´n de Mamı´feros del Centro Nacional Patago´nico (CNP); Chile, Coleccio´nde Mamı´feros del Instituto de Ecologı´a y Evolucio´n, Universidad Austral de Chile (IEEUACH); United States, Museum of Vertebrate Zoology, University of California, Berkeley (MVZ).

Species Catalog number Locality Source

1 Abrothrix andinus AY277418 (747) 2 Abrothrix longipilis AY277419 (747) 3 Abrothrix longipilis AY163577 4 Abrothrix jelskii AY277442 (747) 5 Abrothrix olivaceus AY277420 (747) 6 Abrothrix olivaceus CNP 813 Argentina, Neuque´n, Volca´n ÃAY277421 Tromen 7 Akodon azarae AY163578 8 Bibimys chacoensis CNP 756 Argentina, Chaco, Dpto. ÃAY277435 Bermejo, Cancha Larga S2710403700 W5814305100 (1078) 9 Blarinomys breviceps CIT 1391 ÃAY277437 10 Calomys lepidus AY163580 11 Chelemys macronyx CNP 753 Argentina, Neuque´n, Laguna DQ069311 Epulafquen S3614901000 W7110404700 # (746) 12 Chelemys macronyx MVZ 155800 AY277441 (747) 13 Delomys sublineatus AY163582 14 Geoxus valdivianus CNP 812 Argentina, Neuque´n, Caviahue ÃAY277448 S3715302500 W7110304700 15 Holochilus chacarius AY163586 16 Irenomys tarsalis AY163587 17 Juliomys pictipes AY163588 18 Nectomys squamipes AY163598 19 Notiomys edwardsii AY163602 20 Oligoryzomys nigripes AY163612 21 Oryzomys AY163621 megacephalus 22 Oxymycterus nasutus MVZ 182701 Uruguay, Maldonado, El ÃAY277468 Pen˜asco 23 Pearsonomys IEEUACH #AY851749 annectens 7056 (1127) 24 Phyllotis xanthopygus AY163632 25 Reithrodon auritus AY163634 26 Rheomys raptor AY163635 27 Rhipidomys nitela AY163636 28 Scapteromys tumidus AY163637 ARTICLE IN PRESS

4 G. D’Elı´aetal.

Table 1 (continued )

Species Catalog number Locality Source

29 Scolomys ucayalensis AY163638 30 Sigmodon alstoni AY163640 31 Thomasomys baeops AY163642 32 Wiedomys pyrrhorhinos AY163644 34 Cricetulus AY326082 longicaudatus 35 Microtus sikimensis AY163593 36 Neotoma lepida AY163599 37 Peromyscus AY163630 maniculatus 38 Scotinomys teguina AY163639 39 Tylomys nudicaudus AY163643

baculum and its anterior processes. Double stain- Rosa, Valdivia Province (391480S, 731140W). ing with alcian blue and alizarin red (Wassersug One specimen is known from this locality, 1976) was conducted on some specimens. Stomach located approximately 41 km to the south of description followed Carleton (1973) and was the type locality. (3) Comuy, Cautin Province based on eight specimens (IEEUACH 3132, 3851, (391040S, 731000W). One specimen is known 5461, 5462, 5463, 5464, 5465, 7140). As in Carleton (1973) excised stomachs were bisected along a from this locality, which is the most northern plane horizontal to the longitudinal body axis; the one known and is approximately 43 km to the descriptions are based on the dorsal half. north of the type locality. (4) Bahı´ a San Pedro, Osorno Province (401540S, 731530W). One specimen is known from this locality that is the most southern one, located Results and discussion approximately 174 km south of the type Distribution locality. Measurements of the specimens which are the basis of this study are provided Pearsonomys annectens is a species so far in Table 2. All known localities (the type known only from the type locality (Near locality and the four reported here) of P. Mehuı´ n, 42 km Nand slightly E of Valdivia, annectens lie in the coastal mountain range 0 Regio´ n de Los Lagos, Chile; 39126 S, within the unique Valdivian temperate rain- 0 73110 W; Patterson 1992). The following four forest. This forest is characterized by ever- localities (Fig. 1), all in southern Chile, green and a few deciduous trees, which grow constitute new records for P. annectens, and in conditions of high annual rainfall are based on specimens collected since 1982; (1500–3000 mm), wet and frost-free winters, those individuals collected prior the descrip- and short dry summers (see details in Muru´ a tion of P. annectens were originally identified et al. 1987). Additional studies, which should as Geoxus sp. (1) Fundo San Martı´ n, include more field work, are needed to clarify 0 0 Valdivia Province (39138 S, 73111 W). This if P. annectens is restricted to the coastal locality is located approximately 22.5 km range, and, if that proves to be the case, to south of the type locality. With 17 collected clarify if this is a relict of a formerly larger specimens, Fundo San Martin is the locality distribution as suggested by Patterson (1992). from which the most P. annectens specimens are known. When describing P. annectens Patterson (1992) suggested that it may occur Phylogenetic analysis at this locality. The two specimens phylogen- etically analyzed by Smith and Patton (1999) The IRBP data set has 446 variable sites. come from this locality. (2) Fundo Santa Amount of observed sequence variation ARTICLE IN PRESS

New data of Pearsonomys annectens (Sigmodontinae) 5

Fig. 1. Map of southern Chile showing recorded populations of Pearsonomys annectens: (1) Fundo San Martı´n, (2) Fundo Santa Rosa, (3) Comuy, (4) Bahı´a San Pedro, (5) Mehuı´n (type locality; Patterson, 1992). See text for locality details.

Table 2. Measurements of the P. annectens reported in this study sorted by collecting localities. Data were taken from specimen tags and field catalogs. For each sample and variable, sample sizes (between parenthesis), medium values, and range are provided. Measurements of the type locality specimen correspond to the holotype (Patterson 1992).

Locality Length Tail Foot Ear Weight

Type locality (1) (1) (1) (1) (1) 201 77 27 19 58.5 Fundo San Martı´n (13) (16) (16) (13) (12) 184.7 77.2 26.6 17.1 34.2 122–215 38–95 19–30 11–21 15.5–50 Fundo Santa Rosa (1) (1) (1) (1) (1) 201 71 28 20 61 Comuy (1) (1) (1) (1) (1) 190 78 25 18 42 Bahı´a San Pedro (1) (1) (1) (1) (1) 208 82 26 19 48 ARTICLE IN PRESS

6 G. D’Elı´aetal. between specimens pairs are low. Our data (JK=100; BS=8). It is formed by Abrothrix set allows three intraspecific comparisons; (including Chroeomys), Chelemys, Geoxus, these values range from 0% (Chelemys Notiomys and Pearsonomys; all genera tradi- macronyx) to 0.27% (Abrothrix olivaceus). tionally considered to be akodonts, and in Comparisons between sigmodontine species some cases even synonyms of Akodon (Reig range from 0.27% (P. annectens vs. Geoxus 1987). The abrotrichine group, also referred valdivianus) to 7.4% (Zygodontomys brevi- as ‘‘Andean clade’’, has been ranked at the cauda vs. Rheomys raptor). Comparisons tribal level by Smith and Patton (1999); these involving P. annectens range from 0.27% authors also indicated that an adequate name (G. valdivianus) to 6.0% (Sigmodon alstoni). for it would be Abrotrichini. However, it Overall 223 sites are phylogenetically infor- must be noted that the group lacks a formal mative. Six-hundred and seven equally most definition and diagnosis. These two issues are parsimonious cladograms of 840 steps re- the focus of an upcoming contribution. sulted from the analysis of this data-set. They Within the abrotrichine radiation Pearson- have an ensemble consistency index (CI) of omys is sister to Geoxus. This relationship, 0.655 and a retention index (RI) of 0.610. The which is weakly supported (JK=66; BS=1), strict consensus of these 607 trees is por- provides support for the phenetic observation trayed in Fig. 2, and defines 22 nodes that pointed to Geoxus as the closest relative belonging to the sigmodontine clade. Support of Pearsonomys (Patterson 1992). In addi- for these nodes is highly variable; bremer tion, our analysis corroborates the previous support values (BS) range from 1 to 18, and finding of Smith and Patton (1999) who in a jackknife support values (JK) range from equally weighted maximum parsimony 53% to 100%. Sigmodontinae appears to be analysis and in a maximum likelihood well supported (JK=100%, BS=18). The analysis of cytochrome b gene sequences also most basal dichotomy within the sigmodon- found a clade composed by Pearsonomys and tine clade leads to Sigmodon and Rheomys on Geoxus. one hand and to a clade composed of all other sigmodontines on the other (Fig. 2). At the base of the ‘‘all sigmodontines less Karyotype Sigmodon–Rheomys’’ clade there is a large Pearsonomys annectens has a diploid number polytomy encompassing eight sigmodontine of 56 chromosomes and a fundamental clades. Three of these eight clades are number of 62 arms (Fig. 3). The karyotype monogeneric, four other clades are groups is formed by one pair of large subtelocentric of genera that correspond to classic sigmo- chromosomes, 23 pairs of medium to small- dontine tribes (e.g., akodontines, abrotri- sized acrocentric chromosomes (pairs 2–24), chines, oryzomyines, and phyllotines), and three pairs of small metacentric chromo- the last one is formed by Irenomys and somes (pairs 25–27), and a pair of sexual Juliomys. Because of the broad taxonomic chromosomes. The submetacentric X chro- coverage of this study, and the complex mosome is the largest chromosome of the taxonomic history of the group, several whole complement, whereas the Y chromo- features of the consensus tree deserve discus- some is a small subtelocentric. sion. However, here we concentrate on Based on information summarized by Reig Pearsonomys and its relationships to other (1987) for several abrotrichine taxa (Abro- abrotrichines. For discussions of the other thrix spp., C. macronyx, G. valdivianus; clades we refer the reader to Smith and Bianchi et al. 1971; Gallardo 1982; Pearson Patton (1999), D’Elı´ a (2003), D’Elı´ a et al. 1984) and data provided by Liascovich et al. (2003), and Weksler (2003). (1989) for A. illuteus and Spotorno et al. IRBP-based results corroborates the cyto- (1990) for additional species of Abrothrix,a chrome b gene-based hypothesis of Smith and diploid number of 2n=52 has been suggested Patton (1999) of Pearsonomys being a mem- as synapomorphy for the abrotrichine group ber of the abrotrichine clade. This natural (Smith and Patton 1999). Unfortunately, the group is highly supported by IRBP analysis karyotype of Notiomys edwardsii remains ARTICLE IN PRESS

New data of Pearsonomys annectens (Sigmodontinae) 7

Fig. 2. Strict consensus tree of the 607 most parsimonious trees (length 840, CI=0.655, RI=0.610) obtained in the maximum parsimony analysis of IRBP gene sequences. Numbers above branches indicate parsimony jackknife (left of the diagonal) and Bremer support (right to the diagonal) values of the nodes at their right. Only jackknife values above 50% are shown. A=common ancestor of the abrotrichine group. ARTICLE IN PRESS

8 G. D’Elı´aetal.

Fig. 3. Non-differentially stained karyotype of Pearsonomys annectens (male, IEEUACH 1745) from Fundo San Martin (see text for locality details); 2n=56, (aFN=62). unknown. However, unpublished results of primary cusps by a wide connecting mure and M. Gallardo show that some abrotrichine lacks an anteroflexus. The procingulum pre- taxa depart from a 2n=52, and also that sents a shallow anteromedian flexus, which some exhibit chromosomal variation. These disappears as tooth wear advances. The facts together with our report of a 2n=56 for anteromedian flexus divides the procingulum P. annectens indicate that a 2n=52 is not a in two conules; the anterolingual conule is diagnostic character of the abrotrichine slightly larger than the anterolabial one. The group. Further studies are needed to assess protocone and paracone are equal in size. abrotrichine chromosome evolution. Similarly, the hypocone and the metacone are equal in size. In young individuals a small mesoloph (but see also Hershkovitz 1993), Morphology which is fused to the paracone, can be Teeth are similar to those of Geoxus (Fig. 4). distinguished. Mesostyle and enterostyle are The upper and lower incisors are delicate. missing. The posteroloph is short and fused The upper incisors, which are orthodont in with the metacone; there is not posteroflexus. orientation and lack any trace of grooves on The M2 has four main cusps arranged in two the anterior surface, are pale orange; lower pairs. The protocone and paracone are incisors are much paler. Molar series are slightly larger than the hypocone and meta- long, narrow, and with simple occlusal cone. The M3 is simple and strongly reduced surfaces, which become even more simplified (less than 2/3 the length of M2) displaying a with wear (see Fig. 1 in Patterson 1992). cilindrodont pattern; the mesoflexus persists Upper molars are crested, with labial cusps as a small fossete. Lower molars are crested slightly taller than lingual cusps. The ar- and transversally compressed, with flexids rangement of the main cusps is opposite. oriented slightly backward. In m1 a shallow Flexi from opposite sides do not reach each anteromedian flexid is present; the anterola- other, and are perpendicular to the main bial and anterolingual conulids are subequal molar axis. The M1 is large. The procingu- and determine a well developed and quadrate lum is distinct, large and attached to the procingulum; an anterolabial cingulum is ARTICLE IN PRESS

New data of Pearsonomys annectens (Sigmodontinae) 9

Fig. 4. Pearsonomys annectens (IEEUACH 3851) molar occlusal views: upper (left) and lower (right) molar series. Scale bar=1 mm. present. The metaconid is anterior to the crater. The urethral flaps are relatively large; protoconid. The hypoflexid is wide. The each bearing at their distal end a medially entoflexid is large. There is not mesolophid. directed spine. The gland penis has three The entoconid is anterior to the hypoconid; digits; the central one is larger than both the posterolophid is well developed and laterals and its tip protrudes from the crater. slightly transverse. In m2 the protoconid is The baculum is ventrally keeled with a clearly larger than the hypoconid; the poster- rounded and prominent head. The base of olophid is well developed. The mesolophid is the bone resembles an equilateral triangle not present. The m3 is shorter than m2; the that possesses a notch on its proximal face. protoconid is large and the hipoflexid is wide. Digits are cartilaginous. Overall, the penis of The penis of P. annectens has a prominent P. annectens resembles much that of G. dorsal hood that extends beyond the terminal valdivianus (reported as Notiomys valdivianus ARTICLE IN PRESS

10 G. D’Elı´aetal. in Hopper and Musser 1964). The presence of corpus, respectively. However, the glandular a dorsal hood is especially noteworthy; this epithelium covers a small area of the corpus structure was previously known only from G. because the bordering fold recurves sharply valdivianus (but see Spotorno 1986), and as and surpass to the left of the orifice of the such Hopper and Musser (1964) considered it esophagus. Among sigmodontines with a as a diagnostic feature of the gland of this unilocular-hemiglandular stomach Carleton later species. Spotorno (1986) studied the (1973) described two gross morphologies. gland of several abrotrichine taxa; in relation The type reported here for Pearsonomys is to that of N. edwardisii he did not mention also present in nine other sigmodontine the presence of a dorsal hood. Therefore, we genera including Geoxus. The second type suggest that the presence of a dorsal hood is a of unilocular-hemiglandular stomach, where synapomorphy of the P. annectens–G. valdi- the glandular epithelium covers a slightly vianus clade. Finally, the fact that the phalli smaller area of the stomach, was reported for of P. annectens is tridigited (complex type), as other nine genera, including Abrothrix. Thus, are those of Chelemys, Geoxus, and Notiomys within the abrotrichine clade both types of (Hopper and Musser 1964; Spotorno 1986) unilocular-hemiglandular stomach are found. indicates that the distal reductions seen in Pearsonomys and Geoxus, which appear to be Abrothrix (Gallardo et al. 1988; Spotorno sister to each other in the phylogenetic 1986, 1992) represent, as suggested earlier by analyses (above, see also Smith and Patton Smith and Patton (1999), an autapomorphy 1999), share the same type; Abrothrix, which of the latter genus. is sister to the remaining abrotrichines, The stomach of P. annectens (Fig. 5) is of the possesses the other type. The study of the unilocular-hemiglandular type (sensu Carle- remaining abrotrichines (Chelemys and No- ton 1973); it is single chambered, with the tiomys) would clarify the abrotrichine pattern incisura angularis barely extending beyond of stomach evolution. the opening of the esophagus. The antrum is slightly smaller than the corpus. The dis- tribution of the glandular and cornified Final considerations epithelia practically coincides with the main Overall, Pearsonomys is most similar in stomachs divisions, the antrum and the morphology to Geoxus, its hypothesized

Fig. 5. Stomach of Pearsonomys annectens (IEEUACH 3851): internal view of the dorsal half. A=esophagus. B=cornified epithelium. C=corpus. D=bordering fold. E=antrum. F=glandular epithelium. G=incisura angularis. ARTICLE IN PRESS

New data of Pearsonomys annectens (Sigmodontinae) 11 sister taxon. In addition to the similarities the forms now considered synonymous of G. noted by Patterson (1992) in the original valdivianus, such as michaelseni from extreme description of the former, both taxa share southern Chile, may probe relevant to several other features. Both have a dorsal address this issue. hood in the gland penis, a character state so far known from only these two taxa. Simi- larly, both share a 2n=56 (Gallardo, unpub- Acknowledgments lished data; but see Pearson 1984), and their teeth and stomach are of the same type. Jim Patton made valuable comments on an Taken as a whole, this evidence casts doubts earlier version of this study, as did Ulyses on the validity of Pearsonomys as a genus; Pardin˜ as and Pablo Teta who also assisted us i.e., the adequacy of the placement of with the dental description. Ulyses Pardin˜ as annectens in its own genus is doubtful, it also drew Fig. 1 and Pablo Teta drew Fig. 5. may represent a large-sized species of Geoxus. Ricardo Ojeda and Benjamı´ n Bender helped However, we do not formally suggest this us with Fig. 4. Financial support was taxonomic change; we consider that this issue provided by DINACYT-FCE 7020 (GD) should be tested in the context of a revision and FONDECYT Grant 1010727 (MHG). of the whole abrotrichine group. Similarly, the inclusion in the phylogenetic analysis of

Zusammenfassung Neue Daten zu Pearsonomys annectens (Cricetidae, Sigmodontinae) und Anmerkungen zur Stellung von Pearsonomys

Die monotypische Gattung Pearsonomys ist eine der am wenigsten untersuchten Gattungen innerhalb der Sigmodontinae. Sie ist bisher nur vom Holotyp bekannt. Das ist die erste Untersuchung von Pearsonomys seit ihrer Erstbeschreibung 1992. Wir belegen vier neue Vorkommen aus der Region Los Lagos (Su¨dchile) von P. annectens, der einzigen Art, die bisher in diese Gattung gestellt wurde. Damit vergro¨Xert sich ihr bekanntes Areal um etwa 275 km.Weiterhin diskutieren wir die phylogenetische Position von Pearsonomys auf der Grundlage von Kern-DNA-Sequenzen. Diese Ergebnisse zeigen, dass Pearsonomys eine Schwesterngattung von Geoxus ist. AuXerdem beschreiben wir die Molaren von P. annectans (tetralophodontes Muster mit reduziertem Mesolophid), den Penis (Komplex-Typ), den Magen (unilocular-hemiglandular) und den Karyotyp (2n=56; FN=62). Die Diskussion dieser neuen Daten ist eingebunden in die Analyse der Ergebnisse der genetischen Untersuchungen. r 2005 Deutsche Gesellschaft fu¨r Sa¨ugetierkunde. Published by Elsevier GmbH. All rights reserved.

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Authors’ addresses: de Zonas A´ ridas, Casilla 507, 5500 Mendoza, Guillermo D’Elı´ a, Departamento de Zoologı´ a, Uni- Argentina versidad de Concepcio´ n, C-160, Concepcio´ n, Chile Fredy Mondaca and Milton H. Gallardo, Instituto de (e-mail: [email protected]) Ecologı´a y Evolucio´ n, Universidad Austral de Chile, Agustina Ojeda, Grupo de Investigacio´ nen Casilla 567, Valdivia, Chile Biodiversidad, Instituto Argentino de Investigaciones