A Remarkable New Mouse (Muridae: ) from Southeastern : With Comments on the Affinities of Rhagomys rufescens (Thomas, 1886)

Lucia Luna Bruce D. Patterson

Abstract

Field surveys of the Manu Biosphere Reserve in southeastern Peru between 1999 and 2001 secured specimens of a remarkable new species of mouse (Rodentia: Sigmodontinae). Curi- ously, this mouse shares numerous traits with the enigmatic Brazilian mouse Rhagomys rufes- cens (Thomas, 1886), known only from a pair of fragmentary specimens collected in Atlantic forest habitats during the 19th century. The position of Rhagomys within the Sigmodontinae radiation has been incertae sedis, owing both to its unique features and the limited materials for phylogenetic analysis. Here we provide a diagnosis and description of the new mouse and assess its relationships to Rhagomys rufescens on the basis of morphology; ongoing studies will shed more light on its phylogenetic relationships using morphological and genetic data in a complete phylogenetic analysis. This newly identified species widens the distribution of the genus in a disjunct pattern of distribution in . As recently suggested by Smith and Patton (1999), the genus Rhagomys may represent an independent lineage of Neotropical sigmodontines, one perhaps deserving of tribal recognition.

Resumen

Evaluaciones de campo en la Reserva de Biosfera de Manu en el sureste de Peru durante 1999 y 2001 resultaron dentro en otros, en la colecta de tres especimenes de una remarcable nueva especie de raton (Rodentia: Sigmodontinae). Curiosamente, este raton comparte nume- rosas caracteristicas con el enigmatico raton brasilero Rhagomys rufescens (Thomas, 1886) conocido solamente de un par de especimenes incompletos colectados en la Mata Atlantica durante el siglo XIX. La clasificacion de Rhagomys dentro de la radiacion de los Sigmodontinae es incertae sedis, debido a sus caracteristicas linicas y al limitado material para realizar analisis filogeneticos. Proveemos aquf una diagnosis y descripcion de esta nueva especie de raton y comentamos sus relaciones con Rhagomys rufescens basados en morfologfa; estudios en marcha daran luz a las relaciones filogeneticas usando datos morfologicos y moleculares. La descripcion de esta especie nueva amplfa el rango de distribucion del genero Rhagomys en un patron de distribucion disjunta dentro de Sudamerica. Como lo sugerido recientemente por Smith and Patton (1999), el genero Rhagomys podrfa representar un lineaje independiente dentro de los sigmodontinos neotropicales, uno que tal vez merezca reconocimiento tribal.

Introduction 1993), and new species are continually being un- covered there (Patterson, 2001). Of the 1,273 spe- Roughly a quarter of the world's spe- cies currently recognized as living within the cies live in the Neotropics (Wilson & Reeder, Neotropics, an overwhelming majority 1,037

FIELDIANA: ZOOLOGY, N.S., NO. 101, APRIL 30, 2003, PP. 1-24 1 species (81%) live in South America (B. Patter- new persj)ectives for assessing them. In this paper, son, unpubl.)- That continent is divided into sev- we focus on the detailed diagnosis, description, eral faunal regions, reflecting internal homoge- and comparisons of the new mouse. neity and external differentiation of its regional faunas (Hershkovitz. 1972; Koopman. 1982). The richest subregions in terms of both species rich- ness and numbers of endemic sp>ecies are the Am- Material and Methods azon Basin, the tropical , and the Atlantic Forest, respectively (Patterson. 2000). Over the Abbreviations and specimens examined and past decade these three subregions have yielded measured are listed in the App>endix. most newly described species of , al- The measurements we used were defined and though perhaps only proportionately to their di- illustrated by Myers et al. (1990). Voss (1991. fig. versity (cf. Mares et al.. 2000). 3). and Musser et al. (1998, 2). All external In 1999. the Field Museum of Natural History fig. measurements except vibrissal length were taken (Chicago) and the Museo de Historia Natural. in the field on fresh using a ruler and Universidad de San Marcos (Lima), initiated a specimens were recorded on skin labels. Cranial measure- new series of expeditions to inventory mammals, ments were taken with a Mitutoyo Digimatic cal- birds, and ectoparasites of the Manu National which was accurate to the nearest 0.01 mm. Park and Biosphere Reserve in southeastern Peru. iper, Vibrissal lengths were measured on study skins This reserve spans habitats representing the Alti- (the longest one in the array of vibrissae was mea- plano. Tropical Andes, and Amazon Basin faunal sured). Dorsal fur length was measured at the regions. Even at the start of our field program, it midline on each Vibrissal and harbored the richest assemblages of mammals and rump's specimen. dorsal fur lengths were measured using a ruler. birds yet recorded anywhere on the planet (Ter- Color nomenclature follows (1912). borgh et al.. 1984: Pacheco et al.. 1993: Patterson Ridgway of external follows Bed- et al.. 1998). Nevertheless, each field season from Terminology anatomy dard (1902). Brown (1971). and Brown and Yal- 1999 to 2001 brought to light new species of den for vibrissal nomenclature, whereas mammals and recorded numerous other species (1971) and manus nomenclature follow's Voss (1988, not previously documented in the area. pes

1991 ) and Musser et al. ( 1998). Cranial and molar Among the new species of mammals taken by terms follow in Hershkovitz 1967, Manu survey teams is a small sigmodontine ro- usages (1962. 1977. Carleton Carleton and Mus- dent unlike any other. The suite of characters not- 1994), (1980),

ser ( 19B9), Voss ( 1988. 1991 ), Voss and Carleton ed at the time of capture and during field prepa- and (1995), whereas Howell ration of the specimens nail on big toe. elongat- (1993), Steppan

( Greene Carieton ( 1980), and ed tongue, and spiny pelage was unlike any de- 1926), (1955), Step- defined and illustrated our scribed for a Neotropical sigmodontine. Although pan ( 1995) terminology for skeletal For we attempted to secure additional examples at postcranial morphology. descrip- both localities where we encountered this mouse, tion of soft-part anatomy, Howell ( 1926) and Voss only three specimens exist on which to base the (1988) are followed for muscles, Tullberg (1899), for the following description and discussion. Despite su- Sonntag (1924), and Vorontzov (1979) for Voss perficial resemblances, this species is easily dis- tongue, Carleton (1973) stomachs, tinguished from other small, spiny sigmodontines (1991) for gallbladder states, Vorontzov (1979) (Xeacomys and Scolomys) by its unique combi- for intestinal tracts, and Voss and Linzey (1981) nation of external and cranial characters. Rather, for male accessory glands. Our designation of numerous characters point to its phylogenetic re- mammary fields follows Voss and Carleton lationship to Rhagomys riifescens (Thomas. (1993). The age categories, based on toothwear 1886). an enigmatic mouse from coastal stages, were described and illustrated by Voss deemed incertae sedis in most appraisals of Sig- (1991). modontinae (Carleton & Musser. 1984: Reig. Abbreviation conventions for the maxillary or 1980. 1984. 1986: McKenna & Bell. 1997: Smith upper molars are Ml. M2, and M3, while man- & Patton. 1999). The discovery of the new mouse dibular or lower molars are represented by ml-3, and its inclusion in the genus Rhagomys raise im- the first molar being M/ml. portant questions about the origin, biogeography. Manual and p>edal digits are represented by Dl- and systematics of South American mice and offer 5, the pollex and the hallux, respectively, being

FIELDIANA: ZOOL(X}Y Dl. In either case, the locations of the digit will be specified in the text.

Results

Rhagomys longilingua, new species

HoLOTYPE The holotype, Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima, Peru (musm 17013), is a male col- lected 20 September 1999 by Lucia Luna Wong (the senior author, field number LLW 661). Skin in good condition with right manus and pes intact; entire carcass (including skull) with unskinned left manus and pes preserved in fluid. Tissue sam- ples preserved in liquid nitrogen are deposited at the Field Museum of Natural History, Chicago as (FMNH 170686). External measurements of the holotype: head and body length (HBL), 103.0 mm; tail length (TL), 96.0 mm; hind foot length (HF), 17.0 mm; ear length (E), 13.6 mm; dorsal fur length (DEL), 8.0 mm; longest mystacial vibrissae length (MVL), 35.0 mm; longest superciliary vibrissae length (SVL), 26.0 mm; longest genal vibrissae length (GVL), 20.0 mm. Type Locality Peru: Departamento de Cuz- co, Provincia de Paucartambo, below "Suecia," a roadside settlement in Manu Biosphere Reserve along the Rio Cosnipata (Fig. 1); coordinates 1306.032'S, 7134.125'W; elevation approxi- mately 1900 m. During our fieldwork, the restau- rant "El Rocotal" stood near the places where the holotype and one paratype (fmnh 170687) were taken.

Etymology The species group name, longi- lingua, a noun in apposition, is formed from the = Latin words longus (= long) and lingua ( tongue), in reference to one of the species's most distinctive features. Diagnosis A small, spiny mouse with this unique combination of characters: digits of manus and pes with broad and square-shaped, blunt, cal- lous tips with embedded claws. Tips are callous and have a crescent-shaped depression appearing heart-shaped in dorsal view. All digits with deep transverse grooves. Manual D3 and D4 are nearly equal in length, with D4 slightly longer. Claws of manus are very short and project little beyond the tip of the fingers. The hallux bears a nail. Plantar pads are structurally well-defined, fleshy, and flat- tened, with a heart-shaped callus on the interdig- Fig. 2. Rhagomys longilingua specimens: a, female paratype, fmnh 170687; b, male paratype, fmnh 175218 (ant damage on face; photograph by C. Dick).

elements; all mandibular molars have a postero- breadth (RB), 5.1; orbital fossa length (OFL), crista. 10.7; nasal length (NL), 8.5; nasal breadth (NB), Paratype Because the holotype is a male pre- 2.9; least interorbital breadth (LIB), 5.5; diastemal pared in the field as a skin with complete carcass length (DL), 7.3; bony palate length (BPL), 6.9; in fluid, certain characters skull morphology, bony palate breadth across first upper molars mammary formula, and part of the alimentary (BPB), 5.2; postpalatal length (PPL), 9.1; incisive system could not be recorded. Description of foramina length (IFL), 3.5; incisive foramina these characters is of the female paratype cata- breadth (lEB), 1.4; maxillary tooth-row length logued by the Field Museum as fmnh 170687. (MTL), 4.5; palatal bridge breadth (PBB), 2.5; The paratype was collected 19 September 1999 at first upper molar breadth (MIB), 1.3; zygomatic the type locality by Sergio Solari (SS 1873); its breadth (ZB), 15.9; braincase breadth (BB), 13.4; skin is in good condition (save for a sewn tear in zygomatic plate breadth (ZPB), 3.3; incisor depth one of the flanks), with right fore- and hind feet; (ID), 1.9; braincase height (BH), 9.0; and mesop- cranium, mandible, hyoid, and skeleton in good terygoid fossa breadth (MFB), 1.7. This specimen condition. The viscera were fixed in formalin and falls in toothwear class 2.

preserved in ethanol, and tissue samples were pre- served in liquid nitrogen. External measurements of the female paratype (measurements in mm): head and body length Description (HBL), 101.0; tail length (TL), 104.0; hind foot length (HF), 20.0; ear length (E), 14.0; dorsal fur Observations of pelage color and texture, ex- length (DEL), 8.0; longest mystacial vibrissae ternal form, postcranial skeleton, and soft anato- length (MVL), 37.0; longest superciliary vibrissae my are based on the holotype and paratype; those length (SVL), 25.0; longest genal vibrissae length of the cranium, dentition, postcranial skeleton, (GVL), 21.5. Cranial measurements (in mm): and part of the soft anatomy (tongue and intes- greatest length of skull (GLS), 28.3; condyloin- tines) are based on the paratype alone. cisive length (CIL), 26.0; condylomolar length External Morphology Rhagomys longilin- (CML), 16.7; length of rostrum (LR), 7.7; rostral gua is a small to medium-sized (25-35 g) Sig-

FIELDIANA: ZOOLOGY modontinae {sensu Carleton & Musser, 1984) mouse, with small ears and a tail that is subequal in length to head and body (Fig. 2). The body pelage is short and close with a mark- edly spiny texture, the dorsal fur more spiny than the ventral fur. There are two types of dorsal and ventral hairs of approximately the same length (8 mm): spiny hairs and long, thin hairs. The former

is slightly transparent, dorsally grooved, flat, rig- id, and stout, broadest (0.25 mm) at its midpoint. The ventral spiny hair is slightly shorter (7.0 mm). On the muzzle, over the eyes, on the cheeks, and between the forefeet and neck, the color cor- responds to Ochraceous-Orange. On the sides the borders between the upper and underparts, the external sides of fore- and hind feet, the backside of the ears, and the chest the color corresponds to Ochraceous-Buff. All the underpart pelage from the chin and the interior sides of the fore- and hind feet is Light Ochra- ceous-Buff with tonalities of Light Ochraceous Salmon when moved under white light. In gen- eral, the body pelage is strongly countershaded. The dorsal pelage is Olive-Brown in appear- ance, but it is difficult to characterize because it has a strongly hispid pattern produced by the Fig. 3. Detail of the manus of Rhagomys longilin- dorsal combination of the two of hair. Dorsal gua, new species: a, view (fmnh 170687), scale types = bar 1 mm; b, detail of digit 5 in ventral view (fmnh spines are transparent Light Olive-Gray at the = 170687), scale bar 1 mm; c, ventral view (fmnh base and almost their entire be- throughout length, 170687), scale bar - 3 mm. coming progressively brown and dark toward the tip. Fur is grayish at the base, with the last quarter of the length Ochraceous-Buff. Some hairs are hairs were counted on the holotype specimen, slightly brownish at the tip. On the underparts, while only two were counted in the female para- spines and fur are silvery-transparent at the base, type. Two carpal vibrissae are present. Both are becoming pinkish or rufescent toward the tips; short, but the longer of the two reaches the prox- hence the ventral surface coloration described imal margin of the hypothenar pad. above. There are six mammae in three pairs: one in- The dorsal pelage of the head is composed pre- guinal, one abdominal, and one postaxial. dominantly of spines. These are more cylindri- The tail is slightly shorter than the head and cal less flat than the spines in the dorsum and body, weakly countershaded, and with a small tuft with tips more orange or brown. The postauricular of hairs in the end. Ventrally, the tail is paler ow- field lacks spines; hairs here have a silvery base ing to absence of pigmentation in the skin and and Ochraceous-Buff tips. Ears are small (average paler hairs (some middle hairs of the triplets are 14 mm), covered internally by dense orange- slightly pigmented in the middle region). Scales brownish hair and externally by golden hairs. The on the tail are arranged in an annular pattern. eyes are well-defined due to a very conspicuous Hairs are arranged in triplets of the same size, black ring of skin. which are shorter at the base of the tail and longer

Facial vibrissae are arrayed in mystacial, sub- toward the tip. Each short hair is about two scale- mental, genal, superciliary, and interramal fields. rows long. The longest mystacial, superciliary, and genal vi- The five digits of the manus have a unique con- brissae reach well beyond the posterior margins figuration for Sigmodontinae (Fig. 3). They are of the pinnae. Interramal vibrissae are composed long with broad, squared, and blunt tips. A cres- of a single tuft of long hairs. Submental vibrissae cent-shaped depression in the middle of the apical heart- are long and border the lower lip. Four of these pad, perpendicular to the claw axis, appears

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU shaped in dorsal view (Figs. 3a and 3b). The sur- face surrounding the depression is callous. Digits have deep transverse grooves along their entire length. The three interdigital pads and single hy- pothenar and thenar pads are structurally well-de- fined, fleshy, and flat. A heart-shaped callus is no- ticeable on each of the three interdigital pads. Thenar and hypothenar pads also have calluses that nearly span the pads. The thenar callus reach- es the margin of the pollical nail (Fig. 3c). Manual D3 and D4 are nearly equal in length, with D4 slightly longer, and D2 and D5 are sub- equal, with D2 slightly longer. Pollex is vestigial with a small nail. Claws of manus are very short and project little beyond the tip of the fingers. Because they are very narrow and short (= three times longer than wide) and embedded in the fin- gertips, the claws are inconspicuous in ventral view, with only the tips visible. In lateral view, claws extend almost straight out and are therefore less concave proximally than in other sigmodon- tines. The surrounding tufts of hair reach the tip of the claws, some projecting slightly beyond the

tip (Fig. 3a). There are five nonopposable digits on the pes, C|it/ similar to those described for the manus (Fig. 4). '^'mh Each is long and has deep transverse grooves, ^m with blunt tips bearing a central crescent-shaped depression surrounded by a callous surface. D2, Fig. 4. Detail of the pes of Rhagomys longilingua, D3, and D4 are increasingly elongated, and D5 = new species: a, dorsal view (fmnh 170687), scale bar reaches the middle of the second of D4. phalanx 3 mm; b, detail of the hallux-bearing nail (fmnh = Hallux is short, level with the anterior margin of 170687)' scale bar 1 mm; c, ventral view (fmnh scale bar = 3 thenar the second interdigital pad and the interphalangeal 170687), mm; th, pad; hy, hypoth- enar pad. joint between phalanx 1 and 2 of D5 (Fig. 4a). There is a nail in the hallux instead of a claw (Fig. 4b). naked; however, long hairs at the sides project The broad has six well-defined and short, pes over the calcaneum area. four one fleshy plantar pads: interdigitals, hypoth- Cranium The skull of R. longilingua is enar, and one thenar. are Interdigital plantar pads strongly built, with a short, blunt, narrow (in re- covered by calluses 4c). The heart-shaped (Fig. lation to the interorbital region) rostrum (Fig. 5). is smaller than the thenar hypothenar pad slightly The interorbital region is short and the braincase and is with the fourth pad contiguous interdigital voluminous. The zygomatic arches are parallel- The lies intermediate at a pad. hypothenar pad sided, enclosing a voluminous orbit, with a thin level between the first and thenar interdigital pads. but conspicuous jugal. The upper incisors do not The distal of the thenar is level with margin pad project beyond the anterior margin of the nasals, the of the Pedal proximal margin hypothenar pad. and the premaxillaries do not protrude beyond the claws are and the claw of is so extreme- short, D5 anterior plane of the incisors. The nasolacrimal short that it is hidden from ly nearly plantar view capsules are flat and inconspicuous in dorsal view, (length 1.25 mm, width 0.34 mm). Ungual tufts appearing like thin pockets opening toward the are level with the end of the digits, slightly be- dorsum of the skull. Their posterior margins lie yond the claws. The soles of the feet are smooth anterior to the anterior margin of the zygomatic except for the calluses on the plantar pads. The plate. The nasals are broad distally, tapering pos- plantar surface, including the heel, is completely teriorly toward the frontals and forming a well-

FIELDIANA: ZOOLOGY Fig. 5. Dorsal, ventral, and lateral views of cranium and lateral view of the mandible of the paratype of Rhagomys = longilingua, new species (fmnh 170687); arrow points to the postorbital process. Scale bar 6 mm.

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU Fig. 6. Detail of the alisphenoid region of Rhagomys longilingua, new species (fmnh 170687): foa, foramen ovale accessorius; aalc, anterior opening of alisphenoid canal; bmt, buccinator-masticatory trough; als, alisphenoid strut; tt, = tegmen tympani. Scale bar 2 mm.

defined triangular suture anterior to the lacrimals. present, but the buccinator-masticatory foramen is Posteriorly, the premaxillae extend slightly be- fused with the anterior opening of the alisphenoid yond the nasals. The zygomatic notch is shallow. canal, hidden by the alisphenoid strut. The carotid The anterior border of the orbit is broad, thick, arterial supply pattern is presumably derived and perpendicular to the longitudinal axis of the (Bugge, 1970), corresponding to pattern three of skull. The zygomatic plate is of moderate width, Voss (1988). The stapedial artery does not divide straight, lacking a zygomatic spine, and closely into supra- and infraorbital arteries, and the squa- pressed to the rostrum. Its anterior margin does mosal-alisphenoid groove and sphenofrontal fo- not overlap the nasolacrimal capsule in lateral ramen are absent. In this pattern of carotid cir- view. The antorbital bridge of the anterior root of culation, the stapedial foramen is absent and the zygomata is situated slightly below the rostrum. pteriotic, usually visible ventrally, is hidden by The first maxillary molar (Ml) is located behind the ectotympanic. The carotid canal is conspicu- the posterior margin of the zygomatic plate. ous, appearing under the eustachian tube. The interorbital region is broad with posteriorly The tegmen tympani overlaps a posterior sus- divergent, beaded margins. The interparietal is pensory process of the squamosal anterodorsal to very broad but does not contact the squamosal. the auditory bulla (see Fig. 6). The hamular pro- The lengths of the supraoccipital-parietal and the cess is broad, with its posterior end loosely fused occipito-squamosal sutures are almost equal. The to the mastoid tubercle of the periotic (Fig. 5). anterior face of the squamosal bone has a narrow The mastoid tubercle and the dorsal anterior por- postorbital process (arrow in Fig. 5) that is visible tion of the ectotympanic both form a contiguous in dorsal view as a small knob inside the orbital ring in the middle ear. The mastoid fenestra of the fossa and serves as the origin for part of the an- periotic is a well-developed aperture in the suture terior temporalis muscle. between the periotic and the exoccipital. The mal- The morphology associated with the orbitofa- leus has a broad lamina completely exposed in cial circulation is unique in this mouse (Fig. 6). lateral view of the skull and has a "parallel" ori- A very broad alisphenoid strut conceals the ap- entation (sensu Carleton, 1980). A prominent or- erture of the anterior opening of the alisphenoid bicular apophysis is one-third as large as the lam- canal, which makes it visible only in frontal-lat- ina. eral view. Instead, the only visible structure is a The subsquamosal fenestra and the postglenoid perfectly defined foramen ovale accessorius. The foramen are present and well-developed (Fig. 5). trough for the masticatory-buccinator nerve is The groove of the postglenoid vein appears shal-

FIELDIANA: ZOOLOGY Fig. 7. Detail of mesopterygoid and parapterygoid fossae oi Rlicigomys longilingua, new species (fmnh 170687): ppp, posterolateral palatal pits; f, fontanelles; pale, posterior opening of the alisphenoid canal; foa, foramen ovale accessorius; cc, carotid canal. Scale bar = 2 mm.

low, owing to the shortness of the lamina of the absent. The palatal surface is smooth, without any periotic that forms the tegmen tympani. The sta- traces of bony palate excrescences. The posterior pedial process of the bulla is inconspicuous, and palatine ridge {sensu Steppan, 1995) is absent or the middle lacerate foramen is absent. indistinct. Posterolateral palatal pits are well-de- The incisive foramina are narrow and short fined depressions within which one or more small (Fig. 5). The distance between the incisive alveoli foramina are located, recalling Carleton's (1980) and the anterior margin of the incisive foramina descriptive phrase, "multiple foramina recessed in equals the length of M2-M3. The distance be- fossa," and the midpoint of the posterolateral pal- tween the posterior margins of the incisive foram- atal pits is level with the anterior margin of the ina and the anterior margins of Ml is equivalent mesopterygoid fossa. The maxillary tooth rows to the length of M2. In shape, both foramina are are subparallel. parallel-sided and slightly narrower anteriorly The anterior border of the mesopterygoid fossa than posteriorly. The most ventral suture of the is rounded. The bony roof of the mesopterygoid premaxillaries and maxillaries is level with the fossa is substantially complete, but constricted last third of the incisive foramina. The maxillary sphenopalatine vacuities are hardly visible be- septum of the incisive foramina is one-fourth the tween the presphenoid and basisphenoid suture length of the incisive foramina. The masseteric (Fig. 7). The hamular processes of the pterygoids tubercle appears as a conspicuous scar for the or- are subparallel but slightly divergent posteriorly, igin of the superficial masseter muscle. appearing lyre-shaped in ventral view. The suture There is a very long palate, with the posterior between the palatines and the pterygoids is in the margin extending half the length of M3 past that anterior third of the pterygoids. tooth. The palate is also wide {sensu Hershkovitz, Cranially, this species is distinguished by its 1962); the distance between the inner borders of particular basicranial configuration, especially the the first molars is greater than the length of either parapterygoid fossa and the carotid circulation tooth. A medial process of the posterior palate is (Figs. 6 and 7). The parapterygoid fossae are shal-

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU cap cop

Fig. 8. Detail of the retromolar fossa in the inner part of the mandible of Rhagomys longilingua, new species third molar. bar (fmnh 170687): rt, retromolar fossa; cop, coronoid process; cap, capsular projection; m3, lower Scale = 2 mm.

low and narrow, extending to contact the anterior pear slightly above the pterygoid lobes. The ec- border of the ectotympanic, totally closing the totympanics have long, well-defined eustachian middle lacerate foramen and giving the skull a tubes that extend anteriorly under the pterygoid solid appearance in ventral view. The fontanelles, process. The carotid canal is well-defined (Fig. 7). border of the and formed by the posterior palatine The ectotympanic covers completely the pteriotic the anterior ventral of the margin alisphenoid of the periotic. Lateral depressions of basioccipital Carleton are ex- (named by & Musser, 1989), are shallow, but there is a conspicuous ridge in tremely large, oval-shaped, and well-defined, with the middle. smooth borders. These one-third of the occupy Mandible and Hyoid The mandible possess- of the in the mesopterygoid fos- length pterygoid es a short angular process that extends only as far sae. In addition, the posterior opening of the ali- as the base of the condyloid process (Fig. 5). The sphenoid canal is small, well-defined, and oval- coronoid process is short and level with the con- shaped, approximately one-fifth the size of the dyloid process. The angular notch is shallow, with fontanelles. There is no groove for the infraorbital its border parallel to the mandibular axis. A dis- branch of the stapedial artery. This artery supplies tinct capsular projection of the incisive alveolus only the middle ear, departing from the most lies underneath the angular notch and forms a primitive pattern. knob in dorsal view. A conspicuous The foramen ovale accessorius is visible in conspicuous inferior masseteric ridge extends slightly beyond ventral view because of the narrow parapterygoid the anterior margin of m 1 . A weak ventromedial fossa. The bony ridge that forms the lateral edge of the mandibular ramus (Steppan, 1995) of the parapterygoid fossa is pronounced only in process is A and broad retromolar fossa is the region anterior to the alisphenoid strut. In the present. deep located between the base of the coronoid alisphenoid strut region, the ridge disappears and process the borders become smooth, rendering the fora- and m3 (Fig. 8). men ovale accessorius. Although the thyrohyal bones of the hyoid ap- The ectotympanics are almost flat. In lateral paratus were poorly preserved, the basihyal bone view, resting on a surface, the ectotympanics ap- is entire and shows no entoglossal process. The

10 FIELDIANA: ZOOLOGY basihyal is arched rather than flat or perpendicular to the thyrohyal. Dentition The upper incisors are orthodont, narrow, and without grooves in the enamel sur- face. The dentine fissure (sensu Steppan, 1995) corresponds to a long, straight slit. The cutting edge appears as an inverted V. Molars are pentalophodont, consisting of para- cone, protocone metacone, hypocone, and meso- loph. The molars are bunodont and relatively low- crowned, with very conspicuous cusps (Fig. 5) and broad, well-defined flexi (Fig. 9, left). Ml is twice as long as M2; M3 slightly exceeds half the length of M2; M2 is squared; M3 is wider than long. The paraflexus and metaflexus in Ml and M2 nearly surround the interior margin of the paracone and metacone. The interpenetration of labial and lingual flexi extends slightly beyond the tooth-row midline. In Ml, the anteromedian flexus is deep, form- ing an anterolabial conule that is larger than the anterolingual one. A unique enamel element pro- jects medially from the anterolabial conule. It seems that this structure, which we call the anter-

omedian crista, does not connect both conules in young adult specimens, such as the paratype spec- imen, which belongs to toothwear class 2. This structure may join both conules in old specimens until the teeth are worn. Thin ridges link the con- ules to the anterior mure of Ml. In addition, a projection links the anterolabial conule to the an-

teroloph. Hershkovitz (1994, fig. 3) called this structure the anterolophule. But here, rather than emerging from the margin of the conule, it issues from the middle of the anterolabial conule and

fuses with the anteroloph at its middle point. The paracone and protocone of Ml and M2 are con- nected to the medium mure by thin ridges. A long and conspicuous anteroloph fuses with FiG. 9. Occlusal views of dentitions, a. Upper left the parastyle in M 1 . A long anteroloph in M2 fus- molars: left, Rhagomys longilingua (fmnh 170687); es with the in its labial This an- paracone margin. right, Rhagomys rufescens (bmnh 86.2.8.5). Arrow and left teroloph projects back to the lingual side, forming points to the anteromedian crista, b. Lower right molars: left, Rhagomys longilingua (fmnh 170687); a conspicuous protoflexus. There are small and right, Rhagomys rufescens (bmnh 86.2.8.5), arrows point shallow posteroflexus in Ml and M2. A long and = to the posterocrista. Scale bars I mm. conspicuous mesoloph fuses with the mesostyle in

M 1 and M2. All of these structures reach the la- bial side of the molar tooth row. The flexi of all loph, protoflexus, and median mure. The meso- molars (save the protoflexus of Ml) terminate at loph and metacone are not evident. an elevated cingulum; the cingulum completely Lower molars are very similar in structure, sub- encircling M2 and M3 gives the teeth distinctly equal in size, with conspicuous cusps, broad, sharp edges. M3 is small and shaped like a blunt, well-defined flexids, and conspicuous cingula. inverted triangle, with a sharp-edged cingula. It The procingulum on ml is without an anterome- has a conspicuous paracone, protocone, antero- dian flexid; the procingulum extends from the an-

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU 11 terolingual conulid labially into an anterolabial and D4 are approximately three times longer than cingulum, which reaches the protoconid. There is wide. no trace of a protostylid. The ml has very con- The metatarsal of D5 is comparatively long, spicuous anterior and median murids. The anter- terminating level with the distal end of metatarsal olophid is absent. The mesolophid and mesostylid of D4. This configuration contributes to a long D5 are fused, reaching the lingual side. The entolo- that reaches the middle point of the second pha- phulid fuses with the last portion of the mesolo- lanx of D4. The hallux is long, its second phalanx phid, forming a mesolophid-mesostylid-entolo- terminating about one-third the length of the first phulid junction. The posterolophid is long, reach- phalanx of D2. ing the entoconid. Viscera The tongue is unusually long and Remarkably, m2 and m3 are almost identical in narrow. The tongues of both specimens from the shape and size. Both have very conspicuous meta- type locality were protruding well outside the conid, protoconid, entoconid, hypoconid, anterior mouth when collected dead. Because the speci- and median murids, and anterolabial cingula that mens were fixed in formalin and then preserved fuse with the protoconids. They differ in that m2 in 70% ethanol prior to examination, measure- has a mesolophid-mesostylid, whereas m3 has ments here do not connote natural dimensions. only an isolated mesostylid. All mandibular mo- The free portion of the tongue (apex linguae; lars share what appears to be a continuation of the Fig. 10) is long, narrow, thick, and tapered toward median murid but is in fact a projection of the the tip. It is cylindrical and similar in shape to the hypoconid that connects to the posterolophid; this tongue of some nectar-feeding bats. The apex lin- is called the posterocrista. In addition, the poster- guae alone is approximately 18 mm long and 2 olophid of these molars reaches the entoconid, mm wide. The dorsal surface of the tongue is cov- forming a posterocingulum. This cannot be con- ered by papillae filiformes. There is a short me- fused with what Hershkovitz (1994) designated a dian sulcus in the corpus that does not reach the distolophulid for Oxymycterus. The entolophid is tip. The torus linguae and the sulcus semilunaris absent on all lower molars. are absent. Only one papillus circumvallatus was POSTCRANIAL SKELETAL MORPHOLOGY Axial found in the corpus, seen as a small protuberance skeletal counts include 13 ribs, 19 thoracicolum- rising from between two lateral lips. In addition, bar (dorsal) vertebrae, 4 sacral vertebrae, and 36 small secondary papillae were detected over the caudal vertebrae. The tuberculum of the first rib papillus circumvallatus in close lateral view of the contacts transverse processes of both the seventh tongue. Six whitish papillae lenticulares were cervical and the first thoracic vertebrae. A con- found behind the papillus circumvallatus. spicuous neural spine is present on the second The stomach morphology corresponds to the thoracic vertebra. The hemal arches (Steppan, unilocular-hemiglandular pattern (Fig. 11), with 1995) are absent from the caudal vertebrae; only an antrum and corpus that are subequal in area. hemal processes are present. These include, in or- The incisura angularis is shallow and broad, while der of conspicuousness, one located at the junc- the ascending antrum and the posterior end of the tion of the third and fourth caudal vertebrae, fol- esophagus form an 80 angle. In cross-section, the lowed by the second and third and the fourth and bordering fold crosses the lesser curvature at the fifth. The hemal processes located at the first and apex of the incisura angularis, and the glandular second junction and after the fifth vertebra are in- epithelium protrudes in a wide bulge into the cor- conspicuous. pus. In the liver, the gallbladder is absent. The humerus lacks an entepicondylar foramen, This species has a relatively short intestine; the and the supratrochlear fossa is not perforated. The total length of the intestine is three times the distal 60% of the tibia and fibula are fused (tibia- length of the head and body. The small intestine fibula fusion 1 1.02 mm, length of the tibia 17.42 is 2.7 times (204 mm) longer than the large in- mm). The trochlear process at the calcaneum is testine (76 mm). The large intestine has several broad, and its position is intermediate (sensu bends and two big ampullae. The caecum is small Carleton, 1980), with a gap in lateral view be- (23 mm), representing 8% of the total intestine tween the proximal margin of the trochlear pro- length. It is thin, with the external diameter equal cess and the posterior articular facet with the as- to that of the adjacent portion of the large intes- tragalus. tine. It has five bends and a small appendix The metatarsals are short, which gives the pes scarcely differentiated from the rest of the cae- a very broad shape. The metatarsals of D2, D3, cum.

12 FIELDIANA: ZOOLOGY Fig. 1 1 . Stomach morphology of Rhagomys longi- = lingua, new species (musm 17013), scale bar 5 mm: c, corpus; a, antrum; bf, bordering fold; ia, incisura an- gularis.

L^>\v> wings fully extended. The deferent ducts appear from the sides of the "butterfly."

Comparisons

Rhagomys longilingua can easily be distin- guished in the field from other Sigmodontinae by its long tongue, the deep transverse grooves in the Fig. 10. Tongue of Rhagomys longilingua, new spe- digits, the square shape of the tips of its digits and cies: a, gross morphology of the tongue (fmnh 170687), = their and the short, scale bar 3 mm; b, detail of papillae: pc, papillus crescent-shaped depressions, circumvallatus; pi, papillae lenticulares. embedded claws. Despite these unique characters, R. longilingua bears a superficial resemblance to other small spiny mice such as Scolomys and Nea- The male accessory gland complement includes comys. From Scolomys, R. longilingua is distin- a pair of well-developed preputial glands that guished by its larger size (Table 1), the well-de- each extends well beyond the ventral flexure of fined countershading between the dorsal and ven- the penis. The bulbourethral glands are thin pro- tral fur coloration, and more delicate dorsal jections, orange-brown in color, that run dorsally spines. Externally, R. longilingua warrants more to the tract, almost reaching the vesicular gland in extended comparisons with Neacomys, which it lateral view (see Voss & Linzey, 1981, fig. 1). The resembles in color and pattern of coloration. Un- lateral ventral prostate is one-third the size of the like Neacomys, however, R. longilingua has con- medial ventral prostate, and the anterior prostate spicuous Ochraceous-Orange cheeks. The ventral surrounds the vesicular glands. Vesicular glands coloration of R. longilingua is completely uniform are typical: J-shaped, robust, compact, and folded Light Ochraceous-Buff with tones of Light Ochra- over so that they initially appear almost rounded. ceous Salmon, while the venter of Neacomys the The dorsal prostates are present. The ampullary varies from whitish (white with the base of of gland is small and shaped like a butterfly with its hair gray) to Cinnamon Buff on the flanks

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU 13 Table 1. External and cranial measurements of Rhagomys longilingua, new species. Rhagomys rufescens, Sco- lomys juruaense, and Neacomys spinosus. Table 1. Continued. Fig. 12. Dorsal, ventral, and lateral views of cranium, lateral view of the mandible of the type of Rhagomys = rufescens (Thomas, 1886), bmnh 86.2.8.5, adult female. Scale bar 6 mm.

mys was closest to Oecomys in terms of external the Rhipidomys- complex, he morphology and palatal structure but far from avoided making statements about their possible that genus in morphology of the incisors and relationships, calling instead for a revision for molars. Although he compared Rhagomys with the whole group.

16 FIELDIANA: ZOOLOGY Many of the cranial characters in Thomas' de- analog images of the skull and skin of the type scription of Rhagomys are evident in R. longilin- specimen (bmnh 86.2.8.5, female) by the muse- gua: incisor capsule prominent, and the most um's staff and colleague Guy Musser, as well as striking feature, molar cusp arrangement. Rhago- on information on Rhagomys published by Thom- mys longilingua has molars with very conspicu- as (1886, 1917), Gyldenstolpe (1932), Ellerman ous cusps and thin ridges connecting the conules (1941), and Moojen (1952). During the manu- with the median mure. The comparison Thomas script's review, we had the benefit of detailed ob- made with phyllostomid bats almost perfectly de- servations of the holotype by curator Paula Jen- scribes the isolated pattern of the conules and con- kins and further inspection by the junior author. ulids in the molars of both R. rufescens and R. Comparisons with Rhagomys rufescens. longilingua. Rhagomys longilingua is readily distinguished ex- Ellerman (1941) added further details to the de- ternally from Rhagomys rufescens by its spiny scription of the external morphology of Rhago- fur; Rhagomys rufescens has soft, lax fur. This mys: condition was confirmed by Paula Jenkins:

The hallux in the type skin appears to lack a claw, ... R. rufescens has long, soft fur on the dorsum but more specimens will be necessary before this and flanks, slightly shorter on the venter and also character can be proved, as the skins examined are slightly shorter and slightly harsher on the head. very old, and not in good condition. D.5 [digit V] Individual hairs are long, thin and soft. The fur of hindfoot lengthened; tail long, not well haired, (p. this species is longer but as soft as that of M. dryas, 377) M. d. humilior [both Microryzomys minutus] and 0[ligoryzomys]. stolzmanni, softer than 0[ligoryzomys]. arenalis and O. n. messorius The digital-length character he identified and [=Oligoryzomys fulvescens] and there is no trace of the absence of a hallical claw are the di- among the spinous texture of N{eacomys]. spinosus. (in agnostic characters for R. longilingua. litt.; February 11, 2002). Moojen (1952) subsequently described Rhago- mys as having a tail covered by hairs increasing Rhagomys longilingua has fingers and toes with in size toward the tip to form an inconspicuous conspicuous, deep, transverse grooves, with the apical tuft. He also noted that the manus and pes claws embedded in the tips of the digits. These were naked, with calluses on their surface, stating: characteristics are faintly evident in the type ma- terial of R. rufescens. The two taxa share incon- . .. [cauda] finamente recoberta de pelos que sao spicuous pelage countershading and tails that are mais longos na ponta formando un pincel pouco roughly equal to HBL. Both have broad feet, with conspi'cuo ... Palmas e solas nuas con grandes ca- a nail a on the hallux and an los.' (p. 51) (not claw) elongated D5 on the pes that reaches the middle of the sec- ond of D4. also share calluses on He used the term calos to designate the calluses phalanx They the soles of manus and as mentioned for R. in the plantar regions, no doubt to specify the pes, presence of calluses rather than simply the plantar rufescens by Moojen (1952). R. and R. are pads. Both of these traits also recall the condition Cranially, longilingua rufescens similar 5 and but also exhibit of R. longilingua. very (Figs. 12), they some differences. The interorbital of R. A more detailed, point-by-point comparison of region is with its narrowest R. longilingua with R. rufescens is warranted. Un- longilingua strongly beaded, while in R. the inter- fortunately, only two old specimens of R. rufes- point anteriorly, rufescens, orbital is smooth and its narrowest cens exist for comparison, both at the Natural His- region point near the middle. The notch in R. lon- tory Museum in London (bmnh). Each consists of zygomatic is shallower than in R. a skin with damaged or lost skull, limiting the gilingua slightly rufescens. The is in R. lon- basis for comparison. During most of our analy- postorbital process conspicuous while in R. no statement sis, the collections of the Natural History Museum gilingua, rufescens, could be remnants of anterior in London were unavailable for study, owing to made; dry tempo- a renovations in the mammal division. Our com- ralis muscle suggest the presence of developed however, because of the frag- parisons were accordingly based on digital and postorbital process; ile condition of the specimen, the skull has been coated with a of cement, which makes con- ' layer "[Tail] finely covered with hairs which are longer at firmation of this character unclear. the tip forming an inconspicuous brush. Palms and soles naked with large calluses." The basicranium of R. rufescens type is incom-

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU 17 pletely known, limiting comparisons of the ali- in R. rufescens seems a questionable basis for sphenoid and basioccipital regions. Although the separating these two taxa into different genera. posterior palate is damaged in the type, Thomas Other genera that show different degrees of pel- (1917) assigned a long palate to R. rufescens after age textures ranging from soft to spiny pelage are examining another bmnh specimen that apparently present in the subfamily as the genera was subsequently lost (V. Pacheco, pers. comm.)- , Maxomys, and Niniventer (M. Apparently, however, the posterior opening of the Carleton. in litt., July 10, 2002). However, com- alisphenoid canal is smaller in R. longilingiia than parison of other characters may indicate it war- in R. rufescens. rants a generic distinction. The upper molar tooth row of R. rufescens is Comments on the Morphology with Respect longer than in R. longilingua (4.73 mm for R. ru- TO Other Muridae The presence of a nail in the fescens, versus 4.52 mm for R. longilingua; P. Jen- hallux of R. longilingua (Fig. 4b) differs from al- kins, pers. comm.), while the width is the same most all Sigmodontinae except R. rufescens, in (P. Jenkins, pers. comm.); consequently, the which this character was first scored by Thomas length-to-width ratio is noticeably smaller in R. (1886) for South American mice. This condition longilingua than in R. rufescens. In both species, is present in many arboreal mammals and is M3 only has two well-defined cusps (protocone sometimes associated with opposability of the hal- and paracone; Thomas [1917] stated this for R. lux, such as in some marsupials, extinct primates rufescens): however. R. rufescens has a bigger un- (Musser, 1979). and some arboreal . As a differentiated heel than R. longilingua, which result of convergence, this character is present in makes M3 more of an inverted triangle. The man- other members of the Muridae family, as in Den- dibular molars are configured in a parallel man- dromurinae and Murinae subfamilies. We exam- ner: the length-to-width ratio is smaller in R. lon- ined this same character in the African climbing gilingua than in R. rufescens, and R. rufescens has mouse Dendromus mesomelas (Muridae: Dendro- longer teeth, with conspicuous posterolophids on murinae). This genus has similar toe morphology, ml and m2. with long digits. D5 elongate, and a very short Shared cranial characters include a strongly hallux with a nail, all as in R. longilingua, but built skull, with short, narrow, and blunt rostrum; with substantially narrower feet. Surprisingly, the a strong alisphenoid strut that hides the aperture feet morphology of the Peruvian taxon is very of the anterior opening of the alisphenoid canal; similar to the one of the genus Chiropodomys foramen ovale visible in ventral view, exposed by (Muridae: Murinae). Chiropodomys has a short the narrow parapterygoid fossa and the absence and broad manus and pes. with the hallux and of a ridge along the lateral edge of the alisphe- pollex each bearing a nail; fingertips with thick noid; middle lacerate foramen completely closed; pads; digits with deep transversal grooves; and and highly cuspidate molar teeth. The mandible similar large plantar pads sculptured with what has a short angular process, extending only as far Musser (1979) called semicircular striae (see as the base of the condyloid process; a capsular Musser. 1979. figs. 13 and 14) that give R. lon- projection of the incisor distinct as a conspicuous gilingua its diagnostic callous pad surface. In knob in dorsal view; a conspicuous inferior mas- spite of these similarities. Chiropodomys has lon- seteric ridge; and deep and broad retromolar fos- ger, sharp-tipped, and more curved claws and sae in both species. Although the coronoid pro- thicker pads on the fingertips. cess is broken in the type of R. rufescens, it was Similarities with members of the family Sig- apparently short and strong as in R. longilingua. modontinae include that, cranially. in dorsal view, Descriptions of R. rufescens do not include the supraorbital ridges of R. longilingua are many of the characters we have noted in R. lon- strongly beaded, as in members of the oryzomyi- gilingua. such as the long tongue, the crescent- ne group of Hershkovitz (1962). shaped depression in the fingertips, cranial char- In ventral view, R. longilingua has a wide pal- acters (such as the fontanelles in the paraptery- ate similar to oryzomyine, phyllotine. and ichth- goid fossae, the ectotympanic structure, and ca- yomyine groups of Hershkovitz (1962). rotid circulation), postcranial characters, and soft Cranially. the most diagnostic characteristics of characters. However, both taxa share a uniquely R. longilingua can be identified in ventral view. derived morphology that has never been seen be- Therefore, the foramen ovale accessorius is con- fore in other Sigmodontinae. The different fur tex- spicuously visible from this view due to the nar- ture spiny fur in R. longilingua and the soft fur row parapterygoid fossa, and this may be associ-

18 FIELDIANA: ZOOLOGY ated with a small internal pterygoid muscle. Al- of the holotype of R. longilingua contained noth- though the foramen ovale accessorius was also ing but insects. Analyzing the finely triturated re- seen (in ventral view) in specimens of the ako- mains, we detected fly larvae (Diptera), a cater- dontines Necromys amoenus, N. laslurus, and pillar (Lepidoptera), and ants (Hymenoptera: For- some Akodon, in this case the foramen is associ- micidae) of the genus Solenopsis. ated with a much larger anterior opening of the The various insect remains in the stomach sug- alisphenoid canal, with which it fuses, forming a gest that this species is insectivorous, at least to a single foramen, which differentiates it from the degree (given that many rodents are granivorous one observed in R. longilingua. or herbivorous, it might generally be opportunis- The retromolar fossa of R. longilingua is deeper tic). An insectivorous diet suits the morphology than in most Sigmodontinae, with the apparent ex- of the molar teeth, which are pentalophodont, ception of R. rufescens. This is the insertion point with conspicuous cusps that may be classified as of one of the bodies of the temporalis muscle. The either crested or terraced {sensu Hershkovitz, anterior part of the temporalis originates on the 1967), and by a relatively short, small intestine temporal ridge, almost reaching to the interpari- and caecum (Vorontzov, 1979). The relative pro- etal. Passing within the orbit, it inserts on the ven- portions of the small intestine and caecum are tral surface of the coronoid process and its base. commonly associated with an insectivorous diet. Perhaps this configuration explains the notably Moreover, Rhagomys seems to have powerful small size of the coronoid process. Dissection will mastication muscles, as judged from the conspic- be necessary to determine further details of this uous postorbital process and broad retromolar re- relationship. gion (for the temporalis muscle) and the conspic- uous inferior masseteric ridge (associated with a strong anterior deep masseter muscle). Where and how this species forages are still Ecological Observations unknown. The first two specimens were collected in a pitfall bucket-line fence, which is generally more effective for terrestrial, ground-foraging Habitat The male holotype (musm 17013) species. However, pitfalls also take arboreal mam- and a female paratype (fmnh 1 70687) were found mals such as Gracilinanus, Oecomys, and Rhipi- freshly dead in two different 50-m pitfall lines on domys. The arboreal nature of this species is sug- consecutive days of sampling in dense cloud for- gested by its highly specialized feet (broad feet est habitats at the type locality. The holotype was with fleshy and conspicuously callous surface, trapped at 1900 m elevation and the paratype was with transverse and D5 taken at about 2100 m elevation. While this de- digits deep grooves, long in relation to D4), and the palmar and plantar tex- scription was in preparation, a third specimen was tures reported in Chiropodomys similar to the trapped in lowland cana brava habitat at 450 m, ones of R. for within a few meters of the banks of the Rio Alto longilingua suggest adaptations movement on above the ground, where Madre de Dios near Maskoitania.- It was taken in supports adhesion to surfaces may be more important than a single-sprung Victor rat trap set 1 m above- grasping supports (Musser, 1979). In addition, the ground along a horizontal cane. The trap was bait- short muzzle and enlarged eyes afford R. longilin- ed at sunset with a ball of oatmeal, peanut butter, gua a wide field of frontal vision, as suggested by vanilla extract, and fish oil wrapped in cheese- Hershkovitz (1972) for arboreal oryzomyines. cloth, and the mouse was found at sunrise the fol- The capture of the third specimen in a distinc- lowing morning. The cane was approximately 5 tively arboreal setting and on smooth cane con- cm in diameter. Assuming that this species is con- firms its ability to exploit aboveground niches. tinuously distributed between both capture sites, Rhagomys longilingua may use its long tongue its range encompasses lowland humid forest, as a to extract ants and other insects from montane forest, and lower cloud forest habitats. probe cavities and crevices. from the Diet and Trophic Adaptations The stomach Judging strongly built skull, this species may open holes in cane or incisors and other plants using its short and broad - This male was as specimen (fmnh 175218) prepared powerful mastication configuration (deep retro- an alcoholic specimen, with cleaned skull, larger ecto- molar fossa, high and short hemimandibles, and parasites in alcohol (CWD P-145), and heart, lung, and masseteric ridges) in order to expose liver tissues in liquid nitrogen. Measurements are tallied conspicuous in Table 1. the resources they contain.

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU 19 Discussion zomyini (Voss & Carleton. 1993). Both species lack the pectoral pair of mammae (Thomas, 1917), Although there have been significant advances having only three pairs of mammae. (The oryzo- in the understanding of Sigmodontinae phyloge- myine Scolomys juruaense also has the same mam- netics. we are still far from a complete picture mary formula [Patton & da Silva, 1995].) Rhago- (D'Elia, 2000). One of the problems is allocating mys longilingua has a broad alisphenoid strut, forms treated as incertae sedis (Reig, 1986; Mc- which does not separate the buccinator-masticatory Kenna & Bell. 1997: Smith & Patton. 1999) or as from the ovale accessorius foramina: rather, they "plesiomorphic Neotropical muroids" (Voss. are fused, and the former cannot be seen in lateral 1993). Each author has a distinct list of genera view. Character states suggesting a close phylo- with uncertain relationships, but problematic genetic relationship with the include forms include Abrawayaomys. Aepeomys, Chilo- the presence of a long palate, the lack of a posterior mys. Phaenomys. Rhagomys, Thomasomys, Wil- suspensory process of the squamosal attached to fredomys, Delomys. Microakodontomys, Pimo- the tegmen tympani, and the absence of a gallblad- mys, Scolomys, Reithrodon, Irenomys, Zygodon- der. Character states that may suggest phylogenetic tomys, and Pseudoryzomys. Insufficient material relationship with the "Thomasomyine" group are and inadequate descriptions or analyses are cer- long ungual tufts, 3 pairs of mammae, 1 3 pairs of tainly responsible for some of this confusion, and ribs, and the mesopterygoid fossae not fenestrated this is certainly the case with the two fragmentary (Voss. 1993, table 3). However, the latter group is samples of R. rufescens. being revised by V. Pacheco, and new definitions The possession of extraordinary unique char- of its comp)onents should soon be available. In ad- acters for R. rufescens and R. longilingua suggest dition, molecular and more detailed morphological a relationship, one exclusive of other sigmodon- studies are now under way that should offer a more tines. To substantiate this will require a compre- thorough investigation of these two grand assem- hensive phylogenetic analysis of Sigmodontinae. blages of mice and their relationships to Rhagomys. With incomplete material and uncertain generic This preliminary report of Rhagomys already affinities (Reig. 1980: Musser & Carleton. 1993). identifies the following presumptive synapomor- the tribal relationships of Rhagomys have invari- phies as supporting their sisterhood: nail in the ably been treated as incertae sedis (Carleton & hallux, cuspidate molars and the very short an- Musser. 1984: Reig. 1986: McKenna & Bell. gular process of the mandible, bony ridge in the 1997: Smith & Patton. 1999). However, the dis- lateral edge of the parapterygoid fossa absent, covery of another species of Rhago?nys. together then the foramen ovale accessorius visible from with the detailed character sets now available for the ventral view related to a very small posterior analysis of R. longilingua, open the door to com- opening of the alisphenoid canal. prehensive revisions of the tribes of sigmodonti- Comments on the Biogeography of the Ge- nes. Given the enormous size of this assemblage nus Although R. longilingua and R. rufescens (currently, more than 400 species in nearly 100 share unique cranial and external characters, they genera), a comprehensive treatment will be time- are widely separated geographically R. rufes- consuming. At present, comprehensive analyses cens is only known from the Atlantic forest of Rio of morphology and gene-sequence divergence are de Janeiro, while R. longilingua is only known in progress. However, preliminary results of phy- from Manu Biosphere Reserve and in external logenetic analyses based on 86 morphological phenotyp)e, without a succession of intermediates characters (external and cranial characters) con- linking them. Either R. longilingua and R. rufes- firm Rhagomys as a monophyletic genus (90% of cens are relicts of a nearly extinct, formerly wide- bootstrap suppK)rt) without a clear tribal associa- spread clade or else scientists have failed to sam- tion (Luna, 2001). ple them in intervening areas. An interesting ex- Thomas (1917) had already noted interesting re- ample of this is the genus , which lationships based on the external and cranial mor- was known for decades solely from two Brazilian phology of Rhagomys, finding that this sp)ecies was species in Lagoa Santa and the Distrito Federal. somewhat related to Oecomys (Oryzomyini) and to Recently, Louise Emmons (1999) described two what he called the Rhipidomys-Tltomasomys com- more species from Bolivia. Regardless, Rhagomys plex C'thomasomyines"). Rhagomys longilingua must have been (or still is) continuously distrib- and perhaps also R. rufescens present characters uted across South America. The report of R. lon- that fall outside of the current diagnosis for Ory- gilingua widens the geographical range of the in-

20 FIELDIANA: ZOOLOGY certae sedis genus Rhagomys, previously consid- panions Paul Velazco, Tatiana Pequeiio, Jessica ered endemic to southeastern Brazil, and, as may Amanzo, Ursula Paredes, Edith Suazo, Carl Dick, be the case with other endemic genera (Phaeno- Don Gettinger, Douglas Stotz, Pepe Tello, and mys, Abrawayaomys, and Microakodontomys), it Brian O'Shea all helped record mammals in the might also represent an independent lineage field. We are particularly grateful to Maximo Car- (Smith & Patton, 1999). eche for his outstanding field skills, which en- a dis- So far as presently known, Rhagomys has sured that our camps were comfortable and pro- Brazilian Atlantic tribution limited to the high- ductive and our collections highly diverse. We ap- and the eastern of the lands (/?. rufescens) slope preciate the professionalism of Instituto de Re- Andes {R. longilingua). It is the first mammalian cursos Naturales, Peru (INRENA), and the group to show this unusual disjunct distribution Jefatura of Parque Nacional del Manu, which is- but similar of distribution have pattern, patterns sued permissions for the collection and exporta- been reported for hylid frogs of the parx'i- tion of this material (Autorizacion Nos. 64-99 IN- ceps group (Duellman & Crump, 1974). Some au- RENA and 003-2001 INRENA-J-DGANPFS). thors have attributed distributional to disjunctions During the preparation of this report, the senior climate the that changes during author held graduate student assistantships funded caused and of forest fragmentation reexpansion by the Manu surveys grant and the Brown Fund. corridors and How- refugia (Vuilleumier, 1971). In addition, tuition fee waivers by the Department ever, the of in re- timing disjunctions Rhagomys of Biological Sciences at the University of Illinois mains and Neotropical disjunc- unspecified, many at Chicago were greatly appreciated. tions antedate the Pleistocene Lund- greatly (e.g., We wish to extend our appreciation to Guy G. et al., 1986). Calibration of the molecular berg Musser (amnh) for lending us his photographs of clock of Rhagomys may be expected to shed light the type specimens of Rhagomys rufescens, which on this question. served as a primary basis of comparisons; to Smith and Patton (1999) concluded that south- Richard Harbord (bmnh) for providing additional eastern Brazil has been an important geographic digital images of this specimen; and to Paula Jen- center in the diversification of the sigmodontines; kins (bmnh) for her very keen and useful obser- some of these have subsequently extended their vations of the Rhagomys rufescens holotype and ranges across South America. We expect to de- hospitality during the junior author's study visit. termine the timing of these events in Rhagomys We are indebted to Robert S. Voss (amnh) for his after the analysis of its phylogenetic relationships excellent advice and insights on drafting the mor- with other Neotropical sigmodontines is complet- phological description, and to Michael Carleton ed. Our preliminary results suggest that Rhagomys (usnm), Barry Chernoff (fmnh), and Guillermo represents a well-differentiated lineage of Sig- D'Elia (ummz), whose comments greatly im- modontinae that warrants taxonomic recognition. proved this report, as well as to Jack Fooden Therefore, in order to understand the sigmodon- (fmnh) for invaluable taxonomic discussions. tine radiation as a whole, we hope to resolve the Many thanks also to Marcelo Weksler (amnh), phylogenetic relationships of this genus in relation Phil Myers (ummz), Alexandre R. Percequillo to the other Sigmodontinae. (Mzusp), and Julian Kerbis (Roosevelt University, Chicago) for sharing their knowledge of muroid systematics with the senior author. of Vertebrate Zool- Acknowledgments James L. Patton (Museum ogy, University of California, Berkeley) kindly loaned us of Scolomys juruaense. Phil- The Manu surveys were supported by the NSF specimens Parrillo (fmnh) identified insects recovered in (DEB-9870191), the Field Museum (especially ip stomach contents. Strack (fmnh) assisted the Marshall Field III Fund, the Barbara E. Brown Betty with the SEM Nancy Holiday Fund for Mammal Research, and a gift from Jake photography. her in scientific and and Catherine Jacobus), and the Museo de His- shared experience drawing, Phil the senior toria Natural, Universidad de San Marcos, Lima, Clara Simpson and Myers provided with invaluable information on im- Peru. We are grateful to Sergio Solari, project co- author digital Bill and ordinator and inveterate fieldworker, and to Victor aging techniques. John Phelps, Stanley, curatorial Pacheco, Irma Franke, and Niels Valencia for Michi Schulenberg (fmnh) provided most their support in hosting the teams. Stalwart com- support, for which we are grateful.

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU 21 Literature Cited . 1977. Teeth 1. Basic crown patterns and cusp homologies, pp. 276-301. In Living New World Mon- Beddard, E E. 1902. Observations the vi- upon carpal keys (Platyrrhini), With an Introduction to Primates, brissae in mammals. of the Proceedings Zoological Vol. 1 . University of Chicago Press, Chicago. Society of London. I(IX): 127-136. 1 994. The description of a new species of South Brown. J. C. 1971. The of mammals. 1. The description American hocicudo. or long-nose mouse genus Ox\- external characters of the head. Mammal Review. mycterus (Sigmodontinae. ), with a critical 1(6): 151-168. review of the generic content. Fieldiana: Zoology, n.s., Brown, J. C, and D. W. Yalden. 1973. The description 79: 1-43. of mammals. 2. Limbs and locomotion of terrestrial Howell, A. B. 1926. Anatomy of the Wood Rat. Com- mammals. Mammal Review, 107-134. 3(4): parative Anatomy of the Subgenera of the American BuGGE, J. 1970. The contribution of the stapedial artery Wood Rat (genus Neotoma). Monographs of the to the cephalic arterial supply in muroid rodents. Acta American Society of Mammalogist. No. 1. Williams Anatomica. 76: 313-336. & Wilkins Co., Baltimore. Carleton, M. D. 1973. A survey of gross stomach mor- KooPMAN, K. E 1982. Biogeography of the bats of South phology in New World Cricetinae (Rodentia. Muro- America, pp. 273-302. / Mares, M. A., and H. H. idea). with comments on functional interpretations. Genoways, eds.. Mammalian Biology in South Amer- Miscellaneous Publications, Museum of Zoology. ica. University of Pittsburgh. Pittsburgh, Pennsylva- , 146: 43 pp. nia.

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. 1967. Dynamics of molar evolution: A Myers, P., J. L. Patton, and M. E Smith. 1990. A re- study based on New World Cricetinae, Family Muri- view of the BoUviensis group of Akodon (Muridae: dae. Journal of Dental Research, Supplement, 46(5): Sigmodontinae), with emphasis on Peru and Bolivia. 829-842. Miscellaneous Publications. Museum of Zoology, of 177: iv -I- 1-104. . 1972. The Recent mammals of the Neotropical University Michigan, region: A zoogeographic and ecological review, pp. Pacheco, v., B. D. Patterson, J. L. Patton. L. H. Em- 31 1-431. //; Keast, A. E. E C. Erk. and B. Glass, eds.. mons, S. SOLARl, AND C. F ASCORRA. 1993. List of Evolution, Mammals, and Southern Continents. State mammal species known to occur in Manu Biosphere University of New York Press, Albany. Reserve, Peru. Publicaciones del Museo de Historia

22 FffiLDIANA: ZOOLOGY Natural, Universidad Nacional Mayor de San Marcos, Voss, R. S. 1988. Systematics and ecology of ichthy- Serie A Zoologia, 44: 1-12. omyine rodents (Muroidea): Patterns of morphological Patterson, B. D. 2000. Patterns and trends in the dis- evolution in a small adaptive radiation. Bulletin of the American Museum of Natural covery of new Neotropical mammals. Diversity and History, 188(2): 260- Distributions, 6: 145-151. 493.

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Patterson, B. D., D. F. Stotz, S. Solari, J. W. Fitz- . 1993. A revision of the Brazilian muroid rodent with PATRiCK, AND V. Pacheco. 1998. Contrasting patterns genus Delomys remarks on "Thomasomyine" of elevational zonation for birds and mammals in the characters. American Museum Novitates, 3073: 1-44. Andes of southeastern Peru. of Journal Biogeography, Voss, R. S., AND M. D. Carleton. 1993. A new genus 25: 593-607. for Hesperomys molitor Winge and Holochilus mag- Patton, J. L., AND M. N. F. Da Silva. 1995. A review nus Hershkovitz (Mammalia, Muridae) with an anal- of the spiny mouse Scolomys (Rodentia: Muridae: Sig- ysis of its phylogenetic relationships. American Mu- modontinae) with the description of a new species seum Novitates, 3085: 1-39. from the western of Brazil. of Amazon Proceedings Voss, R. S., AND A. V. LiNZEY. 1981. Comparative gross the Biological Society of Washington, 108(2): 319- morphology of male accessory glands among Neo- 337. tropical Muridae (Mammalia: Rodentia) with com- Reig, O. a. 1980. A new fossil of South American cri- ments on systematic implications. Miscellaneous Pub- cetid rodents allied to Wiedomys, with an assessment lications of the Museum of Zoology, University of of the Sigmodontinae. Journal of Zoology, London, Michigan, 159: 1-41. 192: 257-281. Vuilleumier, B. S. 1971. Pleistocene changes in the fau-

. 1984. Distribui9ao geografica e historia evolu- na and flora of South America. Science, 173:771-780. tiva dos roedores Muroideos sulamericanos (Criceti- Wilson, D. E., and D. M. Reeder. 1993. Mammal Spe- dae: Revista Brasileira de Sigmodontinae). Genetica, cies of the World: A Taxonomic and Geographic Ref- 333-365. 7(2): erence. Smithsonian Institution Press, Washington,

. 1986. Diversity patterns and differentiation of D.C. high Andean rodents, pp. 404-439. In Vuilleumier, E, and M. Monasterio, eds.. High Altitude Tropical Bio- geography. Oxford University Press, London. RiDGWAY, R. 1912. Color Standards and Color Nomen- clature, 1st ed. Author, Washington, D.C. 44 pp. + 54 Appendix plates. Smith, M. E, and J. L. Patton. 1999. Phylogenetic re- Abbreviations lationships and the radiation of sigmodontine rodents in South American: Evidence from b. cytochrome Abbreviations for institutions are as follows: Field Journal of Mammalian Evolution, 6(2): 89-127. Museum of Natural History, Chicago (fmnh); Sonntag, C. E 1924. The comparative anatomy of the Natural London Mu- tongues of the Mammalia. X. Rodentia. Proceedings History Museum, (bmnh); of the Zoological Society of London, 1924: 725-741. seum of Vertebrate Zoology, University of Cali- Steppan, S. J. 1995. Revision of the Tribe Phyllotini fornia, Berkeley (mvz); Museo de Historia Natu- with a (Rodentia: Sigmodontinae), phylogenetic hy- ral, Universidad Mayor de San Marcos, Lima, pothesis for the Sigmodontinae. Eieldiana: Zoology, Peru (musm); University of Michigan Museum of n.s., 80: 1-112. Zoology, Ann Arbor (ummz). Terborgh, J. W, J. W. Eitzpatrick, and L. H. Emmons. 1984. Annotated checklist of bird and mammal spe- cies of Cocha Cashu Biological Station, Manu Na- tional Park, Peru. Fieldiana: Zoology, n.s., 21: 1-19. Specimens Examined Thomas, O. 1886. Description of a new Brazilian spe- cies of Hesperomys. Annals and Magazine of Natural This report is based on examinations of 36 spec- History, 17(6): 250-251. imens, as follows. . 1917. On the arrangement of the South Amer- Dendromus mesomelas (2) TANZANIA, 2. Put- ican rats allied to Oryzomys and Rhipidomys. Annals Mbizi Moun- and Magazine of Natural History, 20(8): 192-198. wa Region, Sumbawanga District, Forest Vi 3 E Wi- Tullberg, T 1899. Ueber das System der Nagetiere. tains, Mbiz Reserve, km S, km Nova Acta Reg. Soc. Upsaliensis, ser. 3, 18: i-v, 1- panga, 0752'30"S, 3140'00", 2300 m (fmnh Al-18 + 57 514, pis. 171306, 171307). VoRONTSOV, N. N. 1979. Evolution of the Alimentary Chiropodomys gliroides (2) MALAYSIA, 2. System in Myomorph Rodents. Indian National Sci- Kuala Lumpur, Selangor, Kepong, Bukit Lagong entific Documentary Center, New Delhi, (published for the Smithsonian Institution and National Science Forest Reserve (ummz 117158, 117159). Foundation). 346 pp. Akodon aerosus (4) PERU, 4. Cusco, Paucar-

LUNA AND PATTERSON: A REMARKABLE NEW MOUSE FROM PERU 23 tambo, Suecia, km 138.5 Carretera Shintuya, 1900 Neacomys spinosus (11) PERU, 2. Inca Mines m (FMNH 170420, 170423, 170427, 170428). (FMNH 20088*, 20089*). PERU, 2. Puno, Santo Necromys lasiurus (3) BRAZIL, 3. Pemambuco, Domingo (fmnh 5271 1*, 525712*). PERU, 1. San Sao Louren90 da Mata, Estagao Ecologica de Ta- Martin, Moyobamba (fmnh 19360*). PERU, 2. pacura (fmnh 123065, 123067, 123068). Rio Cayumba (fmnh 24762*, 24763*). PERU, 1. Necromys amoenus (3) PERU, 3. Arequipa, Pasco, Pozuzo, Rio Pachitea (fmnh 24765*). Chivay,"5 km NNE, 12000 ft (-=3600 m) (fmnh PERU, 1. Puno, Segrario (fmnh 52710*). PERU, 107665, 107666, 107680). 1. Poco Tambo (fmnh 19691*). PERU, 1. Puerto Rhagomys longilingua (3) PERU, 2. Cusco, Victoria (fmnh 51358). Paucartambo, km 138.5 Shintuya Road, 1900 m Scolomys juruaense (7) BRAZIL, 2. Amazonas, (FMNH 170687, MUSM 17013). PERU, 1. Madre Penedo, right bank Rio Jurua (mvz 183165*, de Dios, Manu, along the Rio Alto Madre de Dios 183166*). BRAZIL, 2. Amazonas, Condor, right near Maskoitania, 450 m (bdp 4000). bank Rio Jurua (mvz 183167*, 183168*). BRA-

Rhagomys rufescens ( 1 ) BRAZIL, 1 . Rio Janei- ZIL, 3. Amazonas, Barro Vermelho, left bank Rio ro [sic] (BMNH 86.2.8.5*). Jurua (MVZ 183169*, 183170, 183171). BRAZIL, 1. Amazonas, Sobral, left bank Rio Jurua, Ama- * Specimens measured; see Table 1 . zonas (mvz 183172).

24 FIELDIANA: ZOOLOGY