Bates, Marston, 1906-1974.

Goodwin, George Gilbert.

MacDougall, Thomas Baillie, 1896-1973.

American Museum of Natural History Scientific Publications

il/lierian%MlusdumoxfitatesPUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORYCENTRAL PARK WEST AT 79TH STREET, NEW YORK 24, N.Y.NUMBER 1738 JUNE 10, 1955New Tree-climbing Rats fromMexico and ColombiaBY GEORGE G. GOODWINIn the collections of mammals recently made by Thomas MacDougallon the Isthmut of Tehuantepec, Mexico, there are two skins and threeskulls of a large tree-climbing rat. One skin and skull of a subadult maleand the skull of an older individual belong to a large-toothed group,possibly allied to Tylomys tumbalensis, and resemble T. gymnurus ofVeracruz in the size of the teeth and in having white under parts and auniform Snuff Brown' back. The other specimen is a small-toothed speciesand belongs in the T. nudicaudus group. This specimen seems to differsufficiently in external and cranial characters from described forms tobe considered a representative of a new subspecies.The Colombian Tylomys was collected by Marston Bates in 1943 andcame from the Cordillera Oriental, northwest of Bogota. It seems todiffer sufficiently from Thomas' species T. mirae from northern Ecuadorand from Anthony's Panamanian species, T. fulviventer, from Tacar-cuna, the two nearest species (though widely separated geographically),to be recognized as a new form.Tylomys nudicaudus microdon, new subspeciesOAXACA TREE RATTYPE: A.M.N.H. No. 165991 skin and skull, teeth well worn, fullyadult male; La Gloria, rain forest at about 2500 feet elevation, 10kilometers so4heast of Santa Maria Chimalapa, Isthmus of Tehuantepec,Oaxaca, Mexico; collector, Thomas MacDougall; April 2, 1954; original1 Capitalized color terms are after Ridgway, "Color standards and color nomen-clature," Washington, D. C., 1912.AMERICAN MUSEUM NOVITATESno. 1313. The skin of the type is in good condition, and the skull is com-plete except that the supraoccipital is broken.GENERAL CHARACTERS: A relatively small tree rat with large ears,dark dorsal stripe, white under parts, grayish muzzle, and small teeth.DESCRIPTION OF TYPE: The color of upper parts in fresh pelage isbetween Cinnamon-Buff and Wood Brown, with a broad, dark dorsalband extending down back from between ears to rump owing to a heavyadmixture of glossy, blackish hairs; cheeks and lower sides of bodynearly clear Cinnamon Buff; top of head grayer than back, and areaaround eye not noticeably darker than rest of head; base of whiskers,nose, lips, and chin Hair Brown; inner sides of forearms and under partswhite to roots of hairs; the line of demarcation moderately well defined;ears blackish, almost naked, with an indistinct, narrow, whitish margin;hind limbs and outer sides of fore limbs like sides of body; upper sidesof fore and hind feet Bister; toes and a narrow edging on outer side ofhind feet white; tail naked except for a few hairs growing between scales,blackish for most of its length, less than terminal third indistinctly dull,soiled whitish. The scales are sharply squared instead of being somewhathexagonal and grouped to form even, circular bands.Skull similar to that of T. tumbalensis Merriam from Tumbala, 5500feet elevation, Chiapas, but with smaller molariform teeth and longer andheavier rostrum. Nasals long and narrowly wedge-shaped, truncate pos-teriorly and scarcely surpassed by premaxillae; zygomatic arches strongand broadly spreading; zygomatic notch' broad and shallow; anteriorpalatine foramina rather long and narrow and extending posteriorly to aline across front of molars; supraorbital ridges strongly developed, witha prominent postorbital angle, from which they extend nearly straightbackward to outer corners of interparietal and are only slightly bowedoutward in the parietal region; interparietal relatively narrow, convexanteriorly and nearly straight across posteriorly; bullae normal for thegenus, moderately large and rounded with well-developed anterior pro-longation; palatal bridge extending backward to a line across posteriorborder of last molars; molariform teeth small and narrow.MEASUREMENTS OF TYPE: Skin, measured in the field: total length,422 mm.; length of tail, 227; length of hind foot, 39 (dry, 37.5); lengthof ear from notch after dampening, 22. Skull: greatest length, 49.5;condylobasal length, 45 (to front of incisors) ; basal length, 42.4; palatallength, 24.2; palatal bridge, 8.2; length of nasals, 18.7; zygomaticbreadth, 26; width of braincase across ridges, 19.7; interorbital width,1 Refers to the notch on the superior surface of the skull at the anterior borderof the zygomatic arch.2 NO-. 1738GOODWIN: NEW RATS9.1; greatest width of rostrum, 9.5; width of palate across m2-m2, 8.6;width of anterior upper molar, 2; alveolar length of upper molariformtooth row, 8.1; crowns, 8.3.REMARKS: Tylomys n. microdon appears to be about the size of T.bullaris Merriam from Tuxtla Gutierrez, 1800 feet elevation, Chiapas,but the bullae in microdon are normal, not large, broadly rounded, with-out anterior prolongation as in bullaris. Tylomys gymnurus Villa fromPresidio, 1000 feet, Veracruz, is about the size of microdon in externalmeasurements, but it has a shorter and narrower skull, shorter rostrum,and much larger molariform teeth than microdon and is as large astumbalensis in cranial measurements. In Villa's figure of the type skull,the zygomatic arches taper evenly forward to the rostrum without show-ing an indication of a zygomatic notch which is quite distinct in microdon.Tylomys n. microdon is apparently nearest to typical T. nudicaudus.It compares favorable with Peters' figures of the type skull, an immaturefemale from Guatemala (exact locality not known), which has a maxil-lary tooth measuring 8.5 mm. In cranial characters microdon also ismuch like a subadult male with small molariform teeth (8 mm.) fromChimoxan, 1500 feet, Guatemala, identified by Goldman and referredby Goodwin, 1934, to T. nudicaudus, but it is smaller than the Guate-malan specimen and differs in some external and cranial details. TheTABLE 1MEASUREMENTS (IN MILLIMETERS) OF TYPE SPECIMENS OFTylomys FROM MEXICOtumbalensis gymnurus microdon bullarisSubadult Adult Adult JuvenileTumbala Presidio La Gloria Tuxtla5500 feet 1000 feet 2500 feet 1800 feetSkinTotal length 448.0 400.0 422.0 324.0Length of tail 234.0 200.0 227.0 158.0Length of hind foot 46.0 38.6 39.0 37.5SkullLength 49.1 49.0 49.5Condylobasal length 43.8 43.8 45.3 36.2Length of nasals 16.1 16.1 18.7Zygomatic breadth 24.3 25.2 26 .0 20.8Interorbital breadth 8.9 8.5 9.1 7.8Maxillary tooth row 9.3 9.0 8.1 8.21955 3AMERICAN MUSEUM NOVITATESsecond Guatemalan specimen referred by Goodwin, 1934, to nudicauduscame from La Primavera, a near-by locality, but it was taken at a higherelevation, 3200 feet, than was the Chimoxan specimen. This individualmay well be tumbalensis, as it has similar buffy brown under parts(which may or may not be a significant character), is even larger thanthe type in external and cranial measurements, and has equally largemolariform teeth (9 mm.).A subadult male from Ixcuintepec, 3000 feet, Oaxaca, is Snuff Brownon upper parts, without a darkened dorsal area, paler on sides of body,and extensively white on the under parts. The skull of this specimen andthat of another older individual without skin from the District of Te-huantepec have large molariform teeth (9.0, 8.8 mm.) and short, wide,palatine foramina. These two specimens are provisionally referred to T.gymnutrus.Tylomys mirae bogotensis, new subspeciesBOGOTA TREE RATTYPE: A.M.N.H. No. 143523, skin and skull, fully adult male, teethshowing considerable wear; Volc'an Caparrapi on the western slopes ofthe Cordillera Oriental, elevation about 1270 meters, 90 kilometersnorth-northwest of Bogot'a and 10 kilometers west of La Palma, Colom-bia; collector, Marston Bates; November 18, 1943; original no. 2643.The skin of the type is in good condition, and the skull complete exceptfor tympanic bullae.GENERAL CHARACTERS: A large, uniformly colored tree rat with com-paratively small ears, long, naked tail, and very long vibrissae (107.5mm.), similar in general characters to Tylornys mirae Thomas fromParamba, 1100 meters elevation, northern Ecuador, but lighter in coloron the back, with dusky instead of white under parts, and smaller teeth.DESCRIPTION OF TYPE: General color of upper parts about SnuffBrown, more buffy on sides of body and grayer on head, with a duskyring around eye; hairs on under parts whitish at extreme base, followedby a broad band of plumbeous and tipped with Light Buff; small areason the inguinal region, on the throat, and on the chest, and a narrowline down inner sides of fore and hind limbs white; an indistinct, verynarrow white line down abdomen; outside fore and hind limbs like sidesof body; upper sides of fore and hind feet Bister; terminal phalanges andclaws white; ears blackish; proximal half of tail blackish brown brokenby narrow yellowish rings between the scales; terminal half of tail yel-lowish white; the junction between light and dark areas sharply defined.Skull large and angular without any indication of a zygomatic notch;4 NO. 1738GOODWIN: NEW RATSnasals truncate posteriorly and ending on a line with premaxillae; supra-orbital ridges with prominent postorbital angle from which they runbackward and are curved strongly outward in parietal region; molari-form teeth relatively small and narrow.MEASUREMENTS OF TYPE: (Those of the type of T. mirae, adult male,teeth much worn, in parentheses). Total length, 470 mm. (496); lengthof tail, 240 (266); length of hind foot, 40, in dry skin with claws, 41.5(s.u., 41); ear, 20, from notch after dampening, 22.2 (28); weight, 265grams. Skull: greatest length, 52.7 (54); condylobasal length, 48; basallength, 45.5; basilar length, 42.3 (42.5); palatilar length, 21.5 (22.2);palatal bridge, 8.3; zygomatic breadth, 27.3 (28); length of nasals, 18.5(19); width of braincase across ridges, 19.8 (20); interorbital breadth,10.5 (11); greatest breadth of rostrum, 10; width of anterior uppermolar, 2.1; diastema, 14.5 (15); alveolar length of upper molariforintooth row, 8.1; of crowns, 8.25 (8.8).REMARKS: A series of six specimens apparently referable to T. miraefrom Barbacoas, southwestern Colombia, are much darker in color thanbogotensis. All have the hair on under parts white to roots and largemolariform teeth averaging 8.7 mm. Tylomys m. bogotensis is not veryunlike the type of T. fulviventer Anthony from Tacarcuna, Panama, asubadult female which has similar small molariform teeth (7.8 mm.),but bogotensis is larger, grayer in color, and the under parts are muchdarker, and it has no indication of a zygomatic notch which is quite dis-tinct in fulviventer.1955 5

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