Toromys Iack-Ximenes et al., 2005
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publication ID |
https://doi.org/ 10.1206/3894.1 |
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persistent identifier |
https://treatment.plazi.org/id/039C2E2F-FFF0-D55E-FE72-FBD2FD06FA6D |
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treatment provided by |
Carolina |
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scientific name |
Toromys Iack-Ximenes et al., 2005 |
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Toromys Iack-Ximenes et al., 2005
TYPE SPECIES: Loncheres grandis Wagner, 1845 .
CONTENTS: Three species, including a new species from eastern Peru (described below).
REVISED DIAGNOSIS: Large, arboreally adapted rats with long backs, short legs, and broad feet ( figs. 6A View FIG , 14A View FIG ). Tails slightly shorter than head and body length. Pelage with dorsal aristiforms of narrow, stiff, flexible bristles banded black and yellow, buff, or rusty; crown brown agouti or black; rust color, if present on the rostrum, does not extend above or posterior to the eyes from the muzzle or cheeks ( figs. 13A, B View FIG ; 14A, C View FIG ). Tail hairs distal to the basal extension of the dorsal pelage are longest dorsally and proximally, where they can cover the scales, and they gradually shorten distally. Cranium narrow and elongate, with parietals elongate and interparietal long at the midpoint of the dorsal view, forming a wide band from ear to ear in dorsal view ( fig. 9A–C View FIG ). The nasal bones widen markedly to slightly anteriorly. Palate narrow ( fig. 10A–C View FIG ), the maxillary toothrows at the anterior root of M1 are closer together than the width of M1, and the maxillary toothrows are long relative to the basilar length of the cranium. Lophs and flexi of the maxillary cheekteeth approximately parallel and at right angles to the line of the toothrow; posteroflexi long, hypoflexi short, and the lophs are of about equal width throughout their lengths. When present, M1–M2 mures are about a third of the way in from the lingual edges of the teeth. Posterior borders of the mandibular cheekteeth nearly straight, with entoconids nearly rectangular, with square lingual edges ( fig. 12A–D View FIG ).
REVISED DESCRIPTION: Pelage with dorsal aristiform hair tips blunt or drawn out into long hairlike processes, not sharp spines ( fig. 4D–F View FIG ), the fur rubbed backward is stiff rather than spiny. If present, wider, more spinelike aristiforms have whiplike tips. Dorsal pelage extends onto the tail base to about the level of the specimen heel; tail pelage abruptly changes to long, straight, unicolor, black or brown hair that can nearly cover the scales either throughout the tail to its tip, or thins gradually down the distal two-thirds to show the scales ( fig. 5C View FIG ), but in all taxa the length of the tail hairs decreases from base to tip ( figs. 14A, C View FIG ; 16 View FIG ); the tail tip lacks a pencillike tapering. Two pairs of functional lateral mammae lie high in the dorsal pelage field. Plantar surfaces of the hind feet have small prominent plantar tubercles covering the spaces between and around the pads ( fig. 6A View FIG ). The four digital pads are small and round or slightly triangular, widely separated, and bordered by rings of tubercles; hypothenar pad wide and long, joined to the smooth naked heel pad by a poorly marked shallow depression, separated from the broad thenar pad by a narrow tubercle-filled fold. First digital pad separated from the thenar pad ( fig. 6A View FIG ). Hallux short, the fleshy part not extending beyond base of the second digit. Forefeet with digital, thenar, and hypothenar pads encircled posteromedially with one or two collars of tubercles, but there are few or no small tubercles on the palm between the pads. Auditory tympanic bullae not inflated in lateral view ( fig. 7A–C View FIG ). Raised rim of the auditory meatus discontinuous, with a wide gap on dorsal edge. A tongue of the squamosal bone often extends into the mastoid process, which is short, adpressed, and enclosed to its tip in bone. The masticatory and buccinator foramina are separate; the posterior opening of the alisphenoid canal is robustly walled, often prominent in lateral view, and separated above the fossa of the foramen ovale ( fig. 17A, B View FIG ). Mandible generally with a long, shallow, sigmoid notch; coronoid process not usually recurved. Spine of the condyloid ridge on the interior of the mandible extends strongly to the top of the condyloid process. Masseteric crest salient and extends as a ridge to below the first cheektooth. Root of the upper incisor extends posteriorly to behind the base of the maxillary portion of the zygoma in adults ( fig. 7A–C View FIG ). Lower premolar pentalophodont, with a triangular anteroloph including a fossetid, a separate metalophid bar and a joined entoconid and posterolophid pair with lingually opening posteroflexid, giving three lingual and two labial flexids ( fig. 12A–D View FIG ). Hypoconid with a flat labial profile. Lophs and flexi of the maxillary cheekteeth approximately parallel and at right angles to the line of the toothrow, producing a laminar appearance; the flexi extend about 2/3 or more across the width of the cheekteeth; the hypoflexi extend about one third or less the distance across the width of tooth. Anterior joined lophs of the maxillary molars open labially, while the posterior pair open lingually, or the posteroloph is variably a separate lamina, especially in T. grandis . Hypoconids have squared labial edges ( fig. 12A–D View FIG ). Iack-Ximenez et al. (2005) described and illustrated some of these and many other characters of T. grandis . However, we note that not all of the characters that they recorded are stable in the specimens that we examined, nor found within other Toromys species.
COMPARISONS WITH OTHER GENERA: Toromys grandis , T. rhipidurus , and T. sp.nov. differ externally from all Echimys , Pattonomys , Makalata , and Leiuromys species by the lack of any sharp, paletipped spines on the dorsum. They differ from Makalata spp. by unicolor, long tail hairs, either thickly covering tail, as in T. grandis , or with longer hair that shortens toward tip on the basal third. Toromys rhipidurus have rusty muzzles, T. sp. nov. much less so, if at all, but all Toromys lack the red facial color above or posterior to the eyes of sympatric Makalata species ( table 3, fig. 13 View FIG ), although not of all allopatric Makalata species. Both Pattonomys and Toromys species have the plantar surfaces of the hind feet with small digital pads that are encircled by rings or collars of small tubercles. Specimens of Makalata and E. chrysurus that we examined have large digital pads lacking collars of tubercles ( fig. 6D–F View FIG ). The tail scales of Makalata species are short and wide and arranged in even, narrow rings ( fig. 5D View FIG ). The cranium of Toromys can be distinguished from sympatric Makalata species by a palate narrower between M1 roots than is the width of that tooth, a longer and shallower sigmoid notch of the mandible, with a coronoid process that is not recurved; short, adpressed tip of the mastoid process, and generally less inflated bullae. Makalata species have smaller teeth and lophs of the upper cheekteeth that are wider anteroposteriorly, more curved, and distinctly tapered labially, with a consequently much less laminar appearance than in any Toromys . The upper premolars of some, but not all, Makalata taxa tend to have both pairs of lophs opening lingually, such that there are three lingual, and one labial flexi, whereas Toromys have two of each.
HABITAT AND GEOGRAPHY: Specimens of Toromys species are all from riverine forests (including várzea and igapó) along the line of the Central Amazon and the lower reaches of its tributaries. The three species replace each other geographically, with the smallest in the westernmost headwaters in Peru and the largest from the central Amazon (Rio Purus) eastward to the river mouth (fig. 1). The known range of T. rhipidurus is small, only about 350 km across, and that of T. sp. nov. is even smaller. There is a large gap between known localities of T. grandis in Brazil and those of T. rhipidurus in Peru (fig. 1). Most specimens of the genus were collected by men of the Olalla family, who acquired large numbers of all arboreal Echimyidae . Some geographic range gaps may reflect gaps in the Olalla itineraries ( Wiley, 2010) rather than species absence. A few Olalla label notes state that Toromys were collected from tree holes (“tirado en hueco de arbol”) or in traps in trees (“trampa alta”), specified in two cases as at 4 m and 5 m. The exceptionally broad feet of the two larger Toromys species should facilitate swimming in the várzea and igapó flooded habitats that they occupy. Throughout their range, Toromys species are sympatric with Makalata macrura and Leiuromys occasius (upstream) or other Makalata species and Echimys chrysurus (downstream). Makalata species are likewise generally restricted to floodplain, riverine, or gallery forests, as are some Isothrix (L.H.E., personal obs.), but the ecology of neither genus has been described. Evidence of close sympatry between Makalata and T. rhipidurus or T. sp. nov. is provided by examined specimens of M. macrura from three Peruvian localities: Nuevo San Juan on the Río Gálvez (AMNH 268269* 5), Genaro Herrera (MUSM 23823), and Yarinacocha (LSUMZ 14408).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.