Santamartamys rufodorsalis ( Allen, 1899 )

Velazco, Paúl M., Vargas, Laura M. & Ramírez-Chaves, Héctor E., 2017, Santamartamys rufodorsalis (Rodentia: Echimyidae), Mammalian Species 49 (948), pp. 63-67 : 63-65

Santamartamys rufodorsalis ( Allen, 1899)

Red-Crested Tree Rat

Isothrix rufodorsalis Allen, 1899:197 . Type locality “Onaca, Santa Marta District, Colombia.”

Echimys (Isothrix) rufodorsalis: Trouessart, 1904:504 . Name combination.

[ Diplomys ] rufodorsalis: Tate, 1935:417 . Name combination.

Santamartamys rufodorsalis: Emmons, 2005:293 . First use of

NOMENCLATURAL NOTES. The genus Santamartamys was segregated from Diplomys based on its distinctive cheektooth occlusal morphology ( Emmons 2005). English common names are red crested soft-furred spiny rat, red-crested tree rat, and Santa Marta toro (Woods and Kilpatrick 2005; Noble et al. 2011; Patterson and Lacher 2011); the German common name is Rotschopf-Baumratte ( Osbahr 2013); local names used include toro de Santa Marta ( Noble et al. 2011) and conocono de la Sierra Nevada (Rodríguez-Mahecha et al. 1995).

The etymology of the genus name, Santamartamys , is derived from the name of the type locality (Santa Marta), and mys (Greek), meaning mouse; the etymology of the specific epithet, rufodorsalis , is derived from rufo (rufus in Latin), meaning red, and dorsalis (Latin), meaning back.

DIAGNOSIS

Santamartamys , Callistomys , Makalata , Pattonomys , and Diplomys have only 2 functional pairs of mammae (corresponding to the medial and posterior lateral pairs of Echimys ), whereas Echimys and Phyllomys species have 3 lateral pairs of mammae that are about equally spaced along the sides in the dorsal pelage field (1 anterior, 1 medial, and 1 posterior), and 1 inguinal pair in the ventral field; species of Isothrix can have 3–5 lateral pairs and lack, or have only 1, inguinal pair. The lateral mammae of S. rufodorsalis are located in the ventral pelage side on the edge of the dorsal side, a unique condition among the subfamily Echimyinae ( Emmons 2005; Emmons and Leite 2015; Emmons and Patton 2015a, 2015b, 2015c, 2015d, 2015e; Emmons et al. 2015; Leite and Loss 2015).

Santamartamys is distinguished from all other species of the subfamily Echimyinae in possessing a highly flattened and ossified junction between the small, flattened, auditory tympanic bulla and the alisphenoid ( Emmons 2005; Emmons and Patton 2015e).

The alisphenoid strut is exceptionally wide in Santamartamys , whereas it is narrow to absent in Dactylomys , narrow in Diplomys , Echimys chrysurus (white-faced spiny tree rat), and Callistomys pictus (painted tree rat), and wide in other Echimyinae ( Emmons 2005:264, figure 6). The buccinator foramen is enclosed by a medial wall, partly enclosing it below the pterygoid process, in Santamartamys , Echimys , Pattonomys , and some Makalata and Phyllomys species, whereas it has a dorsal shelf partly enclosing it in some species of Phyllomys and Makalata . The foramen is open and unenclosed medially in Isothrix , Diplomys , and Dactylomys . The mandibular foramina of Santamartamys , Dactylomys , Diplomys , Isothrix , and Echimys are dorsal and anterior to the condyloid ridge, whereas the foramen of Makalata is either directly on the spine of the condyloid ridge or dorsal to it, and immediately posterior to the molar toothrow and on the condyloid ridge in Phyllomys ( Emmons 2005; Emmons and Leite 2015; Emmons and Patton 2015a, 2015b, 2015c, 2015d, 2015e; Emmons et al. 2015a, 2015b; Leite and Loss 2015).

The maxillary cheek teeth of Santamartamys are large and rectangular in occlusal view, whereas they are small and nearly circular in Isothrix , and are large and roughly square in some Makalata and Echimys . Santamartamys has the mesoflexid and hypoflexids of m1–3 united across the tooth, creating 1 free anterior loph, whereas the metaflexids do not traverse the teeth in Diplomys and Phyllomys , and the lophids of m1–3 are W-shaped and differ chiefly in the angle and breadth of the hypoflexids in all the other genera ( Emmons 2005; Emmons and Patton 2015a, 2015b, 2015c, 2015e; Emmons et al. 2015a; Leite and Loss 2015).

GENERAL CHARACTERS

Santamartamys rufodorsalis ( Fig. 1 ) is a medium-sized arboreal rat with soft, almost woolly, long dorsal fur (20–38 mm in length). The dense woolly fur covers the legs to ankles and wrists; additionally, it presents a crest of long hair on crown between ears. The dorsal fur is a deep rufous ( Fig. 1 ) with long, lax slender overhairs difficult to distinguish from the rest of the fur; the underfur is dense, wavy and gray. The longest genal and mystacial vibrissae reaches 50 mm in length; carpal vibrissae are present. Tail is longer than the head and body, robust, thickly haired with rusty fur for 20 mm at the base but abruptly changing to fine brown or black hair that covers the scales for three-fifths the length but with a terminal two-fifths pure white. The feet lack tubercles between the pads. The pollux presents a nail ( Allen 1899; Emmons 2005; Emmons and Patton 2015e).

The cranium is curved in dorsal profile, with a short, broad rostrum ( Fig. 2 ). The auditory tympanic bullae are small, flattened, and merged with the alisphenoid at a shallow angle ( Fig. 2 ). The auditory meatus is small, placed high near the squamosal; the auditory tube is short, strongly directed anteriorly; the mastoid process is extremely short. The alisphenoid strut is exceptionally long ( Fig. 2 ). The condyloid process of the mandible is deep, and there is a mandibular foramen in a fossa beside the condyloid ridge ( Emmons 2005; Emmons and Patton 2015e).

The dental formula of S. rufodorsalis is i 1/1, p 1/1, m 3/3, total 20 ( Emmons 2005). The maxillary cheek teeth are rectangular, longer than wide, bowed inward; P4–M3 split by a deep flexus into 2 parts, anterior lophs with flexi opening labially and posterior lophs with flexi opening lingually. Lower molars split by meso- and hypoflexid into 2 parts, a curved, laminar anterolophid, and a somewhat wishbone-shaped entoconid/posterlophid. The lower premolar is split by 2 flexids into a small closed triangular anterior loph apparently lacking a fossette. The hypoflexids are strongly oblique; protoconids large and squarish. The lower incisors are strongly curved ( Emmons 2005; Emmons and Patton 2015e).

External measurements (mm) of the holotype (AMNH [American Museum of Natural History] 14606-male) and the only other known specimen (AMNH 34392-female), respectively, were: total length, 457, –; length of tail, 267, –; length of hind foot (without claws), 35, 34; length of hind foot (with claws), 40, 37; length of ear, 12, 10 ( Allen 1899; our measurements). Craniodental measurements (mm) of the same specimens were taken based on those delimited by Voss et al. (2001:figures 33–34): condyle-incisive length, 47.4, 46.4; least interorbital breadth, 13.4, 13.0; breadth of braincase, 18.7, 19.0; zygomatic breadth, 24.5, 24.8; zygomatic length, 19.0, 19.2; length of rostrum, –, 17.5; length of nasals, –, 17.9; length of diastema, 11.4, 10.4; length of incisive foramina, 4.2, 3.6; breadth of incisive foramina, 1.8, 1.6; breadth of palatal bridge, 3.8, 3.8; breadth of zygomatic plate, 2.8, 2.6; length of maxillary toothrow, 10.9, 11.6; length of molars, 8.2, 8.6; breadth of M1, 2.4, 2.4.

DISTRIBUTION

Santamartamys rufodorsalis is known from the localities of Onaca (11°11 ′ N, 74°04 ′ W; 680 m) and El Dorado Nature Reserve (11°06 ′ 02.93 ″ N, 74°04 ′ 19.36 ″ W; 1,958 m), both located in the Department of Magdalena, northern Colombia ( Allen 1899; Noble et al. 2011; Fig. 3 ). A 3rd record (AMNH 34392) lacks a precise locality inside the Sierra Nevada de Santa Marta. The limits of the range of distribution are poorly known, but all 3 records are inside the limits of the Endemism Area, Sierra Nevada de Santa Marta ( Müller 1973; Cracraft 1985; Hernández-Camacho et al. 1992), an isolated mountain massif located in the Departments of Cesar, La Guajira, and Magdalena, in the Caribbean region of Colombia. No fossils are known.

Figures

Fig. 1.—An adult Santamartamys rufodorsalis (sex unknown) from El Dorado Nature Reserve, Department of Magdalena, Colombia. Used

Fig. 2.—Dorsal, ventral, and lateral views of skull and lateral view of mandible (inverted) of an adult male Santamartamys rufodorsalis (AMNH [American Museum of Natural History] 14606; holotype) from Onaca, Santa Marta, Department of Magdalena, Colombia; collected by Herbert H. Smith on 24 December 1898. Condyle-incisive length of the skull is 47.4 mm.

Fig. 3.—Geographic distribution of Santamartamys rufodorsalis. S. rufodorsalis is known only from the localities of Onaca (holotype— white triangle) and El Dorado Nature Reserve (unvouchered record— black triangle). A 3rd record (AMNH 34392) lacks a precise locality inside the Sierra Nevada de Santa Marta.