Deltamys araucaria, Quintela & Bertuol & González & Cordeiro-Estrela & Freitas & Gonçalves, 2017

Quintela, Fernando Marques, Bertuol, Fabrício, González, Enrique Manuel, Cordeiro-Estrela, Pedro, Freitas, Thales Renato Ochotorena De & Gonçalves, Gislene Lopes, 2017, A new species of Deltamys Thomas, 1917 (Rodentia: Cricetidae) endemic to the southern Brazilian Araucaria Forest and notes on the expanded phylogeographic scenario of D. kempi, Zootaxa 4294 (1), pp. 71-92 : 78-84

Deltamys araucaria sp. n. Araucaria Grass Mouse Figures 5,8, Table 4

Holotype. FURB 20296 (field number PRM 137), adult female with skull (left zygomatic arch and incisors damaged), skin, post-cranial skeleton, ethanol-preserved forefoot and hind foot, collected by F. M. Quintela on 17 August 2012. Frozen tissue sample ( PRM 137) and suspension of bone-marrow in Carnoy’s fixative ( PRM 137) were deposited in the Department of Genetics at UFRGS (DG-UFRGS).

Type locality. São Francisco de Paula municipality (29°29’73”S, 050°13’49”W; 913 m above sea level), Rio Grande do Sul State, Brazil.

Paratypes. Seven topotypes ( FURB 20220, 20240, 20244, 20297, 20330, 20954 and 20955) were collected between 1 April and 12 October 2012. A frozen tissue sample (FQ 84-86; PRM 10, 103, 104, 106, 124, 138) and a suspension of bone marrow in Carnoy’s fixative (FQ 85 and 86) were deposited in the Department of Genetics at DG-UFRGS.

Distribution. Known only from shrub and herbaceous palustrine systems in São Francisco de Paula municipality (altitude ca. 913 m above sea level), Serra Geral highlands, Rio Grande do Sul state, southern Brazil. This region is within the biogeographic domains of Araucaria Forest, Atlantic Forest biome.

Diagnosis. A markedly tawny furred Deltamys species; 2n=34, FNa=34; protostyle present; M1 anterior alveolus parallel to or above posterior border of zygomatic plate in ventral view.

Description. Pelage dense and soft, uniformly tawny brown on dorsum ( Fig. 5 ), slightly lighter on face and cheeks; guard-hairs about 9 mm over back, all eumelanic; overhair about 7 mm on back, three-banded, eumelanic on distal tip and most of length, and pheomelanic in distal section; under-hair about 5 mm on back, all eumelanic. Ventral pelage ( Fig. 5 ) grayish-brown, clearly demarcated from browner flanks; dichromatic overhair about 6 mm in middle chest, pheomelanic in distal segment and eumelanic in central and proximal segments; dichromatic under-hair about 3.7 mm in middle chest, with same banding pattern as ventral overhair. Presence of superciliary and inconspicuous mystacial and submental vibrissae; measurements of largest vibrissae from holotype FURB 20330: mystacial 16.3 mm, superciliary 9.8 mm, submental 6.5 mm; longest mystacial not reaching bases of pinnae when laid back along head. Ears rounded, not reaching eyes when laid forward, densely covered with 2.4 mm eumelanic thick hairs. Tail about 75% of head-body length; unicolor and dark; hair coverage barely visible; hair arranged in triplets on each scale, subequal in size, with central hair reaching two and half scales; 4-5 mm terminal pencil. Mammae eight, in pectoral, axial, abdominal and inguinal pairs.

Hind foot about 26% of head-body length; plantar surface dark; densely covered with short melanic hair; digits II, III and IV subequal in size; digit I conspicuously longer than digit V; claws grooved, about 2.5 mm long in digit III; ungueal hair most melanic, not reaching tip of claws; thenar pad about 2.5 x interdigital pad; interdigital pads subequal in size; hypothenar pad slightly shorter than interdigital pads. Forefoot sparsely covered with melanic and bicolor hair on metapodial and digits; digits III and IV subequal in size; digits II and V subequal in size; welldeveloped claws, extending about 1.7 mm past extremity of digits III and IV; ungueal hair not covering claws; dark palmar surface; hypothenar pad slightly longer than thenar pad; interdigital pad 3 conspicuously longer than interdigital pads 1 and 2.

Skull ( Fig. 8 ) delicate, with narrow elongated rostrum and narrow zygomatic arches; gnathic process little developed, not exceeding anteriormost extremity of incisor in lateral view; well-developed anterior process of premaxillary but not forming rostral tube (trumpet) with nasal extremity; slightly inflated incisive capsular projection; nasofrontal suture “V”-shaped; shallow zygomatic notches; rounded lacrimal; narrow nasolacrimal foramen, similar to M 1 in size; broad zygomatic plate, directed backward, with posterior border positioned behind of anterior plane of M1; elongate incisive foramina with their broadest point around premaxilla-maxillary suture, posterior extremity reaching protoflexus or protocone; narrow antorbital bridge; posterior palatine foramina small and ovate, located in maxillopalatine suture at height of M2 hypoflexus; hourglass-shaped interorbital region, with rounded margins and posteriorly broader; conspicuous ethmoid foramen; sphenopalatine foramen horizontally elongated, reaching from M1 metacone to M2 posterior border; large optic foramen, vertically elongated and located behind M3; large anterior lacerated foramen, similar to optic foramen in size; zygomatic arches narrow, anteriorly convergent and posteriorly slightly divergent, surpassing border of braincase in dorsal view; frontalparietal-squamosal suture at exact point of parietal anterior process extremity or slightly behind this process; conspicuous elongated jugal; shallow glenoid fossa; mesopterygoid fossa narrow, extending from slightly behind M3 alveoli to posterior border of zygomatic arches, straight along most of its length and divergent posteriorly; presphenoid posteriorly wider; sphenopalatine vacuities elongated, similar to M 1 in size, and divided by narrow presphenoid strut; basisphenoid plane; basioccipital with prominent median crest; parapterygoid fossa shallow and narrow; hamular processes of pterygoid straight and divergent; coronal suture “U”-shaped; carotid as circulatory pattern 1 of Voss (1988); large and oval stapedial foramen; large petrotympanic fissure, varying in width; littledeveloped stapedial spine; broad Eustachian tube; moderately inflated tympanic bulla, similar in size to superior molar row; punctual carotid canal; large jugular foramen; thin malleus; orbicular apophysis present; broad hamular process of squamosal; postglenoid foramen conspicuously larger than subsquamosal foramen; braincase moderately inflated; interparietal varying in length and width; mastoid slightly inflated, similar in size to external auditory meatus, bordered posteriorly by elongated foramen; exoccipital conspicuously trilobed, without prominent crests; occipital condyle slightly inflated; well-developed paraoccipital process; large foramen magnum.

Mandible ( Fig. 8 ) gracile, length without incisors about 49% of greatest skull length; height about 41% of length without incisors; elongated ramus; short diastema, similar in size to molar row, anterior extremity located parallel to molar plane; conspicuous mental foramen, visible from lateral and occlusal views; little-developed masseteric ridge; conspicuous capsular projection; delicate coronoid process isolated from condyloid by shallow elongated sigmoid notch, strongly concave anteriorly; condyloid process robust, markedly thickened distally; shallow mandibular notch; little-developed angular process, distally thickened and perpendicularly projected.

Upper incisors orthodontt and orange; lower incisors much paler. Upper molars ( Fig. 9 ) parallel, crested; lingual cusps higher than labial cusps. Main cusps (paracone, metacone, protocone, hypocone) parallel. M1 with well-developed anteromedian flexus in specimens with little-worn molars, dividing procingulum into anterolingual and anterolabial conules subequal in size; anteroloph and mesoloph present but reduced; little-developed but conspicuous protostyle and enteroloph ( Fig. 6 ); protocone and paracone equal in size; hypocone and metacone equal in size; deep paraflexus and metaflexus, curved backward parallel to median mure; shallow protoflexus and hypoflexus; little-developed posteroloph, visible mainly in specimens with unworn dentition (e.g. FURB 20244). M2 lacking anteroconule; anteroloph visible in specimens with slight or moderate wear; protocone and paracone subequal in size; hypocone and metacone subequal in size; anteroloph and mesoloph present but reduced, visible in specimens with all degrees of wear; hypoflexus deep and straight; paraflexus deep and curved backward parallel to median mure; narrow median mure between hypoflexus and paraflexus. M3 with three visible cusps, protocone, paracone, and metacone; protocone conspicuously larger than paracone and metacone; presence of two or three fossetes in specimens with dentition little worn. Lower molars ( Fig. 9 ) parallel and crested, with lingual cusps higher than labial ones. Main cusps slightly alternated; m1 with well-developed procingulum; shallow anteromedian flexid visible only in specimens with unworn or slightly worn molars; anterolabial conulid larger than anterolingual conulid; well-developed protostylid; anterolophid conspicuous, parallel to protostylid; protoflexid deep and straight; anteroflexid and metaflexid shallow; protoconid larger than metaconid; mesoflexid deep and straight; hypoflexid deep and upward-curved; mesoflexid and hypoflexid separated by narrow median mure; well-developed ectolophid; mesolophid fused with entoconid; shallow and straight entoflexid; welldeveloped posterolophid, separated from entoconid by deep and upward-curved posteroflexid. m2 lacking anteroconulids; well-developed protostylid, separated from protoconid by deep protoflexid; protoconid larger than metaconid; hypoconid larger than entoconid; mesoflexid deep and curved upward; hypoflexid deep and diagonal; mesoflexid and hypoflexid separated by narrow median mure; ectolophid visible in specimens with dentition little worn; mesolophid fused with entoconid; well-developed posterolophid, separated from entoconid by deep and upward-curved posteroflexid; m3 with six visible cusps in specimens with little-worn dentition; inconspicuous protostylid, fused with protoconid; protoconid larger than metaconid; hypoconid larger than entoconid; mesoflexid deep and upward-curved; hypoflexid deep and straight; mesoflexid and hypoflexid separated by narrow median mure; mesolophid fused with entoconid; well-developed posterolophid, separated from entoconid by deep and diagonal posteroflexid (or fossete in specimens with moderately worn dentition).

Axial skeleton composed of 13 ribs, 7 cervical vertebrae, 13 thoracic vertebrae, 4 sacral vertebrae, 26 caudal vertebrae; presence of conspicuous neural spine on second thoracic vertebrae. Scapula wide, thin and translucent except at borders; shallow supra- and infraspinous fossae; acromion delicate, with shallow concavity; deep notch, reaching about one-third of spine length. Humerus shorter than scapula; well-developed head; conspicuous greater and lesser tubercles; well-developed and thick deltoid tuberosity. Radius longer than humerus, fused with ulna except for small segment behind trochlear notch, which forms a slightly elongated foramen. Elongated ilium, showing conspicuous iliac crest. Robust ischium, translucent at center and internal border. Large obturator foramen. Femur thin and curved; well-developed head; conspicuous median tuberosity; medial and lateral condyles little developed; shallow patellar groove.

Karyotype. Diploid number (2n) of 34 chromosomes and an autosomal fundamental number (FNa) of 34 arms. Autosome complement characterized by 15 acrocentric pairs and 1 pair of small metacentric chromosomes. Sex determination system XY/XX; chromosomes X and Y acrocentric ( Fig. 4 ).

Etymology. Refers to Araucaria angustifolia (Bertol) Kuntze (Pinopsida: Araucariaceae ), the major arboreal element in the Araucaria Forest or Mixed Ombrophilous Forest, the vegetation domain where the type locality is inserted. Proposed as a noun in apposition.

Natural history. Specimens of D. araucaria were collected in palustrine savanna with a predominance of Eryngium pandanifolium (Apiaceae) and Baccharis sp. ( Asteraceae ) and unidentified treelets, in areas with soggy soil. The species was found in sympatry with the didelphid Monodelphis dimidiata Wagner and the sigmodontines Akodon montensis Thomas , Oligoryzomys flavescens Waterhouse , Oxymycterus nasutus Waterhouse and Scapteromys meridionalis Quintela et al. Parallel sampling in dense forest habitats of the region produced no additional individuals, which indicates that D. araucaria is associated with the open herbaceous/savannic palustrine systems.

Figures

FIGURE 4. Karyotype (conventional Giemsa staining) of Deltamys araucaria sp. n. showing 2 n = 34 and FNa = 34. The small metacentric pair corresponds to pair 16.

FIGURE 5. Dorsal (upper), ventral (middle) and flank (bottom) views of skins of Deltamys araucaria sp. n. (holotype, FURB 20296; above) and Deltamys kempi (FURB 20308). Bar = 20 mm.

FIGURE 6. Morphological distinctive traits in Deltamys. Above, first upper molar of Deltamys araucaria sp. n. (FURB 20330; left) and D. kempi (TR 2136; right), showing the presence of protostyle (A) and enteroloph (B) in D. araucaria (bar = 0.5 mm; 30 x). Middle, position of M 1 anterior border in relation to posterior border of zygomatic plate in D. auraucaria sp. n. (left) and D. kempi (right) (bar = 1 mm). Bottom, proportion of interparietal in D. araucaria (left) and D. kempi (right) (bar = 2 mm).

FIGURE 8. Dorsal (left), ventral (middle) and lateral (right) views of skull and labial view of mandible (bottom right) of Deltamys araucaria sp. n. (holotype, FURB 20296; above) and Deltamys kempi (AMNH 206139). Bar = 5 mm.

FIGURE 9. Left maxillary molars (left) and right mandibular molars (right) of Deltamys araucaria sp. n. holotype (FURB 20296) (bar = 1 mm).