Sooretamys, WEKSLER & PERCEQUILLO & VOSS, 2006

WEKSLER, MARCELO, PERCEQUILLO, ALEXANDRE REIS & VOSS, ROBERT S., 2006, Ten New Genera of Oryzomyine Rodents (Cricetidae: Sigmodontinae), American Museum Novitates 3537 (1), pp. 1-29 : 23-25

Sooretamys , new genus

TYPE SPECIES: Mus angouya Fischer, 1814 . CONTENTS: angouya Fischer, 1814 (including buccinatus Olfers, 1818 ; angouya

Desmarest, 1819; leucogaster Wagner, 1845 ; ratticeps Hensel, 1872 ; rex Winge, 1887 ; paraganus Thomas, 1924; and topicius Thomas, 1924).

DISTRIBUTION: In tropical and subtropical moist forests of the Atlantic littoral in southeastern Brazil and in interior subtropical moist forests of eastern Paraguay and northern Argentina.

MORPHOLOGICAL DIAGNOSIS: Dorsal pelage coarsely grizzled-brownish (the overall effect varying from drab grayish-brown to warm reddish- or yellowish-brown); ventral pelage abruptly paler (superficially whitish or yellowish), but ventral hairs always gray-based. Pinnae small, not reaching eye when laid forward. Mystacial vibrissae extending posteriorly well beyond pinnae when laid back against cheeks; superciliary vibrissae much shorter, not extending posteriorly to caudal margins of pinnae. Pes with conspicuous tufts of long ungual hairs at bases of claws on dI–dV; plantar surface densely covered with distinct squamae distal to thenar pad; hypothenar pad present and distinct; claw of dI extending to middle of phalange 1 of dII; claw of dV extending to or just beyond first interphalangeal joint of dIV. Tail unicolored (all dark) in most specimens and much longer than combined length of head and body.

Skull with long, broad rostrum flanked by deep zygomatic notches; interorbital region hourglass-shaped, with squared supraorbital margins; braincase oblong and usually without distinct temporal crests, but lambdoidal and nuchal crests often well developed in older adults. Posterior margin of zygomatic plate dorsal to M1 alveolus. Jugal present but not large (the maxillary and squamosal zygomatic processes overlapping in lateral view but not in contact). Nasals short, not extending posteriorly beyond lacrimals; lacrimals equally sutured to maxillary and frontal bones. Frontosquamosal suture colinear with frontoparietal suture in most specimens. Parietals with broad lateral expansions. Incisive foramina long, usually extending posteriorly to or between M1 alveoli; usually widest at midlength and tapering symmetrically anteriorly and posteriorly. Posterolateral palatal pits large, usually complex, and recessed in deep fossae; mesopterygoid fossa penetrating anteriorly between maxillae but not between molar rows; bony roof of mesopterygoid fossa perforated by large sphenopalatine vacuities. Alisphenoid strut absent (buccinator–masticatory foramen and accessory foramen ovale confluent). Stapedial foramen and posterior opening of alisphenoid canal small; squamosal–alisphenoid groove and sphenofrontal foramen absent; secondary anastomosis crosses dorsal surface of pterygoid plate (5 carotid circulatory pattern 3 of Voss, 1988). Postglenoid foramen large and rounded; subsquamosal fenestra large and patent. Periotic exposed posteromedially between ectotympanic and basioccipital but usually not extending anteriorly to carotid canal; mastoid perforated by conspicuous posterodorsal fenestra. Capsular process of lower incisor alveolus strongly developed posteroventral to base of coronoid process; superior and inferior masseteric ridges converge anteriorly as open chevron below m1.

Labial and lingual flexi of upper molars not (or shallowly) interpenetrating. First upper molar (M1) anterocone not divided into labial and lingual conules (anteromedian flexus absent); anteroloph well developed and fused with anterostyle on labial cingulum, separated from anterocone by persistent anteroflexus; protostyle present but often inconspicuous; paracone connected by enamel bridge to middle or to anterior moiety of protocone. Second upper molar (M2) protoflexus present; mesoflexus usually present as two internal fossettes. Third upper molar (M3) with posteroloph and persistent hypoflexus. Labial accessory root of M1 absent.

First lower molar (m1) anteroconid without an anteromedian flexid; anterolabial cingulum present on all lower molars; anterolophid present on m1 but indistinct or absent on m2 and m3; ectolophid variably developed on m1 and m2; mesolophid present and distinct on m1 and m2; m2 hypoflexid short. Accessory labial root of m1 usually present, accessory lingual root usually absent; m2 and m3 each with one large anterior root and one large posterior root.

Fifth lumbar (17th thoracicolumbar) vertebra with well-developed anapophysis. Hemal arch between second and third caudal vertebrae with posterior spinous process. Supratrochlear foramen of humerus absent.

Stomach without extension of glandular epithelium into corpus. One pair of preputial glands present. Distal bacular cartilage of glans penis large and trifid (with robust central digit); nonspinous tissue of crater rim does not conceal bacular mounds; dorsal papilla spineless; urethral processes without subapical lobules.

COMPARISONS: ‘‘ Oryzomys ’’ angouya was consistently recovered as an isolated lineage within clade D by Weksler (2003, 2006), but some analyses of mtDNA sequences weakly support a sister-group relationship with Cerradomys (see Bonvicino and Moreira, 2001; Bonvicino, 2003). The hypothesis that Sooretamys and Cerradomys might be sister taxa was not explicitly stated by Musser et al. (1998), but it is implicit in their concept of the ‘‘ subflavus group’’ of Oryzomys sensu lato. Despite such indications, we are not aware of any compelling morphological evidence that Sooretamys and Cerradomys are more closely related to one another than they are to other members of clade D; indeed, they are strikingly divergent in many respects.

Among other anatomical contrasts, Sooretamys differs from Cerradomys by its much longer vibrissae (the mystacial vibrissae of Cerradomys do not extend posteriorly beyond the pinnae); unicolored tail (the tail is more or less bicolored in Cerradomys ); hourglassshaped interorbital region with squared supraorbital margins (the interorbital region is anteriorly convergent and the supraorbital margins are strongly beaded in Cerradomys ); lack of distinct temporal crests (temporal crests are well developed in Cerradomys ); lack of a labial accessory root on M1 (a labial accessory root is present on M 1 in Cerradomys ); lack of a lingual accessory root on m1 (a lingual accessory root is present on m 1 in Cerradomys ); lack of a supratrochlear foramina of the humerus (this foramen is present in Cerradomys ); and a trifid bacular cartilage bearing a robust central digit (the bacular cartilage is bifid because the central digit is vestigial or absent in Cerradomys ).

REMARKS: The assumption that all of the nominal taxa currently synonymized with S. angouya are conspecific has not been tested by any revisionary study.

ETYMOLOGY: From sooretama, the old Tupian name for the Atlantic rainforest region of eastern Brazil ( Por, 1992).