Uromys (Cyromys) Thomas, 1910

Groves, C. P. & Flannery, Tim F., 1994, A revision of the genus Uromys Peters, 1867 (Muridae: Mammalia) with descriptions of two new species, Records of the Australian Museum 46 (2), pp. 145-169 : 149

Uromys (Cyromys) Thomas, 1910

Type species. Mus imperator Thomas, 1888 .

Revised diagnosis. The species of Uromys (Cyromys) can be distinguished from species of U. ( Uromys ) by possessing the following features: i) molar rows relatively short, molars relatively broad; ii) M3 larger relative to other teeth; iii) anterior lophid of Ml distinct even in worn molars; iv) molars more complex, individual cusps more distinctly defined, with Ml retaining a well-developed fossa lingual to posterior cingulum; v) anterior and ventral orbital walls slope away from centre of orbitotemporal fossa, so that walls can be seen in dorsal view; vi) frontotemporal sutures markedly ridge-like; vii) coronal suture strongly convex or biconvex backwards; viii) preorbital foramen slopes backwards, so that inferior margin readily visible in dorsal view; ix) ascending ramus flares laterally; x) tail scales consist of small central prominence surrounded by large fleshy area. All of the dental features listed here are probably plesiomorphic for the species of Uromys and closely related genera (see discussion). However, the tail morphology is unique among near relatives and is presumably synapomorpbic for the subgenus.

Additional useful diagnostic features for the subgenus are as follows. The rostrum is broad, and the incisive foramina are strongly bowed outward; although the temporal sutures are markedly ridge-like, there are no post-sutural processes. The nasals are posteriorly broadened, and the posterior part of the lateral walls of the rostrum are steep, nearly vertical and partially concealing the lachrymal in dorsal view. The zygomatic arches do not swing down to the level of the molar alveoli. The nasal tips are abbreviated and slightly downturned. The incisors are opisthodont. The paroccipital processes are long, their tips level with the inferior margins of the occipital condyles and the auditory bulla. The insertion scar of the M temporalis on the mandible is marked by a strong anterior ridge.

Although U. ( Cyromys ) differs strongly from U. ( Uromys ), and a good case could be made for separating them generically, we prefer at least for the present to retain them in one genus in order to emphasise their sister-group status with respect to their closest relatives ( Melomys , Solomys ).