Uromys (Cyromys) porculus (Thomas, 1904

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 : 150-151

Uromys (Cyromys) porculus (Thomas, 1904 )

Type material. HOLOTYPE, adult male BM 89.4 .3.8, collected at Aola, Guadalcanal, by C.M. Woodford.

Revised diagnosis. Smaller than any other species of Uromys (Cyromys) , and brown rather than grey above with fur not woolly in texture; also unique by virtue of its possession of grey based belly fur and in having a more finely scaled tail (13-14 scales per cm). The skull is longer and narrower than in U. rex , and the molars relatively narrower than in U. imperator . It differs additionally from U. rex , and resembles U. imperator , in its less prominent frontotemporal ridges and its subvertical ascending ramus, and from both U. rex and U. imperator in its more nearly parallel zygomatic arches and broad-arched nasofrontal suture.

Discussion. Although the only known specimen was described in 1904, the date of registration (1889), and the fact that it was collected by Woodford at Aola, suggest that this specimen was probably collected at the same time as the original U. rex and U. imperator material or shortly thereafter. The very short tail of this species suggests that it may have been terrestrial. Questioning local people by one of us (TFF) reveals that today there is no clear local knowledge of this species, and it is probably extinct. If this is so, then evidently both terrestrial species of Guadalcanal Uromys are probably now extinct, while the only arboreal species survives.

The only known skull of U. porculus has the molars so worn that few details of the crown remain. The soft palate is unknown. We assign it to Uromys (Cyromys) , rather than to Solomys , for the following reasons. The anterolateral spur of the bulla is very large, as is typical of the species of Uromys , but not Solomys or Melomys . This enlargement of the anterolateral spur of the bulla appears to be synapomorphic of Uromys if any other of the Melanesian mosaic-tailed murid genera ( Melomys , Solomys , Pogonomelomys ) is taken as an outgroup. A second feature typical of the species of Uromys is that the bony palate extends to a level near the posterior end of M3. This is also a derived condition for Uromys , being unknown in other mosaic-tailed rats. Furthermore, the palate shows no sign of thickening or the development of a large post palatal spine as is seen in the species of Solomys . The skull is elongate and narrow (a common feature in Uromys ). As U. porculus shows no derived features typical of other Melanesian murid genera, we are confident that we are correct in placing it within Uromys . The placement within Uromys (Cyromys) is somewhat more problematic; but it lacks all of the derived features for U. ( Uromys ), and possesses the apparently derived states of the orbitotemporal fossa, frontotemporal and coronal sutures, preorbital foramen and ascending ramus orientation which characterise U. ( Cyromys ). Also, the tail scales are widely spaced, mainly flat but slightly raised distally, rounded or bluntly pointed, and some have one to three longitudinal ridges. Within the subgenus it clearly retains primitive features in its external morphology and the morphology of the zygomatic arches and posterior nasals. Cladistically, it is the sister taxon to U. rex and U. imperator .