Rattus feliceus Thomas, 1920

Rattus feliceus Thomas, 1920 View in CoL

Type material studied. The type specimen ( NHMUK ZD 1920.7.26.7 ) is an adult female collected at 6000 feet (1830 m) on Gunung Manusela, Seram Island , South Maluku ( Figs 5–10 View Figure 5 View Figure 6 View Figure 7 View Figure 8 View Figure 9 View Figure 10 ). This specimen was caught by the Pratt brothers in February 1920 and described by Oldfield Thomas in the same year ( Thomas, 1920) . Four other specimens were collected by the Pratt brothers between 1200 m and 1830 m (NHMUK ZD 1920.7.26.4–6 and NHMUK ZD 1920.7.26.8). The zoological expedition to Seram that produced the original specimens was undertaken by three of the four sons of the Victorian naturalist A. E. Pratt from late 1919 to early 1920. Oldfield Thomas (1920) remembered Felix Pratt, for whom he named “this fine species.” The label states that it was collected “in heavy jungle in precipitous limestone country.” All of these specimens are held by the Natural History Museum, London (NHMUK).

Referred specimens. Three adult females and one subadult male were captured by an Australian Museum field team in 1993 between 300 and 400 m ( Flannery, 1995; Helgen, 2003). An additional specimen from Gunung Manusela was collected more recently by Museum Zoologicum Bogoriense ornithologists (MZB 22684).

Distribution. Rattus feliceus is found from lowland to highland contexts (0–2000 m) at several localities on Seram, and may be widespread on the island.

Emended diagnosis. Rattus feliceus is a large-bodied rat with spiny, reddish-brown fur over the upperparts and softer white fur covering the belly; the dorsal fur contrasts sharply with the white ventral fur ( Fig. 5 View Figure 5 ). The mammae formula (given in pairs plus total number) is: 1 pectoral, 1 post-axillary, 0 abdominal and 2 inguinal (1+1+0+2=8). This Rattus species is characterized by the following features: (1) a single-coloured pale brown tail shorter than the head-body length (TL/HB = 68–91%; see also Table 2 View Table 2 and Fig. 5 View Figure 5 ), (2) slender and elongated hind feet, but of medium length compared to the head-body length, (3) a moderately long and broad rostrum, (4) prominent temporal, interorbital and post-orbital ridges ( Fig. 6 View Figure 6 ), (5) the palatal bridge protruding well beyond M3 to form a moderately large bony shelf ( Fig. 7 View Figure 7 ), (6) a wide and deep zygomatic notch and a wide zygomatic plate, (7) viewed laterally, the upper edge of the skull is almost flat between the nasals and the occiput, (8) the eustachian tube is shorter and narrower than in R. ceramicus , (9) the angular process of the dentary is broad, (10) the large incisors are opisthodont, (11) the incisor blade is broad, with a size equal to or greater than its longest basal width, (12) the posterior cingulum forms a small bulge on M1 ( Fig. 9 View Figure 9 ), (13) cusp t3 is present on both M2 and M3, (14) t1 bis is absent on M1, (15) cusp t1 on M1 is posterior to cusps t2 and t3 and forms a pinched lingual bulge on the M1 lamina, (16) cusp t8 on M1 and M2 is well developed compared to other cusps, (17) there is no anterolabial cusp on m1 ( Fig. 10 View Figure 10 ), (18) the posterolabial cusplet is always present on m1, (19) anterolabial cuspid and posterolabial cusplet are present on m2, (20) the presence of posterolabial cusplet is variable on m3 (present in two specimens).

Comparisons between Rattus ceramicus and Rattus feliceus : Despite a relatively small molecular divergence (4% Cytb nucleotide divergence) between R. ceramicus and R. feliceus ( Fig. 2 View Table 1 View Figure 2 ), these two taxa are strikingly different in their external and cranial morphology.At the same time, they share features that clearly distinguish them together from other Moluccan Rattus ( Figs 2 View Table 1 View Figure 2 , 5–10 View Figure 5 View Figure 6 View Figure 7 View Figure 8 View Figure 9 View Figure 10 ). The very distinct external appearance of these two species of Seram rats masks their close relationship. Rattus feliceus is a large-bodied rat with a clearly defined dorsal and ventral coat, and is at least twice the mass of the small, dark, single-coloured R. ceramicus ( Figs 3 View Figure 3 and 5 View Figure 5 ; Table 2 View Table 2 ). In terms of coat texture, R. feliceus has a harsh and very spiny coat compared to the soft, short coat of R. ceramicus . Tail proportions are also different, as R. feliceus has a low TL/HB ratio (68–91%) compared to the almost equal TL/HB ratio of R. ceramicus .

Regarding the skull ( Figs 6–8 View Figure 6 View Figure 7 View Figure 8 ), the interorbital, postorbital and temporal ridges are well developed in R. feliceus compared to R. ceramicus . The dorsal contour of the skull in lateral view is almost flat from the nasals to the highest point of the skull (occiput) in R. feliceus , whereas it is slightly convex in R. ceramicus . The rostrum of R. ceramicus is thinner and longer relative to the size of the skull than the bulky rostrum of R. feliceus . The zygomatic plate and arch are narrower and more slender in R. ceramicus than in R. feliceus . In R. ceramicus , the maxillary root of the zygomatic plate is at the level of the first upper molar; this, together with the slender rostrum, is in many ways reminiscent of the structure found in some shrew rats, such as Archboldomys ( Musser, 1982; Balete et al., 2012), or to a lesser extent Melasmothrix naso and Tateomys macrocercus ( Musser, 1982) . Most of the maxillary root in R. feliceus is located anterior to the first upper molar. The jugular process is also proportionally longer in R. feliceus . The posterior palatal foramina reach the middle of M3 in R. feliceus but extend posteriorly to M3 in R. ceramicus . The incisive foramina of R. ceramicus are short and do not reach M1, compared to the long and wide incisive foramina of R. feliceus , in which the posterior margins of the incisive foramina reach the anterior edge of M1. The palatal bridge extends well beyond M3 in R. ceramicus compared to R. feliceus ; although other species have a long palatal bridge, that of R. ceramicus is relatively longer and extends further posteriorly than in most members of the Rattus Division. The tympanic bullae of R. ceramicus are slightly more distended than those of R. feliceus relative to the length of the skull. The zygomatic notch is closer to the zygomatic plate in R. feliceus than in R. ceramicus . The incisors are opisthodont and the enamel is orange, but the incisor blades of R. ceramicus are narrower than those of R. feliceus . On M1 the cusp t1bis is present in R. ceramicus and absent in R. feliceus ( Fig. 9 View Figure 9 ). Cusp t3, present on M3 of R. feliceus , is absent on M3 in R. ceramicus . Cusp t1 on M1 differs in its position in relation to t2 and t3; the latter two cusps are more anterior to t1 in R. feliceus compared to R. ceramicus . The cusps on the upper molars are more divided in R. feliceus compared to R. ceramicus , giving a more chevronate structure, and each upper molar appears more elongate. The shape of the lower molars ( Fig. 10 View Figure 10 ) is similar in both taxa, with some differences in the cusplets–the anterolabial cusplet of m1 is absent in R. feliceus and present in R. ceramicus , and the posterior cingulum of m1 and m2 is proportionally smaller in R. feliceus than in R. ceramicus . Ecology. Little is known about the ecology of Rattus feliceus , except that the few existing specimens were collected in forest ranging from coastal forest at sea level to primary montane moss forest up to 1830 m. This species co-occurs with species of Melomys ( M. aerosus , M. fraterculus , M. fulgens , and M. paveli ) as well as R. ceramicus and at least two introduced species of Rattus , R. exulans and R. nitidus ( Helgen, 2003) . Rattus feliceus is probably terrestrial in lifestyle ( Flannery, 1995), especially judging by its short tail and long hind feet relative to head and body length ( Table 2 View Table 2 ).