Rattus feileri, Fabre & Miguez & Holden & Fitriana & Semiadi & Musser & Helgen, 2023

Rattus feileri sp. nov.

urn:lsid:zoobank.org:act:BEB15FE6-3CA4-439E-9688-BE8A07C59E75

Figs 6e View Figure 6 , 7e View Figure 7 , 8e View Figure 8 , 9e View Figure 9 , 10e View Figure 10 , 11a,d View Figure 11 , 12b View Figure 12 , 13g View Figure 13 , 14g View Figure 14 , 18a View Figure 18

Holotype. The holotype (in Staatliche Naturhistorische Sammlungen Dresden, Museum für Tierkunde, SNSD 11429 ) is a young adult (scrotal) male collected by J. J. Menden on 30 September 1938 (original number 68) on “ Insel Taliaboe Molukken ” (Taliabu Island, Maluku). Method of collection and exact locality are not known. The skin is very well preserved. The skull is intact except for the zygomatic arches which are detached from their squamosal roots. Known only from the holotype .

Type locality. Taliabu Island ( Fig. 1 View Figure 1 ), Maluku, Indonesia.

Etymology. We name this species in honour of German zoologist Alfred Feiler, who worked at the Staatlichees Naturhistorische Sammlunggen in Dresden until his retirement. Feiler kindly arranged the loan of Taliabu Island specimens to G. G. Musser, assisted K. M. Helgen on several visits to the museum in Dresden, and helped with our research in many other ways. We commemorate his significant contributions to knowledge of the mammal fauna of the Indo-Pacific region, and to Wallacea and Maluku in particular.

Distribution. Known only from the type locality, Taliabu Island ( Fig. 1 View Figure 1 ), Maluku, Indonesia.

Diagnosis. Rattus feileri is of medium size, with a spiny coat overall, which is reddish grey on the upperparts and pale ochraceous, buff or whitish on the undersides, with a rusty wash on parts of the chin, forelegs and chest ( Fig. 11 View Figure 11 ). The tail is long in relation to the length of the head and body (TL/HB = 134%; Table 2 View Table 2 ), with a terminal tuft or “pencil” ( Fig. 12 View Figure 12 ). This species is also characterized by the following features: (1) a dark brown tail much longer than the length of the head and body; (2) moderately long and wide hind feet relative to the length of the head and body ( Table 2 View Table 2 ); (3) upper incisors orthodont, with orange enamel faces; (4) wide incisor blade, width at tips greater than longest basal width ( Fig. 7 View Figure 7 ); (5) short and wide rostrum with shallow zygomatic notch ( Fig. 6 View Figure 6 ); (6) viewed laterally, the top of the skull is convex between the nasal tips and the occiput ( Fig. 8 View Figure 8 ); (7) posterior palatal foramina level with the posterior portion of M2; (8) posterior margin of palatal bridge does not extend beyond the posterior margins of M3, which is unusual in the species of Rattus examined here; (9) wide and moderately long eustachian tube; (10) the post-glenoid vacuity is not fused with the middle lacrimal foramen; (11) the incisive foramina are long and narrow with their posterior margins aligned with the anterior surface of M1; (12) M2 is bulky and slightly wider than M1 and M3 ( Fig. 9 View Figure 9 ); (13) posterocone is absent on M1; (14) cusp t3 is present on M2 and M3, and is wider on M3; (15) t1 bis is absent on M1; (16) cusp t1 on M1 is slightly posterior to cusps t2 and t3 and forms a well separated cusp; (17) anterolabial and anterolingual cuspids as well as an anterocentral cusplet are present and fused to form the anteroconid on m1, likely due to dental wear ( Fig. 10 View Figure 10 ); (18) an anterolabial cuspid and posterolabial cusplet are present on m2; (19) m3 shows a ridge-like anterolabial cuspid but lacks the posterolabial cusplet. The mammae formula is unknown, the only available specimen being male.

Description and comparison with Taliabu Rattus and R. morotaiensis , R. halmaheraensis and R. obiensis . Rattus feileri is of medium body size with a distinctive long tufted tail ( Table 2 View Table 2 and Figs 11–12 View Figure 11 View Figure 12 ) and moderately long hind feet, and is similar in proportions to Rattus halmaheraensis sp. nov. and Rattus obiensis sp. nov. Apart from its superficial resemblance to these two species in external proportions, Rattus feileri has no morphological counterpart elsewhere and cannot be confused with any known species of Indo-Pacific Rattus . Its unusually long tail has a rare feature found only in this Rattus lineage and to a lesser extent in the Rattus morotaiensis group: a rufous, tufted tail ( Fig. 12 View Figure 12 ). Other murine species, such as Chiropodomys karlkoopmani , have similarly developed tufted tails ( Musser, 1979), but a pencil tail has never been reported in any other Rattus species. Rattus feileri is also characterized by distinctive brown, square or hexagonal tail scales. For most of its length, the tail is covered with fine reddish-brown hairs the length of a single scale; near the tip, the hairs are less abundant but longer, forming a tuft that extends 10 mm beyond the tip of the tail. There are approximately 9–11 scale rows per centimetre measured near the base of the tail, each scale bearing 3 hairs. The dorsal coat bears a mixture of (1) spines with white bases and rufous or dark rufous tips, (2) soft guard hairs, (3) charcoal grey undercoat that is almost woolly, and (4) long and stiff guard hairs that are dense with white or buff bases and rufous tips ( Fig. 11 View Figure 11 ). The dorsal fur is generally spiny and greyish-reddish chestnut with a few ivory thin spines. The spines of R. feileri are shorter than the stiff guard hairs which are thin and tubular, shorter on the shoulders (1.0–1.7 mm) and longer on the rump (3.0–3.5 mm). The rump hairs are longer than other areas of the dorsal coat such as the head and shoulders. Like R. taliabuensis and some spiny rats (e.g., Halmaheramys ), R. feileri has longer guard hairs and longer spines on the rump. The guard hairs and spines do not completely cover the undercoat, giving a layered appearance. There appears to be a lateral line separating the dorsal and ventral coats. The ventral coat is softer and less dense than the dorsal coat and is predominantly buff or pale ochre with thinner spines and a greyish white woolly undercoat, except on the chin, throat and chest. Here the coat darkens to a chestnut colour, probably the result of staining. Some of the ventral spines have brown tips and are more sparsely distributed from the pectoral region caudad to the pelvic region. Compared to the Rattus morotaiensis group, R. feileri has a less spiny coat, a more rufous dorsal coat and a denser undercoat. The skin of the forelegs is brownish dorsally and ventrally, covered with tiny pale hexagonal scales. The fur on the forefeet is greyish-white with buff or rusty patches. Coloration of the dorsal and ventral sides of the foreleg are well defined. Considering the forefoot, the first digit is reduced, leaving only a small first interdigital pad projecting medially. The other four digits are long and appear to be of equal length. All four have digital pads and the scales on the digits are annular. The forefeet have three almost equal interdigital palmar pads and two large thenar and hypothenar pads, similar to the R. morotaiensis group. The fingers are elongated compared to R. taliabuensis , with large terminal digital pads and long curved claws with silvery hairs on their anterior edges. The claws also bear some silvery hairs that are nearly as long as the claw lengths. On the hindfeet the first digit is reduced and appears approximately half the length of the other four, which are subequal in length. All the digits have digital pads, and as on the hands the scales on the digits are annular. The first and fourth interdigital pads are larger than the second and third, the metatarsal pads are elongated. The head is characterized by moderately long bicoloured ears clothed with creamy or brownish fur near the notch (11 mm) and dark brown fur at the apex (4 mm). A distinctive trait that aids in identification of R. feileri is the presence of dark eye-rings encircled by dark brown hairs that are well demarcated from the paler facial fur. The mystacial whiskers are long (55–70 mm maximum length) and rufousbrown throughout their length or tipped in silver. The three superciliary and genal whiskers are also moderately long and caudal to the eyes. There is a tuft of blond ulnar carpal vibrissae above each wrist.

The coat colour and skull proportions of R. feileri appear similar to the R. morotaiensis group, but the skull bears several discrete features not present in other Moluccan rats. Dorsally, the rostrum is short and broad compared to R. morotaiensis and R. halmaheraensis sp. nov. ( Fig. 6 View Figure 6 and Fig. 18 View Figure 18 ). The rostrum appears to be enlarged posteriorly with a proportionally wider nasal area. The zygomatic plate does not extend significantly anteriorly as in the R. morotaiensis group. The postorbital region is only slightly ridged, similar to R. halmaheraensis sp. nov. Another clear distinction from the R. morotaiensis group is a zygomatic arch that does not curve as strongly posteriorly as in R. elaphinus . Compared to R. elaphinus , the rostrum of R. feileri is very short and the braincase is wider. In lateral view, the braincase of R. feileri is curved, with the height of the braincase dropping significantly from the top of the parietal bones to the tip of the nasal bones. The zygomatic plate of the holotype does not extend significantly anteriorly, and the squamosal root of the zygomatic arch inserts high above the auditory bulla. The zygomatic arch does not extend ventrally and does not reach the upper molar row in lateral view. The tympanic bulla is not inflated. The skull of R. feileri appears more bulky in ventral view than the skull in species of the R. morotaiensis group ( Fig. 7 View Figure 7 , Fig. 18 View Figure 18 ). In ventral view, the incisor blades are wide compared to their basal length, as in R. elaphinus and R. taliabuensis ( Fig. 7 View Figure 7 ). The incisive foramina are long and extend towards M1. One of the most distinctive features distinguishing R. feileri from the R. morotaiensis group is the wide and bulky upper molars (M2 is wide compared to M1 and M3) and a palatal bridge that does not extend beyond M3. The molars are generally much wider and more massive than those of the R. morotaiensis group. The tympanic bullae are also proportionally larger in R. feileri than in R. morotaiensis species. The jaw of R. feileri is similar to that of the R. morotaiensis group, with a narrow incisor alveolus and a short angular process that does not extend beyond the articular process. The jaw of R. feileri is more gracile compared to larger rats such as R. taliabuensis and R. feliceus .

As discussed above, the dentition of R. feileri is easily distinguished from all Taliabu Rattus and species within the R. morotaiensis group by its wider and more robust molars. The teeth of the R. xanthurus species group from Sulawesi are very similar in shape to R. feileri and are also wide and robust ( Figs 13–14 View Figure 13 View Figure 14 ); however, cusp t3 on the M1 of R. xanthurus group species is larger and has a well-defined boundary in the first lamina as compared to all Moluccan Rattus ( Fig. 13 View Figure 13 ). In R. feileri , M2 is wider than M1 and M3 and square in shape ( Fig. 9 View Figure 9 ), and both M2 and M3 have a cusp t3 on the holotype. Cusp t3 on the third upper molar is well developed and wider than on M2, a feature also found in the R. xanthurus species group. On M1, the first lamina has a well-separated cusp t1 posterior to cusps t2 and t3 and the posterocone is absent. The lower molars of R. feileri are also relatively wide ( Fig. 10 View Figure 10 ) and likewise bear resemblance to species in the R. xanthurus species group. Anterolabial and anterolingual cuspids, as well as an anterocentral cusplet, are present and are fused together to form the anteroconid on m1, likely due to dental wear. An anterolabial cuspid and posterolabial cusplet are present on m1 and m2; m3 has only a ridge-like anterolabial cusplet.

Ecology. Little is known about the ecology of this species. Judging from its morphological features it is probably arboreal or at least scansorial. The presence of a long, tufted tail and a short, chunky rostrum are usually associated with arboreal habits in murines. Given ongoing habitat disturbance on Taliabu due to logging, agriculture, and forest fires ( Rheindt, 2010), this species may be threatened or even possibly extinct, though much more survey work is required to more fully understand the extant mammal fauna of Taliabu. Rattus feileri probably co-occurs with Rattus taliabuensis and Rattus elaphinus .