Melomys matambuai Flannery, Colgan, and Trimble, 1994

Pine, Ronald H., Mack, Andrew L. & Timm, Robert M., 2017, Marsupials And Rodents Of The Admiralty Islands, Papua New Guinea, Occasional Papers of the Museum 352, pp. 1-30 : 16-21

Melomys matambuai Flannery, Colgan, and Trimble, 1994

Manus Melomys

Flannery, Colgan, and Trimble (1994) named Melomys matambuai and placed it in the Melomys rufescens (Alston, 1877) complex, an assigned affinity with which we agree. They regarded it as the only known non-volant, endemic mammal inhabiting Manus. Judging from the literature, other members of the complex are M. arcium (Thomas, 1913) ; M. bougainville Troughton, 1936 ; M. caurinus (Thomas, 1921) ; M. cooperae Kitchener, 1995 ; M. dollmani Rümmler, 1935 ; M. fulgens (Thomas, 1920) ; M. gracilis (Thomas, 1906) ; M. leucogaster (Jentinck, 1908) ; M. paveli Helgen, 2003 ; and M. talaudium (Thomas, 1921) . Various members of this group have been unusually successful in colonizing far-flung islands. (One wonders if their apparent semi-arboreality has made it more likely that they would be transported and survive on floating masses of woody vegetation.) Flannery et al. (1994) noted that Rattus exulans , Spilocuscus kraemeri , and Echymipera kalubu had been recorded from Manus, but they regarded these species as having been introduced by human agency during the Holocene. Helgen and Flannery (2004), however, concluded that S. kraemeri and E. kalubu might be native to the island. In 1995(b), Flannery mentioned Rattus praetor ( Thomas, 1888) as an additional species occurring on Manus (where it is not actually known to occur), but he probably regarded this animal as also having been introduced by humans, because he wrote (p. 199) “It has been introduced prehistorically into most of its insular distribution ….” Musser and Carleton (2005), in their account of Melomys matambuai , referred to “ M [elomys]. bougainville on Manus Isl,” but they did not list Manus in their account of Melomys bougainville and we know of no records from there.

The original description was based on two specimens, with the holotype being of an adult female taken 15 June [non-lactating according to Flannery (1995b)] and consisting of a damaged and incomplete skin, undamaged skull, spirit-preserved carcass, and a frozen liver sample. This specimen was taken at “ 200 m near Polomou DPI Station, south-central Manus (2°08′S, 147°05′E).” The paratypic specimen is also of a female, variously referred to in the description as an “adult” and “subadult,” and consists of a skin, “fragmented skull,” and a carcass in spirit, and was taken “at the western end of Manus Island.”

Both the holotype and paratype were shot, the holotype in low secondary growth about 1.5 m above the ground at the edge of a cacao plantation “climbing on a cacao bush” according to Flannery (1995b:140). The paratype was shot in a “sago palm.” Trapping efforts on the ground failed to capture this species, which led its describers to suggest that the animal is largely arboreal, as is also suggested to us by its morphology and coloration, and is in keeping with the habits of its nearest relatives (see Flannery 1990, 1995a, b). Aplin et al. (2015) also failed to obtain specimens or images of this animal by means of both live traps and camera trapping on the ground. By contrast, they noted that camera trap images had been obtained of it in trees in 2013 and 2014.

The University of Kansas has now acquired, from Manus, the third and elements of the fourth known specimens of this species, and the Papua New Guinea National Museum & Art Gallery also a portion of the fourth, allowing us to provide additional details concerning its morphology and natural history, beyond what Flannery et al. (1994) provided. The specimens are KU 163717 , adult female, well-prepared skin ( Fig. 8 ) with intact skull and first two cervical vertebrae and part of the third, taken 9 August 2002 by Ann Williams ; KU 163722 / PNGMAG 28051 , an adult female, intact skull and first three cervical vertebrae ( KU), well-prepared skin ( PNGMAG), and taken on 6 August 2002 by Williams at “Tulu No 1,” at 1°57.371′ S, 146°50.282′ E . KU 163717 was acquired at “Sokai Camp” at 1°58.267′S, 146°47.773′E, “ captured in live trap on ground—in base of large tree” according to the skin tag but in “trap set in large dead tree buttress/hole” and “foetus preserved” according to the field catalog . KU 163722 / PNGMAG 28051 was taken in trap “set on ground under rattan in sparse undergrowth” “foetus inside.” One of these individuals, freshly killed, is shown in Fig. 9 . Its pelage, as it appears in the photograph, is much more reddish than in the KU skin .

The nipples in both of the two new specimens are hypertrophied and consist of two inguinal pairs [according to Helgen (2003:169) this pattern is found in all “ Melomys (sensu stricto) and closely related genera (excluding Mammelomys …)”]. External measurements taken by the collector of KU 163717 and KU 163722/PNGMAG 28051, respectively, are: head plus body, 162, 165; tail, 180, 175; ear (from notch), 19, 19; hind foot without claw, 36, 36; hind foot with claw, 39, 39; mass, 170 g, 200 g. As noted in the original description, M. matambuai is the largest species in the Melomys rufescens species group. A cryptic note on the tag of KU 163717 and concerning the tail reads “not visible white tip.” This was noted in contrast to the situation in KU 163722/PNGMAG 28051, which had a white-tipped tail according to the field catalog, but this is not apparent in a photograph of this specimen. The tail in the holotype is mostly missing, so whether it had a white-tipped tail is unknown. Compared to the skins of six specimens of mainland Melomys rufescens sensu Flannery (1995a) from Eastern Highlands Province, Simbu (= Chimbu) Province, and Gulf Province, at elevations ranging from 50 m to 1450 m, the fur of KU 163717 appears less dense, coarser, crisper, and less woolly. The dorsal fur at midback on KU 163717 is no longer than 10 mm, about the same as for a specimen of M. rufescens (KU 163715) from an elevation of 50 m. Although Flannery et al. (1994) stated that the fur is shorter in M. matambuai than in M. rufescens , it is not always absolutely shorter, although it is relatively shorter. The dorsal fur length on the remaining M. rufescens ranges up to at least 15 mm. The ventral fur at midbelly on KU 163717 is very short, ca. 4 mm, again matched by that on M. rufescens KU 163715, but exceeded in length by that of M. rufescens from higher elevations. The colors and their distributions are essentially the same as in some M. rufescens examined. Dorsally, the fur appears to be between Snuff Brown and Buffy Brown of Ridgway (1912) and between Prout’s Brown and Brussels Brown of Smithe (1975). The coloration as shown in our photographs of the skin of KU 163722/PNGMAG 28051 is variable, sometimes appearing darker than in KU 163717, sometimes redder, and sometimes about the same. Probably there is little difference between the two in this regard. In both specimens, the venter is broadly self-colored white from the lower lip, the naked palms, the ankles, and the vulva, with very little encroachment of gray-based white hairs laterally. Some M. rufescens seen have much less extent of white on the extremities. The description that follows is based mostly on KU 163717. Vibrissae of the head are long and numerous, ranging in length to at least 60 mm. The heaviest vibrissae are black, finer ones unpigmented, with a few black basally and unpigmented near the tips. Vibrissae at the wrist are few in number and unpigmented. The outside surface of the pinna is well-furred basally and provided with minute pale hairs distally. The manus is provided with sparse dark hairs dorsally grading into less-pigmented hairs on the digits. Scalation is quite evident dorsally on the digits. The palm is without pigment. The dorsal surface of the pes possesses very short, mostly unpigmented hairs. Scalation is evident on the toes. The sole is either unpigmented or very lightly so. The claws are very large, curved, and thick. Although Flannery et al. (1994) stated that the tail in their specimen is “uniformly black,” in the specimen at hand it is quite definitely brown, not black, above and below, although it is somewhat paler below and proximally. The tails of the M. rufescens available for comparison are darker than that of KU 163717, although, for the most part, they are merely a darker brown, rather than being actually black, in spite of the vernacular name “Black-tailed Melomys ” and statements in the literature that the tail is black. The tail scales are flatter, less raised in KU 163717 than in the M. rufescens at hand and many are concave within a raised outer border. Their shape ranges from roughly circular to squarish to roughly hexagonal. Dorsally and proximally, they number 14 per cm; laterally, midway along the tail, 11 per cm. Distally, there is one hair per tail scale; proximally, this number can be exceeded. Tail tip without scales.

The skulls of the two new specimens of M. matambuai , compared with those of nine mainland New Guinea M. rufescens sensu Flannery (1995a) , are much larger and more massively constructed, with proportionally shorter and heavier rostra and indications of postorbital processes of the frontals, which are not present in the M. rufescens nor, apparently, in the holotype and paratype of M. matambuai . Although the describers of M. matambuai noted its relatively robust rostrum, they stated that “the parietal cresting is less well-developed.” In the KU specimens, however, the lambdoidal crests, including their extension onto the parietals, are more prominent than in the specimens of M. rufescens at hand. The braincase is less inflated in M. matambuai . Otherwise, the skulls of the two species are similar ( Fig. 10A, B ). Because the skull of the paratype is “fragmented,” only a single value has been available for many cranial measurements. Therefore, the availability of the skulls for the new specimens is especially welcome.

One additional difference between M. matambuai and M. rufescens is that the bone in the orbital region, and/or just anterior to that and medial to the zygomatic bridge, consists of very thin bone and one wonders if it is always bony at all or merely, at least in part, replaced by a membrane. This is because in all nine skulls of M. rufescens at the University of Kansas, there is a bilateral vacuity in this region (see Fig. 10B ). This is also the case in 15 skulls labeled as being of M. rufescens at the ( U.S.) National Museum of Natural History. A 16th skull, USNM 58640, so identified, but atypically small and with unusually large teeth, with body in fluid, may lack this hole or have it barely manifested on the right side. This vacant space in the bone varies in size, shape, and position and may be doubled. It appears that the cleaning process, perhaps starting with the dermestid stage, removed the very thin bone that presumably must have been there originally.

Cranial measurements (for KU 163717, then for KU 163722/PNGMAG 28051) are: greatest length of skull (occiput–nasals), 39.9, 39.7; condylobasal length, 37.9, 37.3; greatest nasal length, 12.3, —; palatal length, 19.5, 19.4; palatilar length, 16.9, 16.5; incisive foramen length, 5.1, 4.7; palatal bridge (left side), 9.0, 8.8; length of upper diastema, 10.1, 10.1; upper molar alveolar length, 7.3, 7.0; width of rostrum, 7.5, 7.9; least interorbital breadth, 7.2, 7.0; zygomatic breadth, 20.7, 20.5; interparietal length, 7.0, 6.2; and interparietal width, 11.5, 10.0.

Both new specimens were pregnant with only a single fetus. This is in keeping with the very small number of young in litters of other species of Melomys and with the small number of mammae.

Ann Williams (in litt.; see Timm et al. 2016) writes that the local name for this animal is “murasu.” This was rendered by Flannery (1995b) as “Musirou” for central Manus. C. Williams (1999) reported skeletal material identified as of “ Melomys sp. ” and as of the “ Manus Melomys .” Flannery (1995b) noted the presence of M. matambuai throughout the Pamwak archaeological site sequence. Aplin et al. (2015) stated that numerous specimens are known from that site but incorrectly indicated that Flannery had not found them among the Pamwak rodents.

The IUCN Red List of Threatened Species lists M. matambuai as “Endangered” ( Leary et al. 2008). Aplin et al. (2015) reported 397 “ground trap nights” in 2014, without catching this species.

Figures

Figure 8. Dorsal and ventral views of a stuffed skin of an adult female Melomys matambuai from “Sokai Camp,” Manus (KU 163717). Total length = 342 mm.

Figure 9. A recently killed specimen of an adult female Melomys matambuai from Manus Island (either KU 163717 or KU 163772/PNGMAG 28051). Photograph courtesy of Ann Williams.

Figure 10. Dorsal, ventral, and lateral views of the crania and lateral view of the right dentaries of adult female Melomys from Papua New Guinea. A—Melomys matambuai from “Tulu No. 1,” Manus Island (KU 163722/PNGMAG 28051, greatest length of skull = 39.7 mm); B—Adult ♀ Melomys rufescens from mainland New Guinea (KU 160752; Ivimka Camp, 11 km SE of Tekadu Airstrip, Gulf Province, Papua New Guinea, 120 m, 7°44′05″S, 146°29′45″E; greatest length of skull = 32.0 mm).