Dendrolagus spadix, Troughton & Le Souef, 1936

Eldridge, Mark D. B., Potter, Sally, Pratt, Renae, Johnson, Rebecca N., Flannery, Tim F. & Helgen, Kristofer M., 2024, Molecular systematics of the Dendrolagus goodfellowi species group (Marsupialia: Macropodidae), Records of the Australian Museum 76 (2), pp. 105-129 : 120-121

Dendrolagus spadix

Troughton and Le Souef, 1936

Common name. Lowland Tree-kangaroo

Holotype. AM M.4561, adult male, skin ( Fig. 1 ). Between Upper Awarra and Strickland Rivers, Western Province, Papua New Guinea.

Paratype. AM M.5978, subadult, unsexed, skin and skull. Bamu , Western Province, Papua New Guinea .

Other material examined. AM M.10789 (skin, adult, precise locality unknown, Papua New Guinea), AM M.15720 (skin and skull, juvenile female) and AM M.15721 (adult, skull, Mt. Sisa, Hela Province); AM M.17212 (skin and skull, adult male, Fogamaiyu, Southern Highlands Province); PNGM 22707 (skin, adult male, Mt. Bosavi, Southern Highlands Province); UPNG 2807(1943), UPNG 2808(1529) (flat skins, adults, labelled as from “Rio Tura south of Yuro”, Karimui area, Chimbu Province, which appears to be where they where purchased at a market but UPNG 2808 was collected from Gurimata, Purari River, Gulf Province), UPNG 3244 (skull and skeleton, adult, Kesigi, Balimo subdistrict, Western Province); USNM 586436 (trophy jaw, Siona Falls, near Fogamaiyu, Southern Highlands Province); uncatalogued specimen formerly at the Papua New Guinea Institute of Biological Research, Goroka, Papua New Guinea (skull, between Wabo and Haia, Chimbu Province).

Leary and Seri (1997) mentioned trophy specimens referred to this species from Kopi in the Kikori Basin (Southern Highlands Province). Additional tree-kangaroo specimens described by Leary and Seri (1997) from the Kikori Basin in Southern Highlands Province, from the localities of Mt. Faru (reported as D. goodfellowi with weakly defined rump stripes), Mt. Kemenagi, and Wasi Falls, probably also represent this species. Two hunters’ skins from Babeio in the Uro Creek Catchment of the Kikori Basin, southern Gulf Province, photographed and referred to D. goodfellowi by Kale et al. (2018a), are dark red over their entire body and tail and in fact represent D. spadix . Kale et al. (2018b) also discussed the possibility that D. spadix occurs in the Wau Creek Catchment of the Kikori Basin.

Distribution. Dendrolagus spadix inhabits sections of the Purari, Kikori and Strickland River catchments, south-central Papua New Guinea, in primary lowland tropical rainforest (small and large crowned hill forest) on limestone and other sedimentary geologies and uplifted alluvial plains, from sea level to 800 m elevation ( Flannery, 1995; Flannery et al., 1996). It is recorded from Western, Hela, Southern Highlands, Gulf, and Chimbu Provinces of Papua New Guinea ( Leary, 2004). Wright et al. (1998:181) suggested it may occur in the Lakekamu Basin in the lowlands in the border region of Gulf, Central, and Morobe Provinces, which would represent the easternmost occurrence. In the west, it may extend into the Trans-Fly region of Papua Province ( Indonesia), where it as yet unrecorded. It is presumably geographically and elevationally parapatric with D. goodfellowi along the southern slopes of the Central Cordillera, occurring at lower elevations.

Most records for the species come from rugged karst terrain on the Papuan Plateau, extending to the coast in Gulf Province, and uninhabited swamp forest southeast of Lake Murray on the Fly River. These regions have little in common except for the fact that people are either absent or exist in extremely low density. Flannery et al. (1996) noted that ‘its distribution hardly overlaps at all with people’. Apparently suitable habitat for D. spadix occurs across a vast area of southern New Guinea, and it seems likely that hunting by people has eliminated the species from much of its potential range.

Captain G.F.W. Zimmer, who collected the type specimen, reported that it came from “unknown and uninhabited country” ( Troughton & Le Souef, 1936). The people of Lake Murray report that the vast uninhabited region lying southeast of Lake Murray was originally inhabited, but was depopulated as a result of D. spadix , which they believe hunts much as people do ( Flannery et al., 1996). The species’ dangerous reputation doubtless provides some protection.

Description. Dendrolagus spadix can be distinguished from other members of the Goodfellow’s group by its largely unornamented dark brown colouration and short, sparse fur ( Fig. 6 ). Uniformly, dark chestnut-brown dorsally, paler ventrally and on limbs and face. The ventral surface is sparsely furred. A faint dark mid-dorsal stripe runs from the head to the rump. Very faint paired pale stripes (of similar dimensions to those seen prominently in D. goodfellowi ) occur on the rump in some specimens. A single hair whorl is present on the dorsal midline on the mid-lower back. The tail is longer than the head-body ( Table 4) and dark brown, with occasional small yellowish markings, more common ventrally ( Eldridge & Coulson, 2015).

Remarks. Listed as ‘Vulnerable’ on the IUCN Red List (Leary et al., 2016c). The species is poorly represented in museum collections and almost nothing is known of its biology.

ACKNOWLEDGEMENTS. We thank the Hermon Slade Foundation and the Australian Museum for funding. Kristin Stewardson, Cassie Vockler, Linda Neaves and Greta Frankham are thanked for expert technical assistance. Abram Powell is thanked for specimen photography. Staff at the Australian Museum (Sandy Ingleby, Anja Divljan, Harry Parnaby), American Museum of Natural History, New York (Eileen Westwig), Australian National Wildlife Collection https://ror.org/059mabc80 (Leo Joseph), Bernice P. Bishop Museum, Hawaii, Museum of Vertebrate Zoology (Allen Allison and Molly Hagemann), University of California, Berkeley (Jim Patton), National Museum of Victoria, Melbourne (Karen Roberts), Natural History Museum, London (Roberto Portela Miguez), Naturalis Biodiversity Center, Leiden (Chris Smeenk), Papua New Guinea National Museum and Art Gallery (Bulisa Iova and Jim Anamiato) and University of Papua New Guinea (Paulus Kei) are thanked for providing access to specimens.

Figures

Figure 1. AM M.4561, holotype flat skin of D. spadix Troughton & Le Souef 1936.An image of this specimen has not previously been published.

Figure 6. Comparison of pelage variation across taxa in the Goodfellow’s group. Left to right: D. g. buergersi (AM M.17213), D. g. goodfellowi (AM M D. matschiei (AM M.6062), and D. spadix (AM M.17212).