Systematic Revision Within the Phalanger orientalis Complex (Diprotodontia, Phalangeridae): A Third Species of Lowland Gray Cuscus from New Guinea and Australia

20 Pages·2001·1.3 MB·English

by  Christopher A. Norris

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3356, 20 pp., 8 figures, 3 tables December 31, 2001
Systematic Revision Within the Phalanger
orientalis Complex (Diprotodontia, Phalangeridae):
A Third Species of Lowland Gray Cuscus from
New Guinea and Australia
CHRISTOPHER A. NORRIS1 AND GUY G. MUSSER2
ABSTRACT
A study of specimens from the mammal collections of the American Museum of Natural
History that were originally assigned to Phalanger orientalis sensu lato revealedthepresence
of three taxa: P. orientalis from northern New Guinea, the Bismarck Archipelago, and the
SolomonIslands;P.intercastellanusfromsoutheastNewGuinea,theD’EntrecasteauxIslands,
the Trobriand Islands, and the Louisade Archipelago; and agroup fromsouthern NewGuinea
and the Cape York Peninsula of Australia that could not be assigned to either of the two
foregoing species. Possession of a distinctive suite of morphological characters warrants rec-
ognition of this group at the species level. The characteristics and habitat of the species are
described, and the zoogeographic implications of its distribution are discussed.
INTRODUCTION phylogentic revision of the cuscuses, by Tate
(1945), placed all species in a single genus,
The taxonomy of the lowland gray cus- Phalanger,whichwassplitintothreespecies
cuses, small- to medium-sized arboreal mar- groups. The largest of these, the ‘‘orientalis
supialsofthefamilyPhalangeridae,hasbeen group’’,contained fourspecies:P.orientalis,
in a state of flux for many years, a situation P. gymnotis, P. vestitus, and P. celebensis.
that was summarized in somedetailbyMen- The first of these species, P. orientalis, was
ziesandPernetta(1986).Thefirstlarge-scale divided into five subspecies, subsumedwith-
1DivisionofVertebrateZoology (Mammalogy),AmericanMuseumofNaturalHistory.e-mail:[email protected]
2DivisionofVertebrateZoology(Mammalogy),AmericanMuseumofNaturalHistory.e-mail:[email protected]
Copyright(cid:113)AmericanMuseumofNaturalHistory2001 ISSN0003-0082
2 AMERICAN MUSEUM NOVITATES NO. 3356
in which were a number of taxa previously of the central cordillera between the Kikori
considered to be of specific rank. These in- and Mimika rivers and encompassing low-
cluded P. ornatus (Gray, 1860), P. lullulae land rainforests, seasonally flooded forests,
(Thomas, 1896), P. vulpecula (Fo¨rster, openwoodlands,andtropicalgrasslands.The
1913), P. brevinasus, P. matsika, and P. mi- absence of specimens is perhaps unsurpris-
crodon (Tate and Archbold, 1935). Subse- ing, as the area has rarely been visited by
quent studies (George, 1979, 1982; Ziegler, Western collectors. Nonetheless, the paucity
1982; Menzies and Pernetta, 1986) resur- of material is frustrating, as the few speci-
rected some of these groups as full species, mens of P. orientalis sensu lato collected
but Tate’s basic concept of a single,morpho- here are distinctive enough to have been de-
logically diverse species, encompassing cus- scribedasaseparatesubspecies(P.orientalis
cuses from the lowlands of New Guinea, to- mimicus, Thomas, 1922), a separate species
gether with those of the Solomon Islands, (P. microdon, Tate and Archbold, 1935), or
Bismarck Archipelago, Louisade Archipela- even assigned to a different genus (Strigo-
go, D’Entrecasteaux Islands, Trobriand Is- cuscus mimicus, Flannery et al., 1987). The
lands, South Moluccas, Timor, and the Cape
results of a discriminant function analysis of
York Peninsula of Australia, has persisted in
metric characters by Menzies and Pernetta
the literature.
(1986)revealboththecleardistinctionofthe
In recentyearsithasbecomeclearthatthe
southern New Guinea population of P. or-
apparently homogenous P. orientalis ofNew
ientalis from the other New Guinea popula-
Guinea, Cape York, and nearby islands may
tions and its affinities with the Cape York
contain within it several populations suffi-
population. On this basis, Menzies and Per-
ciently distinctto warrantrecognitionasspe-
netta recognized the two populations as a
cies in their own right. Menzies andPernetta
separate subspecies, P. orientalis mimicus.
(1986) identified seven populations on the
TheAmericanMuseumofNaturalHistory
basis of palatal dimensions and non-metric
possesses a large series of phalangerid mar-
morphological characters, but declined to
supialsresultingfromtheeightArchboldEx-
recognize these as anything more than sub-
peditions of 1933 to 1964 to New Guinea
species of P. orientalis. An electrophoretic
and the Cape York Peninsula of Australia
study by Colgan et al.(1993)showedtheex-
(Archbold and Rand, 1935; Rand and Brass,
istenceof twopopulationswithinNewGuin-
1940; Archbold et al., 1942; Brass, 1953,
ea that were sufficiently divergent to suggest
1956, 1959, 1964; Van Deusen, 1978). Re-
they represented two species: P. orientalisin
curation of these collections by Musser and
northern New Guinea and the Bismarck and
Helmut Sommer in the 1990s provided an
Solomon Islands, and P. intercastellanus in
opportunity to reassess the taxonomy of the
southern New Guinea and the southeastPap-
lowland gray cuscuses. It became apparent
uanIslands.Theresultsoftheelectrophoretic
that while the majority of P. orientalissensu
study were supported by an analysis of mor-
lato specimens could be assigned to eitherP.
phological characters, which can be used to
orientalissensustrictoorP.intercastellanus,
distinguish between the two species (Colgan
there remained a set of specimens, collected
et al., 1993).
Colgan et al.’s combination of molecular in the southern lowlands of New Guinea and
andmorphologicalevidencefortheexistence the Cape York Peninsula of Australia,whose
of two species within Phalanger orientalis distinctive morphological characteristics fit-
sensu lato is compelling. However, the spec- ted into neither of the species described by
imens used as the basis of the study are Colgan et al. (1993). This report describes
drawn from a comparatively limited sample, these specimens, and forms part of series of
taken primarily from offshore islands and a reports, either published (Musser and Som-
restricted number of sites in mainland New mer, 1992) or in preparation, that reflect the
Guinea. There are no specimens from the Department of Mammalogy’s efforts to gain
southern lowlands of New Guinea(including a better understanding of the species diver-
the area known as the Trans-Fly),aregionof sity and zoogeography of mammals in New
around125,000squaremilesextendingsouth Guinea.
2001 NORRIS AND MUSSER: PHALANGER ORIENTALIS COMPLEX 3
Fig. 1. Collecting localities for specimens of Phalanger intercastellanus, P. mimicus, and P. orien-
talis in the AMNH collections, and for non-AMNH specimens used in the description of P. mimicus.
Solomon Islands and Australian localities are not shown on the map. For details of all localities see
appendix 1. Locality 33 ((cid:53) ‘‘New Britain’’) is not shown because it is nonspecific.
MATERIALS AND METHODS diagnosticcharactersdefinedbyColganetal.
(1993) resulted in the species distribution
Specimens of Phalanger orientalis sensu
seen on the map, with a clear zone of sepa-
lato from the American Museum of Natural
ration at the watershed of the Markham/
History, Department of Mammalogy
Ramu Valley. Specimens of both species
(AMNH);theNaturalHistoryMuseum,Lon-
don, Mammal Collections (BMNH); and the were collected at Umi River Camp (fig. 1,
Bernice P. Bishop Museum (BBM) were ex- localities 1 and 34) during the Sixth Arch-
amined. A list of specimens is attached as bold Expedition to New Guinea, although
appendix 1. Measurements were taken using this should not be taken as evidence of sym-
vernier calipers. Becausethecraniumofcus- patry. The expedition mammalogist Hobart
cusescontinuestogrowthroughoutadultlife Van Deusen frequently obtained specimens
(MenziesandPernetta,1986)onlyspecimens from local hunters, which could have been
in which M4 was fully erupted were mea- brought to the camp from either side of the
sured. Dental terminology follows Luckett Markham/Ramu watershed. Dimensions for
(1993). the skulls of mainland New Guinea popula-
tions of P. intercastellanus and P. orientalis
RESULTS are given in table 1.
The AMNH collections contain 1162 A third group of specimens, from the
specimens assigned to Phalanger orientalis Western Province of Papua New Guinea,
sensu lato. The main collecting localities for could be distinguished from both P. orien-
these are listed in appendix 1 and are shown talis and P. intercastellanus by their smaller
in figure 1. Assignment of specimens from overall size; their particularly small molars;
mainland New Guinea to P. orientalis sensu the presence of a well-developed postpara-
stricto and to P. intercastellanus, using the cristaonM1,withapronouncedbuccalkink;
4 AMERICAN MUSEUM NOVITATES NO. 3356
TABLE1
Descriptive Statistics for Cranial and Dental Measurements (mm) for New Guinea
Population Samples of Phalanger orientalis and Phalanger intercastellanus
(Mean and observed range [in parentheses] are listed.)
the reddish-brown pelageofthefemales;and ther P. orientalis (BismarckArchipelagoand
most strikingly by the distinctive alignment SolomonIslands)orP.intercastellanus(East
of the zygomatic arches, which are parallel Papuan Islands). However, the Cape York
to the midline of the skull or diverge ros- population showed clear affinities with the
trally, rather than converging rostrally. Skull WesternProvincespecimens,includingsmall
dimensions for these specimens are listed in size of molars and the alignment of the zy-
table 2. gomaticarches,althoughfemalesofthispop-
The study was then expanded to include ulation lacked the reddish pelage of the New
specimensfromtheEastPapuanIslands,Bis- Guinea females. Cranial dimensions of this
marck Archipelago, Solomon Islands, and population are listed in table 2.
the Cape York Peninsula of Australia. Al- Examination of the holotype of P. orien-
though significantly smaller than the main- talis mimicus Thomas, 1922, in the collec-
land populations of the two species defined tions of the Natural History Museum, Lon-
by Colgan et al. (1993), it was possible to don, revealed that it possessed the same dis-
assign the majority of these specimens to ei- tinctive cranial charactersseenintheAustra-
2001 NORRIS AND MUSSER: PHALANGER ORIENTALIS COMPLEX 5
TABLE2
Descriptive Statistics for Cranial and Dental Measurements (mm) for
New Guinea and Australian Population Samples of Phalanger mimicusa
(Mean and observed range [in parentheses] are listed.)
lian and Western Province specimens at the Phalanger mimicus (Thomas, 1922)
AMNH. They were also seen in three spec-
Phalanger intercastellanus Thomas, 1895.
imens of ‘‘P. orientalis’’ from the Bishop Phalanger orientalis mimicus Thomas, 1922.
Museum, which were collected on the lower Phalanger microdon Tate and Archbold, 1935.
slopes of Mount Bosavi, in the Southern Phalanger orientalis peninsulae Tate, 1945.
Highlands Province of Papua New Guinea. HOLOTYPE AND TYPE LOCALITY: BMNH
11.11.11.93, puppet skin with skull and den-
DISCUSSION taries of an adult male. Collected by G. C.
Shortridge, Parimau, Mimika River, Dutch
On the basis of the consistent morpholog- New Guinea ((cid:53) Irian Jaya), 4(cid:56)31(cid:57)S,
ical differences between the southern New 136(cid:56)36(cid:57)E, 250 ft, 4 October 1910.
Guinea and Cape York populations of Pha- DIAGNOSIS: Skull and teeth small, molars
langer orientalis sensu lato, we recognize a especially so. Lachrymal contribution to the
third species of lowland gray cuscus in the face is short. Zygomatic arches run parallel
P. orientalis complex (fig. 2). or diverge from midline of skull rostrally.
6 AMERICAN MUSEUM NOVITATES NO. 3356
Fig. 2. Captive specimen of a female Phalanger mimicus. Third Archbold New GuineaExpedition,
1936–1937. Gaima, Western Province, Papua New Guinea.
Well-developed postparacrista on M1, with a absence of lingual cingulum on protocone of
pronounced buccal kink. Distinguished from M2.
P. orientalis and P. intercastellanus by its DESCRIPTION: Critical skull dimensions are
smaller size, lack of convergence of zygo- listed in table 2. The most notable feature of
maticarchesrostrally,andbywell-developed the skull is the shape of the zygomatic arch-
postparacrista. Distinguished from P. orien- es.InallotherspeciesofPhalangerthearch-
talis by absence of white tail tip in females. es reach their widest point at the caudal end,
Distinguished from P. intercastellanus by near the suture between the jugal and the
2001 NORRIS AND MUSSER: PHALANGER ORIENTALIS COMPLEX 7
squamosal, and converge toward the midline ing that, unlike the condition seen in Austra-
of the skull rostrally. In P. mimicus thearch- lian P. mimicus, the dorsal stripe continues
esrunparalleltothemidline,orevendiverge almosttothebaseofthetail,albeitbecoming
rostrally, giving the skull a different shape more diffuse caudally. The question of
(fig. 3). In general the skull shows less de- whether the differences in pelage between
velopment of the supraorbital, parietal, and the Trans-Fly and Cape York populations
sagittal crests than is seen in other speciesof warrant taxonomic recognition cannot be an-
the genus; indeed, it is not unusual for the swered without a larger sample from south-
parietal crests to remain unfused, even in west New Guinea.
very old individuals. The facial extent of the HABITAT: Rand and Brass (1940) provide
lachrymal is comparatively small, as in P. descriptions of the southern New Guinea re-
intercastellanus.Thefrontalsaredeeplypen- gion that containsthecollectinglocalitiesfor
etrated by the nasal bones; the nasals do not P.mimicus.Intheareaalongthecoast,south
taper abruptly at their caudal extremity, but of the estuary of the Fly River (which in-
arerounded(fig.4).Theteethareremarkably cludes the Oriomo River: fig. 1, locality 62),
small, even given the overall small size of the predominant vegetation type is scrub sa-
the animals. In this respect P. mimicus is vanna. Rainforest occurs chiefly as fringing
similar to the rare montane Telefomin cus- strips of no more than 100–200 m in depth
cus, P. matanim (Flannery, 1987). The well- along creeks and streams, and in isolated
developedpostparacristaonM1,withitspro- patches on ridge tops (fig. 6). The rainforest
nounced buccal kink (fig. 5), is seen in sev- is described by Rand andBrassas‘‘poorand
eral species of Phalanger, but not in either light’’, with some areas that ‘‘could only be
P. orientalis or P. intercastellanus, the two describedasdensebrush’’.Savannatrees,in-
species within which P. mimicus was for- cluding Acacia and Tristania, intrude into
merly reduced to synonymy. the rainforest. The savannas are dominated
The tail wedge of P. mimicus is short, as by Melaleuca; on ridges this genus mixes
in P. intercastellanus. Adult males of the with Tristania, Eucaplyptus, and Acacia to
Australian population have upper parts that form savanna forests with a thin, high can-
are gray, with a well-defined dark dorsal opy and a ground cover of grasses. During
stripe finishing well short of the haunches, the rainy season the flat savannas become
and silver-tipped guard hairs. Three speci- boggy, and can flood up to a foot (Brass and
mens, including the holotypes of P. orien- Rand,1940).Incontrast,theareasaroundthe
talis mimicus (BMNH 11.11.11.93) and P. Palmer River Camp (fig. 1, locality 63) and
orientalis peninsulae (AMNH 108905),have the Black River Junction (fig. 1, locality 64)
an off-white pelage with dark guard hairs. in the northern part of Western Province are
This coloration is often seen in old males of typified by steep ridges rising up to 100 m
both P. orientalis and P. intercastellanus. above sea level (Brass and Rand, 1940). The
With the exception of aged specimens, how- vegetation type is classic lowland rainforest
ever, P. mimicus appears to show little or no richinepiphytesinboththelowerlayersand
sex-based color dimorphism, at least in its the canopy (fig. 7).
Australian populations. The situation is less The Australian localities for P. mimicus
clear for the New Guinea population, be- aredescribedbyBrass(1953),andbearstrik-
cause only one adult male, the aforemen- ing similarities in vegetation to those seen in
tioned BMNH 11.11.11.93, is known. Fe- southern New Guinea. At Shepheard’s Bat-
males of the New Guinea population have a tery site, on the Upper Peach River (fig. 1,
striking reddish-brown pelage, which was locality60),Brassreportedthatspecimensof
one of the characteristics used by Tate to de- P. mimicus were ‘‘found in numbers’’ in the
scribeP.microdon.Juvenilemalesalsoshow rainforest fringing Bonanza Creek. Rainfo-
this coloration, but given the generaltenden- restwasconfinedtothemarginsofthecreek,
cy toward a reddish pelage in juveniles of while the remainder of the flats and sur-
both P. orientalis and P. intercastellanus, rounding ridges were covered inopensavan-
this may be of limited significance in distin- na forests of box, bloodwood, and ironbark
guishingbetweenthespecies.Itisworthnot- trees. In the Iron Range (fig. 1, locality 59)
8 AMERICAN MUSEUM NOVITATES NO. 3356
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2001 NORRIS AND MUSSER: PHALANGER ORIENTALIS COMPLEX 9
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10 AMERICAN MUSEUM NOVITATES NO. 3356
Fig. 5. Right molar tooth rows of (a) AMNH 104400, P. mimicus; (b) AMNH 108569, P. inter-
castellanus;(c)AMNH109435,P.orientalis.Abbreviations:lc(cid:53)lingualcingulumofM2;bk(cid:53)buccal
kink in postparacrista of M1. Approximately 3.5 (cid:51) natural size.
lowland rainforests predominated (fig. 8), the other New Guinea populations and, sec-
though therewere stillpatchesofopenforest ond, its affinities with the Cape York popu-
in which rainforest was limitedtocreekmar- lation. On this basis, Menzies and Pernetta
ginsandgullies.AswiththeFlyRiverbasin, recognized the two populations as a separate
there was seasonal inundation of the rainfo- subspecies, P. orientalis mimicus. Our study
rests on the floodplains, in some areas to supportstheresultsoftheiranalysis,theonly
depths of 6–10 ft (Brass, 1953). difference being their retention of mimicus
COMMENTS:Anumberofauthorshaverec- within P. orientalis. Except for its consis-
ognized the distinctive nature of the lowland tently smaller size, Menzies and Pernetta
gray cuscuses from southern New Guinea could find no distinctive characters to sepa-
(Thomas, 1922; Tate and Archbold, 1935; rate the taxa. In fact, as we havedemonstrat-
Menzies and Pernetta, 1986; Flannery et al., ed, the qualitative differences in cranialmor-
1987; George, 1987). Particularly notewor- phology between mimicus and theotherpop-
thy among these earlier studies is that of ulationsofP.orientalissensulatoareatleast
Menzies and Pernetta (1986), who used a as great as those that define a number of
discriminantfunctionanalysisofmetricchar- well-established species of phalangerids,and
acters(largelydrawnfromthepalatalregion) arecertainlysufficienttojustifyseparationat
to distinguish different populations of P. or- the species level.
ientalis sensu lato. Their analysis revealed The systematicplacementofP.mimicusis
first, the clear distinction of the southern problematic. The characteristics that were
New Guinea population ofP.orientalisfrom originally proposed by Flanneryetal.(1987)