Records of the Western Australian Museum Supplement No. 57: 239-253 (1999).

Wanburoo hilarus gen. et sp. nov., a lophodont bulungamayine kangaroo(Marsupialia: Macropodoidea: Bulungamayinae) from the Miocene deposits

of Riversleigh, northwestern Queensland

Bernard N. Cooke

School of Life Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001;email: b.cooke@qut.edu.au

and, School of Biological Science, University of New South Wales, Sydney, NSW 2052

Abstract - Wanburoo hi/ants gen. et sp. novo is described on the basis ofspecimens recovered from a number of Riversleigh sites ranging in estimatedage from early Middle Miocene to early Late Miocene. The new species ischaracterized by low-crowned, lophodont molars in which hypolophidmorphology clearly indicates bulungamayine affinity.

The relatively close temporal proximity and lophodont molar morphologyof the new species invites comparison with the Late Miocene macropodids,Dorcopsoides fossilis and Hadronomas puckridgi. While there is a number ofphenetic similarities between the species, many of these appear to besymplesiomorphic. However, a number of apomorphies are suggested asindicating a phylogenetic relationship between the new species and early,non-balbarine macropodids represented by D. fossilis and H. puckridgi. Ofthese two taxa, the relationship appears stronger with Hadronomas than withDorcopsoides. Balbarine-like characters present in Dorcopsoides are likelyplesiomorphic or the result of convergence. While bulungamayines areherein regarded as more likely than balbarines to be ancestral tomacropodids, the possibility of a diphyletic origin for macropodids cannotbe dismissed. The suggested relationship between bulungamayines andmacropodids casts doubt on the inclusion of Bulungamayinae withinPotoroidae.

INTRODUCTION

The Oligo-Miocene freshwater limestone depositsof the Riversleigh World Heritage area of northernAustralia have yielded a wealth of kangaroo fossilmaterial. Sixteen new fossil kangaroo species havebeen described thus far and more awaitdescription. Described species includerepresentatives of the Hypsiprymnodontinae:Hypsiprymnodon bartholomaii Flannery and Archer,1987a; Propleopinae: Ekaltadeta ima Archer andFlannery, 1985 and E. jamiemulvaneyi Wroe, 1996;Potoroinae: Gumardee pascua/i Flannery, Archer andPlane, 1983 and Bettongia moyesi Flannery andArcher, 1987b; Bulungamayinae: Wabularoonaughtoni Archer, 1979, Bulzmgamaya delicataFlannery, Archer and Plane, 1983, Nowidgee matrixCooke, 1997b and Ganguroo bi/amina Cooke, 1997b;and Balbarinae: Ba/banJO gregoriensis Flannery,Archer and Plane, 1983, Nambaroo couperi Cooke,1997a, Wururoo dayamayi Cooke, 1997a and threespecies of Ganawamaya Cooke, 1992. Ga/anarlatesse/ata Flannery, Archer and Plane, 1983 remainsunassigned to a subfamily. No specimensrepresenting unequivocal macropodines orsthenurines have so far been recovered from anypre-Pliocene Riversleigh site.

Possible exceptions to the above are kangaroocranial remains recovered from Gag Site, a sitewithin the Riversleigh System C of Archer et al.(1989), regarded by those authors as middleMiocene in age. Flannery (1989: 32) provided anoutline description of these remains, referring tothem as belonging to "the Gag Site macropodine".Molar teeth in these remains are low-crowned andbilophodont, but the M

1trigonid is transversely

broad, in contrast to the transversely narrow M1

trigonid characteristic of balbarines, considered atthat time to be the most abundant group oflophodont macropodoids occurring at Riversleigh.If the specimens could be shown to be of anundoubted macropodine they would represent theoldest member of the subfamily so far known andtherefore be of considerable phylogeneticsignificance.

The Gag Site specimens have been re-examinedand they, together with material from the morerecently discovered Dome and Encore Sites, aredescribed more fully in this paper. A new genusand species is proposed to accommodate this fossilmaterial.

QM F prefixes Queensland Museum, Brisbane,fossil collection catalogue numbers. These

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supersede the catalogue numbers (prefixed by AR)of the Vertebrate Palaeontology Laboratory of theUniversity of New South Wales, used by Flannery(1989). Numbers in the latter series are indicated inparentheses where appropriate. The abbreviationUCMP = University of California Museum ofPaleontology, Berkeley, California, U.s.A.Measurements are in millimetres.

SYSTEMATIC PALAEONTOLOGY

Suprageneric classification follows Aplin andArcher (1987), molar homology follows Luckett(1993) and premolar homology follows Flower(1867). Cusp homology of upper molars is that ofTedford and Woodburne (1987). Molar descriptiveterminology is used as in Cooke (1997a).Authorities for higher category names are notincluded in the References but may be found inAplin and Archer (1987).

Supercohort Marsupialia (Illiger, 1811)

Order Diprotodontia Owen, 1866

Superfamily Macropodoidea (Gray, 1821)

Family incertae sedis

Subfamily Bulungamayinae Flannery, Archer andPlane, 1983

Wanburoo gen. noy.

Type SpeciesWanburoo hilarus sp. novo

DiagnosisRobust, lophodont bulungamayines in which I] is

deep-bladed in relation to its length, enamel isconfined to its buccal surface, and both dorsal andventral enamel flanges are present. The dorsalflange of I] occludes with cutting edges on P and F.P is small and caniniform in shape; P is large,unornamented, with a long occlusal edge, crownshortening towards the base. Upper caninespresent, in close proximity to incisors. Lowermolariform teeth with an anterobuccally directedcristid, from the entoconid; hypolophid formed byan elevated, transversely oriented posthypocristid;pre-entocristid, when present, directed anteriorly.In young animals at least, the ventral margin of thedentary is not convex below the cheek teeth andmay be straight or slightly concave in this region.Posterior section of inferior dental canal reduced inlength to the extent that its anterior opening intothe masseteric fossa is overlapped by themandibular foramen.

EtymologyThe name Wanburoo is derived from the Gulf of

B.N. Cooke

Carpentaria coastal Aboriginal word wanbu, whichmeans ghost (Breen 1981), and roo, a commonAustralian vernacular diminutive for kangaroo.Gender is considered to be masculine.

Wanburoo hilarus sp. noy.Figures 1-5; Table 1

Gag macropodine incertae sedis: Flannery 1989: 39

Material Examined

HolotypeQM F20525 (formerly AR4965), the badly

crushed remains of the skull of a subadult animal(Figure I), including parts of the left premaxilla andmaxilla preserving 13, C], dp2, dp3 (P3), M]·2 and M3within its crypt, isolated right premaxillary teethincluding P'3, part of the right maxilla with dp2 andthe badly damaged buccal parts of dp3 and Ml,together with the crown of the unerupted right P3.Associated mandibular remains include most of thehorizontal ramus and part of the ascending ramusof the left dentary with I], dP2, dP3 and M].2 in situand the detached crowns of Py M3 and M

4, as well

as teeth detached from the right mandible,including the tip of I], dPy the crown of theunerupted Py and M].

ParatypesQM F37021 (formerly AR3651), a left dentary

including most of the horizontal ramus and muchof the ascending ramus, including the condyle. I],dP2, dP3(P) and M] are present.

QM F19942, the anterior portion of the horizontalramus of a left dentary containing 1

1, dP2, dP3 and

the damaged remains of M] and M2. The crown ofP3is present and has been removed from its crypt.

QM F30346, a fragment of a left horizontal ramusfrom an adult animal, preserving I). P3 anddetached M].2' The fragment is in two pieces,broken just anterior to the M2alveolus.

Type Locality and AgeThe holotype and QM F37021 are from Gag Site,

low in the sequence of Riversleigh System C sites(Archer et al. 1989) on Gag Plateau. Those authorsconsidered Riversleigh System C to be Early toMiddle Miocene in age. QM F19942 is from EncoreSite, and QM F30346 is from Dome Site. A possiblemid to late Middle Miocene age has been suggestedfor Dome Site and a possible early Late Mioceneage for Encore Site (Anonymous 1994).

DiagnosisAs for the genus until new species are described.

EtymologyThe specific name hilarus is Latin for mirthful or

A new bulungamayine kangaroo from Riversleigh 241

A

B

c

o

Figure 1 QM F20525, holotype of Wanburoo hilarus gen. et sp. novo A, B. Buccal and lingual views of left premaxillaand maxilla. C, D. Buccal and lingual views of left dentary. Scale bars = 10 mm.

jocund, a reference to Gag Site from which theholotype was recovered.

Description

Premaxilla and MaxillaThe holotype is very badly fragmented and

little detail of the premaxillary and maxillaryregions can be determined (Figure 1). There are

two small foramina in the palatine wing of themaxilla medial to the diastemal region. Part ofthe zygomatic process of the maxilla is preservedand does not reach the level of the alveolarmargin. There appears to be no definitemasseteric sulcus between the alveolar processand the zygomatic process of the maxilla. Thelower margin of the infraorbital foramen isvisible dorsal to dp3.

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A

B

B.N. Cooke

Figure 2 Isolated right p-3 of QM F20525, holotype of Wanburoo hilarus gen. et sp. novo Teeth have been mounted inplasticene to indicate their original arrangement. A. Buccal view. B. Lingual view. Scale bar = 4 mm.

Upper DentitionThe upper cheek tooth row is straight in lateral

view but buccally convex in occlusal view. dp2 isaligned with the molar row.

P is the smallest of the incisors (Figure 2). It isalmost caniniform in shape and slightly recurved.Enamel covers most of the crown except for thelingual surface and is thickest close to the crownapex. There is a recess which neatly accommodatesthe anterior end of 12, in the enamel of the lingualface of the crown apex. There is a narrowinterdental facet on the right P, indicating the areaof contact with the missing left P. There is evidenceof slight wear of the enamel of the buccal surfacejust below the crown apex.

The crown and part of the root of the right 12 isalso preserved. This tooth shows much greaterwear than is present on other upper incisors. Thecrown is triangular in buccal view with an almostvertical posterior margin and a sloping anteriormargin. There is a short groove rising nearly

vertically up the buccal surface from the occlusalmargin close to the posterior end. The occlusalsurface is divided by the distal end of this grooveinto a larger, triangular anterior region and a short,diagonal, posterior blade. The enamel in theanterior occlusal region is breached by wear, as isthe enamel of the lingual margin at the level of theposterior groove. The straight lingual margin iselevated to form a ridge which projects posteriorlyto form a small prominence lingual to a small notchin the posterior margin which accommodated theanterior end of 13, helping to lock these teeth inalignment.

13 remains in situ in the left premaxilla and thecrown of the right P has also been preserved. Thetooth has a long occlusal edge and is triangular inlateral view but the crown is taller posteriorly thananteriorly. There are no grooves or ridgesornamenting the buccal surface. In its presentposition the in situ tooth is angled anteriorly withthe occlusal edge sloping ventrally from anterior to

A new bulungamayine kangaroo from Riversleigh

posterior, but it is not certain that this orientationhas not resulted from deformation occurring duringthe depositional process. The blade-like occlusaledge of the tooth is straight, but is flexed linguallyout of alignment with the cheek tooth row ­possibly also the result of taphonomic deformation.

The alveolus of Cl lies immediately posterior tothat of P. The broken root of Cl is exposed withinthe maxilla and runs horizontally posteriorl)'. Thecrown is short and conical, inclined anteriorly withits apex flexed slightly lingually. The extremelyclose proximity of incisor and canine is approachedonly by that in species of Bettongia among extantmacropodoids, but also occurs in at least oneundescribed balbarine species from Riversleigh.The diastema separating Cl from dp2 is about equalin length to P3.

dp2 is a short, low-crowned, bulbous-based toothwith a short occlusal margin which overhangs theposterior crown base (Figure 3A). In occlusal viewthe lingual margin is relatively straight while the

243

buccal margin is strongly convex. The lingualsurface of the crown inclines steeply to the occlusalmargin from its bulbous base while the less steeplyinclined buccal surface slopes uniformly from thecrown base to the occlusal margin. There are fourseparate cuspules on the occlusal margin anteriorto a less-defined cuspule close to the posterior end.Transcristae associated with the four anteriorcuspules are much longer than those associatedwith the most posterior cuspule. The anteriormargin of the occlusal blade is delineated by acrista sloping from the apex of the most anteriorcuspule to the crown base.

The crowns of both left and right p3 have beenfreed from their crypts. p3 is very long, more than1.5 times the length of Ml (Figure 3B). The crown islow with a serrated occlusal margin and a large,wedge-shaped posterior lingual cuspule. The rightp3, although damaged lingually, has a partiallypreserved, broad, lingual cingulum extendinganteriorly from this cuspule. This portion of the

A'

Figure 3 Stereo views of upper dentition of QM F20525, holotype of Wanburoo hilants gen. et sp. novo AIN. Left

maxilla with dp2-3, Ml -2. BIB'. Left P3. Scale bar = 10 mm.

244

crown is not preserved in the left P3. In occlusalview the outline of the crown is elliptical. The eightcuspules present on the occlusal margin are moreclosely spaced posteriorly than anteriorly. The sixmost anterior of these cuspules are clearly definedand have long transcristae reaching from theirapices to the base of the crown and, on the right p3,extending onto the lingual cingulum. The seventhcuspule has little development of the buccalcomponent of the transcrista, a shorter lingualcomponent, and is itself imperfectly delineatedfrom a longer posterior 'heel' adjacent to theposterior lingual cuspule. The anterior end of theocclusal blade is defined by a crista slopinganteriorly from the apex of the anterior cuspule tothe crown base. A shorter, more vertical cristadefines the posterior margin.

dp3 is much smaller than M'. It has a straightbuccal margin which is longer than the lingualmargin. The central region of the anterior marginis concave as it abuts the posterior margin of dp2and the posterior margin is convex. The protolophis narrower than the metaloph. The paracone isnarrow and is taller than the metacone. Thepreparacrista forms a prominent blade-like ridgewhich projects beyond the anterior margin,meeting the posterobuccal side of the occlusalmargin of dp2. The preparacrista, paracone andvery prominent postparacrista form a posteriorextension of the occlusal blade of dp2. Theprotoloph is convex anteriorly and lowest justlingual of its midpoint. Enamel has been brokenfrom the apex of the protocone. The postprotocristais buccally inclined on the posterior face of theprotocone but turns posteriorly to cross theinterloph valley, meeting the anterior face of the

B.N. Cooke

metaloph on the lingual side of the midline. Thebuccal moiety of the interloph valley is narrower(antero-posteriorly) than the lingual moiety. Apremetacrista runs anteriorly from the metacone tothe interloph valley but does not contact thepostparacrista. The metaconule is taller than themetacone and there is a distinct neometaconuleforming a short, rounded ridge on the posteriorface of the metaloph at about its midpoint. Aprominent postmetaconule crista inclines buccallyas it runs from the metaconule apex towards thecrown base before turning buccally across thecrown base to form a posterior cingulum andmeeting the equally prominent postmetacristawhich inclines lingually towards the crown basefrom the apex of the metacone.

M1 is a large tooth, almost square in occlusaloutline. Protoloph and metaloph are of about equalwidth and all cusps are of about equal height. Thepreparacrista inclines slightly lingually as it runsanteriorly from the paracone apex to the anteriormargin where it meets a long, narrow anteriorcingulum which crosses the entire width of theanterior margin. The postparacrista andpremetacrista are inflected lingually and meet inthe interloph to form a continuous centrocristalinking the apices of protocone and metaconeacross the interloph valley. Stylar cusp C is visiblein buccal view as a low prominence on theposterobuccal flank of the protocone, close to thefloor of the interloph valley and separated fromthe postparacrista by a flat, stylar shelf. Thepostprotocrista is prominent as it crosses theinterloph valley and meets the crest of themetaloph at a low point just lingual to theprominent, centrally-positioned neometaconule

Table 1 Dental parameters for type specimens of W. hilarus gen. et sp. novo Abbreviations: h = height; hw =width athypolophid; I = length; mw = width at metaloph; pw = width at protolophid or protoloph; TCN = no. oftranscristids; w =width.

Catalogue No. P P P Cl dP2 p3 dP3QMF AR h I h I h h I w h TCN I w h TCN I pw mw

20525 4965 5.7 4.8 4.3 6.3 4.7 4.9 5 11.2 6.0 4.3 7 5.8 4.5 5.13.6 4.2 3.5 6.2 4.5 11.2 5.8 4.2 7

MI M2

I pw mw I pw mw

20525 4965 6.2 6.9 6.4 6.9 6.6 6.0

I, dP2 P3 dP3 M, M2I w I w h TCN I w h TCN I pw hw I pw hw I pw hw

19942 15.7 3.8 6.0 4.1 5.1 4 11.8 5.7 5.5 6 5.7 3.4 4.3 6.7 5.4 7.920525 4965 13.5 3.1 10.1 4.1 4.7 5 6.8 4.8 4.9 6.3 5.2 5.1

10.3 3.6 4.4 537021 3651 15.8 2.8 11.1 3.8 3.6 7 6.3 4.2 4.530346 3.4 9.7 5.0 5.5 7 6.7 4.4 4.6 6.5 4.3 4.6

A new bulungamayine kangaroo from Riversleigh

which forms a rounded ridge on the posterior faceof the metaloph. The protoloph has a low point onthe lingual side of its midpoint. Postmetaconulecrista, posterior cingulum and postmetacrista areas described for dpJ.

M2 closely resembles Ml in morphology but has aless prominent neometaconule and stylar cusp C,and the centrocrista is interrupted in the interlophvalley.

Dentanj

Holotype. The angular process of the holotype hasbeen lost, as has the entire dorsal margin of thediastema (Figures 1 and 4). Parts of the anteriorand posterior margins of the ascending ramus arepresent but the coronoid process and condyle aremissing. The lingual surface of the M

3alveolus

and the crypt of M4

have been lost. The ventralmargin is relatively straight below the cheektooth row anterior to the M

3alveolus but is

inclined dorsally posterior to this. The absencehere of marked ventral convexity of the

245

horizontal ramus, common in potoroids and otherbulungamayines, may be age related. The poorpreservation of the only adult specimen makesassessment of the adult condition speculative.There is a small posterior mental fora men belowM/M3• The masseteric fossa narrows anteriorlyand it is unlikely that masseteric insertionreached much farther anteriorly than M

3• The

ascending ramus rises at an angle of 112° relativeto a straight line extending along the molarocclusal surfaces. The mandibular symphysisextends posteriorly to the level of the anteriormargin of dP

2•

Para types. The adult diastema preserved in QMF30346 exceeds the length of P

3and is longer than

those of the subadult animals. The masseteric canalin this specimen can be seen to be confluent withthe inferior dental canal as far forward as the M

3alveolus.

Most of the dentary is preserved in QM F37021with the exception of the dorsal margin of the

r+----------59.3---------_

A

B

-------·---80.1-----···---·----··.....,

cFigure 4 Dimensions of QM F20525, holotype of W. hilarus gen. et sp. novo A. Buccal view of premaxilla and maxilla

B, C. Buccal and lingual views of dentary.

246

diastema, the dorsal part of the anterior margin ofthe ascending ramus and the tip of the coronoidprocess. The mandibular symphysis extendsposteriorly to the level of the anterior root of dP3•

The ventral margin of the dentary is undulating, itslowest points occurring beneath dP/dP3 and M3,

the posterior of these points representing thedigastric process. Beneath the ascending ramus theventral margin curves dorsally in an arc to theposterior margin of the angular process. Thealveolar margin of the horizontal ramus is concavesuch that central alveolar margins are lower thanthose at the ends of the molar row. The mentalforamen is close to the dorsal margin of thediastema, just anterior to P

3and there is a small

posterior mental foramen below the anterior edgeof the Mz alveolus. The ascending ramus is inclinedat an angle of about 117° relative to a straight lineextending along the molar occlusal surfaces. Thelateral margin of the masseteric fossa is low on thehorizontal ramus and is straight antero-posteriorly.The masseteric canal opens well anteriorly withinthe masseteric fossa and is confluent with theinferior dental canal. The mandibular foramenopens into an extremely abbreviated length of theposterior part of the inferior dental canal and is

B.N. Cooke

overlapped by the masseteric foramen, the anterioropening of this length of canal into the massetericfossa. The degree of overlap is such that indorsobuccal view it is possible to see directly fromthe masseteric fossa to the pterygoid fossa, thusapproaching the condition common in Pleistoceneand modem macropodoids, in which there is alarge opening between the fossae visible in lateralview. The condyle is low, elliptical in outline andhas a flat surface. Its long axis is markedly inclinedanteromesially-posterolaterally relative to the longaxis of the horizontal ramus. In shape and positionabove the molar row, the condyle more closelyresembles those of potoroids than those ofmacropodids.

Lower dentition

Holotype. The cheek tooth row is straight inocclusal view (Figure 5). Molar teeth are fullybilophodont but crown height is lower than thatseen in most extant macropodids. Molar sizeincreases from M

1to M2 and then decreases from

M2

to M4

•

I1

has a short, leaf-shaped crown which is verydeep in relation to its length. The anterior tip of the

Figure 5 Stereo views of lower dentition of QM F20525, holotype of WanbllToo hilants gen. et sp. novo AIA'. Left P3

.

BIB'. Left dPZ_3' MI_z' in left dentary. Scale bar = 10 mm.

A new bulungamayine kangaroo from Riversleigh

crown of the left I) has been lost in the holotype butcan be seen to be sharply pointed in the remainingportion of the right 1

1and in those of paratypes.

Enamel is confined to the buccal surface and thereare prominent dorsal and ventral enamel flanges.The root is circular in cross section but the crown isnarrowly elliptical in cross section. The dorsalenamel flange forms the occlusal edge of the toothand the enamelled buccal surface is subvertical. Theblade-like dorsal enamel flange on this tooth, thelong and narrow occlusal edge on P and the wearpatterns on the occlusal surface of F indicate thatocclusion of upper and lower incisors induced acutting action.

dP2

is a short, blade-like tooth with a convexbuccal margin and a concave lingual margin. Thelingual face of the occlusal blade is more steeplyinclined than the buccal face. The occlusal marginis relatively straight in lateral view and overhangsthe posterior base of the crown. There are fourclearly delineated cuspids on the occlusal marginanterior to a posterior 'heel' on which twoadditional cuspids are incompletely differentiated.Distance between cuspids decreases posteriorly.Sharply-defined transcristids are associated witheach of the four anterior cuspids. The anteriormargin of the occlusal blade is defined by a cristidthat slopes anteriorly to the crown base from theapex of the most anterior cuspid. A shorter cristiddefines the posterior margin.

dP3 is narrower anteriorly than posteriorly. Thetrigonid is dominated by a very tall protoconidfrom which the short protolophid crest inclinesbuccally. A cristid, the presumed postmetacristid,descends to the interlophid valley from theposterior end of the lophid, the metaconid beingotherwise undifferentiated. A short paracristiddescends anteriorly from the protoconid to theprominent paraconid at the anterior margin. Acristid descends almost vertically towards thecrown base anterobuccal to the paraconid. Theentoconid is taller than the hypoconid. The cristidobliqua runs anterolingually from the apex of thehypoconid, crossing the interlophid valley andascending the posterobuccal flank of theprotoconid. The hypolophid is formed by theelevated and lingually directed posthypocristid. Ashort cristid from the entoconid descends steeplyanterobuccally from the entoconid apex. Ananteriorly directed pre-entocristid is also presenton the right dPy confirming the separate identitiesof the cristids originating from the entoconid.

P, is blade-like, low-crowned and more than halfas long again as M) (Figure SA). It has a narrow,crescentic occlusal outline with the buccal marginconvex and the lingual margin concave. Bothmargins are constricted close to the posterior end.Lingual and buccal surfaces are inclined at aboutthe same steep angle. In lateral view the occlusal

247

margin is relatively straight, with the posterior endslightly higher than the anterior end, and in occlusalview can be seen to curve lingually towards itsposterior end. The anterior two-thirds of theocclusal margin has five cuspids with whichtranscristids are associated, spacing between bothcuspids and transcristids becoming progressivelyless from anterior to posterior. Immediatelyposterior to this region of the occlusal margin thereis an imperfectly differentiated cuspid lackingtranscristids, but the remaining portion of theocclusal margin is unserrated. Anterior andposterior margins of the occlusal blade are definedby cristids descending to the crown base.

Mj

is larger than dP3• Protolophid and hypolophidare about equal in width and lingual and buccalcuspids are subequal in height. Lingual surfaces ofthe crown are more steeply inclined than the buccal.The paracristid runs horizontally directly anteriorlyfrom the base of the protoconid, turns linguallyacross the anterior margin bordering a shortanterior cingulid, before inclining posterolinguallyto terminate at the base of the metaconid. Thecristid obliqua is lingually inclined as it descendsthe anterior face of the hypoconid but turnsanteriorly to cross the broad interlophid valley andascend a short distance on the posterior face of theprotoconid. The hypolophid is formed by the much­elevated posthypocristid which links the apices ofhypoconid and entoconid. A short, anterolinguallydirected, cristid descends steeply from theentoconid apex. There is a slight posterior bulge ofthe crown base below the hypolophid.

M2

is larger than Mj

but closely resembles it incrown morphology except that the paracristidoriginates close to the apex of the protoconid.

M3

is smaller than M2

and is similar to it inmorphology apart from having a less obviouscristid associated with the entoconid and having adistinct premetacristid whose anterior end isseparated from the lingual termination of theparacristid by a narrow cleft. The posterior bulgeof the crown base below the hypolophid is morepronounced on this tooth.

M4

is smaller than M3

and resembles that tooth inmorphology but has a less distinct cristid obliquaand premetacristid.

Para types. Except for the variations noted below, themorphology of the lower dentition in the paratypesclosely resembles that described for the holotype.More cuspids are differentiated on the occlusalmargin of P

3in the paratypes, there being seven

cuspids anterior to the unserrated, posterior 'heel'in QM F37021 and in QM F19942 in which P

3is also

larger, and six or seven in QM F30346. Conversely,dI\ in the holotype has more differentiatedposterior cuspids than those of the paratypes. TheM

janterior cingulid is shorter in para types, apart

248

from QM F30346, in which it is longer. Theparacristid links more strongly to the protoconidapex in QM F19942 and QM F30346 than it does inQM F37021 and the holotype.

DISCUSSION

Flannery (1989) considered the lophodontbalbarines to be ancestral to both macropodinesand sthenurines. However, lophodonty alsoevolved in Oligo-Miocene bulungamayinekangaroos in parallel with the evolution of thischaracter within balbarines. Cooke (1997b)described a mechanism of hypolophid evolutionwithin Bulungamayinae in which the ancestralhypolophid in bunolophodont lower molars,formed by a strong cristid linking the entoconidapex to the lingual face of the hypoconid, wasreplaced by a neomorphic hypolophid derivedfrom the posthypocristid which became elevatedand transversely oriented. This mechanism isclearly different from that proposed by Flanneryand Rich (1986) as leading to hypolophidformation in Balbarinae. The lophodontbulungamayine, Bulungamaya delicata retains aremnant of the ancestral bunolophodonthypolophid in the form of an anterobuccallydirected cristid, on the anterior face of theentoconid. Such a cristid, distinct from the pre­entocristid, is also retained in the lowermolariform teeth of Wanburoo hilarus. It is on thatbasis and its possession of elongate and crescenticlower premolars, that W. hilarus is assigned toBulungamayinae rather than Macropodinae,although it is recognized that monophyly of theBulungamayinae is not demonstrated.

The otherwise macropodine-like characters notedby Flannery (1989) as occurring in the species nowdescribed as Wanburoo hilarus, are consistent withthe suggestion of Cooke (1997b) thatbulungamayines must be considered as potentiallyancestral to macropodines. This raises doubtsregarding both the monophyly of the subfamilyBulungamayinae and its status within Potoroidae.These considerations, discussed more fully below,are the subject of a phylogenetic analysis (inpreparation) of Macropodoidea which incorporatesmorphological data derived from the new speciesand other Oligo-Miocene species from Riversleighand elsewhere. Postcranial remains of balbarineand bulungamayine kangaroos from Riversleighare currently under study by B. Kear at theUniversity of New South Wales, and the results ofthat study are likely to impinge significantly onthese considerations (Kear pers. comm.). Pendingthe results of these studies and their potentialimpact on macropodoid systematics, the systematicposition of Bulungamayinae is here regarded asincertae sedis.

B.N. Cooke

The morphology of the preserved upper incisorsof Wanburoo hilarus and patterns of wear on 12,indicate that the blade-like occlusal crest of P andthe smaller, posterior occlusal crest of F produceda cutting action in occlusion with the dorsal enamelflange of 11, Taken together with the bilophodontmolar morphology, this is indicative of aherbivorous diet, but the relatively low condyleand brachyodont molar morphology suggest thatplant material consumed was not high in fibrecontent. Wanburoo hilarus was thus most likely abrowser.

Sanson (1989) suggested that basal macropodoidswere omnivores in which premolar shearingplayed an important role in initial reduction ofrelatively large food items before final processingthrough a crushing and grinding action of themolars. Elongate premolars, a "twisted" molar rowand deep insertion of the masseter within themasseteric canal were postulated as occurring insuch animals. (Although elongate premolars morelikely represent the derived macropodoidcondition, see below.) Sanson's next evolutionarylevel was a "browser grade" of macropodine inwhich elongate premolars are retained but themolar row is flat and no longer twisted. Dentalmorphology in W. hilarus fits this "browser grade"model in most respects. However, one of theparatypes, QM F37021, differs from the model inthat the lower molar row is ventrally concave. Thisprobably represents individual variation since thecondition is not obvious on other type specimens,and there is no matching ventral convexity of theupper molar row in the holotype.

Within Bulungamayinae, the lophodont molarmorphology of Wanburoo hilarus ranks it with thederived, lophodont species such as Bulungamayadelicata and Ganguroo bilamina. However, it differsfrom these species in being much larger, having arelatively shorter and much more broad-bladed 1

1,

and a dentary whose ventral margin is not stronglyconvex, at least in subadult individuals. Molarmorphology in W. hilarus is more similar to that ofB. delicata in that both species retain traces of theirbunolophodont ancestry in having an anterobuccalridge from the entoconid, a remnant of the ridgelinking entoconid and hypoconid and forming thehypolophid crest in bunolophodont lowermolariform teeth.

The macropodid-like characters observed in thederived, lophodont bulungamayine Wanburoohilarus prompt its comparison with more recentlyevolved bilophodont macropodids. Apart from thebalbarine Balbaroo camfieldensis Flannery, Archerand Plane, 1983, the next oldest such species areDorcopsoides fossilis Woodburne, 1967 andHadronomas puckridgi Woodburne, 1967, both fromthe late Miocene Alcoota Fauna. Although D. fossiliswas originally included in the Potoroinae within

A new bulungamayine kangaroo from Riversleigh

Macropodidae by Woodburne (1967), Bartholomai(1978) moved it to the Macropodinae. Hadrollonzaspllckridgi was described illcertae sedis by Woodburne(1967), but Murray (1991) placed it in theSthenurinae within Macropodidae. These twospecies are here considered collectively as earlymacropodids rather than as representives ofparticular macropodid subfamilies. While there isconsiderable phenetic similarity between W. Izilarusand both these species, the polarity of the commoncharacter states is problematic.

Both Walllmroo Izilarus and Dorcopsoides fossilishave a deeply penetrating masseteric canalanterior!y confluent with the inferior dental canal.The unique significance of masseteric insertionwithin the body of the dentary in macropodoidswas first noted by Abbie (1939). He postulated asequence of development of this insertion in whichdeep insertion of the masseter and coalescence ofthe masseteric and inferior dental canals to form acommon canal (the condition seen in potoroids)represented the most derived condition. Since thattime, the latter condition has been widely acceptedas a potoroid synapomorphy (e.g., Woodburne1984; Case 1984; Flannery et al. 1984). Abbie'ssequence of development of this condition wasbased on comparisons of extant species, but thefossil record of macropodoids, as presently known,is not in agreement with this sequence. Deeppenetration of the masseter and the developmentof a common canal within the horizontal ramus ofthe mandible can be argued to represent theplesiomorphic condition within Macropodoidea: itis apparently universal in the oldest known fossilkangaroos, including the Oligocene/Miocenespecies of Balbarinae, Bulungamayinae,Hypsiprymnodontinae, Propleopinae andPotoroinae. Conversely, a more shallowpenetration of the masseter and, probably moreimportantly, separation of the masseteric andinferior dental canals by a bony lamina is thecondition seen in macropodines and sthenurineswhich appear later in the fossil record. Observationof deep masseteric penetration within the mandibleprompted Woodburne (1967) to include the lateMiocene Dorcopsoides fossilis and the extant speciesof Dorcopsis and Dorcopsulus within his Potoroinae.

Macropodoids had already achieved a high levelof diversity by the Late Oligocene to Early Mioceneand their origins are likely to lie much earlier inthe Oligocene perhaps even in the Eocene, assugg!ested by 1989). It is conceivable thatthe development of masseteric insertion within thebody of the mandible evolved within the ancestralkangaroos in a manner similar to that described byAbbie (1939), achieving the 'potoroid' condition bylate Oligocene times, with subsequent reversion toa more plesiomorphic state occurring by about theLate Miocene. Unfortunately, no kangaroo remains

249

older than Late Oligocene are known and thepolarity of deep masseteric insertion andconfluence of masseteric and inferior dental canalscan only be argued on the basis of the evidencethat is available. That evidence favours the viewthat this condition is plesiomorphic. It may wellhave evolved quite rapidly among ancestralkangaroos as the developing masseteric fossabreached the inferior dental canal, therebyimmediately allowing an anterior insertion of partof the masseter within the newly common canal.

In Riversleigh balbarines and most species ofbulungamayines, the masseteric foramen openinginto the inferior dental canal is distinctly separatedfrom the mandibular foramen by a short posteriorlength of that canal. In both macropodines andsthenurines, this posterior section of the inferiordental canal is reduced to the extent that there is asingle fora men connecting the masseteric andpterygoid fossae of the dentary. The condition inW. hilarus, in which there is overlap between themandibular and masseteric foramina, isintermediate between these two states. In view ofthe age difference between Riversleigh balbarinesand bulungamayines, and macropodines andsthenurines, separation of the two foramina is thelikely plesiomorphic condition, seen also inDorcopsoides fossi1is (Woodburne 1967).

In both Wallburoo Izilarus and in the figuredholotype, UCMP 70563, of Hadrollomas pllckridgi(Woodburne 1967: 87), the mental foramen ispositioned close to the dorsal margin of thediastema, just anterior to Py the position in whichit occurs consistently in bulungamayines. Inbalbarines the foramen is consistently lower on thelateral wall of the diastemal region and moreanterior to Py similar to the position in which itoccurs in the figured paratype, UCMP 65912, ofDorcopsoides fossilis (Woodburne 1967: 59). Theposition of the mental foramen in phalangerids isvariable, making assessment of the polarity of thischaracter state impossible on the basis of outgroupcomparison.

Elongate premolars, postulated as plesiomorphicfor macropodoids by Sanson (1989), occur inWallbllroo hi/antS, Dorcopsoides fossilis andHadronomas puckridgi. Similar premolars occur inmacropodines such as Dorcopsis, Dorcopsulus andDendrolagus, and are universal in both potoroinesand bultmgamayines. Their widespread occurrencein this diversity of macropodoid taxa is inagreement with Sanson's view. However, tallerand shorter premolars occur in balbarines,hypsiprymnodontines and propleopines,resembling in shape, if not always in relative size,those seen in phalangerids or even burramyids.While balbarines are truly lophodont, their molarmorphology is in many ways more plesiomorphicthan that of other macropodoid taxa: a narrow M)

250

trigonid is universal, a protostylid and ahypoconulid on M

jare retained in some species, as

are stylar cusps C and 0 on upper molars.Outgroup comparison and the simultaneousoccurrence of short premolars and plesiomorphicmolar characters both suggest that elongatepremolars represent a more derived conditionwithin Macropodoidea. Flannery (1989), on thebasis of outgroup comparison with phalangerids,also regarded the hypsiprymnodontine/propleopine premolar type as plesiomorphic. Sincelophodont bulungamayines and early macropodidsboth have the derived premolar condition, thischaracter suggests that such macropodids have acloser phylogenetic relationship withbulungamayines than with balbarines.

p3 in both Dorcopsoides fossilis and Wanburoohilanls has a wedge-shaped posterolingual cuspule.Similar cuspules occur in this position in otherbulungamayines and also in balbarines fromRiversleigh. They also presumably representretained plesiomorphic characters. Hadronomaspuckridgi is more derived in this respect since thecuspule is there reduced to a strong posterolingualridge. p3 in W. hilanls has a slight lingual cingulum,a character not present in more plesiomorphicbulungamayines, while p3 of H. puckridgi has bothlingual and buccal cingula. p3 in D. fossilis hasabrupt lateral flarings at the base of the crown,although Woodbume (1967) hesitated to considerthese cingula. Well-developed lingual cingulaoccur on upper premolars of early macropodinesand sthenurines, and the structures on the upperpremolars of W. hilanls, D. fossilis and H. puckridgimay represent stages in the evolution of suchcingula.

Upper molars in both Dorcopsoides fossilis andWanburoo hilanls retain stylar cusp C (the mesostyleof Woodbume 1967). This cuspule, commonlypresent in bulungamayines, is considered here tobe stylar cusp C since it is associated with theposterobuccal base of the paracone. In balbarines asecond cuspule, stylar cusp 0, associated with theanterobuccal base of the metacone, is alsocommonly present. Woodbume (1967) describedtriangular postparaconal and premetaconal"facettes" in D. fossilis and Hadronomas puckridgi.Similar structures also occur in Riversleighbulungamayines and balbarines, in which theirdevelopment is associated with stylar crests linkedto stylar cusps C and D. Molar "facettes" are thusalso probably retained plesiomorphies.

Lower molar morphology in Wanburoo hilanls ismore closely similar to that of Hadronomas puckridgithan that of Dorcopsoides fossilis. In both W. hilanlsand H. puckridgi there is an anterior cingular shelf,bordered anteriorly by a lingual extension of theparacristid which tums posteriorly to terminate atthe base of the metaconid, from which it is clearly

B.N. Cooke

separated by a notch or "emargination", in theterm of Woodbume (1967). There is very littledevelopment of a precingulid in either species. InW. hilarus and H. puckridgi M

jprotolophid and

hypolophid are of similar widths and molar size isleast at the ends of the molar row. Lower molars ofboth W. hilarus and H. puckridgi have posteriorbulging of the crown base below the hypolophid,although this is more developed in H. puckridgi. InDorcopsoides the M

jprotolophid is narrower than

the hypolophid, there is a precingulid buccal to themore centrally positioned paracristid on this tooth,and molar size increases posteriorly.

Dorcopsoides fossilis differs from both Wanburooand Hadronomas in having a posterior cingulid onlower molars, being, in this character at least, moresimilar to derived balbarines such as Balbaroo thanto bulungamayines. This structure may beneomorphic in D. fossilis, and its incipientdevelopment may be represented by the slightposterior bulge of the molar crown base in W.hilarus and its stronger development in H.puckridgi. Similar posterior cingulids have arisenapparently independently within othermacropodid lineages including Protemnodon (e.g. P.anak Owen, 1874) and Troposodon (e.g. T. bowensisFlannery and Archer, 1983, T. gurar Flannery andArcher, 1983). There is therefore no conclusiveevidence indicating that the posterior cingulid ofDorcopsoides is homologous with the posteriorcingulid of balbarines, argued by Cooke (1997a) tobe a hypocingulid.

Increased width of the protolophid relative to thehypolophid, and lingual extension of theparacristid across the anterior margin to terminateat the metaconid base, may well representsynapomorphies uniting Wanburoo andHadronomas, since a narrow trigonid region hasbeen regarded as plesiomorphic (Flannery et al.1983, who termed it "a greatly compressedtrigonid"). Derivation of the lower molarmorphology of H. puckridgi from that of W. hilanlswould require only minor morphological changes:loss of the remnant of the entoconid crest andexpansion of the posterior base of the hypolophid.Derivation of a Hadronomas-like morphology froma derived balbarine, such as a species of Balbaroo,would also involve increase in the width of the M

j

protolophid to approximate that of the hypolophid,together with loss of the postentocristid and theassociated hypocingulid.

Derivation of the Mj

morphology of Dorcopsoidesfrom a Wanburoo-like form would require a greaternumber of changes. In addition to those listedabove for Hadronomas, lingual extension of theparacristid, expansion of the precingulid andacquisition of a neomorphic posterior cingulidwould also be required. Such a cingulid is presenton lower molars of Balbaroo species in which

A new bulungamayine kangaroo from Riversleigh

trigonid morphology is also more similar to that ofDorcopsoides, the latter resemblance being likelysymplesiomorphic. However, evolution ofDorcopsoides from a Balbaroo-like ancestor wouldalso require acquisition of elongate premolars,regarded here as being the derived condition.

Besides elongate premolars, lophodont molarsand p 3 lingual cingula (incipient only inDorcopsoides), there are but few potential dentalsynapomorphies uniting Wanbllroo, Dorcopsoidesand Hadronomas. However, lateral expansion of theM j trigonid represents a further synapomorphysuggesting a closer relationship of Wanbllroo withHadronomas than with Dorcopsoides.

A character potentially of great importance indefining relationships among these taxa IS

alisphenoid-parietal contact on the lateral wall ofthe neurocranium. This occurs in Hadronomaspllckridgi and also among all Riversleighbulungamayines in which this region of the skull ispreserved (including remains referable toBlIlzmgamaya, Ganguroo and probably Wablllaroo).Unfortunately, this region of the skull is not knownin either Wanburoo or Dorcopsoides. All knownRiversleigh balbarine skulls preserving this region(including remains referable to Nambaroo andBalbaroo) have squamosal-frontal contact. Hitherto,squamosal-frontal contact has been known to occuronly in potoroids, and previous workers, includingPearson (1950), Woodburne (1984) and Case (1984),have regarded the condition as representing thederived state among Macropodoidea, a viewsupported by outgroup comparison withphalangerids. Discovery of the occurrence ofalisphenoid-parietal contact in skulls ofHypsiprymnodon bartllOlomaii and Bettongia moyesiprompted Flannery and Archer (1987b) to concludethat squamosal-frontal contact could "clearly nolonger be recognised as a synapomorphy forpotoroids." However, it is significant thatsquamosal-frontal contact has not been observedwithin what are currently regarded as macropodidtaxa other than balbarines.

It may be argued on the basis of parsimony thatsquamosal-frontal contact is the plesiomorphiccondition within Macropodoidea and thatalisphenoid-parietal contact is derived. If so, thenalisphenoid-parietal contact must have evolvedindependently within Bulungamayinae,Hypsiprynmodon, the potoroine lineages indicatedabove, and, if Balbarinae is considered ancestral toMacropodinae and Sthenurinae, at least oncewithin Macropodidae, possibly in a post-balbarineancestor common to both those taxa. However, ifBulungamayinae is the common ancestor toMacropodinae and Sthenurinae, then therequirement for independent evolution of thecondition within Macropodidae is removed. If, onthe other hand, it is assumed that alisphenoid-

251

parietal contact is plesiomorphic, then squamosal­frontal contact must have arisen independentlywithin Balbarinae, Propleopinae, Hypsiprymn­odontinae, Bettongia and, according to Flannery andArcher (1987b), the species of Potorous and theAepyprymnlls / Caloprynmus clade.

As indicated above, Hadronomas and Dorcopsoideshave been used for comparison with Wanbllroohilarlls on the basis of their status as early, non­balbarine, macropodids, closest in age to that ofthe new taxon. Suggested synapomorphiesindicating a phylogenetic relationship betweenbulungamayines, as represented by Wanburoo, andearly macropodids, represented by Hadronomasand Dorcopsoides, include lophodont molars,elongate premolars with at least incipientdevelopment of lingual cingula on upperpremolars, lateral expansion of the M

jtrigonid

(although Dorcopsoides is closer to theplesiomorphic state for this character), andpossibly alisphenoid-parietal contact on the sidewall of the braincase.

In arguing the case for inclusion ofBulungamayinae within Potoroidae, Flannery et a1.(1984) identified three skeletal character states thatthey considered to be synapomorphic forPotoroidae: a convex ventral margin of the dentary,deepest below the central portion of the molar row(although noting that this is not universal inPotoroidae, being absent from Potorous andPropleoplls), deep insertion of the masseter withinthe dentary, and an elongate and finely serratepermanent premolar. Elongate premolars are hereconsidered to be apomorphic withinMacropodoidea, not merely Potoroidae, and deepinsertion of the masseter is considered to beplesiomorphic for Macropodoidea. While otherbulungamayines, e.g. BlIlllngamaya delicata, have aconvex ventral margin of the dentary, this is notthe case in Wanbllroo hilarlls, at least in subadultanimals, although its molar and premolarmorphology is closely similar to that of B. delicata.Dorcopsoides now an accepted macropodid,shows ventral convexity of the dentary(Woodbume 1967), although maximum convexityis somewhat more posteriorly located in thatspecies. Earlier bulungamayines, such as B. delicata,share the derived condition of convexity of theventral margin of the dentary with potoroids,suggesting a potoroid origin for bulungamayines,but reversion to the plesiomorphic condition mayhave occurred in later species such as W. hilarus. Ifbulungamayines, in tum, are phylogeneticallyancestral to macropodids, the condition inDorcopsoides may represent a retention of whatwould then be the plesiomorphic condition for abulungamayine-macropodid clade.

Bulungamayines exhibit variation in othercharacters, notably in molar morphology, with

252

basal members of the group, e.g. Nowidgee matrix,exhibiting bunolophodont morphology, and morederived species such as W. hilarus, Bulungamayadelicata and Ganguroo bilamina exhibiting undoubtedlophodonty. Bulungamayines thus exhibit aspectrum of characters ranging (phenetically­speaking) from potoroid-like to macropodid-like,and it is not surprising that they have been thesubject of debate regarding their status as potoroids(Flannery et al. 1984) or macropodids (Woodbume1984; Case 1984). The range of variation exhibitedby the group does cast doubt on its monophyly,although crescentic lower premolars represent apossible bulungamayine synapomorphy. Evolutionof lophodonty within Bulungamayinae is anexample of phyletic gradualism which makes itdifficult to establish boundaries for the taxon. Thesame process appears to continue beyondBulungamayinae into basal members of theMacropodidae in which molar teeth display notrace of bunolophodont ancestry and becomeincreasingly hypsodont, and premolars are elongate(though no longer crescentic) and have developedelevated lingual cingula. In view of this, and theabsence of other synapomorphies withinBulungamayinae, it is most likely thatBulungamayinae is a paraphyletic, stem groupbasal to Macropodidae, occupying the phylogeneticposition formerly assigned to Balbarinae byFlannery (1989). As a corollary to this hypothesis,the systematic status of Balbarinae withinMacropodidae is rendered uncertain.

The fossil record at Riversleigh and elsewhereprovides some circumstantial evidence supportinga likely bulungamayine origin for macropodids.Only a single, and as yet undescribed balbarinespecies has so far been identified from the youngersystem C deposits at Riversleigh (Cooke 1997c).The Riversleigh record discovered to date suggeststhat balbarines were in decline by the middleMiocene, while the number of lophodontbulungamayine species was increasing. However,balbarines were present, then and possibly later, asindicated by Balbaroo camfieldensis, known from theCamfield beds at Bullock Creek, estimated byMurray and Megirian (1992) to be middle Miocenein age. Several balbarine-like characters, at leastsome of which (such as the posterior cingulid onlower molars) are apparently apomorphic, arepresent in the late Miocene Dorcopsoides. If thehomology of these characters can be demonstrated,then the uncomfortable possibility of a diphyleticorigin for the early macropodids represented byDorcopsoides and Hadronomas must be considered.

Considerable numbers of cranial and postcranialremains of both balbarines and bulungamayineshave now been recovered from Riversleigh. Thesepreserve new morphological data which canprovide the basis for a more comprehensive

B.N. Cooke

phylogenetic analysis of Macropodoidea than hashitherto been possible. It is to be hoped that theresults of such an analysis will clarify thephylogenetic relationships of both Bulungamayinaeand Balbarinae.

ACKNOWLEDGEMENTS

Research grants provided to Michael Archer bythe Australian Research Council and the Universityof New South Wales have been the primarymechanism for providing the research materialexamined in this study. Additional support for theRiversleigh project has come from the NationalEstates Program grants to M. Archer and A.Bartholomai, the Australian Geographical Society,The Australian Museum, The Riversleigh Society,ICI Pty Ltd, Century Zinc Limited, the Mt Isa Shireand private donors.

Thanks are due to the palaeontological andphotographic staff of the Queensland Museum fortheir assistance during the course of thepreparation of this manuscript. Thanks also toMike Archer and all staff, past and present, at theVertebrate Palaeontology Laboratory, University ofN.5.W. for their advice, many forms of help, hardwork in the recovery process and skill in thepreparation of the fossil material on which thiswork is based.

Ken Aplin, Gavin Prideaux and Alex Baynesprovided much-appreciated constructive criticismof earlier drafts of this paper.

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Manuscript received 24 December 1997; accepted 3 September1998.