J. R. BRAMMALL

8RAMMALL,J.R. 1998:03:31. Anew petauroid possum from the Oligo-Miocene of Riversleigh, northwestern Queensland. Alcheringa 23,31-50. ISSN 0311-5518. Djaludjangi yadjana sp. nov. represents a previously unknown genus of petauroid possum from Riversleigh in northwestern Queensland. Of known phalangeridans Djaludjangi most closely resembles the , but lacks synapomorphies previously used to define that family. Although considered likely a plesiomorphic petaurid, D. yadjana is referred here to : incertae sedis, pending comprehensive revision of phalangeriforrn dental character state distributions. Small possum diversity at Riversleigh indicates a complex and finely partitioned environment such as that found in present-day tropical forests; the discovery at Riversleigh of 's first Tertiary dactylopsiline also argues for a rainforest palaeohabitat.

J.R. Brammall, Vertebrate Palaeontology Laboratory, School of Biological Science, Uni- versity of New South Wales, NSW 2052, Australia; received 4 February, 1998; revised 11 June, 1998.

Keywords: Petauroidea, Petauridae, Djaludjangi ya4iana, Dactylopsilinae, Oligo-Miocene, Riversleigh

THE PRE-PLEISTOCENE fossil record of the Djaludjangi yadjana is the only species known Petauridae has hitherto been remarkably poor, of its genus, appears to have closest affmities to with taxa described only from the early Pliocene Petauridae,and may be the most primitive petaurid Hamilton Local Fauna.The Hamilton Local Fauna known. However, it possessesa number offea- contains nine teeth or partial teeth which have tures previously unknown in the Petauridaewhile been referred to at least two speciesof , lacking others that have, until now, been regarded one near P. norfolcensis and one near P. austra- as diagnostic for the family. Pending revision of lis (Turnbull et al. 1987). Miocene petaurid speci- family-level synapomorphies within Phalangeri- mens previously reported from the Tarkarooloo formes, Djaludjangi is left incertae sedis. Local Fauna (Rich et al. 1982) were subsequently referred to the (Woodbume Materials and methods 1986). Archer et al. (1989) note one new petaurid Dental homology follows Flower ( 1867) for pre- genus-and species from the early Miocene Up- molar numbering and Luckett (1993) for the pre- per Site Local Fauna of Riversleigh, and Archer molar/ molar boundary. Higher level systematic et al. ( 1994) report another ?petauridspecies from nomenclature follows Aplin & Archer (1987). Riversleigh. It is now clear that the Riversleigh System nomenclature and assignation of sites to local faunas have produced two new petaurid Systems is based on Archer et al. (1989) and genera containing at least three new species.Two Creaser ( 1997). System A sites are considered to other undescribed small petauroid species are be late Oligocene in age (Myers & Archer 1997). referrable to the . Another new System B sites are regarded to be early Miocene petauroid species is described herein. and System C sites are interpreted to be middle 031l/5518/99/01031-20 $3.00 @AAP Miocene to early late Miocene (Archer et al. 32 J. R. BRAMMALL ALCHERlNGA

1995). Etymology. The species name yadjana means The prefix QMF designates specimens held 'first' in the Waanyi language. This is the first in the QueenslandMuseum fossil collection, Bris- petaurid-Iike species known to possess the ro- bane. Measurements in millimetres (mm) were bust and relatively unreduced dentition charac- madeto the nearest0.01 mm using a WildMMS235 teristic of the genus. Digital Length-Measuring Set attachedto a Wild M5A stereomicroscope.. Molar lengths and widths, and molar row lengths, were measuredas Material examined. Holotype QMF 30510, a the maximum dimensions of the enamel-covered left dentary with P2-3 MI-4' alveoli for Ii and P], crown/s with the teeth in occlusal view, with and a mostly complete ascending ramus and an- lengths measured along the anteroposterior axis gular process. Dentary proportions and low de- of the tooth and widths measured perpendicular gree of dental wear suggest that this individual to that axis. For p 3in dorsal view and p3in ventral was subadult at death. Paratype QMF 30532, a view, maximum length was measured along the right maxillary fragment with P3MI-2and alveoli longitudinal axis of the tooth, and anterior, pos- for M3-4; broken through lingual and posterior terior and maximum widths were measured per- alveoli of M4, broken immediately anterior to pendicular to that axis; buccal and lingual heights p2, dorsal to infraorbital foramen, and palate were measuredfrom the base of the enamel at the broken 1-2 mm from, and approximately paral- saddle between the roots, to the dorsal (for p 3) or lel to, tooth row. Paratype QMF 30523, a left ventral (PJ) apex. dentary with p 1-3Ml-4 and possible 12alveolus; broken posteriorly part way along the ascend- ing ramus and angular process, and anteriorly Systematicpalaeontology through the Ii alveolus, oblique to the longitu- dinal axis of the dentary. Paratype QMF 30529, Class MAMMALIA Linnaeus, 1758 a left dentary fragment with IlP 2-3Ml-3and alveoli Supercohort MARSUPIALIA IIIiger, 181 I for PI, M4 and possibly 12; broken posteriorly Order Owen, 1866 near the base of the ascending ramus and Superfamily PETAUROIDEA (Gill, 1872) anterolingually and anteroventrally around the Family incertae sedis I, alveolus.

Djaludjangi gen. nov. Referred materia/, Boid Site East Site: QMF Type and only species. Djaludjangi yadjana 12458, dentary fragment with RlIP 2-3'Camel Spu- turn Site: QMF 20733, LM4; QMF 30521, dentary Diagnosis. As for species by monotypy. fragment with LP 3MI-2; QMF 30523, dentary with LP 1-3Ml-4;QMF 30524, dentaries with LI1P j-3M1, Etymology. Djalu means 'heavy' or 'strong' and RljPI-3Ml3; QMF 30527, LM1; QMF 30529, dja~gi means 'mouth' or 'teeth' in the Waanyi dentary wi't11LI1P 2-3Ml-3;QMF 30531, maxilla with language, as spoken by the late Ivy George of RP2-3MI-3; QMF 30532, maxillary fragment with Riversleigh Station; in reference to the large P3s, RP3MI-2, Creaser's Ramparts Site: QMF 24662, relatively high-cusped molars and unreduced M2; QMF 24663, LM1; QMF 30470, LMI, Dirk's posterior molars previously unknown among Towers Site: QMF 30510, dentary with LP 2-3Ml-4' petaurids, with which Djaludjangi shows clos- Henk's Hollow Site: QMF 30513, RM4; QMF est affmity . 30520,RM1o Mike's Menagerie Site: QMF30530, maxillary fragment with Lp3Ml-2, Upper Site: QMF 30522, dentarywith RlJP 3Ml; QMF 30526, dentary Djaludjangi yadjana sp. nov. (Figs 1-3; Table with LP 2-3Ml-4°Wang Site: QMF 30525, dentary I) with RIjP 2-3MJ-4° Wayne's Wok Site: QMF ALCHERlNGA RIVERSLEIGH PETAURom POSSUM 33

23547, dentary with LM4; QMF 30472, RM, of skull; upper molar row gently curved (con- QMF 30473, RM.. cave lingually) in occlusal view; Mi without protoconule; M' anterior edge lies almost at Type locality. Dirk's Towers Site, Riversleigh right angle to lingual and buccal edges; no World Heritage property, Lawn Hill National marked buccal indentation in crown outline be- Park, northwestern Queensland. tween paracone and metacone; paraconule and neometaconule participate in en eche/on fash- Distribution and age. System B, Riversleigh ion to form transverse crests; M2 slightly World Heritage property, Lawn Hill National Park, smaller than Mi; deep transverse cleft between northwestern Queensland (early to middle Mi- metaconid and entoconid, and protocone and ocene): Boid Site East Site, Camel Sputum Site, metaconule, respectively. Creaser's Ramparts Site, Dirk's Towers Site, Mike's Menagerie Site, Upper Site and Wayne's Remarks. Djaludjangi yadjana differs from all Wok Site. System C, Riversleigh Station, north- vombatiform diprotodontians (Vombatidae, western Queensland (middle to ?early late Mi- , Ilariidae, Wynyardiidae, ocene): Henk's Hollow Site and Wang Site. Thylacoleonidae, Diprotodontidae, Palorchest- idae) in its diminuitive size and from all but Diagnosis. Small (molar row length 9.0-9.5 thylacoleonids by the possession of P 1-2and pl- mm) non-macropoid phalangeridan with dental 2. It further differs from thylacoleonids in the formula r/,-2'pi-J/I-J' MI-4/1-4;Ii elongate, slen- lack of a greatly enlarged P3. der, procumbent and slightly curved; PI-3 and It is distinguished from all macropodoids by MI-4 each two rooted, M'-4 each three rooted; its smaller size, by the presence of PI and the no diastema between PI-J; P3 colinear with mo- absence of a masseteric canal, and from most lar row; P3 with large central, conical primary macropodoids by the possession of P3s with cuspid from which a ridge extends anteriorly and one central primary cusp/id and without verti- posteriorly; PJ apex slightly lower than MI pro- cal ridglets along its length and extending its full toconid; PJ interlocks posteriorly with small height. notch in anterior face ofM,; MI-P J form shear- It differs from phalangeroid phalangeridans ing unit; bunoselenodont, quadrituburcular up- (, Miralinidae, Ektopodontidae) in per and lower molars; lower molar row straight that the MI cristid obliqua lacks an anterior 'kink' in occlusal view, slightly bowed at alveolar level and terminates on the posterior flank of the pro- in lateral view; slight overall anteroposterior toconid, rather than at the protoconid or reduction gradient in tooth length, height and protostylid. It further differs from phalangerids relative width along molar row except that Mi in lacking a protostylid (present in phalangerids, shorter posteriorly and narrower than M2; tall though developed to varying degrees) in that P3 Mi protoconid slightly buccal to transverse mid- is not markedly out-tumed from the molar row, point of trigonid; non-kinked cristid obliqua ter- and from most phalangerids in the possession minates on posterior flank of protoconid; two of two small lower premolars (P I-J between 12 low cuspidate transverse crests on each molar; and P3; in phalangerids PI is usually lost. Dis- posterior molars without longitudinal median tinguished from miralinids and ektopodontids groove; molar surfaces lightly crenulated; en- in having molar surfaces less crenulated and toconid taller than hypoconid; protostylid ab- molar loph/ids less serrate, and from miralinids sent; maxillary origin of zygomatic arch lateral in that P3 is not in-tumed relative to the molar to anterior end of MJ; infraorbital canal exists row. through single ovoid foramen dorsal to pJ; pl-J It differs from burramyids in its larger size; closely approximated; p2 lies at angle (lingual far less pronounced anteroposterior molar row anterior) to P3, molar row and longitudinal axis reduction gradient with less simplified molars 34 R. BRAMMALL ALCHERlNGA

Fig. 1. A-C, Djaludjangi yadjana n. sp. holotype QMF 30510 (Dirk's Towers Site, Riversleigh). Left dentary with p 2. 3M,.. in (A) buccal, (8-8') occlusal stereopair and (C) lingual views. Scale = 5 mm.

and much less reduced M4s; the Mi with proto- steeply inclined; anteroposterior molar row re- cone more anteriorly-positioned and duction gradient far less pronounced; M4 and M4 protoconule absent (in burramyids there is a of much less reduced crown height, length and variably-developed protoconule anterior to the width relative to those of MJ and MJ; relatively protocone); anterior root of zygomatic arch wide M4 talonid; posterior molars without a lon- commencing further back along the molar row; gitudinal median groove and with transverse II thicker relative to its length; and Mi cristid cristids of talonid much less reduced; slightly obliqua terminating at a point lingual to the pro- greater median transverse constriction of the toconid or lingual postprotocristid, whereas in lower molars when seen in occlusal view; and burramyids it heads towards or merges with the molar row less bowed at alveolar level in lateral buccal postprotocristid. view. It differs from pseudocheirids in having a It differs from acrobatids in that the upper less lingually-displaced Mi protoconid; in hav- premolars are not 'secodont'; pl-2 much shorter ing the MI cristid obliqua terminating on the relative to pJ; metaconule of MI-4 less reduced; posterior flank of the protoconid between the M4 and M4 present; metaconid far less promi- protoconid and metaconid, rather than extend- nent; and entoconid taller than hypoconid. ing to the top of the metaconid; and in having It differs from species of , upper and lower molars that are less selenodont Gymnobelideus and Petaurus in the following and which exhibit a degree of transverse features: dentary relatively thicker lophodonty. mediolaterally but relatively shallow dorsoven- It differs from pilkipildrids in having II less trally; ascending ramus proportionately thicker, aCHERINGA RIVERSLEIGH PETAUROID POSSUM 35

commencing further back with respect to mo- less reduced in comparison to M2. lars and ascending more steeply; angular proc- Djaludjangi yadjana further differs from ess less reduced; there are two subequal mental species of Gymnobelideus and Petaurus in hav- foramina, one below the saddle between the ing M4 with a less reduced posterolingual cor- roots ofMI and another below the posterior root ner and M4 with a less reduced metaconule. ofP 2; I1 straighter and more procumbent, curv- ing anterodorsally to a lesser degree; PI and P2 Description less simplified and slightly larger relative to mo- lars; PI slightly smaller than P2; no diastemata Dentary. A number of specimens(including QMF between P I-J;PJ and pJ absolutely and relatively 30525) were used in addition to the holotype for taller, less transversely compressed, more mas- description and comparison of the dentary be- sive, and not oblique to molar row axis; lower cause the holotype appears to have belonged to and upper molar rows with less anteroposterior a young and not to have reached adult reduction; MI shorter anteroposteriorly and nar- proportions. rower than M2; M2-4gradient less steep; Mi not The dentary of D. yadjana appears to be in- turned lingually towards premolar series and termediate in size between those of extant with taller and less lingually-displaced protoco- Petaurus breviceps and P. norfolcensis. Rela- nid and better-developed transverse crests be- tive to dentaries of extant petaurids, it is thick tween hypoconid and entoconid; M2-4with deep mediolaterally, but shallow dorsoventrally. In transverse cleft between metaconid and entoco- particular, it is relatively deep below the poste- nid, taller cusps, deeper central and cingular ba- rior molars and at the base of the ascending ra- sins and better-developed transverse crests; MJ mus; below P3' at the base of the deep I1 alveo- much less reduced in comparison with M2 and lus, it is (relatively) less deep. The dorsal edge is with more anteriorly positioned entoconid; M4 gently concave beneath the molars, so it appears less reduced; maxillary origin of zygomatic arch to be slightly less deep below M2-3than below more posteriorly located, being lateral to the an- P3MI or M4. In buccal view, it is otherwise of terior end ofMJ; infraorbital canal exits through approximately uniform depth anterior to the as- a single foramen dorsal to pJ; pl-J closely ap- cending ramus until a point below P3' where it proximated; p2 less transverely compressed,less abruptly begins to rise, following the ventral out- reduced, and lying at an angle (lingual anterior) line of II. In lingual view, it is of approximately to pJ, molar row, and longitudinal axis of skull; uniform depth between the ascending ramus and upper molars less bunodont, more crenulated M2, anterior to which it becomes deeper until and more selenodont, with no marked buccal the dorsal inflection beneath P3. The mandibu- indentation in crown outline between paracone lar symphysis is rugous and forms an ovoid plane and metacone; curvature of upper cheektooth extending from below P3 to the anterolingual ex- row less pronounced; anterior edge of Mi ap- tremity of the dentary .The ascending ramus is proximately at right angles to lingual and buc- thick, rises steeply and commences at a point cal edges, both of which are more straight in below the front of the posterior root ofM4. The occlusal outline; MI-J with protocone and meta- angular process is thicker and more extensive conule taller and more widely separated and a than that of extant petaurids. In dorsal view its deep transverse channel between them, paracone medial border is straight and runs parallel to the and metacone taller, and paraconule and molar row. Coronoid and condylar processesare neometaconule larger, more clearly defmed and not known for D. yadjana. A large inferior dental participating in en echelon fashion to form low foramen opens on the lingual side of the dentary , transverse crests; M2 less reduced in compari- dorsolateral to the junction of the angular proc- son with MI, being only slightly smaller than it; ess and ramus. There are two mental foramina M2 with larger posterior cingulum; MJ much of approximately the same size: one below the 36 J. R. BRAMMALL ALCHERlNGA

Fig. 2. A-C, Djaludjangi yadjana n. sp. paratype QMF 30532 (Camel Sputum Site, Riversleigh). Right maxillary fragment with P2.JMI.2 in (A) buccal, (8-8') occlusal stereopair and (C) lingual views. Scale = 5 mm.

saddle between the roots of Mi, just over half ridges is slightly concave, as is the surface be- way from the top to the bottom of the dentary, tween the more dorsal of these ridges and the and another higher on the dentary below the pos- longitudinal dorsal ridge. The surface between terior root of p 2; the single exception to this is the ventral ridge and the lower of the lingual specimen QMF 30522 in which the foramina ridges is quite flat and evidently contacted the are both shifted slightly further forward. opposing I1 in life. 12is not known for D. yadjana, although it Lower dentition. Ii is elongate and procumbent, occurs in all extant petaurids. However, QMF tapering to a dorsally-uptumed point. In dorsal 30523 appears to have a shallow alveolus ante- view Ii is gently concave lingually and convex rior to PI which may have housed a small 12,In a buccally, particularly the anterior part of the number of other specimens there is some tooth, which curves lingually before terminating. suggestion,albeit equivocal, of an 12alveolus in Also in dorsal view, a strong longitudinal ridge the easily-damaged region between I1 and PI. run.s from the lingual side of the posterodorsal PI is a small, double-rooted, cap-Iike tooth margin of the tooth, across the dorsal surface to with a variably-positioned weak longitudinal dor- merge into the tip along its buccal margin. A simi- sal ridge, sloping away from which are the sub- lar ridge occurs in the centre of the anteroventral semicircular lingual and buccal halves of the surface, running straight back from the tip and crown. It is only known from two specimens and terminating approximately half way along the ex- is a slightly different shape in each of these; pre- posed portion of the incisor. Lingually, the tooth sumably, this reflects intraspecific variation. is marked by two longitudinal ridges, one about P2 is similar in morphology to PI but is a quarter of the way up from the ventral margin slightly larger; in particular, it is both relatively and the other about halfway down from the dor- and absolutely wider. As with PI, shapeof the P2 sal margin. The surface between the two lingual crown outline is variable, ALCHER/NGA RIVERSLEIGH PETAUROID POSSUM 37

ridge reverses gradient at this point, rising to the posterior edge. In these specimens P3 ap- pears to be less worn. In lateral view the ante- rior edge of the crown rises dorsoposteriorly towards its apex and is never wider than at its base. Posteriorly, the crown expands as it rises (until it meets the posterior dorsal ridge) and therefore extends beyond the posterior root in lateral view. The posteriormost point of the tooth fits into a small notch in the anterior face ofM.. In dorsal view, the crown extends further on the buccal side of the longitudinal dorsal ridge than on the lingual side, particularly over the posterior root. This forms a pronounced buccal projection in the crown outline, which is otherwise approximately ovoid. Also in dor- sal view, two minor ridges, which extend on the lingual and buccal sides of the dorsal apex, re- spectively, form slightly acute angles anterolingually and posterobuccally with the primary, longitudinal ridge. The lingual and buc- Fig. 3. Djaludjangi yadjana n. sp. A, paratype QMF cal profiles of the tooth are similar to one an- 30529 (Camel Sputum Site, Riversleigh). Right IIP 2.3M,. 3 in buccal view. Scale = 5 mm. B, paratype QMF 30523 other. The main cuspid forms a slightly rounded (Camel Sputum Site, Riversleigh). Left P ,.3MI-3 in buccal isosceles triangle rising above the roots, with view. Scale = 2 mm. the base of a further triangular projection or 'heel' adjoining approximately two-thirds of the p 3 is large and double-rooted, with roots of posterior face of the main triangle and extend- approximately the same size and with a single ing posteriorly to an apex which abuts MI. Be- main conical cuspid, the apex of which is dorsal tween the small apical lingual ridge and the an- to the saddle between the two roots or, in some terior portion of the longitudinal dorsal ridge specimens,positioned slightly anterior. The apex the crown is slightly concave. There are also of p 3 is slightly lower than the protoconid of slight concavities on the lingual and buccal faces MI except in two specimens, QMF 30525 and where the main cuspid and the heel intersect. QMF 30522, in which it is slightly taller, possi- In dorsal view the lower molar row is bly because the protoconid in these two speci- straight. The lower molars are slightly longer mens is more worn. A thickened ridge of enamel buccally than lingually, giving the molar row the runs from the dorsal apex anteriorly towards the appearance of being very slightly arced ( con- base- of the enamel-covered crown, and cave lingually) in some specimens. All lower posteriorly from the apex towards the back of molars are double-rooted. From M.-M3 they the tooth. In dorsal view, the anterior and poste- progressively become relatively narrower, but rior ridges are colinear and are parallel to the M4 is relatively (but not absolutely) wider than longitudinal axis of the molar row. In lateral M3. Similarly, the slight anteroposterior gradi- view, the posterior ridge changes gradient sud- ent of each tooth (obtained by dividing anterior denly about a third of the way back from the width by posterior width) increases from MI- dorsal apex, continuing at a much reduced gra- M3 but has the same value for M4 as for M3. dient until terminating at the posterior margin The trigonid ofM. rises high above its ante- of the crown. In some specimens the posterior rior root and expands beyond it anteriorly as it 38 J. R. BRAMMALL ALCHERlNGA

ean n OR ~~ C" branch of the longitudinal dorsal ridge ofP 3.Im- I lDWOJ'luIh I P1 L 1.14 2 1.10- 1.18 0.057 4.96 mediately below this point, a small notch in Mi P1 MW 0.98 2 0.97 -0.99 0.014 1.« I"z L 1.24 1.16 I 7 1.02 -1.24 0.071 6.11 interlocks with a small protuberance on the back I"zMW 1.23 1.11 I 7 1.02 -1.23 0.063 5.68 of P 3. The lingual postprotocristid runs P3 L 1.85 1.80 I 9 1.68 -1.87 0.066 3.68 p3AW 1.22 1.32 I 9 1.20 -1.41 0.084 6.33 posterolingually from the protoconid to a small p3Pw 1.48 1.45 1 9 1.32 -1.60 0.108 7.44 P3 IR 1.57 1.50 9 1.36-1.70 0.115 7.69 metaconid, from which it swings back more P3 BH 1.85 1.80 9 1.63 -1.93 0.093 5.15 sharply as the postmetacristid and terminates M1 L 2.29 I 2-41 12 2.22-2.53 0.094 3.90 M1AW 1.4f 11.49 12 1.41- 1.55 0.046 3.06 ventrally in a buccal channel that separatesthe M1 PW 1.59 ' 1.62 112 1.52 -1.80 0.080 4.92 M2 L 2.49 2-45 6 2.36 -2.53 0.065 2.66 talonid and the trigonid, about three-fifths of the M2AW 1.71 1.72 5 1.64 -1.77 0.054 3.17 M2PW 1.78 1.76 6 1.70 -1.82 0.042 2.34 distance from the front edge of the tooth to the M3 L 2-35 2-29 5 2.19- 2.38 0.075 3.27 back edge. The entoconid is taller and more M3 AW 1.75 1.77 5 1.73 -1.85 0.048 2.74 M3PW 1.67 1.71 5 1.67 -1.75 0.038 2.22 crescentic than the hypoconid. A transverse M4 L 2.30 .2-26 5 2.15- 2.36 0.078 3.43 M4 AW 1.56 I 1.55 5 1.50 -1.63 0.050 3.21 crest is produced buccal to the entoconid but is M4PWM1-2 4.731.51 1 4.831.51 5 1.« -1.55 0.047 3.14 I 6 4.68 -5.03 0.124 2.58 only weakly met by a corresponding crest from M1-3 7.06 7.08 I 5 6.94 -7.27 0.131 1.86 the hypoconid. Posterior to this incomplete M1-4 9.28 9.25 4 9.12- 9.46 0.157 1.70 Upptr f..I" lophid, a shallow posterior cingulum is bordered I"' L 1.43 1.43 2 1.43 -1.« 0.007 0.49 p2 MW 0.98 0.95 2 0.92 -0.98 0.042 4.47 by the postentocristid and posthypocristid p3 L 1.97 i 2-07 3 1.97 -2.13 0.087 4.21 which swing posteriorly then buccally and lin- I p3 AW 0.99 I 0.98 3 0.95 -0.99 0.023 2.37 I p3pw 1.41 1.36 3 1.32 -1.41 0.046 3.37 gually, respectively, to define the edge of the I03MW 1.60 1.66 3 1.60 -1.72 0.060 3.62 crown posteriorly. The cristid obliqua runs f)3lli 1.63 1.74 3 1.63 -1.!x) 0.142 8.15 _»BH 1.56 1.62 3 1.56 -1.75 0.110 6.76 anterolingually from the hypoconid and termi- M1 L 2-48 2-50 3 2.45 -2.57 0.062 2.50 nateswhen it meetsthe steepposterobuccal flank M1 AW 2-26 2-28 : 3 2.22 -2.35 0.067 2.94 M1 pw 2.37 2.42 I 3 2.37 -2.48 0.056 2.30 of the postprotocristid-premetacristid. The M2L 2.35 2-37 4 2.34 -2.39 0.026 1.11 M2pwM2 AW 2-302-32 I 2-362-30 I 4 2.32-2.38 0.029 1.22 crown surface is crenulated, mainly in the cen- 4 2.21 -2.36 0.067 2.89 tral basin of the tooth, lingual to the cristid M3L I 2-29 1 2.29-2.29 M3 AW -I 2-22 1 2.22-2.22 obliqua. In most specimens, the crenulation is M3pw -2-01 1 2.01 -2.01 more or less obliterated by wear; QMF 30510, M4L -I 1.76 1 1.76 -1.76 M4AWM4pw -1.36- 1 1.77 1 1.77 -1.77 -- which is relatively unworn, and QMF 30524, a 1 1.36 -1.36 pair of subadult dentaries, are the only speci- M1-2 4.72 4.72 , 3 4.60 -4..85 0.125 2.65265 M1-3 mens in which crenulations are visible. In QMF 30510 and QMF 30524 the crenulations radi- Table I. Measurements of Djaludjangi yadjana n. sp. ate from the central basin of the tooth. Type = dimensions of type specimens; lower dentition M2 is larger than Mi. It has a rounded rec- measurements from holotype QMF 30510; upper denti- tangular outline. The metaconid and entoconid tion measurem~nts from paratype QMF 30532. n = number of specimens, OR = observed range, SO = stand- are quite crescentic; while the protoconid and ard deviation, cy = coefficient of variation, L = length, hypoconid are crescentic, they are also more A W = anterior width, PW = posterior width, MW = rounded. The metaconid and entoconid are close maxi!11um width, LH = lingual height, BH = buccal height. to the lingual side of the tooth and lie slightly cy not given where n < 2. anterior to the protoconid and hypoconid; the metaconid is taller than the entoconid and the rises. A large protoconid dominates the trigo- protoconid is taller than the hypoconid. Weak nid and is situated slightly buccal to the trans- but distinct lophids, interrupted by crenulations, verse midpoint of the trigonid. Extending connect the metaconid and protoconid, and the anteroventrally from the protoconid, a entoconid and hypoconid respectively. The preprotocristid terminates at the anterobasal ex- postmetacristid terminates in a deep lingual cleft treme of the enamel-covered crown, where it which separates it from the pre-entocristid. In meets, and appears colinear with the posterior some specimens,there is a small metastylid pos- ALCHER/NGA RIVERSLEIGH PETAURom POSSUM 1Q

terior to the postmetacristid, immediately an- M2" The transverse crest between the hypoco- terior to the cleft. From the hypoconid, the nid and entoconid is weakly developed, although cristid obliqua curvesanterolingually, then turns it is quite prominent in specimens exhibiting a buccally as the postprotocristid to meet the pro- mild degree of wear" In some specimens, this toconid. In some specimens the cristid obliqua posterior transverse crest connects to the bears a small hyposty lid anteriorly, directly prior posthypocristid and postentocristid rather than to its junction with the postprotocristid. The directly to the hypoconid and entoconid, thereby preprotocristid and premetacristid each arc me- reducing the size of the posterior cingulum. The dially to join the anterior cingulum and enclose hypoconid is more lingually positioned than in a large, shallow anterior cingular or trigonid Mi or M2, also reducing the size of the posterior basin which is longer on the buccal side of the cingular basin. The hypoconid and protoconid tooth than on the lingual side, since the meta- are of approximately equal height, and the ento- conid is further forward than the protoconid. The conid and metaconid are less disparate in size curved preprotocristid forms a sharp angle than those of M2, where it intersects with the straight anterior M4 is similar to MJ except for being smaller border of the tooth, whereas the arc of the and relatively more narrow, with the premetacristid merges cleanly into the anterior posterolingual comer more reduced and the trigo- border. As with MI' the postentocristid and nid proportionately slightly larger" Anteroposte- posthypocristid swing posteriorly then buccally rior width reduction ofM4 is no greater than that and lingually, respectively, to defme the poste- ofMJ' rior edge of the crown and enclose a shallow posterior cingulum. The crown surface of the Maxilla. Only fragmentary maxillary remains are relatively unworn QMF 30510 is crenulated, known for D. yadjana and no substantial palatal both in the central basin, the anterior and poste- fragments are known. The posterior edge of the rior cingula, and up onto the transverse lophids. maxillary origin of the zygomatic arch is level with Other, more worn specimens generally show no the anterior end of MJ in all specimens except crenulation, though there is evidence of QMF 30466, in which it is further forward, about crenulation on QMF 30521. As M2 becomes half way along the length of M2. However, the more worn, the lophids become more clearly little-wom teeth of this specimen suggest that it defined, the protoconid and hypoconid are may belong to an animal that was not fully grown rounded off and decreasein height, and the an- at death. Extant petaurids with fully erupted den- terior cingulum is reduced to a large, flat, tition may nevertheless not have reached full anterobuccal surface that eventually extends adult skeletal dimensions and in these younger onto the protoconid until the latter is worn down. extant , the teeth are further back with In advanced stages ofwear, the lophids become respect to the zygomatic arch than they are in reduced as the whole of the buccal side of the adults. A large, ovoid infraorbital canal exits the tooth is levelled. maxilla above pJ. MJ is anteroposteriorly slightly shorter than M2. The trigonid is slightly wider than that ofM2 Upper dentition. pI is not known for D. and is also wider than the talonidofMJ, which is yadjana. In extant petaurids it is a transversely narrower than that of M2. The metaconid and compressed, double-rooted tooth with a single entoconid are further in advance of the protoco- central cusp and is larger than P2. There is a nid and hypoconid, respectively, than are those small gap between pI and p2 in extant petaurids. of M2, so the transverse crest between the pro- In QMF 30530 there is a large alveolus directly toconid and metaconid is more oblique to the in front of the p2 alveoli and perhaps the remains longitudinal axis of the tooth. In particular, the of a further, possibly smaller alveolus, in front metaconid is more anteriorly positioned than in of that. Specimen QMF 30531 shows a similar 40 I. R. BRAMMALL ALCHERlNGA

configuration. These alveolar fragments suggest in some P3S. In lateral view the anterior profile a fairly large, double-rooted pI which is never- of the crown, between the apex and the dorsal theless probably smaller than P2. terminus of the anterior ventral ridge, is slightly p2 is known from two specimens: QMF concave in p3 whereas it is convex in p 3. The 30531 and QMF 30532. It lies parallel to the base of the crown is inflated lingually above the buccal edge of the maxilla, which turns medi- saddle between the roots and buccally, to a lesser ally anterior to P3. Thus p2 turns in anterolin- extent, above the posterior root, so that the ven- gually relative to p3 and the anteroposterior axis tral outline approximatesa rounded diamond with of p2 forms an angle lingually with that of p3 the lingual apex of the diamond skewed more and the molar row. p2 is small, with two subequal anteriorly than the buccal apex. In QMF 3053 I roots, and although similar to p 2 is longer and and QMF 30530 the lingual projection is quite narrower and lacks the large posterolingual ex- long and pointed and extends further in an tension of some p 2S.In ventral view the crown anterolingual direction than it does in the outline approximates a diamond shape with paratype QMF 30532, in which is more rounded rounded comers. The crown is produced into a and less extensive; this is assumed to represent small apical cusp ventral to the posterior root; intraspecific variation. In ventral view, the ante- from this cusp, a ridge extends posterobuccally rior and posterior ridges are not colinear; as with to the back of the tooth. A weak ridge also runs p2, an angle is formed between them buccally. anteriorly from the cusp to the anterior edge of This angle is not formed right at the apex but the tooth and a short, weak ridge extends posterior to it, at a point about halfway along the posterobuccally from the cusp about half way posterior ridge, where the ridge changes gradi- down the buccal face of the crown. The anterior ent abruptly before ascending at a much reduced and posterior ridges are not colinear; an angle gradient to the posterior margin of the crown. is subtended between them buccally at the api- Posteriorly the crown abuts the anterobuccal cal cusp. In lateral view, the crown extends be- comer ofMl ; the posterior ridge ofp3 terminates yond the posterior root, terminating at the end slightly buccal to the anterior terminus of the MI of the posterior ventral ridge and at that point, preparacrista. abutting p3 at the anterior terminus of its ven- In occlusal view the molar row is gently tral ridge. The area of contact between p2 and p3 curved, concave lingually. Each of the upper is much less than that between p 2and p 3; p2 does molars has three roots, with two alveoli on the not appear to buttress p3 as in the lower buccal side of the tooth and a larger lingual al- premolars. The portion of the crown anterior to veolus. Molar widths decrease from the front the ventral apex is longer than the posterior por- of the molar row to the back, but the gradient is tion and the anterior tip of the crown is more steeperposteriorly. Posterior widths of each mo- dorsally positioned, i.e. closer to alveolar level, lar decreaseprogressively with respect to ante- than the posterior tip, which ,extends further rior molar widths. Molar length decreases at a ventrally. Thus the posterior ventral ridge slopes steady rate from front to back except that M4 is to~ards the maxilla more steeply than does the proportionately much shorter than M3. Moving anterior ventral ridge. back along the molar row, molar length de- p3 is of similar morphology to p 3' with a single creaseswith respect to anterior molar width, but dominant cusp from which ridges extend to the increases with respect to posterior molar width. anterior and posterior ends of the tooth and mi- MI is quadrituburcular and bunoselenodont, nor ridges extend lingually and buccally; but it with an approximately square outline reduced at differs in a number ofways. It is shorter dorsov- the rounded posterolingual comer. The paracone entrally and the central cusp is more posteriorly is the largest cusp and the protocone is the positioned, being ventral to the saddle between smallest. The metacone and metaconule are the roots in p3 but slightly anterior to the saddle subequal in height. The metacone is slightly ALCHER/NGA RIVERSLEIGH PETAUROID POSSUM 41

more buccally positioned than the paracone. The paracone to the paraconule. The posterior protocone is more anteriorly positioned than the cingular basin is floored by a groove which is paracone and the metaconule is even further obliquely oriented (anterior lingually) due to the anterior to the metacone. The posterolingual anterior displacement of the metaconule. simi- comer of the tooth is consequently reduced. larly, the central basin is dominated by an ob- Each of the four primary cusps is weakly se- lique groove which is parallel to that of the pos- lenodont. The pre- and post- paracristae and terior basin and runs from the junction of the metacristae form an approximately straight row postparacrista and premetacrista towards the of blades parallel to the buccal side of the tooth. base of the protocone. As the tooth wears down A lingual preprotocrista extends anterolingually the crenulations are obliterated and the from the protocone to the anterolingual comer paraconule, neometaconule and lophs are gradu- of the base of the crown. The buccal ally reduced towards the level of the basins. preprotocrista and postprotocrista together form M2 is similar to MI except as noted below. It is a crescent-shaped blade, concave buccally, slightly narrower and is shorter. The metaconule which merges with the anterior cingulum. is not as far ahead of the metacone and the Posteriorly, it terminates at a lingual, trans- posterolingual comer of the tooth is less reduced. versely-oriented channel that separates the The protocone is larger than that of MI and ~s crests of the protocone and metaconule. The subequal to the metaconule. The paracone and premetaconulecrista and postmetaconule-crista metaconeare each smaller than their counterparts similarly form a crescent-shaped blade which on MI; the metaconule is about the same size. merges with the posterior cingulum and the lin- The paracone-paraconulecrista originates on the gual transverse channel. The postmetacrista preparacrista, anterior to the paracone. The curves buccally when it reachesthe postobuccal paraconule is slightly smaller than that ofM1 and comer of the stylar shelf, and partially encloses is more clearly distinguished from both the para- a small basin which merges into the flank of the cone and the anterior cingulum, into which it does metacone on its buccal side. A similar, but not impinge; the anterior cingulum is therefore smaller indentation is enclosed by the lingually- more complete. The small anterobuccal pocket is curving anterior portion of the preparacrista at seento be virtually continuous with the anterior the anterobuccal comer of the tooth. In the cen- cingulum, being separated from it only by the tre of the buccal margin, stylar cusps C and D preparacrista before it turns buccally to defme are visible on the buccal edge of a pocket which the pocket. The posterobuccal pocket is smaller is bound anteriorly, posteriorly and lingually by than in Mi and stylar cusps C and D are less the swollen flanks of the paraconeand metacone. clearly defmed. The primary crests associated Crenulations radiate from the centre of the with the paracone and metacone are more central and posterior cingular basins of M'. crescentic than are those of MI, with the crests Crenulations interrupt a slightly oblique metaloph, concave lingually. The anterior half of the tooth which connects the metacone and metaconule is slightly wider than the posterior part, whereas and incorporates a small neometaconule lingual MI is slightly wider posteriorly than anteriorly. to the metacone. Anterolingual to the paracone A damaged MJ is known only from QMF and interrupting the small anterior cingulum is a 30531. It is smaller and more reduced paraconule, which is slightly larger than the posteriorly than M2, but otherwise appears to neometaconule and occupies a considerable por- be similar .A crest from the paraconule connects tion of the poorly-defmed paraloph. The paraloph, with the paracone, as in MI, rather than joining like the metaloph, is interrupted by crenulations. the preparacrista, as in M2. A crest runs from the metacone down its flank M4 is only known from an isolated molar anterolingually to connect with the QMF 20773. It is referred to D. yadjana on the neometaconule; a weak crest also runs from the basis of its size and its morphological congru- 42 J. R. BRAMMAl ALCHERlNGA

ency with MI-J. Compared with MJ it is much Phenetic similarities aside, the phylogenetic reduced, especially posteriorly and position of Djaludjangi is difficult to ascertain. posterolingually. The metaconule is much re- It possessesa unique array of dental character duced and the metacone is much smaller than states which, taken in isolation, give conflict- the paracone or protocone. The crown outline ing indications of family-level affmity. Either is trapezoidal, with the posterior end narrower Djaludjangi represents a new family of non- than the anterior end. The metacone and meta- macropodoid phalangeridans, or current family conule are both close to the posterior edge of defmitions require revision to accomodate this the tooth and to the buccal and lingual edges, new genus. Other small possum taxa from respectively. The anterior cingulum is clearly Oligocene and Miocene deposits at Riversleigh defmed, but the posterior cingulum is very small. also challenge current understanding of charac- There is no large posterior cingular basin. Pre- ter state distributions and polarities within sumably M4 was crenulated, as are MI-J in unworn . A comprehensive review of specimens, but QMF 20773 is worn and no phalangeridan dental character states is beyond crenulations remain. A transverse crest extends the scope of this paper. The following discus- from the paracone lingually to about half way sion of character state distributions in possum across the central basin, and a short blade con- families is directed specifically towards clari- nects the metacone and metaconule, just in front fying the affinities of D. yadjana. of the posterior cingulum. The central basin Aplin & Archer ( 1987) refer possumsto four occupies most of the crown surface. The sim- superfamilies: Burramyoidea, containing the fam- plicity of the crown (lacking crenulations, lack- ily Burramyidae only; ,comprised ing paraconule and neometaconule, with trans- of Phalangeridae together with the extinct fami- verse blades only weakly defmed) is similar to lies Ektopodontidae and Miralinidae; that seen in worn specimens ofM2-J. M4 is more Petauroidea, containing Petauridae and reduced and much shorter than M4. Pseudocheiridae; and Tarsipedoidea, containing Acrobatidae and Tarsipedidae. The extinct fam- Discussion ily Pilkipildridae is left incertae sedis . Woodbume, Pledge & Archer (1987) place Djaludjangi yadjana is clearly a non- pilkipildrids within the Phalangeroideaas the sis- macropodoid phalangeridan, but its affmities ter-group of an ektopodontid-miralinid clade, but within the possum radiation are more difficult Archer et at. (1987) favour a petauroid affmity to determine. Of all diprotodontian families, D. for pilkipildrids. Albumin immunology yadjana is morphologically most similar to ex- (Baverstock et at. 1990) and DNA-DNA hybridi- tant petaurid species, sharing similar dentary sation (Edwards & Westerman 1995) studiescon- morphology, a long, slender, procumbent and sistently indicate that acrobatids, tarsipedids, slightly curved Ii, bunoseleno~ont molars and petaurids and pseudocheirids form a mono- dental formula of r/I-2' C?/O'PI-3/1-3' MI-4/1-4. phyletic group, but interfamilial relationships D~ntary size and molar row length also indicate within this clade remain unresolved. Marshall et that it falls within the size range of extant at. (1990) place the Burramyidae within their petaurids. It is smaller than all known Petauroidea, but this is not supported by any phalangerids, ektopodontids, miralinids and ex- other morphological or molecular studies. In this tant pseudocheirids(but only slightly smaller than paper, three higher level possum taxa are recog- the Miocene pseudocheirids Pildra antiquus, Po nised: Burramyoidea and Phalangeroidea (sensu tertius and Paljara tirarensae, and perhaps Aplin & Archer 1987) and Petauroidea, which is slightly larger than praecursor), and taken to include the families Petauridae, larger than any known burramyid, acrobatid or Pseudocheiridae, Acrobatidae and Tarsipedidae tarsipedid. as well as the Pilkipildridae. This classification ALCHERINGA RIVERSLEIGH PETAUROID POSSUM

is congruent with the taxonomic conclusions of dont. However, reduced selenodonty is charac- Edwards & Westerman (1995). teristic of acrobatids, burramyids and petaurids as well as phalangeroids, and the molars of ex- Phalangeroidea: Djaludjangi yadjana differs tant petaurids are also bunodont (though more from all phalangeroids in lacking an so than in phalangeroids) and semi-selenodont anterolingually-kinked Mi cristid obliqua, a fea- (though less so than in phalangeroids). ture cited by several authors (e.g. Archer et al. Djaludjangi yadjana also differs from 1987; Marshall et al. 1990) as a phalangeroid phalangerids in its much smaller size and in that synapomorphy. It does not possess an p3 and p 3are not markedly out-tumed in relation anterobuccal notch in the anterior cingulum of to the molar row, and from miralinids in thatP 3is the lower molars. Within possums this feature not intumed. The molar loph/ids of D. yadjana has been observed only in phalangeroids, but are less serrateand molar surfaces less crenulated since it does not occur in all phalangeroids (Ar- than those of miralinids or ektopodontids and D. cher et al. 1987) its absence in D. yadjana is yadjana does not show the modified Mi cristid of limited phylogenetic interest. Djaludjangi obliqua characteristic of those families yadjana also lacks an Mi protostylid, the pres- (Woodbumeetal.1987). ence of which is cited by Woodbume et al. Thus, the strongest evidence for D. yadjana ( 1987) as a phalangeroid synapomorphy, but having its closest affinities within the which in some phalangerid taxa is indicated by Phalangeroidea is the possession of conules in little more than a groove posterobuccal to the the upper and lower molars that are arranged in protoconid (Flannery & Archer 1987). In an en echelon fashion between the primary cusps phalangeroids the cristid obliqua of MI termi- to form transverse loph/ids. Against this is the nates either at the protostylid or protoconid, fact that the molars of extant petaurids -univer- whereas in D. yadjana it terminates on the pos- sally agreed not to be phalangeroids -show a terior flank of the protoconid, posterobuccal to similar configuration to those of D. yadjana in the centre of the premetacristid-buccal this respect. Although considerably reduced in comparison to those of D. yadjana, the interme- postprotocristid. In common with phalangeroid taxa, D. diate conules arid transverse ridges of extant yadjana has conules arranged into transverse petaurids could easily have been derived from a ridges or loph/ids on the upper and lower molars. condition such as that seen in Djaludjangi. The However, molar conules and crenulations are absence in D. yadjana of typical phalangeroid less elaborated, and transverse ridges consider- modifications of the cristid obliqua further in- ably less developed, in D. yadjana than in any dicates that it does not belong within the phalangeroid species examined with the possi- Phalangeroidea. ble exception of the Miocene phalangerid Trichosurus dicboni. In addition, tmwom mo- Burramyoidea: Few dental synapomorphieshave lars of some extant petaurids in the genus previously been identified for the Burramyidae Petaufus possesstransverse ridges that are simi- or Burramyoidea. Nevertheless, D. yadjana dif- lar, though poorly-developed in comparison, to fers from all known species of and those seen in D. yadjana. Other phalangeroid on a number of features including dental synapomorphies reported in the literature its considerably greater size. include reduction of selenodonty (Woodbume The molars are more simplified, M4s much et al.1987) and the possession of bunodont more reduced and molar row reduction gradient semi-selenodont molars (Archer et al. 1987). much steeper in burramyids than in D. yadjana. The molars of D. yadjana are certainly less se- All burramyids lack the distinct conules and the lenodont than those of pseudocheirids and could loph/ids present in D. yadjana. Burramyids have be described as both bunodont and semi-seleno- a protoconule anterior to the Mi protocone 44 J. R. BRAMMALL ALCHERlNGA

(though in some species of Cercartetus the only. protoconule is only very weakly developed). In extant acrobatids both pI and p2 are tall, There is no protoconule in D. yadjana and the 'secodont' teeth (Aplin & Archer 1987), and p2 Mi protocone is closer to the anterior edge of the is taller than pJ. In D.. yadjana p'-2 do not ap- tooth than in any burramyid. The anterior root of proach this secodont condition, and pJ is dis- the zygomatic arch commences further back tinctly taller than P2.In acrobatids the metaconule along the cheektooth row in D. yadjana than in is much reduced, but this is not the case in D. burramyids. In all burramyids the MI cristid yadjana. Extant acrobatids have lost M4 and M4, obliqua heads towards or merges with the poste- but M4s of D. yadjana are unreduced. In rior end of the buccal postprotocristid, whereas acrobatids the entoconid is by far the shortest in D. yadjana it terminates lingual to the proto- cusp on the lower molars, being distinctly lower conid or postprotocristid, with a sloping vertical than both the metaconid and hypoconid. In D. channel clearly separating the lingual yadjana the entoconid is higher than the hy- postprotocristid and the cristid obliqua. Ii is poconid and is only a little shorter than the meta- stouter in D. yadjana than in burramyids. Reduc- conid. The M, metaconid of D. yadjana is far tion ofPI-2 has been cited as a diagnostic fea- less prominent than that of acrobatids. D. ture ofburramyids (e.g. Archer 1984; Turner & yadjana clearly is not an acrobatid. McKay 1989; Marshall et al. 1990). The PI-2 of D. yadjana are slightly less reduced than in Tarsipedidae: The dentition of Tarsipes rostra/us some burramyids. Djaludjangi yadjana also is characterisedby extreme reduction; the dentary differs from species ofBurramys in that it lacks is splint-like and the teeth vestigial, with premolars a plagiaulacoid third premolar, has pI present and molars undifferentiated. D. yadjana shows and has much less simplified molars; and from no resemblance to and shares no apparent den- Cercartetus species in that the latter have more tal apomorphies with T ros/ra/us. triangular upper molars, mainly by virtue ofre- duction of the posterolingual comer of each Pseudocheiridae: Djaludjangi yadjana lacks the tooth. There is little reason to suggest a following pseudocheirid synapomorphies (from burramyoid affmity for D. yadjana. Archeretal. 1987; and Woodbumeetal. 1987): Mi protoconid displaced to the lingual side of Petauroidea: It is difficult to establish or refute the trigonid (in D. yadjana it is midway or membership of the Petauroidea on the basis of slightly buccal to midway across the transverse dental synapomorphies, since none have been axis of the trigonid); Mi cristid obliqua extend- reported except by Marshall et al. (1990) for their ing to the top of the metaconid rather than to Petauroidea, which includes Burramyidae. Each the protoconid or protostylid (in D. yadjana it of the petauroid families will be dealt with in turn. terminates on the posterior flank of the proto- conid at a point between the apices of the pro- Acrobatidae: Djaludjangi yadjana differs from toconid and metaconid); and hypoconids and the extant acrobatids Acrobates pygmaeus and posterior protoconids extend across each lower Distoechurus pennatus in many respects,includ- molar to the lingual side of the crown (in D. ing its greater size. Work is in progress on fos- yadjana the valleys separating the hypoconid sil material from Riversleigh that apparently from the entoconid and the protoconid from the represents two extinct Miocene acrobatid spe- metaconid (respectively) are approximately cies, both of which may challenge some cur- medial on the posterior molars, and slightly buc- rently recognised synapomorphies for the cal to the transverse midpoint of the anterior Acrobatidae. Pending completion of analysis of molars). Pseudocheirids show no trace of the these Miocene acrobatids, the following obser- transverse lophids seen in D. yadjana and in vations apply to A. pygmaeus and D. pennatus various phalangeroids. Rather, there are uninter- ALCHERINGA RIVERSLEIGH PETAUROm POSSUM 45

rupted deep valleys between the hypoconid and cristid obliqua extending to the top of the meta- entoconid, and the protoconid and metaconid, conid; hypoconids and entoconids that occupy respectively. comparatively more of the lingual side of the Other features diagnostic for pseudocheirids molar crowns; and a complete absence oftrans- are cited by McKay (1989). Some of these would verse lophiids. D. yadjana is not a exclude D. yadjana from the Pseudocheiridaebut pseudocheirid. are equally inapplicable to Miocene pseudocheirid taxa. The molars of D. yadjana Pilkipildridae: In both pilkipildrid species for are considerably less selenodont than those of which sufficient material is known (D. gillespieae most pseudocheirids and slightly less so than and P. handae; Archer et al. 1987; Archer 1989), those of Pildra antiquus. D. yadjana does have in lateral view the lower molar row is consider- three upper premolars (as do pseudocheirids and ably bowed (higher at the anterior and posterior extant petaurids, acrobatids and Cercartetus endsthan in the middle) at alveolar level, whereas spp.), but pJ has only one primary cusp. How- in D. yadjana bowing of the molar row is very ever, pJs of Miocene pseudocheirids such as slight. Although Ii of D. yadjana is quite robust, Pildra antiquus and Marlu kutjumarpensis are it is less steeply inclined than that of pilkipildrids also single-cusped. In buccal view the PJ of ex- (known only by the Ii alveolus of D. gillespieae). tant pseudocheirids is about the samelength and Djilgaringa gillespieae has a more massive p 3 height as Mi, but, in all Miocene pseudocheirids than does D. yadjana, and unlike the p 3 of D. for which PJ is known it is, in buccal view, con- yadjana, that of D. gillespieae has a bladed dor- siderably shorter anteroposteriorly than MI. The sal edge with three cuspids, from each of which condition in D. yadjana is unlike that in extant is produced a buccal and a lingual vertical ridge. pseudocheirids and similar to that in known However, P3 of Pilkipildra handae appears to Miocene pseudocheirids. In both D. yadjana have been more slender, shorter and less and those species of Pildra, Paljara and Marlu sectorially specialisedthan that of D. gillespieae, for which PJ is known, it is a large tooth with and was possibly no larger than the P3 of D. one primary cuspid (PJ is, however, larger rela- yadjana. The upper molars of D. yadjana have tive to the size of the lower molars in D. comers less rounded than those of D. gillespieae, yadjana than in any Miocene pseudocheirid). but since upper molars have not yet been re- Lower molars of D. yadjana are all approxi- ported for any other pilkipildrid species, it is dif- mately equal in size similar to the condition ficult to say whether upper molars with rounded found in extant pseudocheirids. However, in the comers are a pilkipildrid synapomorphy. In D. small Miocene pseudocheirids P. antiquus and gillespieae there is a marked anteroposterior M kutjumarpensis, but not P. tirarensae, M4 is lower molar row reduction gradient and M4 is more reduced relative to M2-J. markedly reduced and low-crowned, with a very Thus there are numerous character states narrow talonid. The lower molar alveoli of P. shared by pseudocheirids but not D. yadjana. handae suggest that its M4 was proportionately Some" relatively plesiomorphic Miocene wider than that of D. gi//espieae, but neverthe- pseudocheirids(especially speciesof Paljara and less smaller than the more anterior molars. The Pildra) resemble D. yadjana in some respects, molars of D. yadjana show only a slight decline including P3 morphology, degree of posteriorly, with M4 only slightly smaller than selenodonty and overall size -features which the other molars and having a relatively unre- may turn out to be symplesiomorphic for these duced talonid. Similarly, transverse cristids on taxa. Paljara and Pildra speciesshare with other the talonids of the posterior lower molars are pseudocheirids a number of features that are less reduced in D. yadjana than in pilkipildrids; absent or less developed in D. yadjana, such as in particular, the hypolophid of M3 is as well- lingual displacement of the Mi protoconid; Mi formed as those of MI-2' whereas M3-4 of D. 46 J. R BRAMMALL ALCHER/NGA

gillespieae have virtually no ectolophid. In D. derived features linked to the increasing spe- gillespieae there is a longitudinal median cialisation by petaurids on soft foods such as groove on the posterior lower molars, but in D. plant and insect exudates and on wood-gouging yadjana the presence of such a groove is pre- as a means of procuring exudates (Cartmill cluded by the retention of the ectolophid. 1974; Kay & Cartmill 1976). More Pilkipildrids share several features with D. plesiomorphic petaurids may be expected not yadjana. Both have large P3S and quadri- to display all of these apomorphic character tuburcular, bunoselenodont molars showing states. A hypothetical ancestral petaurid might some degree of crenulation, with low transverse be predicted to have less reduced P3s, a less loph/ids formed by an en echelon arrangement steep anteroposterior molar reduction gradient of cusps and cuspules (although the lophids of and therefore less reduced M4s, and less sim- D. yadjana are better-formed than those of D. plified molar crown morphology. Djaludjangi gillespieae ). Like D. yadjana, pilkipildrids have yadjana possessesexactly this combination of reduced selenodonty in comparison with features, whilst lacking key synapomorphies for pseudocheirids. Selenodonty is slightly more each of the other possum families. Although D. reduced in D. gillespieae than in D. yadjana. yadjana lacks character states regarded as In spite of these similarities, the features dis- synapomorphic for the Petauridae, the differ- cussed above are sufficient to exclude D. ences between it and extant petaurids are a mat- yadjana from the Pilkipildridae. ter of degree rather than of kind. Supposed petaurid dental synapomorphies have generally Petauridae: Djaludjangi shows none of the been described ( e.g. Archer et al. 1987) as apomorphies that characterise the petaurid sub- states of reduction from presumed family Dactylopsilinae. The only feature it shares plesiomorphic stateswhich could quite conceiv- with dactylopsilines to the exclusion of petaurines ably be those seen in Djaludjangi. Indeed, no is the plesiomorphic retention of a relatively un- plesiomorphic petaurid could satisfy current reduced molar row. As noted above, D. yadjana definitions of the Petauridae, which are based shareswith aU extant petaurids small size, similar on highly-derived, modem taxa. dentary morphology, along, slender,procumbent In summary , Djaludjangi sharesa number of and slightly curved I1 and quadrituburcular, derived features with pilkipildrids and some with bunoselenodont molars. Nevertheless, many pseudocheirids (see above). It shows no close synapomorphies that have been proposed for the ties with burramyids and lacks phalangeroid Petauridae are absent from D. yadjana, includ- synapomorphies such as a kinked cristid obliqua. ing (most from Archer et al. 1987) marked re- Its affmities certainly appear to lie within the duction of P3, loss of distinction of conules of Petauroidea, rather than within or close to the the upper molars, reduction of en echelon crest Phalangeroidea or Burramyoidea. Djaludjangi relationships, reduced selenodonty, very low- either represents a new family of non- crowned posterior molars, M4 reduced with very phalangeroid, non-burramyoid possums, or is a reduced talonid width, transverse cristids on plesiomorphic petaurid. Although it possesses talonids of posterior molars reduced, and pres- character states consistent with those predicted ence of a longitudinal median groove on the pos- for a plesiomorphic petaurid, it cannot confi- terior lower molars. , dently be placed in Petauridae until a thorough However, it seems possible that this combi- review of petaurid dental synapomorphies is nation of molar and premolar characteristics, to- completed and the redefined family found to gether with the curved II of extant petaurids ( de- encompassthe new genus. Incorrect placement veloped to greatest degree in species of of Djaludjangi within Petauridae would render Dactylopsila, in which it is strongly curved and that family paraphyletic, so for the present it is greatly enlarged), represent a suite of relatively preferable to assign Djaludjangi to Petauroidea 46 J.R.BRAMMALL ALCHERlNGA

gillespieae have virtually no ectolophid. In D. derived features linked to the increasing spe- gillespieae there is a longitudinal median cialisation by petaurids on soft foods such as groove on the posterior lower molars, but in D. plant and insect exudates and on wood-gouging yadjana the presence of such a groove is pre- as a means of procuring exudates (Cartmill cluded by the retention of the ectolophid. 1974; Kay & Cartmill 1976). More Pilkipildrids share several features with D. plesiomorphic petaurids may be expected not yadjana. Both have large P3S and quadri- to display all of these apomorphic character tuburcular, bunoselenodont molars showing states. A hypothetical ancestral petaurid might some degree of crenulation, with low transverse be predicted to have less reduced P3s, a less loph/ids formed by an en echelon arrangement steep anteroposterior molar reduction gradient of cusps and cuspules (although the lophids of and therefore less reduced M4s, and less sim- D. yadjana are better-formed than those of D. plified molar crown morphology. Djaludjangi gillespieae). Like Doyadjana, pilkipildrids have yadjana possessesexactly this combination of reduced selenodonty in comparison with features, whilst lacking key synapomorphies for pseudocheirids. Selenodonty is slightly more each of the other possum families. Although D. reduced in Do gillespieae than in Do yadjanao yadjana lacks character states regarded as In spite of these similarities, the features dis- synapomorphic for the Petauridae, the differ- cussed above are sufficient to exclude Do encesbetween it and extant petaurids are a mat- yadjana from the Pilkipildridaeo ter of degree rather than of kind. Supposed petaurid dental synapomorphies have generally Petauridae: Djaludjangi shows none of the been described (e.g. Archer et a[. 1987) as apomorphies that characterise the petaurid sub- states of reduction from presumed family Dactylopsilinae. The only feature it shares plesiomorphic stateswhich could quite conceiv- with dactylopsilines to the exclusion of petaurines ably be those seen in Djaludjangi. Indeed, no is the plesiomorphic retention of a relatively un- plesiomorphic petaurid could satisfy current reduced molar row. As noted above, D. yadjana definitions of the Petauridae, which are based shareswith aUextant petaurids small size, similar on highly-derived, modem taxa. dentary morphology, a long, slender, procumbent In summary , Djaludjangi sharesa number of and slightly curved Ii and quadrituburcular, derived featureswith pilkipildrids and some with bunoselenodont molars. Nevertheless, many pseudocheirids (see above). It shows no close synapomorphies that have been proposed for the ties with burramyids and lacks phalangeroid Petauridae are absent from D. yadjana, includ- synapomorphies such as a kinked cristid obliqua. ing (most from Archer et al. 1987) marked re- Its affmities certainly appear to lie within the duction of P3, loss of distinction of conules of Petauroidea, rather than within or close to the the upper molars, reduction of en echelon crest Phalangeroidea or Burramyoidea. Djaludjangi relationships, reduced selenodonty, very low- either represents a new family of non- crowned posterior molars, M4 reduced with very phalangeroid, non-burramyoid possums, or is a reduced talonid width, transverse cristids on plesiomorphic petaurid. Although it possesses talon ids of posterior molars reduced, and pres- character states consistent with those predicted for a plesiomorphic petaurid, it cannot confi- teriorenceof lower a longitudinal molars. median, groove on the pos- dently be placed in Petauridae until a thorough However, it seems possible that this combi- review of petaurid dental synapomorphies is nation of molar and premolar characteristics, to- completed and the redefined family found to gether with the curved II of extant petaurids ( de- encompass the new genus. Incorrect placement veloped to greatest degree in species of of Djaludjangi within Petauridae would render Dactylopsila, in which it is strongly curved and that family paraphyletic, so for the present it is greatly enlarged), represent a suite of relatively preferable to assign Djaludjangi to Petauroidea ALCHERlNGA RIVERSLEIGH PETAUROID POSSUM 47

incertae sedis. System B, specimens of D. yadjana are known Djaludjangi shares with pilkipildrids, from sites thought to be low in the sequence phalangerids, miralinids and sometimes (Creaser'sRamparts, Wayne's Wok) to those high ektopodontids, but not with extant petaurids, fea- in System B (Upper Site, Boid Site East), as well tures such as a tendency to form cuspidate trans- as themid-B sitesMike's Menagerie, Camel Spu- verse crests by elaboration of the paraconule and turn and Dirk's Towers. Henk's Hollow and Wang neometaconule; an M.-P 3shearing unit incorpo- Sites are both high in the System C sequence.At rating a large P3; and the development of trigonid Henk's Hollow, D. yadjana is represented only basins on M2-3with associatedmetalophids. That by isolated molars, and small metrical features pilkipildrids share these features with place the single Wang Site dentary at the edge of phalangeroids but not extant petaurids (or other size distributions for D. yadjana. The Wang and petauroids) has previously (Woodbume et al. Henk's Hollow specimens are referred to D. 1987)been interpreted as supportfor a pilkipildrid- yadjana here but small differences between them phalangeroid clade; their presence in the and other specimensof D. yadjana may, with the petauroid Djaludjangi refutes this argument, recovery of further material, prove sufficient to since these features now appear either to be warrant taxonomic distinction or at leastthe iden- symplesiomorphic, or to have been independ- tification of a morphocline. Djaludjangi yadjana ently derived in both the Phalangeroidea and appears,therefore, to extend through Systems B Petauroidea. The form of the transverse crests in and C, but may turn out to be restricted to Sys- the upper molars of D. yadjana may provide fur- temB. ther evidence (see Archer et al. 1987) that the The small burramyid species Burramys poorly- formed transversecrests of extant petaurid brutyi (Brammall & Archer 1997) also persists molars developed from transverserows of cones through along sequence of assemblages at and conules, such as are possessed by Riversleigh, from System A to high in System pilkipildrids. Archer (1976) suggeststhe opera- C. Two undescribed acrobatid species span Sys- tion of a similar mechanism in the evolution of tem B and extend up to lower System C local transverse lophodonty in . faunas but have not yet been recorded from any P3 morphology of D. yadjana also lends sup- sites higher in the sequence than mid-System port to a previously-developed hypothesis C. (Archer et al. 1987) regarding the evolution of The I1 of D. yadjana is similar in shape and the MI-P 3 shearing unit. An MI-P 3 shearing unit size to that of G. leadbeateri which, like spe- occurs in members of the Macropodoidea, cies of Petaurus, uses its lower incisors to scar Miralinidae, Pilkipildridae, Phalangeridae, trees to obtain exudates. Despite having larger Burramyidae, Thylacoleonidae and now P3s (combining with MI to form afunctional Petauroidea(possibly Petauridae). Its occurrence sectorial shearing unit) and more selenodont in a primitive member of yet another molars than extant petaurids, D. yadjana, like diprotodontian family increases the possibility extant petaurids, probably fed on plant and in- of this being a symplesiomorphic feature of sect exudates to satisfy the bulk of its energetic diprotodontians, rather than having evolved in- needs as well as insects and perhaps pollen to dependently in each of these groups. meet its protein requirements. Energetic con- siderations imply that D. yadjana was too small to have relied solely upon plant foliage for its Distribution and palaeoecology nutritional requirements (Kay & Hylander 1978; Djaludjangi yadjana is so far known only from Smith & Lee 1984). Similar arguments could seven assemblages in the System B sequence be forwarded for small Miocene pseudocheirids and two (Henk's Hollow Site and Wang Site) in (Pildra, Paljara and some Marlu spp.). The the System C sequence at Riversleigh. Within extant Pygmy Ringtail mayeri, 48 J.R.BRAMMALL ALCHERlNGA

with a body weight of around 150 9 (Flannery specimens; it is therefore possible that petaurid 1994), has teeth and dentary slightly larger than diversity within communities at Riversleigh ex- the small Miocene pseudocheirids. It has been ceeded that known in any area today. suggested (e.g. Flannery 1994) that P. mayeri Total possum diversity at Riversleigh cer- may be too small to be exclusively folivorous. tainly exceeds present-day maxima. Up to six Nevertheless, there is evidence from stomach small possum species (2-3 petaurid, 1-2 contents that P. mayeri may practise significant acrobatid and 1-2 burramyid) are found together folivory (I.D. Hume, pers. comm. cited in Cork in some assemblages at Riversleigh together 1995). Although leaf-eating is extremely rare with larger possum taxa including phalangeroids below 700 g body mass, there are a number of and, at some sites, up to nine pseudocheirid spe- exceptions including some microtine and cri- cies of varying sizes (Archer et al. 1994). Over cetid rodents, primates and marsupials -though fifteen possum species appear to have occurred none of these are exclusively folivorous at such sympatrically in some Riversleigh assemblages. small body masses (Cork 1995; Hume 1995). Today, up to thirteen possum species occur The selenodont molars of pseudocheirids shear sympatrically in parts of New Guinea and up to leaves finely to break them into tiny pieces, nine species in the montane rainforests ofnorth- which speedsthe digestion of this high-fibre diet eastern Queensland (Flannery 1994). The high (Kay & Hylander 1978) and contributes to their diversity of possum species in several sites at ability to practise significant folivory at smaller Riversleigh ( e.g. Upper Site, Gag Site) suggestsa body massesthan may otherwise have been pre- complex resourcebase, fmely partitioned by such dicted. Small selenodont or bunoselenodont mechanisms as distinct activity times, selection petauroid taxa such as Djaludjangi, Pildra, of different portions of the habitat, and diet dif- Paljara and Marlu may have included signifi- ferentiation (seee.g.Leite et al. 1996 on resource cant quantities of foliage in their diets. partitioning withinpresent-day tropical forests). Up to twelve living petaurid species are rec- Djaludjangi yadjana is similar in tooth size and ognised (Flannery 1994). New Guinea and Aus- morphology to some relatively plesiomorphic tralia each have six petaurid species, but only P. pseudocheirid species ( e.g. Pildra spp. ). In breviceps and D. trivirgata inhabit both areas. Miocene times at Riversleigh, petaurids and Presently there are three undescribed petaurid pseudocheirids had not achieved the almost com- species recognised from Riversleigh in addition plete eco-morphological separation seen be- to D. yadjana (possibly a primitive petaurid). tween extant representatives of these families. Within a given assemblage, species diversity It has been hypothesised (Archer 1984; appears to be similar to that in extant communi- Archer et al. 1994) that the scarcity ofpetaurids ties. Up to three petaurid specieshave been iden- in the pre-Pliocene fossil record may reflect tified in a number of Riversleigh local faunas the fact that open forests, the present habitat of and today, up to three species of petaurid may these small, and today mostly gliding, possums, be sympatric within a given area. Petaurus were not widespread until the end of the Terti- bre\liceps, P. norfolcensis and P. australis are ary .The Riversleigh local faunas show that sympatric over a significant portion of their petaurids were indeed present and were a mor- range in Queensland,New South Wales and Vic- phologically diverse group in the Miocene, al- toria (Ziegler 1981) and up to three petaurid though at least some Tertiary petaurid and species may be sympatric in some regions of petaurid-like species were quite different to New Guinea (Flannery 1994). Petaurid species extant gliding forms. diversity at Riversleigh is probably underesti- mated because the scarcity of material (relative Acknowledgments to that available for living taxa) necessitatescon- servative interpretation of variation between Comparative material was generously supplied ALCHERINGA RIVERSLEIGH PETAUROID POSSUM 49

by L. Gibson of the Australian Museum. The fol- Origins, E.S. Vbra, G.H. Denton, T .C. Partridge, & L.H. lowing supporters of research at Riversleigh are Burckle, eds, Yale University Press,New Haven, 77-90. ARCHER, M., TEDFORD,R.H. & RICH, T.H., 1987. The also gratefully acknowledged: the Australian Pilkipildridae, a new family and four new species of Research Grants Scheme (grants to M. Archer); ?petauroid possums (Marsupialia: Phalangerida) from the National Estate Grants Scheme(Queensland; the Australian Miocene. In Possums and Opossums: grants to A. Bartholomai and M. Archer); the Studies in Evolution, M. Archer, ed., Surrey Beatty & Sons and the Royal Zoological Society of New Commonwealth Department of Environment, South Wales, Sydney, 607-627. Sports and Territories; the Queensland National BAVERSTOCK,P.R., KRlEG, M. & BIRRELL,l., 1990. Evolu- Parks and Wildlife Service; the Commonwealth tionary relationships of Australian marsupials as as- World Heritage Unit; the University of New South sessed by albumin immunology. In from Pouches and Eggs: Genetics, Breeding and Evolu- Wales; IBM Australia Pty Ltd; ICI Australia Pty tion of Marsupials and Monotremes, l.A. Marshall Ltd; the Australian Geographic Society; Wang Graves, R.M. Hope, & D.W. Cooper, eds, CSIRO, Australia Pty Ltd; the Queensland Museum; the Melbourne,131-145. Australian Museum; Century Zinc Pty Ltd; BRAMMALL, l. & ARCHER, M., 1997. A new species of Burramys (Marsupialia, Burramyidae) from the Mount Isa Mines Pty Ltd; Surrey Beatty & Sons Oligo-Miocene deposits of Riversleigh, northwest- Pty Ltd; the Riversleigh Society Inc.; the Royal ern Queensland. Memoirs of the Queensland Mu- Zoological Society of New South Wales; the Lin- seum 41, 247-268. nean Society of New South Wales; and many CAR1MILL,M., 1974. Daubentia, Dactylopsila, woodpeck- ers and klinorhynchy. In Prosimian Biology, R.D. private supporters. Thanks to Anna Gillespie for Martin, G.A. Doyle, & A.C. Walker, eds, Duckworth, skilled preparation of the specimens described London,656-670. herein. CORK, S.l., 1995. Digestive constraints on dietary scope in small and moderately-small mammals: How much do we really understand? In The Digestive System in REFERENCES Mammals: Food, Form and Function, D.l. Chivers & P. Langer, eds, Cambridge University Press, Cam- bridge, 337-369. APUN, K. & ARCHER,M., 1987. Recent advances in mar- CREASER,P ., 1997 .Oligocene-Miocene sediments of supial systematics with a new syncretic classifica- Riversleigh: the potential significance of topogra- tion. In Possums and Opossums: Studies in Evolu- phy. Memoirs ofthe Queensland Museum 41,303-314. tion, M. Archer, ed., Surrey Beatty & Sons and the EDWARDS,D. & WES1ERMAN,M., 1995. The molecularrelation- Royal Zoological Society of New South Wales, Syd- ships of possum and glider families as revealed by DNA- ney,15-72. DNA hybridisations. Australian Journal ofZoology 43, ARcHER,M., 1976. Phascolarctid origins and the potential of 231-240. the selenodont molar in the evolution of diprotodont FLANNERY,T.F., 1994. Possums of the World: A Mono- marsupials. Memoirs ofthe Queensland Museum 17,367- graph of the Phalangeroidea, GEO Productions and 371. the Australian Museum, Sydney. AROIER,M., 1984. The Australian radiation. In Ver- FLANNERY,T. & ARCHER,M., 1987. reidi and tebrate Zoogeography and Evolution in Australasia, Trichosurus dicksoni, two new fossil phalangerids M. Archer & G. Clayton, eds, Hesperian Press, 633-808. (Marsupialia: Phalangeridae) from the Miocene of ARcHER,M., 1989. Emendations to the nomenclature ofre- northwestern Queensland. In Possums and Opos- cently established palaeontological taxa. Australian sums: Studies in Evolution, M. Archer, ed., Surrey Zoologist 25,67. Beatty & Sons and the Royal Zoological Society of ARc~ M.,GoDrnELP, H.,HAND, S.J. & MEGIRIAN,D.,1989. New South Wales, Sydney, 527-536. Fossil mammals ofRiversleigh, northwestern Queens- FLOWER,W.H., 1867. On the development and succes- land: Preliminary overview of biostratigraphy, cor- sion of teeth in the Marsupialia. Philosophical Trans- relation and environmental change. Australian Zo- actions of the Royal Society, London 157, 631-641. ologist 25, 29-65. HUME,I.D., 1995. Gut morphology, body size and digestive ARcHER,M., HAND, S.J. & GODrnELP,H., 1994. Riversleigh: performance in rodents. In The Digestive System in Mam- The Story of Animals in Ancient Rainforests of In- mals: Food, Form and Function, D.l. Chivers & P. land Australia. Second edition. Reed Books Pty Ltd, Langer, eds,Cambridge University Press,Cambridge, 315- Balgowlah, N.S.W. 323. ARcHER, M., HAND, S.J. & GoDnIELP, H., 1995. Tertiary KAY, R.F. & CAR1M1lL,M., 1976. Cranial morphology and ad- environment and biotic change in Australia. In aptations of Palaechthon nacimienti and other Paleoclimate and Evolution. with Emphasis on Human Paromomyidae (Plesiadapoidea, ? Primates), with a de- 50 J. R. BRAMMALL ALCHERlNGA

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