Maradidae: a new family of vombatomorphian marsupial from the … (2007) Marada.pdf · marsupial from the late Oligocene of Riversleigh, northwestern Queensland KAREN BLACK BLACK,

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Maradidae: a new family of vombatomorphian

marsupial from the late Oligocene of Riversleigh,

northwestern Queensland

KAREN BLACK

BLACK, K., March 2007. Maradidae: a new family of vombatomorphian marsupial from the late Oligocene ofRiversleigh, northwestern Queensland. Alcheringa 31, 17-32. ISSN 0311-5518.

Marada arcanum gen. et sp. nov. is described from the late Oligocene Hiatus Site, Riversleigh World HeritageProperty, northwestern Queensland. Although known from only a single dentary, it is assigned to a new familyMaradidae, based on a unique combination of both plesiomorphic and apomorphic features. Of the knownvombatomorphians, Marada is most similar to primitive wynyardiids and diprotodontoids (palorchestids anddiprotodontids). Further clarification of the phylogenetic position of Maradidae within Vombatomorphia requiresdiscovery of upper dentitions and crania.

Karen Black [[email protected]], Vertebrate Palaeontology Laboratory, School of Biological, Earth andEnvironmental Sciences, University of New South Wales, Sydney, 2052, Australia; received 17.1.2005, revised 1.6.2005.

Key words: Maradidae, Marada arcanum, Vombatomorphia, Vombatiformes, Marsupialia, Riversleigh.

SIX FAMILIES are recognized within theinfraorder Vombatomorphia: Ilariidae, Wy-nyardiidae, Thylacoleonidae, Vombatidae,Palorchestidae, and Diprotodontidae. Ofthese, five families are extinct, two families(Wynyardiidae and Ilariidae) are not knownfrom deposits younger than early Miocene,and all exhibit highly autapomorphic denti-tions. Aplin & Archer (1987) noted thatknown vombatomorphian families repre-sent the remnants of a far more diversepre-Oligocene radiation. Although mono-phyly of the infraorder is strongly supportedby cranial and postcranial morphology,resolution of phylogenetic relationshipsbased solely on dental morphology hasproven difficult. Marada gen. nov., de-scribed herein, is known from a single rightdentary from the late Oligocene Hiatus Site,Riversleigh World Heritage Property,northwestern Queensland. It expresses a

unique combination of primitive and de-rived features and cannot be assigned to anyknown vombatomorphian family. Conse-quently, a new family, Maradidae, has beenestablished.

Material is deposited in the palaeonto-logical collection of the Queensland Mu-seum (QMF). Cusp nomenclature followsRich et al. (1978) and Archer (1984). Molarhomology follows Luckett (1993). Premolarhomology follows Flower (1867). Mandib-ular terminology follows Stirton (1967).Higher-level systematic nomenclature fol-lows Aplin & Archer (1987).

Systematic palaeontologySuperorder MARSUPIALIA Illiger, 1811Order DIPROTODONTIA Owen, 1866Suborder VOMBATIFORMES Wood-burne, 1984Infraorder VOMBATOMORPHIA Aplin& Archer, 1987Family MARADIDAE new family

ISSN 0311-5518 (print)/ISSN 1752-0754 (online)� 2007 Association of Australasian PalaeontologistsDOI: 10.1080/03115510601123601

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Diagnosis. Maradidae differs from all othervombatomorphian families in the followingcombination of features: Dentary gracile,narrow, elongate and mediolaterally com-pressed; less posteriorly extensive mandibu-lar symphysis; non crest-like or inflatedascending ramus at its point of origin;ascending ramus originates more posteriorlyand at a point behind and less lateral tothe molar row; less extensive post-alveolarshelf and weak post-alveolar process; lowercrowned cheek teeth; short molar rowlength (50% length of horizontal ramus); awell-developed cristid obliqua; and a well-developed cuspate lingual cingulum on M1.

Marada gen. nov.

Type and only species. Marada arcanum gen.et sp. nov.

Generic diagnosis. The generic diagnosis isthat for the family until additional taxa areknown.

Etymology. Marada is the Waanyi (the localAboriginal language of Riversleigh) wordfor flat in reference to the narrow, medio-laterally compressed dentary and the shal-low fossae for muscle attachment. Gender ismasculine.

Remarks. Distinctions from all other vom-batomorphian taxa are previously listed inthe familial diagnosis. Further differencesfrom more specific groups are listed below.(Note that comparisons are made using theprimitive members of the respective groups,which are detailed in the proceeding char-acter anaylsis.)

Marada differs from all other vombati-forms (except Wakaleo Clemens & Plane,1974, 508; and Warendja wakefieldi Hope &Wilkinson, 1982, 56-598) in having a poster-iorly inclined ascending ramus where theangle of the anterior border of the ascendingramus (Fig. 1C) is less than 608 (relative tothe plane of the horizontal ramus).

Marada differs from all other vombato-morphians except diprotodontids and pa-lorchestids in having an elongate diastemaand a simple, bicuspid P3. Marada differsfrom all other vombatomorphians exceptwynyardiids, in having a posterolingualpocket between the entoconid, posthypo-cristid, and posterior cingulum. Maradadiffers from diprotodontids, palorchestids,and wynyardiids in having an M1/M4 lengthless than 1.

Marada differs from diprotodontids andpalorchestids (i.e. diprotodontoids) in hav-ing: smaller teeth; an anteriorly convexrather than concave ‘hypolophid’ and ‘pro-tolophid’; a better-defined paraconid on M1;reduced posterior molars (i.e. M4/M1 length51); less well-developed preprotoconidcrests on P3; a reduced posterior cingulumon the molars; a better-defined paraconidand paracristid on M1 (except Raemeother-ium Rich et al. 1978); and a well-developedpostmetacristid, postentocristid, posthypo-cristid, preentocristid, and preprotocristid(in M2-4).

Marada differs from palorchestids in:lacking a well-developed posterior cingulumon P3; and lacking the posterior, buccal, andlingual crests of the protoconid on P3.Marada differs from diprotodontids in hav-ing: less lophodont molars; a longitudinalwear pattern along the buccal cuspids onlower molars (rather than a transversepattern of wear across the lophids); a morelingually positioned protoconid on M1 (ex-cept Raemeotherium); a proportionatelylarger P3 relative to M1; and a distinctposterior cuspid at the terminus of thepostprotocristid on P3. Marada differs fromilariids and wynyardiids in lacking theneomorph cuspid (Pledge 1987a, Tedford& Woodburne 1987) on M1. Marada differsfrom wynyardiids in that the P3 is not bladedand is considerably shorter than M1; and inhaving more open, U-shaped transversevalleys on the lower molars. Marada differsfrom ilariids in: lacking a tricuspid, bulbousP3 and a well-developed anterior cingulum

18 KAREN BLACK ALCHERINGA

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Fig. 1. Marada arcanum gen. et sp. nov. Holotype QMF42738. A, buccal view of right dentary; B, lingual view; C,schematic diagram of right dentary of M. arcanum showing measurements used in Table 4 and throughout the text.Abbreviations: AAR, angle of anterior border of ascending ramus; DL, diastema length; HRL, horizontal ramuslength; MRL, molar row length; SL, symphysis length. Hatching represents broken areas on dentary. Bar¼ 50 mm.

ALCHERINGA NEW VOMBATOMORPHIAN FAMILY 19

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on the lower molars; and in having lesscomplex molars. Marada differs from thyla-coleonids in lacking: an elongate, bladed P3;a well-developed, deep masseteric fossa; adeep, rounded symphysis; a highly inclinedcaniniform I1; and in having a single lowerpremolar.

Marada arcanum sp. nov. (Figs 1-2, Tables1-4)

Holotype. QMF42738, right dentary withP3, M1-4. I1 crown broken. Dental formulaI1, C0, P3, M1-4. The posterior area of thedentary is damaged and missing the coro-noid process, articular condyle, and angularprocess.

Type locality. Hiatus Site, RiversleighWorld Heritage Fossil Property, northwes-tern Queensland (see Creaser 1997).

Distribution and age. Hiatus Site is a SystemA deposit (Creaser 1997) which, on the basisof stratigraphy and contained faunas, isinterpreted to be of late Oligocene age.

Species diagnosis. The diagnosis for thespecies is that for the family until additionaltaxa are known.

Specific etymology. Arcanum, meaning mys-tery in Latin, alludes to the unknowntaxonomic position of the species and thestrange combination of primitive and de-rived features exhibited by the single knownspecimen.

Description

Dentary (Fig. 1). Right dentary with P3,M1-4. I1 crown broken. The posterior area ofthe dentary is poorly preserved and missingthe coronoid process, articular condyle, andangular process. The dentary is very gracileand slender with a narrow horizontalramus. It is unlike the characteristicallymore robust vombatomorphian dentarieswith the exception of the relatively delicateprimitive ?diprotodontid Raemeotheriumyatkolai Rich et al. 1978. The lingual(medial) surface of the horizontal ramus isflat and straight, as is the ventral border.The maximum depth of the horizontalramus is 27.9 mm below the anterior baseof M1. The horizontal ramus thickensopposite M3 with a maximum width of14.6 mm. The diastema is relatively long

Fig. 2. Marada arcanum gen. et sp. nov. occlusalstereopair of QMF42738. Bar¼ 10 mm.

P3 M1 M2 M3 M4

L 8.7 11.4 10.9 10.8 10.0AW 7.4 8.0 8.4 7.2PW 5.2* 7.3 7.5 7.3 6.3DR 27.4 27.4 26.3 25.9 26.1

Table 1. Measurements (mm) of dentition ofMarada arcanum. *Maximum width of P3. DR,depth of horizontal ramus below respective toothtaken between the roots.


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(38.7 mm) with a distinct dorsal diastemalridge reminiscent of diprotodontoids. Thelingual surface of the diastema drops steeplyaway to a very rough, short unfused sym-physis (50.3 mm long, Fig. 1B). The sub-lingual fossa is narrow and shallow.The symphysis lies at an angle parallel tothe dorsal surface of the diastema, dippingslightly posteriorly. The symphysis termi-nates posteriorly at a point directly belowthe anterior root of P3.

A relatively large canal-like mental fora-men lies 11.6 mm anterior to the base of P3

and 3 mm ventral to the dorsal surface ofthe diastema. A smaller nutrient foramen

lies within the entrance to the mentalforamen. Three small nutrient foraminaare positioned approximately 15.5 mm ven-tral to the M1-2 alveoli.

The length of the slightly curved cheektooth row is 51.8 mm. A slightly decreasingposterior molar gradient is evident (M4/M1

length¼ 0.9). A striking feature is therelatively short molar row compared withthe overall length of the dentary. Proportio-nately, this specimen has a relatively shortermolar row (50% relative to the length of thehorizontal ramus) than any other Vomba-tomorphian (Table 4). A longitudinal line ofwear is evident along the tooth row mainly

CHARACTER 1 2 3 4 5 6 7 8 9 10 11 12

Marada 1 0 1 2 1 0 0 1 0 0 1 1Trichosurus 0 1 1 0 0 0 0 0 0 0 0 0Madakoala 0 1 0 0 0 0 0 0 1 1 ? ?Wakaleo 0 1 0 ? 1 2 0 1 0 0 1 0Kuterintja 1 1 0 2 1 0 0 2 1 1 ? ?Warendja 1 0* 1 1* 1 1* 0 2 0 1 2 0Muramura 1 1 1 1 1 1 1 1 0,1 1 1 0Namilamadeta 1 1 1 1 1 1 1 1 0 1 1 0Propalorchestes 1 0 2 2 1 1 1 2 1 1 1 1Raemeotherium 1 ? 2 2 0 1 1 2 0 1 ? 0Ngapakaldia 1 0 2 2 1 2 1 2 1 1 1 1

Table 3. Character state polarities for select vombatomorphians. Plesiomorphic state¼ 0; apomorphicstate¼ 1; most apomorphic state¼ 2; missing data¼ ?; character polarised using V. ursinus¼ *.

CHARACTER PLESIOMORPHIC APOMORPHIC

1. Inclination angle of I1 High (�308) Low (5308)2. P3 morphology Bicuspid Multi-cusped/bladed3. Degree of bilophodonty Absent Fully bilophodont4. Development of paraconid and paracristid Well developed Weak or absent5. Development of a protostylid on M1 Present Absent6. Presence of a cristid obliqua Well developed Weak or absent7. Posteriorly increasing molar gradient M4/M1 51 �18. Crown height Low-crowned High-crowned9. Angle of anterior border of ascending ramus Low (5708) High (�708)10. Posterior extent of symphysis Short Elongate, deep11. Masseteric foramen Absent Present12. Diastema length relative to horizontal ramus 530% �30%

Table 2. Character states used in character analysis of Vombatomorphia.


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on the buccal cusps with the hypoconid ofM1 and the protoconid of M2 showing themost wear.

The posterior area of the dentary isincomplete with only the area of theascending ramus encompassed by the mas-seteric fossa preserved on the lateral face.Medially, the fragile area of the pterygoidfossa was covered in rice paper for addedstrength during preparation of the speci-men. Consequently, the position of themandibular foramen cannot be determined.The masseteric fossa is flat and shallow withno distinct anterior border, fading outanteriorly onto the lateral face of thedentary. A small masseteric foramen ispresent on the ventral border of themasseteric fossa approximately 27.1 mmposterior to and 12.0 mm below the poster-ior border of M4. The masseteric eminenceis not preserved, but the flatness of thevertical ramus suggests it would have beenweak and low on the dentary.

The ascending ramus is inclined poster-iorly, its anterior border positioned at anangle of 558 relative to the horizontalramus. The ascending ramus originates ata point opposite the posterior border of M4,which is further posterior and less lateralthan in all other vombatomorphians. Thereis no distinct post-alveolar process on the

lingual face of the dentary. In occlusal view,the ascending ramus can be seen to risegradually along the buccal margin of thepost-alveolar shelf. It is such a gradual risethat it is difficult to determine its point oforigin. The anterior ‘crest’ of the ascendingramus is thick and non-carinate.

The pterygoid fossa is very flat and notvery laterally expansive. However, this areais obscured slightly by the flaking of thebone. The digastric fossa is a shallow, linearfossa that runs parallel to the ventral borderof the horizontal ramus. It is deepest belowM3-4 and extends anteriorly to below thelevel of the M1 talonid and fades outposteriorly below the post-alveolar shelf.

Dentition (Fig. 2, Table 1). The dentalformula is I1 C0 P3 M1-4 like all othervombatomorphians (except some thylaco-leonids, which retain two lower premolarsand may have lost M4). Only the distal16.2 mm of the incisor is preserved, but theelliptical cross-section suggests that it waslanceolate. Enamel is distributed on theventral and lateral surface. The I1 projects atan angle of 288 from the horizontal plane ofthe diastema.

The premolar is simple, small, narrow,bicuspid and two-rooted. A large, very worn(on its anterolingual face), sub-central

DENTARYCHARACTERS

DL(mm)

MRL(mm)

HRL(mm) MRL/HRL DL/HRL M4/M1 LENGTH

Marada arcanum 38.7 51.8 101.0 0.51 0.38 0.9Warendja wakefieldi 16.8 32.5 57.8 0.56 0.29 0.8 – 0.9Wakaleo oldfieldi 6.0 36.9 52.7 0.70 0.11 0 (no M4)Kuterintja ngama – 44.2 – – – 0.9Muramura pinpensis 12.0 36.3 51.0 0.71 0.24 1.0Namilamadeta sp. 14.0 41.8 62.4 0.67 0.22 1.0Raemeotherium yatkolai 13.0 52.7 82.0 0.64 0.16 1.0Ngapakaldia tedfordi 40.3 64.0 112.2 0.57 0.36 1.1Propalorchestes novaculacephalus – 69.5 – – – 1.0

Table 4. Measurements and proportions of the dentary used in character analysis. Abbreviations: DL,diastema length (measured from P3 alveolus to I1 alveolus on dorsal surface); HRL, horizontal ramuslength (measured from incisor alveolus to post-alveolar process); MRL, molar row length (measuredfrom anterior of P3 to posterior of M4, taken at base of crown).


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protoconid dominates the premolar and isconnected to a small posterior cuspid(possibly the metaconid) by a weak, steeplysloping posterior crest. A weak poster-olingual cingulum extends anterolinguallyfrom the small cuspid, fading into the baseof the crown at a point opposite thetransverse valley between the large andsmall cuspids. A buccal cingulum isabsent. The anterior, buccal, and lingualfaces of the tooth are steeply sloping to thebase of the crown. The enamel is slightlywrinkled at the posterior base of the maincuspid.

The molars are low-crowned, bunolo-phodont, and characterized by very wide,U-shaped transverse valleys. The M1 is asub-rectangular, four-cusped tooth consist-ing of a small lingual metaconid (the leastworn of the major cuspids) and large buccalprotoconid on the trigonid and a largelingual entoconid and buccal hypoconid inthe talonid. It is difficult to determine therelative height of each cuspid due toconsiderable wear. It appears that theprotoconid may have been the tallest cuspin its unworn state, followed by the meta-conid, entoconid, and hypoconid. The pro-toconid and hypoconid exhibit the mostwear.

The protoconid of M1 is positionedlingually such that the apex appears to havebeen just buccal to the horizontal midline ofthe tooth. There is no protostylid. In theunworn state, the apices of the protoconidand metaconid may have been joined by ashort transverse ridge (which is tentativelyreferred to as a protolophid, though lessdeveloped than in wynyardiids and dipro-todontoids). The base of the protoconid islarge and rounded. A well-developed butconsiderably worn preprotocristid (or para-cristid) extends anterolingually from theprotoconid apex and terminates in a slightswelling at the anterior tooth margin,posterolingual to the posterior cuspid ofP3. This swelling may represent a weak

paraconid. A similarly weak, short, anteriorcingulum runs buccally from the paraconid.The buccal face of the paraconid slopessteeply to the base of the crown.

The apex of the metaconid lies 2.0 mmlingual to the protoconid apex. The ante-rolingual and posterolingual faces of themetaconid slope steeply to the base of thecrown. A weak postmetacristid extendsposterolingually to meet the lingual cingu-lum at the lingual border of the transversevalley.

The transverse valley of M1 is wide,shallow, and U-shaped, and separates theanterior trigonid and posterior talonid. It isclosed off lingually by a well-developedcuspate lingual cingulum. The homologyof this lingual cusp with the metastylid ofphascolarctids is doubtful because it doesnot originate as a swelling of the postmeta-cristid (as it does in koalas). A similar cuspis variably expressed in diprotodontids, anda thickening of the enamel on the preen-tocristid is evident in some NamilamadetaRich & Archer, 1979, specimens (Dirk’sTowers Local Fauna, System B, River-sleigh) although not to the extent seen inMarada. The lingual cingulum connectsanteriorly to the postmetacristid and poster-iorly to the weak preentocristid.

A well-developed, worn cristid obliquaconnects the apices of the protoconid andhypoconid, effectively sealing off the trans-verse valley buccally. In its unworn state,the cristid obliqua may have been cuspate.

A weak swelling at the buccal base of theentoconid meets a similar swelling at thelingual base of the hypoconid, resulting in aweak lophid (tentatively referred to as thehypolophid) that traverses the longitudinalvalley between these cusps. In its unwornstate, the hypolophid is unlikely to be acontinuous crest linking the apices of theentoconid and hypoconid. The lingual baseof the entoconid slopes steeply to the base ofthe crown. The hypolophid is longer thanthe protolophid.


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A buccal cingulum is absent; however,there is a slight swelling or bulge in theenamel at this point. A weak postentocristidand posthypocristid are continuous with aweak posterior cingulum that runs thelength of the posterior border of the tooth.A resultant postero-lingual pocket is formedbetween the posterior base of the entoconid,the posthypocristid and the posterior cingu-lum. This feature is also found in the lowermolars of wynyardiids such as Namilama-deta.

The M2 is similar to M1 except for thearrangement of the cusps on the trigonid.The protoconid is positioned more buccallythan in M1, but the bases of the metaconidand protoconid are connected so thattransverse wear across the tooth gives theimpression of a weak protolophid. Themetaconid is larger than in M1, and its apexmore worn. The lingual cuspid is reduced,and the lingual cingulum is a short crescen-tic ridge connecting the weak postmetacris-tid and weak preentocristid, effectivelysealing off the transverse valley lingually.The cristid obliqua is well developedalthough less so than in M1, and it is non-cuspate. The buccal cingulum is more ridge-like than in M1 where it constitutes aswelling of the enamel. A small crenulatedpocket is formed between the buccal base ofthe cristid obliqua and the lingual border ofthe buccal cingulum. The connection be-tween the entoconid and hypoconid occursfurther down their bases and is not lophid-like as in M1. The ‘protolophid’ and‘hypolophid’ are similar in length.

The less worn M3 is similar to M2 exceptfor the following: the lingual cingulum isreduced, and the talonid is noticeablynarrower than the trigonid; the protolo-phid and hypolophid are better developed,with the protolophid being longer than thehypolophid; the protoconid is the mostworn of the cuspids followed by thehypoconid; the metaconid is only slightlyworn, and the entoconid is unworn. In

lingual view, the apices of the metaconidand entoconid are relatively tall and wellrounded (i.e. no sharp peaks).

The M4 is similar to M3 except for thefollowing: M4 smaller with a rounded, lesslinear posterior tooth margin; the cristidobliqua is more prominent as a result of lesswear, and of the major cuspids, only theprotoconid and hypoconid are worn; thehypolophid is shorter than the protolophid;the posterolingual pocket between theentoconid, posterior cingulum, and posthy-pocristid is deeper; the protoconid andhypoconid are positioned slightly more pos-teriorly than the metaconid and entoconid,respectively. Consequently, the protolophidand hypolophid curve posteriorly in thebuccal half of the molar. This feature is morereminiscent of other semi-lophodont taxasuch as ilariids and phascolarctids whereinthe lingual cuspid is positioned more ante-riorly than its transversely opposing buccalcuspid (i.e. the metaconid is more anteriorthan the protoconid, and the entoconid ismore anterior than the hypoconid).

Character analysisRecent classifications (e.g. Aplin & Archer1987, Marshall et al. 1989) acknowledgedthat phascolarctids are the sister group ofVombatomorphia. Hence, character polari-ties were determined using the plesio-morphic phascolarctid Madakoala devisiWoodburne et al. 1987c, as an outgroup.Trichosurus vulpecula (Kerr, 1792) (Dipro-todontia, Phalangeridae) was used as amore distant outgroup of the SuborderVombatiformes.

The following taxa, which have compar-able dentary material, are considered ple-siomorphic for their respective families:Kuterintja ngama Pledge, 1987b (Ilariidae);Warendja wakefieldi (Vombatidae); Propa-lorchestes Murray, 1986 (Palorchestidae);andWakaleo oldfieldi Clemens & Plane, 1974(Thylacoleonidae). Species of Muramura


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Pledge, 1987a and Namilamadeta (Wynyar-diidae) are both considered because theirphylogenetic relationships have yet to bedetermined by a cladistic analysis. Rae-meotherium yatkolai is tentatively assignedto Diprotodontidae and is possibly the mostprimitive member of the group, but Ngapa-kaldia tedfordi Stirton, 1967 (an unques-tionable diprotodontid: see Murray 1990,Black 1997) is also considered. Species ofKoobor Archer & Wade, 1976, are excludedfrom the analysis, as lower dentitions areunknown for this taxon. Three of thecharacters of the dentition cannot bepolarized for Warendja wakefieldi due toextreme wear on the molars. Consequently,unworn, juvenile Vombatus ursinus (Shaw1800) specimens have been used to polarizecharacters 2, 4, and 6 in Table 3. Onlycharacters of the dentary and lower denti-tion are used in the analysis, as the cranium,upper dentition, and postcranium are un-known for Marada. Consequently, a com-puter-generated parsimony analysis was notperformed due to the high level of missingdata: many cranial and postcranial char-acters used in previous analyses to delineatevombatomorphian phylogeny cannot beemployed here, resulting in a significantlybiased analysis. Character states and char-acter state polarities are listed in Tables 2and 3, respectively.

1. Inclination angle of I1. A synapomorphyused by Marshall et al. (1989) for awynyardiid/ vombatid/diprotodontoid cladeto the exclusion of ilariids and thylacoleo-nids. A high inclination angle (�308) isconsidered primitive and is found in Tricho-surus, Madakoala, and Wakaleo. A lowinclination angle of I1 (5308) is present inMarada, Kuterintja, Ngapakaldia, Propa-lorchestes, Namilamadeta, Raemeotherium,Muramura, and Warendja.

2. P3 morphology. Diprotodontids andpalorchestids possess a simple bicuspid P3

with a large central protoconid and a smallposterior cuspid (metaconid), the apices ofwhich are joined by a postprotocristid. Thispremolar morphology has changed littlefrom the plesiomorphic P3 of peramelamor-phians and dasyuromorphians. Muramura,like the diprotodontoids, has a simple P3,but three cusps lie along the longitudinalmidline: an anterior protoconid, medialmetaconid, and posterior hypoconid. Thesecusps are linked by a longitudinal crestresulting in a bladed appearance to the P3.Kuterintja has a tricuspid P3 with a largeprotoconid, a well-developed posterior cus-pid (metaconid), and a well-developedposterolingual cuspid. A P3 is unknown forRaemeotherium. Due to the extremely wornnature of the Warendja P3, this feature hasbeen polarized with V. ursinus, which showsthe plesiomorphic bicuspid condition. Thepremolars of both outgroups are highlyspecialized. Trichosurus vulpecula has amulti-cusped, bladed P3. Madakoala devisihas a 6-cusped premolar: 4 cusps aresituated along a longitudinal crest in addi-tion to a posterobuccal cusp and a muchweaker lingual cusp. Wakaleo oldfieldi has abladed P3, the blade extending posterobuc-cally from an apex positioned above theanterior root, then curving lingually alongthe posterior third of the blade. Thebicuspid P3 of Marada arcanum is consid-ered the primitive condition.

3. Degree of bilophodonty. Bilophodonty hasdeveloped independently in several diproto-dontian lineages including Macropodidae,Phalangeroidea (to a lesser extent), Wynyar-diidae, Palorchestidae, Diprotodontidae, andVombatidae (in unworn molars). Absence ofbilophodonty is considered plesiomorphicfor Vombatomorphia. Madakoala devisi, K.ngama, and W. oldfieldi do not possessbilophodont molars. Trichosurus vulpecula,Muramura, Namilamadeta, and Warendjaexhibit semi-bilophodont molars. Maradaarcanum possesses semi-bilophodont molars


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with weak transverse crests linking theapices of the metaconid and protoconid, andthe entoconid and hypoconid respectively,forming a weak protolophid and hypo-lophid. Raemeotherium, Ngapakaldia, andPropalorchestes possess fully bilophodontmolars. Selenodonty/bunodonty¼ 0; semilo-phodonty¼ 1; bilophodonty¼ 2.

4. Development of the paraconid and para-cristid (¼ preprotocristid) on M1. Theparaconid and paracristid are well devel-oped in most marsupial taxa includingdasyuromorphians and peramelemorphians;hence their presence is considered plesio-morphic. Madakoala and Trichosurus pos-sess the primitive state. Muramura andNamilamadeta possess a distinct paracristidculminating in a weak paraconid. Marada,Kuterintja, Raemeotherium, Propalorchestes,and Ngapakaldia possess weak or absentparacristids and paraconids. This charactercannot be polarized for Warendja; V.ursinus shows the apomorphic condition.The M1 of Wakaleo oldfieldi has a simpleanterior apical cusp on the trigonid (themetaconid of Woods 1956). From this cuspextends an anterior ridge that occupies asimilar position to a paracristid; however,the homology of this ridge is uncertain, as isthe case for the main cuspid on the trigonid.Hence, this character is designated ‘un-known’ for this taxon. Character coding is:presence of a triangular trigonid (i.e. para-conid present and paracristid well devel-oped)¼ 0; paracristid present but low¼ 1;absent paraconid and weak or absentparacristid¼ 2.

5. Development of a protostylid on M1. Aprotostylid on M1 is present in plesio-morphic macropodoids (Cooke 1997), pseu-docheirids (Woodburne et al. 1987b),pilkipildrids, petaurids, miralinids (Wood-burne et al. 1987a), phascolarctids andpossibly ilariids (Tedford & Woodburne

1987). Archer (1978) and Marshall et al.(1989) interpreted the presence of a proto-stylid on M1 as plesiomorphic for Diproto-dontia. Cooke (1997) suggested that theformation of a protostylid is plesiomorphicin macropodoids but is reduced or absent inmore derived members of the group. Alter-natively, in phascolarctids, the protostylidranges from weak in the plesiomorphicgenus Madakoala to very large in morederived forms such as species of NimiokoalaBlack & Archer, 1997, Litokoala Stirtonet al. 1967, and Phascolarctos (Black &Archer 1997). In T. vulpecula, the proto-stylid is reduced to a ridge (Cooke 1997),but a small protostylid is present in theplesiomorphic phalangerids Strigocuscus re-idi and Trichosurus dicksoni (Flannery &Archer 1987). The absence of a protostylidin Marada, vombatids, wynyardiids, thyla-coleonids, and diprotodontoids (except pos-sibly Raemeotherium [Rich et al. 1978]) isinterpreted as derived. Kuterintja ngama isinterpreted as lacking a protostylid follow-ing Myers & Archer (1997).

6. Presence of a cristid obliqua. A cristidobliqua is well developed within mostdiprotodontian groups. In Madakoala, T.vulpecula, Kuterintja, and Marada, it ex-tends anterolingually from the hypoconidapex to meet the postprotocristid, effectivelysealing off the transverse valley buccally. InMuramura and Propalorchestes, the cristidobliqua is more anteriorly directed, origi-nating from a more lingual position on thehypolophid and meets the protolophid justbuccal to or on the longitudinal midline ofthe M1, hence the derivation of the term‘midlink’. A moderate anterolingually direc-ted cristid obliqua is present in Raemeother-ium but terminates at the base of theprotoconid. A cristid obliqua is absent inNgapakaldia and Wakaleo. This charactercannot be polarized for Warendja; V.ursinus has a moderately developed cristid


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obliqua. Character states are coded: well-developed anterolingual cristid obliqua con-nected to postprotocristid¼ 0; anteriorlydirected midlink¼ 1; Weak or absent cristidobliqua¼ 2.

7. Posteriorly increasing molar gradient. Aposteriorly increasing molar gradient isfound in several derived vombatomorphiantaxa, in particular the diprotodontoids. It ispossibly associated with an increase in theabrasiveness of the diet. An increase in thesize of the posterior molars increasesthe masticatory force posteriorly towardsthe temporomandibular joint, effectivelyreducing some of the stress placed on themandibular symphysis (Beecher 1977). M4/M1L ratios are listed in Table 4. Tricho-surus, Madakoala, Kuterintja, Warendja,and Marada exhibit the plesiomorphiccondition with an M4/M1L ratio less thanone. Namilamadeta, Muramura, Raemeo-therium, Ngapakaldia, and Propalorchesteshave an M4/M1L ratio greater than or equalto one. An M4 is completely lost in Wakaleooldfieldi; hence this character is coded asprimitive.

8. Crown height. Low-crowned bunodont/selenodont molars are common amongdiprotodontians and are consequentlycoded plesiomorphic within Vombatomor-phia. Both Trichosurus and Madakoalapossess low-crowned molars (coded 0).Marada and wynyardiids are moderatelycrowned (coded 1) and diprotodontoids,vombatoids and ilariids are high-crowned(coded 2). In W. oldfieldi, the functionalteeth (P3 and M1) are moderately crowned(coded 1), whereas M2-3 are lower crownedas a consequence of their vestigial nature.

9. Angle of the anterior border of theascending ramus (Fig. 1C). Hope & Wilk-inson (1982, p. 116) listed the angle ofinclination of the ascending ramus for

various marsupial taxa. Dasyurids, perame-lids, and most diprotodontians have anglesless than 708. Consequently, a posteriorlyinclined (5708) ascending ramus is consid-ered plesiomorphic, and a more uprightascending ramus (�708) is derived. Theangle is low in Wakaleo oldfieldi (508), T.vulpecula (658), Raemeotherium (628), Ware-ndja (56-598), Namilamadeta (658), andMarada (558). It is upright in Kuterintja(708), Ngapakaldia (708), phascolarctids (70-808), and Propalorchestes (708). Both char-acter states are displayed by species ofMuramura (65-708).

10. Posterior extent (elongation) of symphy-sis. The mandibular symphysis in Maradaextends posteriorly to the anterior border ofP3 (Fig. 1C). The symphysis is proportio-nately shorter in Trichosurus and Wakaleo,but extends further posteriorly to below theposterior root of P3. The symphysis becomesmore posteriorly elongate in Ngapakaldia,Kuterintja, Namilamadeta, Muramura, Rae-meotherium, Warendja, and Madakoala,extending to below the anterior root ofM1. The most posteriorly extensive symphy-sis is evident in Propalorchestes, extendingto below the posterior root of M1. A longsymphysis is deemed apomorphic for Vom-batomorphia.

11. Masseteric foramen. A masseteric fora-men is absent in Trichosurus. It is small inMarada, Wakaleo, Namilamadeta, Mura-mura, Propalorchestes, and Ngapakaldia,and large in Warendja. It is unknownfor Raemeotherium, Kuterintja, and Mada-koala. Absence of a masseteric foramen isdetermined to be plesiomorphic forVombatomorphia¼ 0; small or moderatemasseteric foramen¼ 1; large massetericforamen¼ 2.

12.Diastema length proportionately430%ofhorizontal ramus length. Dasyuromorphians,


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peramelemorphians and most diprotodon-tians lack a diastema between I1 and P3 due tothe presence of C1 and P1-2. Hence, theabsence of a functional diastema is regardedto be plesiomorphic, and therefore elonga-tion of the diastemawith respect to the lengthof the horizontal ramus is deemed derived.Measurements of diastema and horizontalramus length for taxa in the current study arelisted in Table 4. The diastema length isgreater than 30% of the horizontal ramuslength in Marada, Propalorchestes, andNgapakaldia. The diastema is less than30% of the horizontal ramus length inWarendja, Wakaleo, Raemeotherium, Nami-lamadeta, and Muramura. This charactercannot be polarized for Madakoala andKuterintja. A diastema is absent in Tricho-surus due to the presence of vestigial I2and P1-2, and deemed absent for Wakaleo(only 6 mm in length) due to the presenceof P2.

DiscussionMarada arcanum gen. et sp. nov. is knownfrom a single dentary recovered in 2001from the late Oligocene Hiatus Site, Riv-ersleigh. It is the first occurrence of the newvombatomorphian family Maradidae de-spite the tonnes of fossiliferous materialprocessed from the Riversleigh depositsover the past 30 years. With the additionof Maradidae, there are now seven familieswithin the infraorder Vombatomorphia.

The monophyly of Vombatomorphia isstrongly supported by both cranial andpostcranial morphology. In particular, mostrecent phylogenetic studies recognize thesquamosal contribution to the tympaniccavity as a synapomorphy uniting vomba-tomorphians to the exclusion of phascolarc-tomorphians (e.g. Murray 1986, Aplin &Archer 1987, Tedford & Woodburne 1987,Marshall et al. 1989, Springer & Wood-burne 1989). However, as Aplin & Archer(1987) noted, the highly autapomorphic

dentitions of vombatomorphian familiesprovide limited use in phylogenetic analyses.Many taxa cannot be assigned at thefamilial level based on dentitions alone.For example, the placement of both Nami-lamadeta and Muramura within Wynyardii-dae is tentative, based on a presumedassociation of dentitions with limb materialwherein the limbs were similar to thoseknown for the type species Wynyardiabassiana (Tedford et al. 1977). Aplin(1987) concluded Wynyardia to be theplesiomorphic sister group to all othervombatomorphians on the basis of itsbasicranial morphology. Aplin & Archer(1987) recognized greater affinities betweenNamilamadeta and Muramura with thediprotodontoids, and Murray (1990) sug-gested affinities specifically with palorches-tids. The enigmatic genus Koobor has beenassigned to both the Phascolarctomorphiaand Vombatomorphia. Similarly, Rae-meotherium could be either a plesiomorphicdiprotodontid or a primitive macropodoid.The affinities of thylacoleonids with Vom-batomorphia have also been questioned.Murray et al. (1987) regarded thylacoleo-nids to be closer to phalangerids thanvombatomorphians. However, Aplin &Archer (1987) included the marsupial lionswithin Vombatomorphia but recognizedthat they are highly plesiomorphic andoccupy a distant position with respect tothe rest of the group.

Placement of Marada within Vombato-morphia has proven difficult due to theabsence of cranial and postcranial data. Ofall previous analyses of vombatomorphianphylogeny (e.g. Archer 1984, Aplin &Archer 1987, Tedford & Woodburne 1987,Marshall et al. 1989, Munson 1992, Murray1998), only one (Tedford & Woodburne1987), recognized synapomorphies of thedentary. These include: 1, widely flaringsubmasseteric crest; 2, long pterygoidflange of the horizontal ramus; 3, uncon-stricted mandibular foramen; and 4,


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narrow, transversely elongate and dorsallycurved mandibular condyles. Unfortu-nately, none of these features are preservedon the Marada dentary.

Marada arcanum is, however, tentativelyplaced within the Vombatomorphia (ratherthan Phascolarctomorphia) based on: itslarge size; the presence of more lophodontmolars; the absence of a well-developedpremetacristid, postmetacristid, and metas-tylid in the lower molars; a reduced cristidobliqua; and the absence of a protostylid onM1.

Within Vombatomorphia, Marada ismorphologically most similar to primitivemembers of the Wynyardiidae, Palorchesti-dae, and Diprotodontidae, sharing fivederived states with each (Table 3). Thelow-crowned semi-lophodont molars, theposition of the major cuspids with respectto each other, the posterolingual pocket inthe lower molars, the development of thepostmetacristid and preentocristid, and inparticular, the construction of the M1, arestrikingly similar to Namilamadeta materialfrom Riversleigh. The main differences inthe dentitions of these taxa are the lack of awell-developed anterior cingulum, the moreopen, U-shaped transverse valleys on thelower molars, the absence of a ‘neomorph’cuspid, and the bicuspid premolar ofMarada. The last feature is most similar tothe simple plesiomorphic bicuspid P3 ofdiprotodontids and palorchestids. Derivedfeatures shared with wynyardiids, diproto-dontids, and palorchestids include a lowangle of inclination of I1 and a tendencytowards lophodont molars. Features sharedexclusively with the diprotodontids andpalorchestids include its large size, a weakparaconid, and paracristid on M1, anelongate diastema with a prominent diaste-mal ridge, and a large mental foramen.

Marada is precluded from being aprimitive member of Diprotodontoideadue to the presence of a postmetacristid,posthypocristid, postentocristid, and preen-

tocristid on the lower molars and theprimitive construction of the weak lophidson the lower molars. The lophids are morereminiscent of ilariids and wynyardiidswherein the protoconid lies posterior tothe metaconid, and the hypoconid liesposterior to the entoconid, resulting in aposteriorly curved or oriented lophid in thelower molars. In diprotodontids and pa-lorchestids, the crescentic lophs curve for-ward and may represent one of the fewsynapomorphies of the superfamily Dipro-todontoidea.

Marada arcanum possesses several un-ique primitive features, including: a gracile,narrow dentary; a less posteriorly extensivesymphysis; a non-crested or inflated ascend-ing ramus at its point of origin; and a moreposterior origin of the ascending ramus.Marada differs from all other vombatomor-phians except Wakaleo, in having a trigonidthat is wider than the talonid and a smallangle of inclination of the ascending ramus.

In addition, Marada exhibits a long-itudinally oriented pattern of wear mostpronounced on the buccal cuspids of themolars, in particular, the protoconids ofM2-3 and the hypoconids of M1-2. This wearis reminiscent of that found in ilariids,wynyardiids, and phascolarctids as opposedto the even wear across the transverse lophsseen in the fully lophodont diprotodontoids.

A striking feature of the dentary inMarada and one that is unique amongvombatomorphians is the short molar rowlength, which occupies only 50% of thelength of the horizontal ramus. It wouldappear that the Marada dentary evolvedalong a similar path to the diprotodontoidsin becoming larger, but this was achieved bylengthening the diastema with little or noincrease in molar row length.

Another unique feature is the flattenedlinear dentary and absence of pronouncedareas for muscle attachment (i.e. the shallowmasseteric, pterygoid, and digastric fossae).The degree to which these features are


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attributable to sexual dimorphism is notknown. The Marada dentary may representa gracile female of the species. Unfortu-nately, the coronoid process and articularcondyle are not preserved in Marada, so it isdifficult to assess the relative strengths of thetemporalis and masseter/pterygoid musclecomplexes. The large mental foramen(which suggests increased innervation tothe anterior lower jaw) may be suggestiveof a large mobile lip. In any case, thelongitudinal pattern of tooth wear, theshortened cheek tooth row, the lack ofpronounced areas for muscle attachment,and the construction of the mandibularsymphysis suggest a unique masticatoryaction and ecological niche for Maradaarcanum that will remain a mystery untilmore complete specimens are known.

On the basis of the dentary and lowerdentition, Marada does not fit into anyknown vombatomorphian family, as theyare currently defined. Most features used inthe generic diagnosis to define Marada areplesiomorphic with respect to Vombato-morphia. However, the combination ofthese primitive features with the possessionof two unique features for Marada (theshort length of the cheek tooth row withrespect to horizontal ramus length; and thepresence of a distinct cuspid on the lingualcingulum of the lower molars) makes thisdentary strikingly different to any othervombatomorphian presently known and,consequently, warrants the establishmentof a new family Maradidae.

Hiatus Site is interpreted to be fromRiversleigh’s stratigraphically oldest sedi-ments and is late Oligocene in age (Creaser1997). Each of the seven vombatomorphianfamilies was distinct by the late Oligocene.However, the lack of an Australian fossilmammal record between 55 and 26 millionyears makes any refined assessment of thetime of familial differentiation difficult.Aplin & Archer (1987) suggested a Paleo-gene origin for Vombatomorphia and con-

cluded that known families represent theremnants of a diverse pre-Oligocene radia-tion. The presence and only known occur-rence of Marada in one of the oldestdeposits at Riversleigh certainly supports ahigher diversity of Vombatomorphia. Likethe wynyardiids, which do not have a fossilrecord younger than the middle Miocene,Marada may represent an early experimentin vombatomorphian evolution that failedto survive beyond the Miocene, possibly asa result of competition with diprotodon-toids and macropodoids.

AcknowledgementsThe author would like to thank AnnaGillespie and Henk Godthelp for theiradvice and support and access to compara-tive material. Thanks to Mike Archer, SueHand, Peter Murray, and Neville Pledge,who critically read a draft of this manu-script and provided many useful comments.Vital support for research at Riversleigh hascome from the Australian Research GrantScheme (grants to M. Archer); the NationalEstate Grants Scheme (Queensland) (grantsto M. Archer and A. Bartholomai); theUniversity of New South Wales; the Com-monwealth Department of Environment,Sports and Territories; the QueenslandNational Parks and Wildlife Service; theCommonwealth World Heritage Unit; ICIAustralia Pty Ltd; the Australian Geo-graphic Society; the Queensland Museum;the Australian Museum; the Royal Zoolo-gical Society of New South Wales; theLinnean Society of New South Wales;Century Zinc Pty Ltd; the RiversleighSociety Inc.; and private supporters includ-ing Elaine Clark, Margaret Beavis, MartinDickson, Sue & Jim Lavarack, and Sue &Don Scott-Orr. Vital assistance in the fieldhas come from many hundreds of volun-teers together with staff and postgraduatestudents of the University of New SouthWales.


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Documents

Maradidae: a new family of vombatomorphian marsupial from the … (2007) Marada.pdf · marsupial from the late Oligocene of Riversleigh, northwestern Queensland KAREN BLACK BLACK,