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A New Family of Vombatomorphian Marsupial from the Late Oligocene Of

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A New Family of Vombatomorphian Marsupial from the Late Oligocene Of 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 of Riversleigh, 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 Heritage Property, northwestern Queensland. Although known from only a single dentary, it is assigned to a new family Maradidae, based on a unique combination of both plesiomorphic and apomorphic features. Of the known vombatomorphians, Marada is most similar to primitive wynyardiids and diprotodontoids (palorchestids and diprotodontids). Further clarification of the phylogenetic position of Maradidae within Vombatomorphia requires discovery of upper dentitions and crania. Karen Black [[email protected]], Vertebrate Palaeontology Laboratory, School of Biological, Earth and Environmental 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. Downloaded By: [University of New South Wales] At: 04:45 25 May 2007 SIX FAMILIES are recognized within the unique combination of primitive and de- infraorder Vombatomorphia: Ilariidae, Wy- rived features and cannot be assigned to any nyardiidae, Thylacoleonidae, Vombatidae, known vombatomorphian family. Conse- Palorchestidae, and Diprotodontidae. Of quently, a new family, Maradidae, has been these, five families are extinct, two families established. (Wynyardiidae and Ilariidae) are not known Material is deposited in the palaeonto- from deposits younger than early Miocene, logical collection of the Queensland Mu- and all exhibit highly autapomorphic denti- seum (QMF). Cusp nomenclature follows tions. Aplin & Archer (1987) noted that Rich et al. (1978) and Archer (1984). Molar known vombatomorphian families repre- homology follows Luckett (1993). Premolar sent the remnants of a far more diverse homology follows Flower (1867). Mandib- pre-Oligocene radiation. Although mono- ular terminology follows Stirton (1967). phyly of the infraorder is strongly supported Higher-level systematic nomenclature fol- by cranial and postcranial morphology, lows Aplin & Archer (1987). resolution of phylogenetic relationships based solely on dental morphology has proven difficult. Marada gen. nov., de- scribed herein, is known from a single right Systematic palaeontology dentary from the late Oligocene Hiatus Site, Superorder MARSUPIALIA Illiger, 1811 Riversleigh World Heritage Property, Order DIPROTODONTIA Owen, 1866 northwestern Queensland. It expresses a Suborder VOMBATIFORMES Wood- burne, 1984 Infraorder VOMBATOMORPHIA Aplin ISSN 0311-5518 (print)/ISSN 1752-0754 (online) Ó 2007 Association of Australasian Palaeontologists & Archer, 1987 DOI: 10.1080/03115510601123601 Family MARADIDAE new family 18 KAREN BLACK ALCHERINGA Diagnosis. Maradidae differs from all other Marada differs from all other vombato- vombatomorphian families in the following morphians except diprotodontids and pa- combination of features: Dentary gracile, lorchestids in having an elongate diastema narrow, elongate and mediolaterally com- and a simple, bicuspid P3. Marada differs pressed; less posteriorly extensive mandibu- from all other vombatomorphians except lar symphysis; non crest-like or inflated wynyardiids, in having a posterolingual ascending ramus at its point of origin; pocket between the entoconid, posthypo- ascending ramus originates more posteriorly cristid, and posterior cingulum. Marada and at a point behind and less lateral to differs from diprotodontids, palorchestids, the molar row; less extensive post-alveolar and wynyardiids in having an M1/M4 length shelf and weak post-alveolar process; lower less than 1. crowned cheek teeth; short molar row Marada differs from diprotodontids and length (50% length of horizontal ramus); a palorchestids (i.e. diprotodontoids) in hav- well-developed cristid obliqua; and a well- ing: smaller teeth; an anteriorly convex developed cuspate lingual cingulum on M1. rather than concave ‘hypolophid’ and ‘pro- tolophid’; a better-defined paraconid on M1; Marada gen. nov. reduced posterior molars (i.e. M4/M1 length 51); less well-developed preprotoconid Type and only species. Marada arcanum gen. crests on P3; a reduced posterior cingulum et sp. nov. on the molars; a better-defined paraconid Downloaded By: [University of New South Wales] At: 04:45 25 May 2007 and paracristid on M1 (except Raemeother- Generic diagnosis. The generic diagnosis is ium Rich et al. 1978); and a well-developed that for the family until additional taxa are postmetacristid, postentocristid, posthypo- known. cristid, preentocristid, and preprotocristid (in M2-4). Etymology. Marada is the Waanyi (the local Marada differs from palorchestids in: Aboriginal language of Riversleigh) word lacking a well-developed posterior cingulum for flat in reference to the narrow, medio- on P3; and lacking the posterior, buccal, and laterally compressed dentary and the shal- lingual crests of the protoconid on P3. low fossae for muscle attachment. Gender is Marada differs from diprotodontids in hav- masculine. ing: less lophodont molars; a longitudinal wear pattern along the buccal cuspids on Remarks. Distinctions from all other vom- lower molars (rather than a transverse batomorphian taxa are previously listed in pattern of wear across the lophids); a more the familial diagnosis. Further differences lingually positioned protoconid on M1 (ex- from more specific groups are listed below. cept Raemeotherium); a proportionately (Note that comparisons are made using the larger P3 relative to M1; and a distinct primitive members of the respective groups, posterior cuspid at the terminus of the which are detailed in the proceeding char- postprotocristid on P3. Marada differs from acter anaylsis.) ilariids and wynyardiids in lacking the Marada differs from all other vombati- neomorph cuspid (Pledge 1987a, Tedford forms (except Wakaleo Clemens & Plane, & Woodburne 1987) on M1. Marada differs 1974, 508;andWarendja wakefieldi Hope & from wynyardiids in that the P3 is not bladed Wilkinson, 1982, 56-598) in having a poster- and is considerably shorter than M1;andin iorly inclined ascending ramus where the having more open, U-shaped transverse angle of the anterior border of the ascending valleys on the lower molars. Marada differs ramus (Fig. 1C) is less than 608 (relative to from ilariids in: lacking a tricuspid, bulbous the plane of the horizontal ramus). P3 and a well-developed anterior cingulum ALCHERINGA NEW VOMBATOMORPHIAN FAMILY 19 Downloaded By: [University of New South Wales] At: 04:45 25 May 2007 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 ramus length; MRL, molar row length; SL, symphysis length. Hatching represents broken areas on dentary. Bar ¼ 50 mm. 20 KAREN BLACK ALCHERINGA on the lower molars; and in having less Holotype. QMF42738, right dentary with complex molars. Marada differs from thyla- P3,M1-4.I1 crown broken. Dental formula coleonids in lacking: an elongate, bladed P3; I1,C0,P3,M1-4. The posterior area of the a well-developed, deep masseteric fossa; a dentary is damaged and missing the coro- deep, rounded symphysis; a highly inclined noid process, articular condyle, and angular caniniform I1; and in having a single lower process. premolar. Type locality. Hiatus Site, Riversleigh World Heritage Fossil Property, northwes- Marada arcanum sp. nov. (Figs 1-2, Tables tern Queensland (see Creaser 1997). 1-4) Distribution and age. Hiatus Site is a System A deposit (Creaser 1997) which, on the basis of stratigraphy and contained faunas, is interpreted to be of late Oligocene age. Species diagnosis. The diagnosis for the species is that for the family until additional taxa are known. Downloaded By: [University of New South Wales] At: 04:45 25 May 2007 Specific etymology. Arcanum, meaning mys- tery in Latin, alludes to the unknown taxonomic position of the species and the strange combination of primitive and de- rived features exhibited by the single known specimen. Description Dentary (Fig. 1). Right dentary with P3, M1-4.I1 crown broken. The posterior area of the dentary is poorly preserved and missing the coronoid process, articular condyle, and Fig. 2. Marada arcanum gen. et sp. nov. occlusal angular process. The dentary is very gracile stereopair of QMF42738. Bar ¼ 10 mm. and slender with a narrow horizontal ramus. It is unlike the characteristically more robust vombatomorphian dentaries with the exception of the relatively delicate P3 M1 M2 M3 M4 primitive ?diprotodontid Raemeotherium L 8.7 11.4 10.9 10.8 10.0 yatkolai Rich et al. 1978. The lingual AW 7.4 8.0 8.4 7.2 (medial) surface of the horizontal ramus is PW 5.2* 7.3 7.5 7.3 6.3 flat and straight, as is the ventral border. DR 27.4 27.4 26.3 25.9 26.1 The maximum depth of the horizontal ramus is 27.9 mm below the anterior base Table 1. Measurements (mm) of dentition of of M1. The horizontal ramus thickens Marada arcanum. *Maximum width of P3. DR, depth of horizontal ramus below respective tooth opposite M3 with a maximum width of taken between the roots. 14.6 mm. The diastema is
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