Gawinga aranaea, ROBERTS & ARCHER & HAND & GODTHELP, 2007

ROBERTS, KAREN K., ARCHER, MICHAEL, HAND, SUZANNE J. & GODTHELP, HENK, 2007, New Genus and Species of Extinct Miocene Ringtail Possums (Marsupialia: Pseudocheiridae), American Museum Novitates 3560 (1), pp. 1-16 : 2-7

Gawinga aranaea , new species

HOLOTYPE: QMF52173, isolated right m1 ( figs. 2A , 3A ).

PARATYPE: QMF52174, isolated left m1 ( fig. 3B ) .

TYPE LOCALITY: Arachnea Ridge Site, Riversleigh World Heritage area, Lawn Hill National Park, northwestern Queensland, Australia.

REFERRED SPECIMENS: QMF52175 ( fig. 3C ) right m2 ; QMF52176 ( fig. 2D , 3I ) left m4 from Arachnea Ridge Site . QMF52177 ( fig. 2B , 3D ) right m2 ; QMF52178 ( fig. 3E ) left m2 ; QMF52179 ( fig. 3F ) right m2 ; QMF52180 ( fig. 2C , 3G ) right m3 from Upper Site . QMF52181 ( fig. 3H ) right m3 from Wayne’s Wok Site .

ETYMOLOGY: From the Latin aranea meaning ‘‘spider’’ or ‘‘spider’s web’’. In reference to the Riversleigh site, Arachnea Ridge.

DISTRIBUTION AND AGE: Riversleigh World Heritage Area, northwestern Queensland. Upper Site and Wayne’s Wok Site are interpreted to be part of Riversleigh’s System B strata ( Archer et al., 1995, 1997b; Creaser, 1997). Biocorrelation of the Riversleigh fossil assemblages, and of Upper Site in particular, suggests an early Miocene age for System B sites. No age has been determined for

Arachnea Ridge Site, but an early Miocene age is also possible given the presence of this new species.

DIAGNOSIS: Gawinga aranaea is characterized by a distinct, lower molar cusp morphology as follows: a reticulated occlusal surface of robust ridges, predominantly normal and lingual to the cristid obliqua; a hypoconid base that is enlarged posterobuccally; an anteriorly placed protoconid with respect to the metaconid on posterior molars; and a bisected posthypocristid on m1. The lower molars of G. aranaea are narrower and longer than in most extinct pseudocheirids, with the exception of Marlu kutjamarpensis Woodburne et al., 1987 , Pildra magnus Pledge, 1987 , and all species of Pseudokoala . It differs from known species of the other extinct genera by having a shorter, weaker, and more posteriorly oriented m1 buccal protocristid; by having a large cuspate protostylid; and a larger entostylid and ridge (entostylid completely absent in species of Marlu and Pseudokoala ). Posterior molars also exhibit a prominent metaconid ridge and an elongate preentocristid that is transversely buttressed at its anterior end.

G. aranaea differs further from Paljara spp. in the following features: m1 anterobuccal cingulum reduced; m1 paraconid smaller; protoconid on posterior molars buccally enlarged; metastylid progressively more complex along tooth row; narrower notch between preentocristid and metastylid; entostylid ridge forms a continuous crest with hypoconulid; larger hypoconulid on posterior molars; more lengthwise orientation of lingual cusps, particularly entoconid; wider buccal cusp angles; buccal cusp apices less lingually curved; shallower trigonid and talonid basins. Features shared with species of Paljara include: m2 longer than m1; reduced or absent anterior margins between paraconid and paracristid; paraconid on posterior molars positioned on lengthwise axis; elongate, blad- ed metacristids; equidistant positioning of the entostylid ridge between posthypocristid and entoconid; and lack of buccal protostylid or cingulum on posterior molars.

G. aranaea differs further from Pildra spp. by the following features: stronger and broad- er anterior cingula (except P. magnus ); anterior margins on posterior molars reduced or absent; m1 paraconid extended further anteriorly; paraconid on posterior molars positioned much closer to longitudinal axis; m1 metaconid relatively lower cusped; wider distance between apices of m1 metaconid and protoconid; narrower notch between metastylid and preentocristid; preentocristid less steep and more bladed; entoconid less conical; entostylid ridge forms a continuous crest with the hypoconulid which is separate from the postentocristid; larger hypoconulid. Features shared with species of Pildra include: m2 longer than m1; presence of a lingual rib extending from the m1 paraconid; lingual enlargement of the protoconid on posterior molars; progressively more complex metastylids along the tooth row; similar orientation of the posthypocristids on m1–2.

G. aranaea differs further from Marlu and Pseudokoala spp. by the following features: stronger anterobuccal cingula; larger m1 paraconid; m1 protoconid more lingually positioned; m1 metaconid relatively larger and separated from protoconid by a deeper notch; greater distance between apices of m1 metaconid and protoconid; metastylids progressively more complex along the tooth row; larger, more distinct hypoconulid. G. aranaea differs further from all species of Marlu and Pseudokoala , except M. praecursor Woodburne et al., 1987 , in the absence of an overlapping or joined metastylid and preentocristid. G. aranaea also differs from species of Pseudokoala in having relatively conical lingual cusps, with steeper cristids; shorter postprotocristid on posterior molars; posthypocristid extending further lingually and absence of a buccal protostylid or cingulum on posterior molars (except P. curramulkensis , originally described as Corracheirus curramulkensis Pledge, 1992 ). Features shared with Marlu and Pseudokoala species include: distinct anterolingual cingula; and broad buccal cusp angles. G. aranaea also shares with Marlu a longer m2 than m1.

In comparison with extant taxa, G. aranaea is smaller than all known species except Pseudochirulus mayeri Rothschild and Dollman, 1933 , and P. canescens Waterhouse, 1846 , and is very similar in size to Petauroides ayamaruensis Aplin et al., 1999 . It also differs from extant taxa (species of Pseudocheirus , Pseudochirulus , Petropseudes , Pseudochirops , Petauroides , and Hemibelideus ) as follows: m1 shorter than m2 (except Petropseudes ); m1 precristid of the protostylid joins anterior end of the anterobuccal cingulum; m1 postcristid of the protostylid welldefined and shelflike, terminating at the cristid obliqua; distinct and strong metaconid ridge present on posterior molars; metastylid progressively more complex along the tooth row; metastylid and preentocristid do not overlap or join; posthypocristid more obliquely oriented.

G. aranaea differs further from species of Pseudochirops and Petropseudes as follows: stronger anterior cingula (anterior cingula absent in Pseudochirops cupreus Thomas, 1897 , and Petropseudes dahli Collett, 1895 ); anterobuccal cingulum present on posterior molars; m1 buccal protocristid shorter and weaker; flat lingual face of metastylid; hypoconulid relatively larger and more distinct from postentocristid and posthypocristid; buccal cusp apices less lingually curved; buccal protostylid or cingulum on posterior molars absent. G. aranaea differs further from Pseudochirops spp. as follows: flat lingual face on m1 protoconid; greater distance between apices of m1 metaconid and protoconid (except P. corinna e Thomas, 1897); m1 premetacristid not linear with very weak postprotocristid; anterior protocristid on posterior molars reduced or absent; larger entostylid and ridge, forming a continuous crest to the hypoconulid apex; entostylid ridge equidistant from entoconid and posthypocristid (except P. archeri Collett, 1884 , and P. winteri Mackness and Archer, 2001 ); wider hypoconid cusp angle. G. aranaea differs further from Petropseudes dahli as follows: m1 metaconid much larger and separated from protoconid by a deeper notch; m1 cristid obliqua connects with metaconid; much shorter postprotocristid on posterior molars; entoconid more conical; entostylid present; less compressed lingual cristids. Features shared with Pseudochirops and Petropseudes species include: lingual rib extending from m1 paraconid and a cuspate protostylid on m1. It also shares with species of Pseudochirops an m1 protostylid basin.

With the exception of Pseudocheirus stirtoni and P. marshalli ( Turnbull and Lundelius, 1970) , which are compared alongside species of Petauroides and Hemibelideus , G. aranaea differs further from Pseudocheirus spp. as follows: stronger and broader anterior cingula; anterior margins of posterior molars reduced or absent; paraconid on posterior molars positioned much closer to longitudinal axis; greater distance between apices of m1 protostylid and protoconid; m1 metaconid relatively larger and separated from protoconid by a deeper notch; premetacristid on m1 does not align linearly with the very weak postprotocristid; wider protoconid cusp angles on posterior molars; protoconid on posterior molars more lingually swollen, forming a slight anterior protocristid in some specimens; much shorter postprotocristid on posterior molars that does not unite with the metastylid; entostylid present; hypoconulid on m1–2 is not ribbed posterolingually, and is perpendicular to hypoconulid cristids; cristid obliqua terminates at same height as postprotocristid; lingual cristids on posterior molars less steep; buccal cusps less lingually curved; shallower trigonid and talonid basins. Features shared with species of Pseudocheirus include: lingual rib extending from m1 paraconid; a cuspate protostylid on m1; and absence of a buccal protostylid or cingulum on posterior molars.

G. aranaea differs further from Pseudochirulus spp. as follows: anterior margins of posterior molars reduced or absent; m1 paraconid smaller and less conical; paraconid on posterior molars positioned much closer to longitudinal axis; m1 metaconid larger and separated from protoconid by a deeper notch; shorter, weaker m1 buccal protocristid; anterior protocristid on posterior molars absent or very reduced; entostylid and ridge present; hypoconulid on m1–2 is not ribbed or curved on the posterolingual surface, and cristids are oriented lengthwise; posthypocristid less curved at lingual termination; lingual cusps less conical (except m1 protoconid); buccal cusp cristids higher crested (except anterior protocristid); cristids are less steep; shallower trigonid and talonid basins. Features shared with species of Pseudochirulus include: broad, distinct anterior cingula and a cuspate protostylid on m1.

G. aranaea differs further from Pseudocheirus stirtoni , P. marshalli and Petauroides and Hemibelideus spp. as follows: anterior margins of posterior molars reduced or absent; paraconid on posterior molars positioned much closer to longitudinal axis; m1 metaconid is a more distinct, independent cuspid (except P. marshalli and P. ayamaruensis ); shorter, weaker m1 postprotocristid; much shorter postprotocristid on posterior molars; entoconid buccally compressed; larger entostylid and much stronger, continuous entostylid ridge on all molars ( H. lemuroides Collett, 1884 , has no entostylid or ridge); hypoconulid more peaked and distinct and lacks a ribbed or curved posterolingual surface; wider hypoconid angles; cristid obliqua terminates at same height as postprotocristid (except P. ayamaruensis ); buccal cusp apices less curved lingually; cristid obliqua and paracristid higher crested; buccal protostylid or cingulum on posterior molars absent; shallower trigonid and talonid basins. It differs further from species of Hemibelideus as follows: buccally enlarged m1 protostylid; m1 paraconid less conical, and independent of paracristid ( P. ayamaruensis also differs in this feature). Features shared with P. stirtoni , P. marshalli and species of Petauroides and Hemibelideus include: distinct anterolingual cingula; an enlarged cuspate protostylid on

TABLE 1 Length (L), Anterior Width (AW), and Posterior Width (PW) of Gawinga aranaea Measurements in millimeters.

m1; and flat lingual surfaces of metaconid/ protoconid and entoconid on m1–2.

Figures

Fig. 2. Stereo occlusal view of m1–4 of Gawinga aranaea. A. QMF52173 (holotype), right m1; B. QMF52177, right m2; C. QMF52180, right m3; D. QMF52176, left m4. Scale bars 5 1 mm.

Fig. 3. Buccal views of Gawinga aranaea. A. QMF52173 (holotype), right m1; B. QMF52174 (paratype), right m1; C. QMF52175, right m2; D. QMF52177 right m2; E. QMF52178, left m2; F. QMF52179, right m2; G. QMF52180, right m3; H. QMF52181 right m3; I. QMF52176, left m4. Scale bars 5 1 mm.