Gumardee springae, Travouillon & Butler & Archer & Hand, 2016

Travouillon, Kenny J., Butler, Kaylene, Archer, Michael & Hand, Suzanne J., 2016, New material of Gumardee pascuali Flannery et al., 1983 (Marsupialia: Macropodiformes) and two new species from the Riversleigh World Heritage Area, Queensland, Australia, Memoirs of Museum Victoria 74, pp. 189-207 : 197-204

Gumardee springae sp. nov.

Tables 3-4, Figures 4-6

Holotype. QM F52816 , partial juvenile skull with left associated P2, dP3, left and right P 3 in crypt, M1-3 and associated left maxilla with dP3, P 3 in crypt, M1-3.

Paratypes. QM F19606 , right juvenile dentary with p2, dp3, p 3 in crypt, m1-2 ; QM F19633 , left maxilla with P3, M1-4 ; QM F19872 , left dentary with p3, m1-4 ; QM F19874 , right juvenile maxilla with broken M2, M 4 in crypt ; QM F31549 , right dentary with i1, p3, m1-4 ; QM F57554 , right dentary with p2, p3, m1-3 ; QM F57557 , partial juvenile skull with left and right P2, dP3, M1-2 ; QM F57611 , right dentary with i1, p2, dp3, m1, m 2 in crypt .

Referred material. QM F57552, left maxilla with P3, M1-3; QM F18948, associated maxillae with right P3, M1, M3-4, left P3, M1-4; QM F19634, left maxilla with M1-3; QM F19679, left maxilla with P3, M1-3; QM F19680, right maxilla with M1-2; QM F19681, left juvenile maxilla with dP3, P 3 in crypt, M1; QM F19990, right maxilla with M1-2, broken M3; QM F19999, left maxilla with P3, M1-2, broken M3; QM F20291, right maxilla with worn M1-4; QM F50432, associated left and right maxillae, with P3, M1-3; QM F52815, partial juvenile skull with broken right dP3, M1-3, M 4 in crypt; QM F57613, right maxilla with M1-3; QM F57553, right dentary with m2-3; QM F57551, right dentary with p3, m1-2; QM F57555, left dentary with dp3, p3, m1-2; QM F57612, left dentary with m1-3; QM F57610, left dentary with p2, dp3, m1, broken m2; QM F57556, left dentary with p3, m1-4; QM F19604, right dentary with broken m2, m3, broken m4; QM F19819, right dentary with p3, m1-4; QM F19922, left juvenile dentary with m3, m 4 in crypt; QM F19995, right juvenile dentary with p 3 in crypt; QM F30292, associated left m1-4; QM F31556, left dentary with m1-3; QM F31559, right dentary with m1-3; QM F41199, right dentary with m2-4; QM F41286, right dentary with p3, m1-4; QM F57783, right dentary with partial m1, m2-3; QM F57784, left maxilla with P3, partial M1, M2-3.

Diagnosis. Gumardee with postprotocrista connected to the metaconule on all upper molars, metaloph does not connect metacone to metaconule on M4, shallow buccinator sulcus, nine cuspules/cuspids with eight transcristae/transcristids on P3/p3, five cuspules on P2, no St C on M2-3, and buccal crest from entoconid well-developed as a hypolophid, with low posthypocristid on all lower molars and dp3, well developed protostylid on dp3, no premetacristid on m1, and well developed paracristid on m1.

Etymology. Named after Kirsten Spring, collection manager of the Geosciences Program at the Queensland Museum, Brisbane, Australia, in recognition of her skilled and careful management of the large and diverse Riversleigh fossil collections.

Age and distribution. All specimens are from White Hunter Site, D-Site Plateau, Riversleigh World Heritage Area, northwestern Queensland, Australia (18°15'35"S, 138°06' 41"E). White Hunter Site is part of Riversleigh’s Faunal Zone A, interpreted to be late Oligocene in age on the basis of biocorrelation of those faunas with Ngama Local Fauna, Etadunna Formation, South Australia, as distinguished by Archer et al. (1989), Archer et al. (1997), Arena (2004) and Travouillon et al. (2006, 2011).

Description. The skull morphology description is based on holotype QM F52816 and paratype QM F57557 (figs. 4–5). The premaxilla is partly preserved in QM F57557 (fig. 5). The alveoli for I1-3 and C1 are present. The alveolus for I1 is the largest for the incisors and ovoid in shape and laterally compressed. The alveoli for I2 and I3 are squarer and the alveolus for I2 is slightly smaller than the alveolus of I3. The alveolus for C1 is almost twice the size as that of I1, but the lateral wall of the alveolus is damaged, preventing full assessment of its size. The alveolus for C1 is bordered by the maxilla posteriorly. An incisive fenestra is present medial to I3 and C1, but only the anterior and lateral portion of its wall are preserved, with the maxilla contributing to the posterolateral wall.

The maxilla is the best preserved part in both specimens (figs. 4–5). The palate is concave in lateral view, contrasting with the molar row that is convex. In ventral view, the molar row curves posteromedially.The lateral borders of the maxillopalatine fenestrae are present, extending as far anteriorly as the midpoint of M1, and as far posteriorly as the posterior of M4. The palatine is preserved in QM F52816, bordering the right maxillopalatine fenestra from M3 to M4. In lateral view, a small ovoid infraorbital canal is present above the posterior root of P 2 in QM F57557, and dorsal to the middle of P 3 in QM F52816. The maxillary-jugal suture is relatively smooth. A masseteric process is present ventral to the maxillary-jugal suture as a short ridge. In lateral view, the dorsal margin of the frontal is perfectly flat. Distinct ridges border the dorsal margins of the frontals, narrowing posteriorly, past the postorbital constriction of the skull, and are at their narrowest at the frontal-parietal sutures. These ridges continue through the parietals and widen posteriorly. There is no distinct sagittal crest at the sagittal suture. Portions of the squamosal, alisphenoid, basisphenoid and ectotympanic are poorly preserved in QM F52816.

Part of the basioccipital, occipital condyle and supraoccipital are preserved in QM F57557 (fig. 5B). The preserved portion of the basioccipital is relatively flat. The occipital condyle is ovoid in ventral view, about twice as wide as it is long. Two foramina lie within the ventral condyloid fossae. The anterior-most foramen, the hypoglossal foramen, is about half the size of the posterior foramen, the condylar foramen. These foramina lead to short canals which open posteriorly into the foramen magnum. Posterolateral to the condylar foramen, another round foramen is present. The posterior wall of the jugular foramen is present just anterolateral to the condylar foramen.

The description of the upper dentition is based on holotype QM F52816 and paratypes QM F19633, QM F19874 and QM F57557.

P2 is a plagiaulacoid-like tooth almost as wide as it is long (figs. 5C–E). In occlusal view, its lingual margin is steeper than its buccal margin, and the tooth is widest at about midlength. The occlusal ridge increases in height posteriorly. There are six cuspules present on the occlusal margin. Lingual and buccal transcristae are associated with the anterior five cuspules. The posterior cuspule is the largest and is much taller than the other cuspules on the occlusal ridge.

dP3 is molariform, and almost square in occlusal view (figs. 5C–E). The paracone is the tallest cusp, followed in decreasing order by the metacone, metastyle?, neometaconule, protocone and metaconule. There is no distinct anterior cingulum or precingulum. The preparacrista is almost horizontal as it runs from the paracone anteriorly. The postparacrista descends the posterior face of the paracone, and meets an anteriorly directed premetacrista from the metacone. No stylar cups are present on the buccal margin of the tooth. The protoloph runs from the protocone buccally, rising gently for the first half of its length and then steeply before contacting the paracone. The postprotocrista runs posterobuccally before curving posteriorly midway in the interloph valley, forming a mid-link contacting the anterior face of the metaloph. A large neometaconule is present midway along the metaloph, with an associated postlink descending the metaloph posteriorly. The postmetaconulecrista is posterobuccally directed before curving bucally to meet a distinctive cusp (metastyle?) at the posterobuccal corner of the tooth. The postmetacrista connects this cusp to the metacone anteriorly.

P3 is an elongate sectorial tooth approximately one and half times to almost twice the length of M1 (fig. 5I). In occlusal view, the tooth is widest midlength, with a distinctive kink, with the tooth narrowing just before the posterior-most cupule. There are nine cuspules on the crown, with the anterior eight having associated transcristae. The posterior-most cuspule is about twice the size of the anterior cuspules. The occlusal crest is straight and runs from the most anterior corner of the tooth through all cuspules to the posterior-most corner of the tooth. Both the lingual and buccal margins of the occlusal ridge are very steep, before reaching rounded lingual and buccal cingula. There are no distinct lingual or buccal cuspules or ridges on either side of the posterior-most cuspule, other than a slight inflation, more prominent on the lingual than buccal side.

M1 is relatively square in occlusal outline, only slightly wider anteriorly (figs. 5E, I). The paracone is the tallest cusp followed in decreasing order by the metacone, protocone and metaconule. The preparacrista is straight and runs anteriorly from the paracone to the anterior margin of the tooth. The postparacrista is straight and slopes directly posteriorly from the paracone apex to the interloph valley where it connects to a straight and steep premetacrista. In most specimens observed, a minute StC is present just buccal to the postparacrista, except in the holotype QM F52816 , QM F19634 , QM F19874 and QM F18948 , where this cusp is absent. The protoloph is short and steeply descends the lingual flank of the paracone until it meets the preprotocrista at about one third of its length from the protocone. The preprotocrista runs from the protocone anterobucally, and curves slightly more anteriorly where it meets the protoloph. An anterior cingulum is present anterior to the protoloph and is bordered by the preparacrista bucally and preprotocrista lingually. A short and low precingulum is present lingual to the preprotocrista. The postprotocrista descends posterobuccally from the protocone toward the interloph valley where it forms a distinct wall before connecting to the premetaconulecrista which connect posterolingually to the metaconule. The metaloph is parallel to the protoloph and descends the lingual flank of the metacone to connect to the low metaconule. The neometaconule is present midway along the metaloph, with an associated postlink or neometaconule crista which extends half way down the posterior face of the metaloph. The postmetacrista runs posteriorly from the apex of the metacone toconnectclosetothecrownbasewiththepostmetaconulecrista, which sweeps across the posterior face of the loph .

M2 is similar in morphology to M1 except as follows (figs. 5E, I): the tooth is slightly longer and wider anteriorly, increasing the length of all anterior cristae; the protoloph is taller and less steep; the anterior cingulum is longer; StC is absent; the precingulum is twice as wide as it is on M1; and the preparacrista is anterobuccally curved.

M3 is similar in morphology to M2 except as follows (fig. 5I): the tooth is smaller in all dimensions but more greatly reduced posteriorly; the precingulum is longer and wider, extending almost to the lingual corner of the tooth; the postparacrista and premetacrista are weak crests that do not meet in the interloph valley; and the neometaconule is greatly reduced to a small inflation on the posterior flank of the metaloph.

M4 is similar in morphology to M3 except as follows (figs. 5F–I): the tooth is further reduced in all dimensions; the protoloph does not connect to the preprotocrista; the postparacrista and premetacrista are barely visible; the metaloph does not connect to the metaconule, instead it is anterolingually orientated and meets the premetaconule crista just anterior to the metaconule; and the precingulum is larger and extends to the lingual corner of the tooth.

Description of the morphology of the dentary is based on paratypes QM F31549 and QM F19872, unless otherwise stated (fig. 6). The ventral margin of the horizontal ramus is slightly convex in buccal view. There is no distinct digastric eminence, but the ramus is at its tallest just below the anterior root of m3. The dorsal margin of the horizontal ramus is markedly concave posteriorly, resulting in posterior molars being elevated with respect to p3 and anterior molars. Anteriorly, the horizontal ramus decreases in height below p3, such that this tooth slants forward. Anterior to p3, the horizontal ramus is straight and constant in depth throughout the diastema. A distinct buccinator sulcus is present on the buccal margin of the dentary, and extends from level with the anterior of m1 to level with the middle of m2. A large ovoid anterior mental foramen is present just below the anterior root of p3, close to the dorsal edge of the diastema. No posterior mental foramen is present in the majority of the specimens observed, but a small posterior mental foramen is present in the juvenile QM F19606 (below the anterior root of m1), QM F57551 (below m2), and two to three posterior mental foramina are present in QM F57556 and QMF19819 (below m1 and m2). In lingual view, the symphysis is relatively smooth and extends posteriorly to the middle of p3. The ascending ramus is inclined at an angle approximately 125 degrees to the horizontal ramus. The masseteric fossa is buccally expanded. The masseteric canal is a large ovoid opening which projects anteriorly from the masseteric fossa to the level of the anterior of m3 and is confluent through the masseteric foramen with the dental canal for most of its length. The mandibular foramen is ovoid in shape and is posterobuccally orientated. The pterygoid fossa is wide and deep. The condyle is barrel-shaped.

Description of the morphology of the lower dentition is based on the least worn adult paratype QM F31549, and unworn juveniles QM F19606, QM F57554 and QM F57611.

The i1 is a short tear-shaped tooth, with a distinct dorsal enamel flange but less distinct ventral enamel flange (figs. 6A–C). The occlusal crest is slightly sinuous. Enamel is confined to the buccal surface of the tooth and extends further ventrally than dorsally. The crown is ovoid in cross-section.

The p2 is plagiaulacoid-like (figs. 6G–I). In lateral view, the occlusal margin is straight but steadily increases in height posteriorly. In occlusal view, the buccal margin is more convex and much less steep than the lingual margin. Four cuspids with associated buccal and lingual transcristids are present on the crown, anterior to a large posterior cuspid. Short cristids descend the crown anterior to the anterior-most cuspid and posterior to the posterior-most cuspid.

The dp3 is a molariform tooth, wider posteriorly than anteriorly, its anterior portion being elevated where it buttresses p2 (figs. 6G–I). The tallest cusp is the protoconid, followed in decreasing order by the entoconid, hypoconid, metaconid, paraconid and protostylid. The trigonid is narrow, with the paraconid, protoconid and metaconid in an almost linear formation, with a posterolingually directed crest running from anterior to the paraconid to posterior to the metaconid, ending at the base of the trigonid in the interlophid valley. A protostylid is present on the buccal margin of the trigonid, just buccal to the protoconid. There is a faint connection between the protoconid and protostylid (possibly due to wear), and another connection between the protostylid and cristid obliqua, which descends the posterior flank of the trigonid into the interlophid valley before ascending the talonid posterobuccally to the tip of the hypoconid. The posthypocristid descends the hypoconid posterolingually, and then curves anterolingually to connect to the postentocristid, which descends from the tip of the entoconid posteriorly. A preentocristid is present, descending the anterior flank of the entoconid to the interlophid valley. A crest runs from the tip of the entoconid buccally.

The p3 has a semilunar occlusal outline and is aligned with the molar row (figs. 6A–F). The occlusal edge lies lingual to the midline and is slightly lingually concave. In lateral view, the occlusal edge is straight and more elevated posteriorly. In the juveniles, nine cuspids are present on the occlusal edge, with the anterior eight cuspids having associated buccal and lingual transcristids, descending only halfway down the crown. In adults, cuspids and transcristids are obscured by heavy wear on the crown. The lingual flank of the tooth is nearly vertical while the buccal flank is less steeply sloping. A short cristid descends anteriorly from the anterior end of the occlusal margin and a much longer cristid runs from the posterior margin, curving to the lingual side of the crown base.

The molar row is straight in occlusal view but concave in lateral view. Molars are bunolophodont with central molars larger than terminal ones.

The m1 is similar to dp 3 in morphology except as follows (figs. 6A–I). The tooth is larger in length and width. The hypoconid is the tallest cuspid followed by the entoconid, metaconid, protoconid and paraconid in juveniles. In the adult QM F31549, buccal cupids are worn well below the level of lingual cuspids, with the metaconid being the tallest cuspid followed by entoconid, protoconid, hypoconid and paraconid (also seen on m2 and m3). The protostylid is absent. The trigonid is wider with the protoconid more buccally placed, forming a 45 degree angle with the paraconid and metaconid. A precingulid is present buccal to the paraconid, and an anterior cingulid occurs on its lingual side. Both the precingulid and anterior cingulid are bordered anteriorly by a crest which runs from the anterobuccal corner of the tooth to the anterior flank of the metaconid, through the paraconid. The sinuous protolophid descends buccally from the metaconid before connecting to the protoconid. The cristid obliqua connects the protoconid to the hypoconid via the interlophid. The buccal crest from the entoconid, the hypolophid, is taller and loph-like and almost reaches the posthypocristid posteriorly. In the adult QM F31549, the buccal side of the tooth is so worn that the hypolophid looks as if it was connected to the hypoconid (also seen on m2 and m3).

The m2 is similar in morphology to m1 except as follows (figs. 6A–I). The tooth is larger in all dimensions. The protoconid is the tallest cusp, followed in decreasing order by the hypoconid, entoconid, metaconid and paraconid. The precingulid and anterior cingulid are larger. A premetacristid is present, connecting the metaconid to the anterior crest bordering the precingulid and anterior cingulid. Both the protolophid and hypolophid are taller.

The m3 is similar in morphology to m2, apart from it being longer and wider, with all cuspids taller and crests longer (figs. 6A–F).

The m4 is similar in morphology to m3 except as follows (figs. 6A–F). The tooth is smaller in all dimensions. The talonid is greatly reduced, especially the entoconid and the hypolophid, which are half the size and length of that of m3.

Figures

Figure 4. Gumardee springae sp. nov., holotype QM F52816, partial juvenile skull with left loose P2, dP3, left and right P3 in crypt, M1-3 and associated left maxilla with dP3, P3 in crypt, M1-3: A, dorsal, and B, ventral views. Scale bar equals 10 mm.

Figure 5. Gumardee springae sp. nov., paratype QM F57557, partial juvenile skull with left and right P2, dP3, M1-2: A, dorsal view of neurocranium; B, ventral view of basioccipital, occipital condyle and supraoccipital; C, buccal, D, lingual, and E, occlusal (stereopair) views of palate; paratype QM F19874, right M4: F, buccal, G, lingual, and H, occlusal (stereopair) views; QM F19633, left maxilla with P3, M1-4: I, occlusal (stereopair) view. Scale bar equals 10 mm.

Figure 6. Gumardee springae sp. nov., paratype QM F31549, right dentary with i1, p3, m1-4: A, buccal, B, lingual, and C, occlusal (stereopair) views; paratype QM F19872, left dentary with p3, m1-4: D, buccal, E, lingual, and F, occlusal (stereopair) views; paratype QM F19606, right juvenile dentary with p2, dp3, p3 in crypt, m1-2: G, buccal, H, lingual, and I, occlusal (stereopair) views. Scale bar equals 10 mm.