Gumardee richi, 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 : 193-197

Gumardee richi sp. nov.

Holotype. QM F57631 , partial left juvenile maxilla with P 3 in crypt, dP2-3 and M1-2.

Paratypes. QM F24723 , left juvenile dentary with broken i1, p2, dp3, m1, m 3 in crypt ; QM F36313 , partial juvenile right dentary with m1-2 ; QM F57632 , left maxilla with M1-4 .

Additional material. QM F30698, left dentary with m2, m 4 in crypt; QM F30875, left dentary with m1-3.

Diagnosis. Gumardee with five cuspules on P2, StC present on M2-3, eight lingual and buccal transcristae on the occlusal margin of P3, shallow buccinator sulcus, postprotocrista not connected to the metaconule on any upper molars, metaloph joins metacone to metaconule on M4, and the posthypocristid is tall, joined to the entoconid, forming an almost complete hypolophid on all lower molars and dp3.

Etymology. Named after Dr Thomas H. Rich, vertebrate palaeontologist and senior curator at Museum Victoria, for his long and significant contribution to Australian palaeontology.

Age and distribution. All specimens are from Dirk’s Towers Site, except for paratype QM F24723 which is from Quantum Leap Site. Dirk’s Towers and Quantum Leap Sites are on D-Site Plateau, Riversleigh World Heritage Area, north-western Queensland, Australia (18°15'35"S, 138°06' 41"E) and are part of Faunal Zone B (interpreted to be early Miocene in age) as distinguished by Archer et al. (1989), Archer et al. (1997), Arena (2004), Travouillon et al. (2006) and Travouillon et al. (2011).

Description. P2 is ovoid in shape in occlusal view, and almost as wide as it is long (figs. 2A–C). There are five cuspules on the occlusal margin. The anterior four cuspules have associated lingual and buccal transcristae. The posterior-most cuspule is the largest. The occlusal margin is straight, but increases in height posteriorly. The lingual margin of the tooth is steeper than its buccal margin.

The dP3 is molariform but with rounded edges in occlusal view (figs. 2A–C). The paracone is the tallest cusp on the crown, followed in decreasing order by the metacone, neometaconule, metaconule and protocone. The preparacrista is straight and descends the anterior face of the paracone. On its lingual side, a steep but short anterior cingulum is present. The postparacrista descends the posterior face of the paracone to meet in the interloph valley an anteriorly directed premetacrista from the metacone. There are no stylar cusps on the buccal margin of the tooth. The protoloph runs bucally from the protocone, rising gently for the first half of its length, then steeply to ascend the tall paracone. The postprotocrista is a weak crest that runs posterobuccally from the protocone and ends in the interloph valley. The metaloph connects the metacone to the metaconule via a large neometaconule, present midway with an associated postlink descending the metaloph posteriorly. The postmetaconulecrista is posterobuccally directed before curving bucally to meet the postmetacrista.

P3 is in its crypt with only the anterior and lateral sides visible (figs. 2A–B). There are 8 transcristae visible on the buccal and lingual sides of the crown. The tooth is as long as the combined length of P2 and dP3 and widest anteriorly at approximately one third its length. It narrows distinctively level with the 7 th and 8 th transcristae. A narrow cingulum is present on the lingual side of the crown. A tall posterolingual crest is present.

M1 is trapezoidal in occlusal outline, with its anterior portion wider than its posterior portion (figs. 2A–F). The paracone is the tallest cusp followed in decreasing order by the metacone, neometaconule, metaconule, protocone and StC. The molar is lophodont, having a fully formed metaloph (connecting metacone to metaconule) but an underdeveloped protoloph, which does not connect to the protocone. The preparacrista descends the paracone anteriorly before curving lingually and joining an anterobuccally directed preprotocrista from the protocone. An anterior cingulum is present between these two crests and the protoloph. No precingulum is present. StC is a gentle inflation on the buccal side of the crown. The postparacrista is straight and descends the posterior face of the paracone before ending in the interloph valley. The postprotocrista runs posterobuccally from the protocone toward the interloph valley before posteriorly ascending half way up the anterior flank of the metaloph. No distinct premetacrista is present. The metaloph is approximately twice the length of the protoloph and parallel to it. A neometaconule and associated postlink are present midway along the length of the metaloph. The postmetaconulecrista and postmetacrista connect at the posterior margin of the crown.

M2 is similar in morphology to M1 except as follows (figs. 2A–F): the tooth is wider anteriorly; the protoloph is longer; the anterior cingulum is wider; a small precingulum is present just lingual to the preprotocrista; the protocone and metaconule are taller.

M3 is similar in morphology to M2 except as follow (figs. 2D–F): the dimensions of the tooth are reduced both in length and width, especially posteriorly; the postparacrista is more posteriorly orientated; the precingulum is wider; StC and the neometaconule are reduced.

M4 is similar in morphology to M3 except as follow (figs. 2D–F): the tooth is smaller in all dimensions and the posterior cusps and posterior width of the tooth are highly reduced; the anterior cingulum and precingulum are wider; the postparacrista and premetacrista are more buccally directed; StC is absent; the postmetacrista and postmetaconulecrista are shortened; there is no neometaconule or postlink on the reduced metaloph.

Description of the morphology of the dentary and lower dentition are based on QM F24723, QM F30698and QM F36313 (fig. 3).

In buccal view, the ventral margin of the horizontal ramus is lightly convex with no distinct digastric eminence (figs. 3A–B). The dorsal margin of the horizontal ramus is markedly concave posteriorly, resulting in posterior teeth being higher than anterior teeth. The horizontal ramus decreases in height anteriorly below p2, so that this tooth slants forward. Two mental foramina are present; one large below the anterior root of p2 and one small below m1. The small posterior mental foramen is more posteriorly positioned in adults, below m2. A distinct buccinator sulcus is present on the buccal margin of the dentary. In lingual view, the symphysis is relatively smooth and extends as far posteriorly as the posterior of dp3. The ascending ramus is inclined at an angle approximately 125 degrees from the horizontal ramus. The masseteric canal is a large ovoid opening which projects anteriorly to below the anterior molars. It is confluent through the masseteric foramen with the dental canal for most of its length. The mandibular foramen is ovoid and posterobuccally orientated.

The i1 is partially preserved. It is a tear-shaped tooth with distinct dorsal and ventral enamel flanges (figs. 3A–C). Enamel is confined to the buccal surface of the tooth. An alveolus for i2 is present posterior to i1, but this tooth is not preserved.

The p2 is plagiaulacoid-like with the occlusal surface, in lateral view, straight but steadily increasing in height posteriorly (figs. 3A–C). In occlusal view, the buccal margin is more convex and much less steep than the lingual margin. Five 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. 3A–C). The tallest cusp on the crown is the protoconid, followed in decreasing order by the metaconid, entoconid, paraconid, hypoconid 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, and 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 wear facet connecting the protoconid and protostylid and a distinct ridge connecting the protostylid to the 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 ascends the posterobuccal flank of the entoconid. There is no distinct postentocristid. A crest runs from the tip of the entoconid buccally. A preentocristid is present, descending the anterior flank of the entoconid to the interlophid valley.

The m1 is similar to dp 3 in morphology except as follows (figs. 3A–F). The tooth is larger in length and width. The entoconid is the tallest cuspid followed by the metaconid, hypoconid, protoconid and paraconid. 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 is present 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. A premetacristid is present, connecting the metaconid to the anterior crest bordering the precingulid and anterior cingulid. 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 posthypocristid is lower and connects to a postentocristid. The buccal crest from the entoconid is more developed but ends below the entoconid buccally.

The m2 is similar in morphology to m1 except as follows (figs. 3D–F). The tooth is larger in length and width. The protoconid is the tallest cusp, followed in decreasing order by the hypoconid, metaconid, entoconid and paraconid. The precingulid and anterior cingulid are wider. Both the protolophid and posthypocristid are taller.

The m3 is similar in morphology to m2 except as follows (figs. 3A–F). The tooth is longer and wider, with all cuspids taller and crests longer.

The m4 is only preserved in its crypt in QM F30698, with its morphology obscured.