Protemnodon dawsonae, Kerr & Camens & Van Zoelen & Worthy & Prideaux, 2024

Kerr, Isaac A. R., Camens, Aaron B., Van Zoelen, Jacob D., Worthy, Trevor H. & Prideaux, Gavin J., 2024, Systematics and palaeobiology of kangaroos of the late Cenozoic genus Protemnodon (Marsupialia, Macropodidae), Megataxa 11 (1), pp. 1-261 : 156-169

Protemnodon dawsonae sp. nov.

LSID of new species: urn:lsid:zoobank.org:act:231A7C0D-FF39-458E-8703-1AF7B6FBCE77

Protemnodon devisi Bartholomai ; Bartholomai (1973) pl. 22, fig. 3. Not P. devisi, Bartholomai, 1973 .

Protemnodon sp. cf. devisi ; Dawson et al. (1999) pp. 276–278, fig. 7.

Holotype: AM F161915 R partial cranium, preserving M1–4, maxilla, and partial lacrimal, frontal, palatine, and jugal. Collected on an excavation at Big Sink by Prideaux and Fusco et al. in 2016.

Type locality:

Big Sink doline, Bone Cave–Phosphate Mine system, Wellington Caves (32°36’ S, 148°55’ E), central eastern New South Wales. The Big Sink unit is made up of pale red-orange, consolidated sediments on the southern wall of the Big Sink doline ( Osborne 1997). Though the deposit has not been dated directly, biochronology and biocorrelation with dated assemblages suggest a Pliocene age for the Big Sink LF ( Dawson et al. 1999).

Paratypes:

Big Sink doline: AM F69835 partial L premaxilla, with I1–I3; AM F69836 L premaxilla fragment; AM F69838 L I1; AM F69839 R I1; AM F69840b partial L maxilla; AM F69841 partial L maxilla; AM F69845 partial R maxilla; AM F69842 L P3; AM F69844 L P3; AM F161923 L P3; AM F69858 & AM F65859 partial LR dentaries (reassociated); AM F69860 partial L dentary; AM F69868 L i1; AM F69869 R i1; AM F161921 R dentary fragment; AM F161920 partial axis vertebra; AM F161914 partial axis vertebra; AM F161918 partial lumbar vertebra L2?; AM F161911 caudal vertebra Ca2?; AM F161912 caudal vertebra Ca3?; AM F161919 ilial fragment; AM F161913 partial R calcaneus; AM F161917 partial L metatarsal IV; AM F109039 R metatarsal IV; AM F106040 L metatarsal V; AM F161916 proximal pedal phalanx IV.

Referred specimens:

South Australia

Stirton Quarry, Lake Kanunka: SAMA P50399 partial juvenile R maxilla with P3 from crypt; UCMP 322655 R P3.

Site 4 (V77015), Lake Kanunka: UCMP 170678 m 4; UCMP 156881 R ilium, partial pubis and ischium.

Queensland

Sand Scree Locality, Chinchilla: QM F7071 partial L dentary.

Chinchilla, Darling Downs (site unknown): QM F4712 partial juvenile L maxilla.

Specific diagnosis:

Protemnodon dawsonae sp. nov. is differentiated from all other species of Protemnodon by one dental autapomorphy and a unique combination of dental and postcranial attributes. The upper dentition of P. dawsonae sp. nov. differs from that of all species of Protemnodon in having upper molars with the postparacrista distinctly inflected lingually then buccally (‘kinked’) in the interloph valley. The i1 of P. dawsonae sp. nov. differs from all species of Protemnodon except P. tumbuna in having a thick, low ventrolingual crest on the i1.

The dentary and dentition of P. dawsonae sp. nov. are most similar to those of P. otibandus , P. mamkurra sp. nov. and P. viator sp. nov. The dentary of P. dawsonae sp. nov. cannot be differentiated from that of P. mamkurra sp. nov. or P. viator sp. nov., but it differs from P. otibandus in having a taller, more robust anterior dentary, particularly around the i1. The dentition further differs from that of P. otibandus in having: a broader, anteroposteriorly shorter I1; relatively larger, broader and more robust i1; and a broader p3 relative to length. It further differs from that of P. mamkurra sp. nov. and P. viator sp. nov. in being lower crowned, with: I1 absolutely narrower and narrower relative to I3; and upper molars with a narrower protoloph relative to the loph base when unworn, and a thinner, more raised preparacrista.

The upper dentition of P. dawsonae sp. nov. differs from that of P. snewini in having: relatively broader P3; and molars with a higher, more distinct preparacrista. The dentary differs from that of P. snewini in being larger and more robust, with: a more robust and more dorsally deflected diastema, and a taller mandibular corpus. The lower dentition differs from that of P. snewini in being larger and higher crowned, with: broader, more robust i1; relatively broader p3; and relatively broader molars with a smaller precingulid.

The postcranial skeleton of P. dawsonae sp. nov. is most similar to that of P. mamkurra and P. viator . The proximal phalanx IV of P. dawsonae differs from those of all species of Protemnodon except P. viator sp. nov. in having a more proximodorsally extensive distal articular surface. Its axial skeleton is differentiated from P. mamkurra sp. nov. by having: a relatively narrower, deeper axis vertebra; lumbar vertebrae with deeper transverse processes and a centrum with relatively slightly broader cranial and caudal extremities, more deeply concave ventrolateral surfaces, a more deeply concave ventral margin in lateral view, and a less raised ventral ridge. The hindlimb differs from that of P. mamkurra sp. nov. in having a pelvis with a relatively smaller caudal iliac spine, less deeply concave gluteal fossa, and a less convex, less rugose caudal margin of the dorsal section of the ischium. The pes differs in having: a relatively taller, narrower calcaneus with a caudally displaced medial talar facet relative to the lateral talar facet and a sustentaculum tali with a rounded (rather than pointed) cranioplantar peak; metatarsal IV with a smaller plantar cuboid facet; and narrower metatarsal V with a more distally extensive lateral plantar tuberosity.

The axial skeleton of P. dawsonae sp. nov. is distinguished from that of P. viator sp. nov. in having: a narrower axis vertebra with a thinner spinous process, more laterally tilted postzygopophyses with less concave articular surfaces, and a rounded (rather than bilobed) ventral margin of the caudal extremity of the centrum; and shorter, more robust caudal vertebrae. The hindlimb differs from P. viator sp. nov. in having a pelvis with a less deeply concave gluteal fossa. The pes of P. dawsonae sp. nov. differs from that of P. viator sp. nov. in having: a broader, dorsoplantarly shorter calcaneus with a more rounded calcaneal tuberosity in cross-section, less deep lateral talar facet, broader medial talar facet, and a more medially projected sustentaculum tali; relatively broader, dorsoplantarly shorter metatarsal V with a more elongate proximolateral process and a more proximally projected medial plantar tubercle; and a more robust proximal phalanx IV with a weaker waist.

The pes of P. dawsonae is distinguished from that of P. otibandus in having: a calcaneus with a less medially displaced head and a narrower calcaneal tuberosity; metatarsal IV with continuous dorsal and plantar cuboid facets, a more concave, less laterally projected metatarsal V facet, larger plantar tubercle, more raised plantar ridge, and a relatively more plantarly projected keel; a more elongate metatarsal V, with a narrower, less dorsally projected cuboid facet; and a more elongate proximal pedal phalanx IV.

Etymology:

Named for Dr Lyndall Dawson, for her contributions to the study of macropodid systematics and the Big Sink assemblage.

Description and comparisons:

Cranium and dentition

Cranium ( Fig. 91d ): jugal has a quite large, slightly posteriorly deflected and laterally projected masseteric process, with morphology very similar to that of P. mamkurra sp. nov. Ventral margin of the orbit is dorsally displaced relative to the maxillary shelf. Maxillary foramen small and round, opens posteriorly. Pterygoid is elongate. No vacuities are present on the preserved section of the palate.

The known portion of the cranium of P. dawsonae sp. nov. differs from that of C. kitcheneri and W. bicolor in having a higher maxillary shelf relative to the position of the base of the masseteric process, and a higher ventral margin of the orbit with a less laterally projected lip.

Upper dentition ( Figs 91 & 92 ): I1: robust, broad and arcuate. Enamel covers the anterior, buccal, and lingual surfaces, and is removed from the sides of the posterior surface by a small amount of wear. Occlusal surface broad and roughly rectangular in slightly worn specimens, becomes longer and rounder with increased wear. I2: arcuate, relatively small and narrow. Enamel covers the buccal and lingual surfaces, with the lingual enamel removed only by very extensive wear. Small posterobuccal crest is removed by a small amount of wear, leaving a slight concavity on buccal surface. I3: elongate, transversely compressed and trapezoidal to roughly triangular in buccal view; buccal enamel convex, buccal length greater than the width of I1 ( Fig. 91a ). Main crest curves anterolingually to sit lingual to the posterior margin of the similarly shaped anterobuccal crest. Anterobuccal crest is around half the length of the main crest.

Cheek tooth row is straight to very slightly curved in adults. DP2: morphologically very similar to P3 but anteroposteriorly truncated; oblong, quite short and broad, broadens posteriorly, with thickened peaks over the anterior and posterior roots linked by the main crest. Main crest high, blade-like, anteroposteriorly to slightly posterobuccally orientated, jagged to gently undulating in buccal view, with a low, dorsoventrally aligned ridgelet on the midpoint of the buccal surface. Lingual crest low, extends from the lingual base of the anterior cusp to the small, secondary posterolingual peak; lingually borders a broad, anteriorly tapering lingual basin with a low transecting ridgelet. Posterior basin small, abuts the posterior margin, sits between the main and secondary posterior peaks; removed by a small amount of wear. DP3: molariform, fairly broad; anterior loph longer and narrower than the posterior loph; lingual bases of lophs swollen; interloph valley width subequal to that of lophs. Precingulum and cristae worn to absence in sole available specimen.

P3: large, oblong and quite elongate, generally slightly broader posteriorly, with thickened peaks over the anterior and posterior roots linked by the main crest; straight to curving very slightly buccally toward the posterior, with posterior section very slightly rotated and swollen buccally, contributing to occasional slightly crescentic shape of the tooth. Main crest high, blade-like and roughly anteroposteriorly orientated with occasional very slight posterobuccal curvature in occlusal view; slightly jagged to gently undulating in buccal view; three dorsoventrally aligned ridgelets on the buccal surface, posterior ridgelets lower, with anteriormost ridgelet typically more raised and angular; in some specimens, small buccal ridgelets form enamel crenulations at the buccal base of the main crest ( Fig. 92g ). Anterior peak quite tall, forms a rounded point; peak intersected by a very brief transverse crest, perpendicular to main crest, extends down buccal and lingual faces as a low ridgelet on posterior margins of anterior cusp, with lingual ridgelet merging into the anterior margin of the lingual crest; small, blunted cusp present at the anterior base, often lingually situated. Lingual crest low, undulating in lingual view, with a single low, smoothly rounded peak near the anterior margin; crest extends posteriorly, from or slightly posterior to the lingual base of the anterior cusp, to merge into the posterolingual peak; lingually borders a broad lingual basin, which is perpendicularly transected by three very low, indistinct ridgelets, roughly opposing the buccal ridgelets. Posterior cuspule broad and posteriorly rounded. Main posterior peak quite tall and rounded, continuous with the main crest, which extends and broadens posteriorly to merge with the low transverse posterior crest. Posterolingual peak rounded, lower than the main peak, linked to the main crest by a thin transverse crest that anteriorly borders the posterior basin. A small posterior basin sits between the main and posterolingual peaks, posteriorly bordered by the transverse posterior crest; removed by a small amount of wear.

Molars: rounded-rectangular in occlusal view, with M1 and usually M2 more rounded than the posterior molars. Precingulum quite broad, slightly narrower than the anterior loph, gently medially tilted, extends from the anterior base of the preparacrista to adjacent to the anterolingual margin; generally becomes slightly larger, broader and more projected toward M4; flat, broad and shelf-like when worn; some specimens (see SAMA P50399) have a small preprotocrista extending very briefly up the anterior of the protoloph from around the midpoint of the precingulum. Preparacrista quite thin but distinct and straight, continuous with the buccal margin of the precingulum and extending to the paracone. Postparacrista thin, raised and distinctly kinked, extends straight posteriorly from the paracone before twisting strongly lingually near the base of the interloph valley and proceeding nearly to the end of the postprotocrista in the lingual valley ( Fig. 92c–d ). Postprotocrista broad and quite straight, extends from protocone to around the midpoint of interloph valley; in most specimens, the postprotocrista extends onto the anterior face of the metaloph. Premetacrista slight, extends from metacone to meet base of postparacrista in interloph valley Postmetaconulecrista quite thick and raised, arises from metaconule and curves dorsobuccally to almost beneath metacone to form moderate oblique shelf beneath posterior basin. Postmetacrista lower, shorter and less distinct, extends straight from metacone to buccal margin of postmetaconulecrista or deflects slightly lingually to merge into buccal margin of posterior basin.

The upper dentition of P. dawsonae sp. nov. differs from that of all other species of Protemnodon in having the postparacrista distinctly inflected lingually then buccally in the interloph valley. It further differs from P. anak in having larger P3 with lower, less distinct buccal and lingual ridgelets and a less jagged, more smoothly undulating and more anteriorly extensive lingual crest, and relatively broader molars with a narrower protoloph relative to the protoloph base when unworn; from P. mamkurra sp. nov. and P. viator sp. nov. in having I1 narrower relative to I3, P3 with slightly more raised and distinct buccal ridgelets, and molars with a thinner, more raised and more distinct preparacrista and a narrower protoloph relative to the loph base when unworn; additionally differs from P. mamkurra sp. nov. in having relatively narrower posterior molars; from P. tumbuna in being larger and slightly higher crowned, with I1 lacking posterobuccal bulge, and generally less rounded molars in occlusal view with a more raised, more distinct preparacrista and lacking a urocrista; from P. otibandus in being generally larger, with broader, anteroposteriorly shorter I1 lacking a posterobuccal bulge and molars lacking a urocrista; from P. snewini in being larger, with relatively broader P3 and molars with a higher, more distinct preparacrista; from C. kitcheneri in being larger and higher crowned, with larger incisors relative to size of cranium and an absolutely and relatively more elongate P3; and from W. bicolor in being much larger, and higher crowned, with P3 with a higher lingual crest and a larger posterior basin, and molars with a thicker postprotocrista distinctly extending to the protocone (rather than merging into the centre of the posterior surface of the protoloph).

Dentary ( Fig. 93a–d ): robust, moderately tall, and gently transversely compressed, with a long, robust and gently tapering anterior dentary ventral to the diastema, projected straight anteriorly or slightly deflected dorsally ( Fig. 93a ). Angle between the dentaries at the mandibular symphysis is ~35–40°. Mandibular symphyseal plate large and elongate, extends along the entirety of the anterior dentary to abut the posterior margin of i1. Mental foramen round to oval, opens dorsolaterally to anterodorsolaterally, located roughly one-fifth of distance from dp2/p3 to i1 and around one-quarter of distance from the diastema to the ventral margin. Mandibular corpus height generally subequal below p3 and m4, with the width at a minimum ventral to m1 and increasing gently posteriorly. Digastric sulcus shallow and broad, extends from beneath the posterior of the molar row to adjacent to the anteroventral margin of the medial pterygoid fossa. Buccinator sulcus distinct but quite shallow, extends along the buccal surface of the mandibular corpus with a slight ventral tilt posteriorly, slightly ventral to the three–four anteriormost cheek teeth.

The dentary of P. dawsonae sp. nov. cannot be differentiated from that of P. mamkurra sp. nov. It differs from that of P. anak in being slightly broader and more robust, with a more dorsally deflected diastema; from P. viator sp. nov. in being generally slightly smaller; from P. tumbuna in being larger, with a more dorsally situated mental foramen; from P. otibandus in being slightly more robust, particularly in the diastema; from P. snewini in being larger and more robust, with a more robust and more dorsally deflected diastema and a taller mandibular corpus; from C. kitcheneri in being larger and more robust, with a relatively shorter, more dorsally deflected diastema, more posteroventrally situated mental foramen, and a taller mandibular corpus; and from W. bicolor in being much larger, with a more dorsally deflected diastema.

Lower dentition ( Fig. 93c–h ): i1: procumbent and slightly dorsally deflected; broad, tilted dorsally and transversely compressed; acuminate when unworn, becomes shorter and rounder in cross-section with wear. Thick enamel completely covers the buccal surface. Dorsobuccal and ventrolingual crests low and thick ( Fig. 93e ). Enamel covers the ventral third of the lingual surface and tapers posteriorly.

p3: very similar in morphology to that of P. mamkurra sp. nov. and P. viator sp. nov.; oblong and elongate in occlusal view, typically with a slight waist; typically subequally broad across posterior and anterior moieties; tall and triangular in cross-section with bulging buccal and lingual bases. Anterior cuspid has a dorsoventrally aligned buccal and lingual ridgelet on posterior margin. Main crest linear, anteroposteriorly aligned and twists slightly lingually over the posterior root. Both surfaces of the main crest with two or three low, rounded, indistinct, roughly dorsoventrally aligned ridgelets extending to the peak of the crest, such that the crest appears slightly undulating in buccal view.

Molars: high-crowned, broad and rounded in occlusal view, with interlophid valley varying from slightly broader to slightly narrower than the lophid bases; when unworn or slightly worn, protolophid and hypolophid are posteriorly convex or have an oblique mesial kink toward the posterior in occlusal view; buccal margins of the lophids are slightly more convex than the lingual margins in posterior view. Precingulid narrow, anteriorly projected, usually forms a rounded corner; a slight raised lip is present around the anterior margin when unworn. Paracristid quite thick and raised; lingual component arises from the anterolingual edge of the trigonid basin, extends buccally then straight posteriorly before the buccal component ascends, curving gently buccally, to the protoconid; the degree of buccal curve and thickness increases with molar wear. Protoconid higher than the metaconid and slightly lingually displaced. Cristid obliqua thick and low, mostly contributed by the talonid; arises slightly buccal to the midpoint of the interlophid valley, curves very slightly buccally and extends to the hypoconid. Preentocristid absent to very low, broad and indistinct, arises midway between the base of the cristid obliqua and the lingual extremity of the interlophid valley and deflects slightly lingually to meet the entoconid. When unworn, the hypoconid is distinctly taller than the entoconid and sits slightly buccal of the midline of the tooth. Postcingulid narrow and slight on m1–m2, becomes broader and occasionally shelf-like in m3 and particularly in m4.

The lower dentition of P. dawsonae sp. nov. differs from that of all compared taxa except P. mamkurra sp. nov. and P. viator sp. nov. in having a lower, thicker ventrolingual crest on i1. It further differs from P. anak in being slightly larger, with a more robust i1, and p3 with lower, less distinct ridgelets on the main crest and generally relatively broader molars; from P. mamkurra sp. nov. and P. viator sp. nov. in being generally smaller and slightly lower crowned, with a ventrolingual crest present on i1; from P. tumbuna sp. nov. in being larger and higher crowned, with relatively broader p3, and narrower molars with less convex buccal margins of lophids; from P. otibandus in being generally larger, with larger, broader and more robust i1 and relatively broader p3; from P. snewini in being larger and higher crowned, with broader, more robust i1, relatively broader p3,and relatively broader molars with a smaller precingulid; from C. kitcheneri in being larger and higher crowned, with broader and more spatulate i1, relatively broader deciduous premolars, absolutely more elongate p3 that is longer relative to molar length, and molars with narrower lophid crests, higher cristid obliqua and a postcingulid present; and from W. bicolor in being much larger, with broader, more spatulate i1, p3 with less raised and distinct ridgelets on the main crest, and molars with narrower lophid crests and a generally more anteriorly prominent precingulid.

Axial skeleton

Axis (C2) ( Fig. 94a–e ): moderately craniocaudally short, quite broad and robust. Dens short, blunt and gently dorsally deflected. Cranial articular surfaces broad and convex; angled laterally and slightly dorsally.Arch mostly crushed or absent in available specimens; appears thick and quite low. Vertebral canal roughly oval and gently domed. Spinous process crushed and caudally abraded, appears quite tall, thin and tilted slightly cranially, with gently convex dorsal margin and cranial extremity projecting past cranial margin of arch. Postzygopophyses fairly small and flared slightly laterally, caudally projected beyond caudal extremity of the centrum and subequally to the caudal extremity of the transverse processes; articular surfaces very slightly concave and facing caudoventrally, with a moderate lateral tilt. Transverse processes quite thick and long, with a strong caudal and slight ventral deflection. Ventral surface of the centrum broad, with a slightly raised medial ridge. Caudal extremity of the centrum incompletely preserved; gently caudally and ventrally projected and slightly dorsally tilted, with a rounded ventral margin.

The axis vertebra of P. dawsonae sp. nov. differs from that of P. anak in being relatively and absolutely much less elongate, with a less elongate, slightly more dorsally deflected dens, dorsoventrally shorter, slightly more convex cranial articular surfaces, much less caudally projected caudal extremity of the centrum, and smaller, less elongate postzygopophyses; from P. mamkurra sp. nov. in being deeper relative to width, with the caudal extremity of the centrum more caudally projected; from P. viator sp. nov. in being smaller and narrower, with a thinner spinous process, more laterally tilted postzygopophyses with less concave articular surfaces and a rounded (rather than bilobed) ventral margin of the caudal extremity of the centrum; from C. kitcheneri in being broader relative to length, with a lower mesial ventral ridge, more laterally tilted caudal articular surfaces, and a relatively larger, broader caudal extremity of the centrum; from O. rufus in being relatively slightly shorter and broader, with a less dorsally deflected dens and the dorsal margin of the spinous process rounded and convex (rather than level); from M. fuliginosus in being larger, with a slightly more convex dorsal margin of the spinous process, longer, more ventrally deflected transverse processes, less laterally flared, slightly more caudally projected postzygopophyses, and a more ventrally projected caudal extremity of the centrum; and from W. bicolor in being larger, with a more rounded dens and more lateral facing cranial articular surfaces.

Lumbar vertebrae (L2?) ( Fig. 94f–g ): robust; centrum short and broad, narrows to a waist; ventrolateral surfaces concave and laterally tilted, with the ventral margin concave in lateral view. Cranial extremity of the centrum gently convex and rounded with a flattened dorsal margin, slightly taller than the caudal extremity. Caudal extremity of the centrum gently concave and broadly rounded with a flattened dorsal margin. Vertebral canal quite low, broad and domed in cranial view. The prezygopophyses and spinous process are completely abraded. Transverse processes mostly abraded; bases highly dorsoventrally compressed, ventrally deflected and situated on the cranial part of the lateral surfaces. Postzygopophyses almost entirely abraded, bases appear thickened and robust. The base of a small anapophysis is present on the arch ventrolateral to the base of the postzygopophysis; transversely compressed and slightly caudally deflected, with a low ridge extending cranially from the base.

The L2? of P. dawsonae sp. nov. differs from that of P. mamkurra sp. nov. and P. viator sp. nov. in being smaller, with deeper transverse processes and a centrum with relatively lower, broader cranial and caudal extremities, more concave ventrolateral surfaces, more concave ventral margin in lateral view and a less raised ventral ridge; from C. kitcheneri in being relatively slightly longer; from O. rufus in being slightly larger, with a broader centrum relative to height and relatively deeper transverse processes; from M. fuliginosus in being larger, with less dorsoventrally compressed cranial and caudal extremities of the centrum and a more concave ventral margin in lateral view; and from W. bicolor in being much larger, with a centrum having a less distinct waist in ventral view and a less ventrolaterally swollen caudal section.

Caudal vertebrae (Ca2 & 3?) ( Fig. 95a–c ): numerical position of the vertebrae is not certain; vertebrae short and robust. Pre- and postzygopophyses heavily abraded in available specimens; prezygopophyses have a thick proximal section that is slightly dorsoventrally compressed and dorsally deflected; postzygopophyses short, robust and caudolaterally projected, with articular surfaces small, flat and round; bases of pre- and postzygopophyses merge at the centre of the arch around the base of the spinous process. Centrum shallow, slightly arched in lateral view, with ventrally tilted cranial and caudal extremities; cranial extremity rounded; caudal extremity slightly dorsoventrally compressed and oval, with that of Ca2 slightly ventrally projected relative to the cranial extremity. Vertebral canal low and broad in Ca2; very low in Ca3. Transverse processes very deep in C2, extend from adjacent to the cranial margin of the centrum to adjacent to the caudal margin, dorsoventrally very thin, particularly cranially, caudally deflected, quite broad cranially and steadily broaden caudally; very abraded in Ca3, extend from slightly cranial of the midpoint of the centrum to abut the caudal margin with some caudal deflection.

The Ca2? and 3? of P. dawsonae sp. nov. differ from those of P. mamkurra sp. nov. and P. viator sp. nov. in being smaller; from C. kitcheneri in being more elongate, with more laterally deflected prezygopophyses; from O. rufus in having Ca2 broader and taller relative to length; from M. fuliginosus in being larger, more robust and in having Ca3 slightly taller relative to length; and from W. bicolor in being larger, with more laterally deflected prezygopophyses.

Hindlimb

Pelvis ( Fig. 95d–f ): ilium robust, quite well-developed and roughly L-shaped in cross-section. Iliac crest epiphysis is not known; ilium gently increases to its maximum width at the iliac crest. Iliac fossa shallow craniomedial to the rectus tubercle, becomes shallower dorsally along the cranioventral surface of the ilium; extends around three-quarters of the length of the ilium. Gluteal fossa broad and moderately concave, particularly around the midpoint; extends to the iliac crest. Caudal iliac spine arises on the medial surface of the base of the ilium, opposite the rectus tubercule, thickens and rises rapidly, extends to the iliac crest; thick and deep ventrally for the origin of a large mm. gluteus, steadily becomes thinner and slightly shallower distally. Sacral surface large, very rugose and concave; articular surface for the wings of the sacrum deep and shelf-like with a strong cranial tilt; cranial margin of the sacral surface projects cranially in a broad, low ridge with a slight crest (cranial iliac spine) and contributes to the depth of the iliac fossa. Lateral iliac spine very broad, thin relative to the caudal spine; lateral margin slightly concave and curving laterally. Rectus tubercule quite rugose, roughly triangular, narrows strongly onto the lateral spine.

Acetabulum quite large, dorsoventrally tall and concave, taller than the craniocaudal depth, due chiefly to an enlarged caudoventral section; acetabular fossa deep, with the angle, width and curvature variable within individuals, partially covered cranially and caudally by lip projecting from the acetabular surface. Caudal surface of the dorsal section of the ischium (caudally adjacent to the acetabulum) broad and gently convex. Ischium badly crushed ventral to the acetabulum in the available specimen; craniocaudally deep and transversely compressed; caudal margin gently rugose and slightly convex from the origin of the mm. gemelli; deflected slightly caudally relative to the axis of the ilium; caudal section broadens toward the ventral margin.

The pelvis of P. dawsonae sp. nov. differs from that of P. mamkurra and P. viator in being smaller, with a smaller caudal iliac spine, shallower gluteal fossa, narrower, less rugose and less convex caudal surface of the dorsal section of the ischium ( Fig. 95e ), and a less deeply concave acetabulum; from P. tumbuna in having a more curved ilium in lateral view, less laterally projected rectus tubercle, acetabulum opening more laterally and less cranioventrally, and a more transversely compressed ischium; from C. kitcheneri , O. rufus and M. fuliginosus in being more robust, with a more dorsally situated sacral surface relative to the position of the acetabulum, shallower, less distally extensive iliac fossa, broader, deeper gluteal fossa, and a smaller, less projected iliopubic eminence; and from W. bicolor in being much larger, with the iliac crest aligned more transversely and less craniocaudally, broader, deeper gluteal fossa, narrower, less distally extensive iliac fossa, broader lateral iliac spine, particularly dorsally, caudal iliac spine lacking a small, pointed eminence on the caudoventral shoulder, and the rectus tubercle having a much smaller, shallower fossa on the lateral surface.

Pes

Calcaneus ( Fig. 96 ): moderately sized, robust and quite low. Calcaneal tuberosity short, broad and low, broadens plantarly and caudally, increases slightly in height caudally; domed in cross-section; lateral surface becomes deeply concave plantar to the fibular facets. Caudal epiphysis broad, thickened and rugose, oval to domed in posterior view; a shallow transverse groove extends across the caudal surface. Plantar surface thickened, rugose and quite broad, tapers gently cranially in plantar view and extends cranially to level with the cranial fibular facet, with the craniomedial margin deflected laterally around the cranial plantar tubercle. Cranial plantar tubercle generally small, rounded to oval, abuts or is caudally adjacent to the plantar margin of the plantomedial facet for the cuboid.

The calcaneal head is large and broad, with a very slight medial rotation in dorsal view. Sustentaculum tali large, medially projected beyond the margin of the medial talar facet, not extensive caudally, caudal margin is rounded with a flat cranioplantar margin; flexor groove quite deep and broad. Medial talar facet slightly caudally displaced relative to lateral talar facet, broad and oval, craniocaudally compressed, slightly projected dorsally, tilted strongly cranially in medial view; caudal margin with a distinct rounded lip, particularly over the lateral part. A small, variable ridge extends caudally from the caudolateral margin of the medial talar facet, tapers and lowers caudally; occasionally present only as a slight swelling. Lateral talar facet broad, craniocaudally short, smoothly convex, roughly semicylindrical and tapering from the lateral margin to the midpoint.Fibular facets large relative to the lateral talar facet, bulbous and projected laterally; cranial component low, elongate, more laterally projected than the caudal component of the facet, and tilted cranially in lateral view; caudal component roughly rounded, gently convex, and facing caudally, with distinct plantar and medial margins.

Facet for the talar head small; abuts the medial margin of the dorsomedial cuboid facet on the medial surface of the calcaneal head. Dorsomedial cuboid facet roughly oval in cranial view, gently convex, slightly broader than the dorsolateral facet, from which it is separated by a tall, quite bevelled step.Dorsolateral cuboid facet tall, cranially projected, very slightly concave and tilted plantarly and slightly medially, curves plantomedially to be continuous with the plantomedial facet. Plantomedial cuboid facet much smaller than the dorsal facets, dorsoplantarly compressed and broad, occasionally rounded. A shallow, oblong fossa is present between the dorsomedial and plantomedial cuboid facets.

The calcaneus of P. dawsonae sp. nov. differs from that of P. anak in being dorsoplantarly shorter, with a narrower plantar surface, slightly shallower lateral talar facet, less rounded, less distinct caudal fibular facet, and a shallower flexor groove; from P. mamkurra sp. nov. in being smaller, lower and narrower, with a more caudally displaced medial talar facet, less bulbous lateral talar and caudal fibular facets, fibular facets less plantarly extensive laterally, and a more rounded sustentaculum tali; from P. viator sp. nov. in being smaller, lower and broader, with a more rounded, less dorsally pointed calcaneal tuberosity in cross-section, craniocaudally shorter lateral talar facet, broader, more transversely aligned medial talar facet, and more medially projected sustentaculum tali; from P. tumbuna in having the head less medially displaced, a flatter, less convex plantar surface, and less medial flaring of the caudoplantar margin of the calcaneal tuberosity; from P. otibandus in having the head less medially displaced, with a narrower calcaneal tuberosity; from C. kitcheneri in being larger and relatively taller, with a less concave, less medially tilted plantar surface; from O. rufus in being broader and relatively lower, with a less elongate tuberosity, no caudomedial facet for the posterior plantar process of the talus, less cranially tilted medial talar facet, shallower fossa cranial to the lateral talar facet, relatively narrower dorsolateral cuboid facet, more bevelled step between the dorsal cuboid facets, more medially projected sustentaculum tali, and a deeper flexor groove; from M. fuliginosus in being larger, broader and relatively lower, with a less elongate tuberosity, shallower fossa cranial to the lateral talar facet, relatively narrower dorsolateral cuboid facet, more bevelled step between the dorsal cuboid facets, more medially projected sustentaculum tali, and a deeper flexor groove; and from W. bicolor in being larger, relatively broader and more robust, with broader medial talar facet and more medially projected sustentaculum tali.

Metatarsal IV ( Fig. 97a–c ): large, long and quite robust. Dorsal cuboid facet very similar to that of P. mamkurra sp. nov.; proximal cuboid fossa small, shallow and plantolaterally situated; plantar cuboid facet quite small, round, very gently concave and tilted distinctly dorsally and slightly medially, extends plantarly partially onto proximal surface of deep, plantarly projected plantar tubercle. Proximal plantar sesamoid facet quite large, broad, flat, round to oval, faces distoplantarly and is tilted laterally. Articular surface for metatarsal III indistinct, situated in an elongate, shallow, rugose metatarsal III fossa on the medial surface of the proximal end, bordered dorsally by an indistinct, low ridge extending plantodistally from the dorsomedial corner of the dorsal cuboid facet. Dorsal facet for the ectocuneiform small and tapering plantarly, facing proximomedially, adjacent to the dorsal section of medial margin of dorsal cuboid facet; small facet for the plantolateral component of ectocuneiform situated on the proximomedial surface of the plantar tubercle, semicontinuous with the plantar cuboid facet. Facet for metatarsal V large, concave, slightly cranially tilted, moderately tall and proximodistally short; shape variable but generally oblong with rounded dorsal and plantar parts; extends plantarly onto the base of the lateral surface of the plantar tubercle.

Plantar ridge quite broad, rugose, squarish to rounded in cross-section, extends distally with a very slight lateral deflection from the base of the plantar tubercle, merges into the plantar surface of the shaft before the midpoint; bordered medially by the fossa for metatarsal III and laterally by the fossa for metatarsal V. Shaft morphology very similar to that of P. mamkurra sp. nov. Distal end broad; fossae for the collateral ligaments circular and quite deep; keel slightly more plantarly projected than the lateral and medial crests.

The metatarsal IV of P. dawsonae sp. nov. does not differ from those of P. anak and P. mamkurra sp. nov. It differs from that of P. viator sp. nov. in being larger, with a relatively broader proximal plantar sesamoid facet and a larger plantar facet for the ectocuneiform; from P. tumbuna in being larger; from P. otibandus in being larger, with continuous dorsal and plantar cuboid facets, a more concave, less laterally projected metatarsal V facet, larger plantar tubercle, more raised plantar ridge, and a relatively more plantarly projected keel; from P. snewini in being larger, with a smaller, more plantolaterally situated cuboid fossa; from C. kitcheneri in being larger and broader, with a larger, more plantarly projected proximal plantar tubercle and a more raised plantar ridge; from O. rufus and M. fuliginosus in being shorter, much broader and more robust, with a larger facet for metatarsal V, the shaft more dorsoplantarly compressed and broadening more to the distal end, a less plantarly projected proximoplantar ridge, and a broader, more planar proximal dorsal surface; and from W. bicolor in being much larger, relatively broader and more robust, with a relatively slightly larger proximal plantar tubercle.

Metatarsal V ( Fig. 97d–h ): quite elongate and gently transversely compressed proximally, with a distinct lateral curve to the distal component in dorsal view accentuated by the lateral expansion of the distal end. Proximolateral process blunt, thick and rugose. Cuboid facet broad, broader than the facet for metatarsal IV, concave, particularly medially, extends across the medial surface of the proximolateral process onto the lateral base of the medial plantar tubercle; dorsolateral margin raised to slight lip over dorsomedial surface of proximolateral process. Facet for metatarsal IV proximodistally deep but tapering laterally, and gently convex; extends from the dorsal surface of the shaft onto the medial plantar tubercle. Lateral plantar tuberosity large, broad, rugose and quite raised, merges with the shaft just past the midpoint; separated from the medial plantar tubercle by a broad, shallow plantar groove curving distally along the medial margin. Medial plantar tubercle small, distinct, rounded, and proximomedially projected. Shaft gently and smoothly arched in lateral view with the highest point around the midpoint. Distal end broad, laterally flared and slightly laterally deflected at base. Distal articular surface very similar to that of P. mamkurra sp. nov. Fossae for collateral ligaments large, rounded and quite deep.

The metatarsal V of P. dawsonae sp. nov. differs from that of P. anak in having less raised lateral plantar tuberosity, less tall proximolateral process and broader cuboid facet; from P. mamkurra sp. nov. in having a narrower cuboid facet and a more distally extensive lateral plantar tuberosity; from P. viator sp. nov. in being longer and slightly less transversely compressed, with a lower, more elongate proximolateral process, narrower cuboid facet, more proximally projected medial plantar tubercle, and a less raised lateral plantar tuberosity; from P. tumbuna in being larger and more elongate, with a longer, narrower proximolateral process, larger medial plantar tubercle, and a narrower cuboid facet; from P. otibandus in being more elongate, with a narrower, less dorsally projected cuboid facet and a slightly narrower distal end; from C. kitcheneri in being larger, broader and more robust, lacking the slight kink of the arch of the shaft immediately proximal to the midpoint in lateral view, with a larger medial plantar tubercle, more medially situated facet for metatarsal IV, and a more raised lateral plantar tuberosity; from O. rufus and M. fuliginosus in being far shorter and broader, less arched and much less transversely compressed, with a longer proximolateral process and a larger medial plantar tubercle; and from W. bicolor in being larger, relatively broader and more robust, with a larger proximolateral process and a more concave cuboid facet.

Proximal pedal phalanx IV ( Fig. 97i–k ): fairly short, robust, and dorsoplantarly compressed. Proximal articular surface mostly abraded in available specimen, appears domed and gently concave. Proximal plantar tubercles partially abraded, appear low and rugose, separated by a shallow valley. Shaft narrows slightly to a waist, broadens very slightly to the distal end. Distal articular surface proximodorsally quite extensive; trochlea broad and quite shallow. Fossae for the collateral ligaments shallow and semicircular.

The proximal phalanx IV of P. dawsonae sp. nov. differs from those of O. rufus and all compared species of Protemnodon except P. viator sp. nov. in having a more proximodorsally extensive distal articular surface. It further differs from P. anak in being shorter and more robust, with less projected plantar tubercles, a slightly broader waist, and a less dorsoplantarly compressed shaft; from P. mamkurra sp. nov. in being shorter, with a slightly broader waist, and a slightly narrower distal end; from P. viator sp. nov. in being more robust, with a broader waist and a narrower distal end; from P. otibandus in being more elongate; from C. kitcheneri in being much broader and more robust, and lacking a small fossa immediately proximal to the dorsal margin of the distal articular surface; from O. rufus in being slightly shorter, much broader and more robust, with a broader waist and a less dorsoplantarly compressed distal shaft; from M. fuliginosus in being larger, far broader and more robust; and from W. bicolor in being larger, relatively broader and more robust.

Remarks:

For discussion of the taxon Protemnodon devisi Bartholomai, 1973 and its relationship to P. dawsonae sp. nov., see the segment below titled, ‘Status of other species previously referred to Protemnodon ’.

The material from Big Sink LF provides evidence for only one species of Protemnodon ( Dawson et al. 1999) , all of which is allocated here to P. dawsonae sp. nov. These fossils are of a large kangaroo, similar in size to P. anak , separated from all other species of Protemnodon by its upper molars with a kinked postparacrista and from other Pliocene species by its large, robust i1 with a low, thick ventrolingual crest. Craniodental fossils from Stirton Quarry, Lake Kanunka, and Sand Scree Locality, Chinchilla that match this morphotype are also allocated to P. dawsonae sp. nov. As the m4 from Site 4, Lake Kanunka, falls within the dental dimensions of and is most similar in morphology to P. dawsonae sp. nov., and as it was found in association with the partial pelvis, we allocate both to that species, albeit with less confidence than the other referred specimens.

Figures

FIGURE 91. (a–c) surface scan images of left I1–3 of P. dawsonae sp. nov. AM F69835 in (a) occlusal, (b) buccal/lateral, and (c) anterior views; and (d) partial right cranium of P. dawsonae sp. nov. holotype AM F161915 in right lateral view, showing M1–4, maxilla, and partial lacrimal, frontal, palatine, and jugal.

FIGURE 92. upper dentition of P. dawsonae sp. nov.: right DP2–M2 of SAMA P50399 in (a) buccal, (b) lingual, and (c) occlusal views; (d) right M1–4 of holotype AM F161915 in occlusal view; (e) left P3 of AM F161923 in occlusal view; and right P3 (removed from crypt) of SAMA P50399 in (f) lingual, (g) occlusal, and (h) buccal views.

FIGURE 93. dentaries and right lower dentition of P. dawsonae sp. nov.: mandible (re-associated dentaries) AM F69858 (right dentary) andAM F69859 (left dentary) in (a) occlusal, and (b) ventral views; right dentary AM F69858 in (c) buccal, and (d) lingual views, and (e) lingual view of i1; and p3–m4 of AM F69858 in (f) occlusal, (g) buccal, and (h) lingual views.

FIGURE 94. vertebrae of P. dawsonae sp. nov.: partial axis vertebra AM F161920 in (a) left lateral, (b) cranial, and (c) dorsal views; partial axis vertebra AM F161914 in (d) right lateral, and (e) caudal views; and (f–g) lumbar vertebra L2? AM F161918 in (f) cranial, and (g) lateral views.

FIGURE 95. caudal vertebra Ca2? of P. dawsonae sp. nov. AM F161911 in (a) lateral, (b) dorsal, and (c) cranial views.(d–f) partial pelvis, predominantly ilium and caudal component of ischium, of P. dawsonae sp. nov. UCMP 156881 in: (d) caudal, (e) lateral, and (f) medial views.

FIGURE 96. partial calcanei of P. dawsonae sp. nov.: (a–e) surface scan images of partial left calcaneus AM F106042 in (a) dorsal, (b) plantar, (c) medial, (d) cranial, and (e) caudodorsal views; and (f) right calcaneus AM F161913 in dorsal view. AM F161913 is dorsoplantarly crushed, the tuberosity is warped medially, and it remains partially embedded in matrix and bone fragments, visible on the medial margin of the tuberosity.

FIGURE 97. pedal elements of P. dawsonae sp. nov.: (a) surface scan image of partial right metatarsal IV AM F106039 in dorsal view; (b–c) surface scan images of partial left metatarsal IV of AM F106041 in (b) proximal, and (c) lateral views; (d–h) surface scan images of left metatarsal V of AM F106040 in (d) dorsal, (e) plantar, (f) lateral, (g) medial, and (h) proximal views; and (i–k) partial right proximal pedal phalanx IV of AM F161916 in (i) dorsal, (j) medial, and (k) plantar views.