Protemnodon snewini Bartholomai, 1978

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 : 188-189

Protemnodon snewini Bartholomai, 1978

Protemnodon snewini Bartholomai, 1978 : Mem. Qld. Mus. 18(2): pp. 131–136, figs 2 & 3, pl. 24, figs 1–4, pl. 25, fig. 1.

Protemnodon Owen Protemnodon sp. ; Archer & Wade (1976) (partim), pp. 390–391, pl. 57a.

Holotype: QM F9061 ( Fig. 107 ), complete R dentary preserving i1, p3–m4. Figured in Bartholomai (1978) pl. 24, fig. 4, pl. 25, figs 1a & b.

Type locality:

Bluff Downs LF, Bluff Downs Station, Allingham Fm. , north Queensland, Australia. The Allingham Fm. is considered early Pliocene, with a minimum radiometric date of 3.62± 0.5 Ma from overlying basalt and a maximum age of 5.2 Ma inferred from the known period of volcanic activity producing the underlying layer containing basalt ( Mackness et al. 2000).

Paratype (s):

None.

Referred specimens:

Queensland

Bluff Downs LF, Allingham: AM F9074 maxillae; AM F7810 partial R maxilla; AM F9072 L DP3; AM F7788 L DP3; AM F9073 R DP3; AM F7786 R P3; AM F9062 R P3; AM F9069 R M1; AM F7809 L M3; AM F9071 L M3; AM F9066 partial L M3; AM F7811 R M4; AM F7824 R dp3; AM F9070 partial L p3; AM F9064 R m1; AM F9068 R m3; AM F9065 L m3; AM F9063 partial R m4; AM F9067 partial R m4; AM F9075 L tibia, fibula, metatarsal IV and middle and distal pedal phalanges IV; AM F9076 L talus, cuboid and partial metatarsal V.

Revised specific diagnosis:

Protemnodon snewini is separated from other species of Protemnodon by several autapomorphic characteristics of the dentition and dentary, and by a combination of other osteological features. The dentary of P. snewini differs from all other species of Protemnodon in being more gracile. The dentition of P. snewini is distinguished from all species of the genus by: its P3 with a lower lingual crest and a narrower posterior width relative to the anterior; and more elongate, lanceolate i1.

The dentary of P. snewini is most like that of P. anak and P. otibandus . It further differs from those of P. anak and P. otibandus in having a more ventrally situated masseteric fossa relative to the cheek tooth row. It is additionally distinguished from that of P. otibandus in having a less dorsally deflected diastema and a more anterodorsally situated mental foramen.

The dentition of P. snewini most closely resembles that of P. anak and P. otibandus . The dentition further differs from that of P. anak in being lower crowned, with a broader P3 relative to length, particularly across the anterior cusp, lower, less distinct and less dorsoventrally aligned buccal ridgelets, and a lower, less jagged and more anteriorly extensive lingual crest. Additionally differs from P. otibandus in its relatively narrower upper molars with a more anteriorly prominent precingulum and a less raised, less distinct postparacrista.

The hindlimb of P. snewini most closely resembles that of P. anak and P. otibandus , but differs from both in having a distal phalanx IV with a more pointed dorsal peak. The hindlimb is differentiated from that of P. anak in having a more gracile tibia, with a relatively less elongate cnemial crest with a less distinct distal peak and a more elongate proximolateral crest relative to total length. The pes further differs from that of P. anak by: talus lacking the small indent present between the cranial margin of the medial trochlear crest and the talar head; cuboid with separate dorsal and plantar metatarsal IV facets and a smaller, less distinct metatarsal V facet; more robust metatarsal IV with a relatively shorter plantar ridge, separate dorsal and plantar cuboid facets, and a more dorsomedially situated proximal cuboid fossa; and middle pedal phalanx IV with much less lateral and medial flaring of the proximal plantar tubercles.

The hindlimb differs from that of P. otibandus in having a tibia with smaller,narrower proximal fibular facet. The pes differs from that of P. otibandus in: talus with a shallower trochlea and a shallower concavity between the posterior plantar tubercle and the talar head; cuboid with a more dorsomedially flared dorsomedial section, much larger talar facet, and a smaller and less plantomedially projected medial plantar tubercle; and metatarsal IV with a taller, more dorsally situated proximal cuboid fossa.

Etymology:

Named for Mr W. Snewin, who discovered the Allingham site with Mr J. Barrett.

Remarks:

Protemnodon snewini was described from a complete right dentary, a maxilla and palatal fragment and a partial hindlimb, all found near to each other in the same stratigraphic unit of the mid-Pliocene Allingham Fm., northern central Queensland. They were deemed likely to belong to the same individual, but were registered separately. The partial hindlimb consists of a left tibia, fibula, metatarsal IV, and medial and partial distal phalanges IV ( Bartholomai 1978, fig. 2). Bartholomai (1978) also described and figured several other disassociated hindlimb elements—a talus, calcaneus, cuboid, partial metatarsal V and proximal pedal phalanx IV—tentatively allocating them to this species. These were all registered as a single specimen (QM F9076), although they represent multiple individuals. Of these elements, only the cuboid, talus and the distal metatarsal V fragment ( Bartholomai 1978, fig. 2) have a morphology that would be consistent with belonging to a single species of Protemnodon . The element referred to as a proximal pedal phalanx IV, in fact, represents the middle phalanx IV of a larger species of macropodid and is thus not allocated herein to P. snewini . The calcaneus is considered to be more akin to that of a species of Macropus , and likewise is not referred to this species.

Protemnodon snewini shares some features with Congruus kitcheneri , such as a gracile i1, procumbent diastema and shallow, elongate dentary. However, the similarities of its cheek dentition to other species of Protemnodon and possession of the characteristic form of the middle pedal phalanx IV—short, very broad and dorsoplantarly compressed—are the chief drivers of its inclusion in the genus Protemnodon .

The material allocated to Protemnodon sp. from Corra-Lynn Cave ( Pledge 1992) on Yorke Peninsula, South Australia, which consists of various partial, isolated craniodental specimens, is here considered morphologically more similar to P. snewini than to any other species of Protemnodon . For the following reasons we refrain from allocating it to a species of Protemnodon . Firstly, due to the presence of various plesiomorphic features in that material, such as a particularly low lingual crest on the P3,which suggest the Corra-Lynn material may be of an unknown, more plesiomorphic species. Secondly, while the deposit has previously been considered early Pliocene in age, recent but unpublished dates suggest an earlier age for the material. Lastly, expeditions are planned to extract further material from the Corra-Lynn deposit, and we do not wish to pre-emptively describe and allocate the material when more may be about to be found that could greatly aid more accurate taxonomic description and placement.

Figures

FIGURE 107. rendered image of the holotype of Protemnodon snewini QM F9061, a right dentary in: (a) buccal, (b) lingual, and (c) occlusal views, with certain diagnostic features labelled.