Wakiewakie

In 1971, a joint expedition by the South Australian Museum and the University of California discovered the remains of a small macropod at Lake Ngapakaldi, north-eastern South Australia. The fossils were later described and named in 1984 as a new genus and species by Michael Woodburne. The type specimen of Wakiewakie, SAM P17897, is a left mandible from the Kutjamarpu Local Fauna of the Wipajiri Formation. Two isolated upper premolars from the same site were also referred to the species.^[1] In 1989, Godthelp and colleagues reported additional remains from the Upper Site at the Riversleigh World Heritage Area, north-western Queensland. It was also reported that a new genus and species of potoroine that closely resembled Wakiewakie had been discovered from the Kangaroo Well Local Fauna in the Northern Territory.^[2]

The generic epithet is an onomatopoetic rendition of an early morning call that was often heard at the field camp during the 1971 expedition. The specific epithet honours Paul F. Lawson, in recognition for his important contributions to science.^[1]

One of the most distinct features of Wakiewakie is its very deep mandible, reaching a maximum depth of 11.2 mm (0.44 in). The masseteric canal is very large, extending from the mandibular foramen of the masseteric fossa to just below the anterior root of the third lower premolar. On the inner side of the mandible, the symphysis (where the two halves of the lower jaw connected) is relatively short. The ascending ramus rises from the horizontal ramus at an angle of nearly 90°. While the lower incisor isn't persevered, the orientation and shape of its alveolus indicates that it was long and slender. A 3 mm (0.12 in) long diastema separates the first lower incisor from the third lower premolar, which would have resulted in Wakiewakie having a shorter snout. The third lower premolar itself is elongate, measuring 11 mm (0.43 in) long, which makes it the relatively longest premolar known for any macropod. The tooth has a rectilinear outline and, unlike Hypsiprymnodon, a horizontal dorsal profile. A cingulum-like bulge is present at the buccal and lingual bases of the premolar, although it is most distinct on the buccal side. The buccal side is also ornamented with 20 vertical ribs called transcristds, with 19 or more being present on the lingual side. These transcristids terminate into cuspids along the ridge running lengthwise across the middle of the tooth. The lower molars are short, low-crowned and bunolophodont, having rounded cusps and prominent ridges running transversely along (across) their occlusal surfaces. They have a squarish occlusal outline, but are slightly longer than wide. The surfaces of the protoconid and metaconule are sloped rather than straight as in potoroids. The protoconid and hypoconid are connected by a transverse crest to the metaconid and entoconid, respectively. The protolophid and hypolophid run parallel to each other.^[1]

The upper third premolar is very similar to the lower premolar but differs in a few key ways. For instance, the blade crest curves towards the cheeks at its back end. The tooth is as broad towards the back as the front. It bears a stronger lingual cingulum-like bulge on its back quarter. None of the buccal or lingual transcristae curve towards the back and bottom of the tooth. None of the transcristae reach the base of the crown. Both sides of the tooth have 17 transcristae, instead of 20.^[1]