Hypsiprymnodon dennisi
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| Hypsiprymnodon dennisi Temporal range: | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Infraclass: | Marsupialia |
| Order: | Diprotodontia |
| Family: | Hypsiprymnodontidae |
| Genus: | Hypsiprymnodon |
| Species: | †H. dennisi |
| Binomial name | |
| †Hypsiprymnodon dennisi Bates, et al. 2014. | |
Hypsiprymnodon dennisi is an extinct species of small macropod marsupial that inhabited Australia during the Middle Miocene. It is known from several skull bones that were found at the Riversleigh World Heritage Area in north-western Queensland. Much like its closest living relative, the musky rat-kangaroo, it was frugivorous.
Hypsiprymnodon dennisi was named and described, alongside Hypsiprymnodon philcreaseri and Hypsiprymnodon karenblackae, by Hayley Bates and colleagues in 2014. Its holotype specimen, QM F20840, is a left maxilla preserving the entire cheek tooth row that was recovered from the Cleft of Ages 4 site, which is classified as a Faunal Zone C deposit at the Riversleigh World Heritage Area, north-western Queensland. The site has been interpreted as being Middle Miocene in age. Several dentaries and isolated teeth from the same site were also referred to this taxon.[1]
The specific epithet was chosen by the authors to honour Dr. Andrew Dennis for his research contributions towards the biology of the living musky rat-kangaroo.[1]
Description
The holotype maxilla preserves a small portion of the jugal process above the first upper molar. Compared to Hypsiprymnodon bartholomaii and Hypsiprymnodon philcreaseri, the process is wider and more robust. When viewed from below, the longitudinal axis of the upper third premolar is flexed anterobuccally (towards the front of the cheek) to the point where it is misaligned with the molar row. The premolar itself is relatively long and robust compared to those of other species of Hypsiprymnodon. It is also plagiaulacoid, with nine ridgelets (transcristae) and cusps intersecting along the ridge running lengthwise across the middle of the tooth. The occlusal surface of the premolar overhangs the front margin of the first upper molar. The molars are low crowned and bunolophodont, having rounded cusps and prominent ridges running transversely along (across) their occlusal surfaces. Unlike all other species of Hypsiprymnodon, the first upper molar possesses both a protostyle and stylar cusp C.[1]
Lower jaw bones referred to Hypsiprymnodon dennisi include QM F24621, which is the most complete dentary referable to this taxon. It retains all of its teeth, with the exception of the first lower incisor, which are all heavily worn. A small foramen is present on the underside of the dentary below the masseteric fossa. Unlike the upper third premolar, the lower third premolar has eight transcristids and cuspids along the middle of the tooth. A protostylid is present on the first lower molar, but is absent on all other lower molars. The talonid basin shows a decrease in size from the first to the fourth lower molar.[1]