Ganguroo robustiter, sp. nov. (Macropodoidea, Marsupialia), a middle to early late Miocene basal macropodid from Riversleigh World Heritage Area, Australia
Authors:
Cooke et al
Abstract:
Cranial and dental remains of the middle to early late Miocene macropodid kangaroo, Ganguroo robustiter, sp. nov., are described. Postcranial remains of G. robustiter were previously described as referable to G. bilamina. Ganguroo robustiter is more robust (approximately 20% larger) and more derived than G. bilamina and G. bites, in having a larger m4, a well-developed posterolingual ridge and lingual cingulum on P3, a longer P3/p3, and no stylar cusp C on M3–M4. We used previously published data matrices to analyze the phylogenetic relationship of G. robustiter. Both phylogenetic analyses, using craniodental and postcranial characters, place G. robustiter within Macropodidae, as the sister taxon to sthenurines and macropodines. Species of Ganguroo are not found to be monophyletic despite their extreme similarity in character scores. This may be due to the large amount of missing data for G. bilamina and G. bites for which no postcranial remains have been identified. Phylogenetic results are ambiguous, recovering unresolved trees with low bootstrap values, but the generic assignment of these taxa is maintained because they are remarkably similar. Species of Ganguroo may represent a phyletic lineage, with species increasing in size and losing cusp/cuspids on their premolars through time, which appears to coincide with a broader record of changing vegetation and climates through the middle Miocene.
Late Pleistocene Australian Marsupial DNA Clarifies the Affinities of Extinct Megafaunal Kangaroos and Wallabies
Authors:
Llamas et al
Abstract:
Understanding the evolution of Australia’s extinct marsupial megafauna has been hindered by a relatively incomplete fossil record and convergent or highly specialized morphology, which confound phylogenetic analyses. Further, the harsh Australian climate and early date of most megafaunal extinctions (39–52 ka) means that the vast majority of fossil remains are unsuitable for ancient DNA analyses. Here, we apply cross-species DNA capture to fossils from relatively high latitude, high altitude caves in Tasmania. Using low-stringency hybridization and high-throughput sequencing, we were able to retrieve mitochondrial sequences from two extinct megafaunal macropodid species. The two specimens, Simosthenurus occidentalis (giant short-faced kangaroo) and Protemnodon anak (giant wallaby), have been radiocarbon dated to 46–50 and 40–45 ka, respectively. This is significantly older than any Australian fossil that has previously yielded DNA sequence information. Processing the raw sequence data from these samples posed a bioinformatic challenge due to the poor preservation of DNA. We explored several approaches in order to maximize the signal-to-noise ratio in retained sequencing reads. Our findings demonstrate the critical importance of adopting stringent processing criteria when distant outgroups are used as references for mapping highly fragmented DNA. Based on the most stringent nucleotide data sets (879 bp for S. occidentalis and 2,383 bp for P. anak), total-evidence phylogenetic analyses confirm that macropodids consist of three primary lineages: Sthenurines such as Simosthenurus (extinct short-faced kangaroos), the macropodines (all other wallabies and kangaroos), and the enigmatic living banded hare-wallaby Lagostrophus fasciatus (Lagostrophinae). Protemnodon emerges as a close relative of Macropus (large living kangaroos), a position not supported by recent morphological phylogenetic analyses.
