Systematics, and Biogeography of Cuscuses (Diprotodontia: Phalangeridae)

Within the gliding mammals has evolved in Three orders, i.e Rodentia, Dermoptera, and Marsupialia. The marsupials include a number of gliding genera believed that the gliding habit evolved independently. Marsupial consist of seven orders, Diprotodontia is the largest and most ecologically diverse. More than 125 living diprotodontian species are currently recognized. Most diprotodontians are herbivorous, but there are also forms specialized for nectarivory, folivory, and insect-omnivory. The family Phalangeridae comprises approximately ± 24 extinct and extant species, including brushtailed possums (Trichosurus), scaly tailed possum (Wyulda) and cuscuses (Phalanger, Strigocuscus, Spilocuscus and Ailurops) (Raterman et al., 2006). Trichosurus and Wyulda are found predominately in Australia whereas Phalanger and Spilocuscus are, for the most part, limited to Maluku, Papua, New Guinea, Timor island and surrounding islands (Flannery, 1994; Kunda et al., 2016; 2017; Widayanti et al., 2015; 2020). Extant species of Strigocuscus are found in Sulawesi and surrounding islands (Flannery 1994). Ailurops contains a single species, A. ursinus, the bear cuscus (Flannery et al. 1987), found on Sulawesi and nearby islands. Two taxa whose phylogenetic placements are key for understanding evolutionary relationships are Ailurops ursinus and Strigocuscus celebensis.

Phalangeridae is one family has generated the most phylogenetic and taxonomic uncertainties of any family within Order Diprotodontia, whether based on morphological or biochemical data (Kirsch and Wolman, 2001; Ruedas and Morales, 2005). The various phylogenetic relationships for this family have led to different biogeographic models in regard to the site of origin (Australia or Sulawesi) and directions of dispersal (Australia to the Sulawesi or from the Sulawesi to Australia, and spred to surrounding islands), for taxa within the family (Ruedas and Morales, 2005). Case et al (2008) stated that oligocene deposits in South Australia from the Etadunna and Wipajiri formations in the Lake Eyre Basin, and from the Namba Formation in the Frome Basin, have produced a wide range and the earliest records of most of possum families extinct at the time and extant until now. Archer (1987), reported that had been no positive sign that Phalangeridae was recovered from deposits of the Etadunna Formation. In addition Springer et al. (1990; 1997) stated that the absence of Phalangeridae in the late oligocene had been confusing considering that the earlier molecular studies which produced divergence time data from molecular sequences, indicated that thePhalangeridae lineage should be present by the Eocene.