Peramelemorphia

Many specimens of modern peramelemorphian (e.g. Perameles spp. and Isoodon spp.) have been recovered in the fossil record from Pleistocene and Holocene fossil localities.[5] However, very few fossil species have been recovered to date. The first species of fossil peramelemorphian was described by R. A. Stirton in 1955. The specimen Stirton described was a partial lower jaw from the Tirari Desert in Central Australia, Pliocene in age. The lower jaw morphology suggested a relationship with bilbies (Family Thylacomyidae), and was named Ischnodon australis.[6]

It was not until 1976 that Archer and Wade described the next fossil bandicoot. A single upper molar was recovered from the Bluff Downs fossil site, Allingham Formation, in northern Queensland, also Pliocene in age. The tooth was similar to that of species of Perameles, and was therefore named Perameles allinghamensis.[7]

In 1995, the first Miocene species was described from Riversleigh, and was named Yarala burchfieldi by Dr Jeannette Muirhead. The species was represented by several upper and lower jaws, which were smaller than any living bandicoots and had a very primitive dentition.[8] A skull was later recovered in 2000, the first for any fossil peramelemorphian to date. Features of the skull and dentition suggested that Yarala burchfieldi was distinct from other peramelemorphians, and for this reason, a new Superfamily Yaraloidea and Family Yaralidae were erected to classify this species.[9]

In 1997, Muirhead, Dawson and Archer described a new species of Perameles, Perameles bowensis, from teeth recovered from two Pliocene fossil localities, Bow and Wellington Caves.[10] The same species was later reported in 2000 from Chinchilla, Queensland by Mackness and colleagues.[11] In 2002, Price described a new species Perameles, Perameles sobbei, from the Darling Downs (Pleistocene in age), south-eastern Queensland. This species was represented by a lower jaw and a few isolated lower molars.[12] Additional material were later described in 2005 from the same site, including upper molars.[13]

A second species of Yarala, Yarala kida, was described in 2006 by Schwartz. This species was recovered from Kangaroo Well, a late Oligocene site from the Northern Territory in Australia. This species is thought to be even more primitive than Yarala burchfieldi.[14]

The second fossil skull of any fossil peramelemorphian was also recovered from Miocene sites of Riversleigh. In fact, more than one skull of this new species was found (and several lower and upper jaws), and was significantly different from any other bandicoot to erect a new genus, Galadi. The species was named Galadi speciosus by Travouillon and colleagues. It was short-snouted unlike modern bandicoots suggesting that it was more carnivorous than its omnivorous modern relatives. Its relationship to other bandicoots is unclear, but it was likely to be less primitive than Yarala but more primitive than living bandicoots.[15] An additional three species of Galadi were later described in 2013 and named Galadi grandis, Galadi amplus and Galadi adversus.[16]

Gurovich et al. (2013) described a new species of mouse-sized bandicoot from Riversleigh and from Kutjamarpu, Southern Australia. The species, named Bulungu palara, is represented by a skull and several lower and upper jaws.[17] Two other species in this genus were also described from the Etadunna Formation in South Australia, Bulungu muirheadae which was the oldest fossil bandicoot recovered as of 2013 (about 24 million years old), and Bulungu campbelli.[18]

The oldest modern bandicoot (peramelid) and the oldest bilby (Thylacomyid) were later discovered by Travouillon et al.,2014 from Riversleigh World Heritage Area, from middle Miocene fossil deposits (around 15 million years old). The peramelid, Crash bandicoot, was named after the famous video game character and is only represented by a single upper jaw. The bilby, Liyamayi dayinamed after geologist and philanthropist Robert Day, is only known from 3 teeth (2 upper molar, 1 lower molar).[19]

The first record of sexual dimorphism (difference in size between males and females) in a fossil bandicoot was reported from two new species from Riversleigh (Travouillon et al. 2014). Named Madju variae and Madju encorensis, they are closely related to modern bandicoots, but do not fall in any modern family, as did Galadi and Bulungu (genus). Instead they are classified as Perameloid, with all known Peremelemorphian, to the exclusion of Yaralids. Madju variae is also unusual in preserving an ontogenetic series (age series from pouch young to adult), the second of any fossil marsupial mammal in Australia. The study of this ontogenetic series lead researchers to think that Madju variae developed slow than modern bandicoots, much more like a bilby, and therefore the rapid development of modern bandicoots must have evolved after the middle Miocene, when Australia started to become more arid.[20]

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• Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 38–42. ISBN 0-801-88221-4. OCLC 62265494.
  • Peramelemorphia