Fossil record
Many fossils of modern bandicoots like Perameles and Isoodon have been found from the Pleistocene and Holocene times. But only a few fossil species have been discovered so far.
The first fossil bandicoot was described in 1955 by R. A. Stirton. It was a part of a lower jaw found in the Tirari Desert in Central Australia from the Pliocene period. This jaw looked like it belonged to bilbies and was named Ischnodon australis.
In 1976, Archer and Wade found the next fossil bandicoot. It was a single upper tooth from the Bluff Downs fossil site, Allingham Formation, in northern Queensland, also from the Pliocene. The tooth was like those of Perameles and was named Perameles allinghamensis.
In 1995, Dr. Jeannette Muirhead described the first Miocene bandicoot species from Riversleigh. It was called Yarala burchfieldi and was smaller than living bandicoots with simple teeth. In 2000, a skull was found, the first for any fossil bandicoot. This skull showed Yarala was different from other bandicoots, so a new family called Yaralidae was made for it.
In 1997, a new species called Perameles bowensis was described from teeth found in two Pliocene sites, Bow and Wellington Caves. Later, in 2000, the same species was found in Chinchilla, Queensland. In 2002, another new species, Perameles sobbei, was found on the Darling Downs in south-eastern Queensland from the Pleistocene. It was known from a lower jaw and some teeth. More teeth were found in 2005.
In 2006, a second species of Yarala, called Yarala kida, was described from a late Oligocene site in the Northern Territory. This species was even more primitive than Yarala burchfieldi.
The second fossil skull of a bandicoot was found in Miocene sites at Riversleigh. Several skulls and jaws of a new species were found and named Galadi speciosus. It had a short nose and was probably more meat-eating than modern bandicoots. Its exact relation to other bandicoots is unclear. Later, three more species of Galadi were described in 2013. An additional three species of Galadi were later described in 2013 and named Galadi grandis, Galadi amplus and Galadi adversus.
In 2013, a new mouse-sized bandicoot species called Bulungu palara' was described from Riversleigh and southern Australia. Two other Bulungu species were found in South Australia, including Bulungu muirheadae, the oldest fossil bandicoot known (about 24 million years old) and Bulungu campbelli.
In 2014, the oldest modern bandicoot and bilby fossils were found in Riversleigh from the middle Miocene (about 15 million years ago). The bandicoot was named Crash bandicoot, after the famous video game character and is known from one upper jaw. The bilby, named Liyamayi dayi, is known from three teeth.
The first evidence of size differences between male and female fossil bandicoots was found in two new species from Riversleigh called Madju variae and Madju encorensis. These species are related to modern bandicoots but belong to a different group called Perameloid. Madju variae also showed growth stages from young to adult, which is rare in fossil marsupials. Researchers think Madju variae grew slower than modern bandicoots, more like bilbies. This suggests that fast growth in modern bandicoots evolved after the middle Miocene when Australia became drier.
