''Tingamarra'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of mammals from Australia. Its age, lifestyle, and relationships remain controversial.

Discovery

''Tingamarra'' was discovered in 1987, when a single tooth was found at the

Murgon fossil site The Murgon fossil site is a paleontological site of early Eocene age in south-eastern Queensland, Australia. It lies near the town of Murgon, some 270 km north-west of Brisbane. The Murgon site is important as the only site on the continent ...

in south-eastern

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

. An ankle bone and an ear bone found at Murgon may also belong to this animal.

Material

Holotype: QMF20564, isolated right lower molar, probably an M2 or M3.

Diagnosis

# Non-twinned hypoconulid and entoconid. # Lack of a well developed buccal postcingulid. # Lack of anteroposteriorly compressed trigonid. # Broadly open trigonid. # Lingually situated paraconid that is also well anterior to the protoconid.

Assumed lifestyle

''Tingamarra'' is believed to be a small (about 20 cm from head to tail) ground-dwelling mammal that ate insects and fruit.

Scientific significance

The age of Murgon fossils was determined as the early

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

. By the shape of the found tooth, ''Tingamarra'' was first classified as a

condylarth Condylarthra is an informal group – previously considered an Order (biology), order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates and is now largely consid ...

. This is a primitive order of mammals which are ancestral to modern

ungulate Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with Hoof, hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined ...

s. If this interpretation is correct, ''Tingamarra'' appears to be the only land-based

placental Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished ...

mammal to have arrived to Australia before about 8 million years ago. The only other placental mammals in Australia that arrived before humans are

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s and

bat Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...

s. Most Australian mammals are

marsupials Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a ...

instead. Before ''Tingamarra'' was found, it was hypothesised that marsupials had done well in Australia only because for many millions of years they had no placentals to compete with. However, both the age and placental nature of ''Tingamarra'' were subsequently challenged by other researchers. Woodburne et al. argued that: 1) the true age of

is the late

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

, and 2) that indeed neither shape nor microstructure of the tooth do not allow to distinguish whether ''Tingamarra'' was marsupial or placental. Then Rose concluded that at present there is no undoubted evidence to change the established views.

References

Theria Condylarths Eocene mammals Prehistoric mammals of Australia Fossil taxa described in 1992 Prehistoric mammal genera {{paleo-mammal-stub