''Tingamarra'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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 paleontology, 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 ...

in south-eastern

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

. 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

1. Non-twinned hypoconulid and entoconid. 2. Lack of a well developed buccal postcingulid. 3. Lack of anteroposteriorly compressed trigonid. 4. Broadly open trigonid. 5. 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 ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

. If it is correct, then these fossils are the oldest Australian mammal ones. By the shape of the found tooth, ''Tingamarra'' was first classified as a

condylarth Condylarthra is an informal group – previously considered an order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates. It is now largely considered to be a wast ...

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

ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, cam ...

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 Marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsup ...

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

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

s and

dingo The dingo (''Canis familiaris'', ''Canis familiaris dingo'', ''Canis dingo'', or ''Canis lupus dingo'') is an ancient (Basal (phylogenetics), basal) lineage of dog found in Australia (continent), Australia. Its taxonomic classification is de ...

s (which arrived here more recently), and

bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". 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 bi ...

s (which presumably flew in). Most Australian mammals are

marsupials Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

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 of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

, 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

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