Marsupial moles, the Notoryctidae family, are two species of highly specialized

marsupial 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 r ...

mammals that are found in the Australian interior. They are small

burrowing An eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of s ...

marsupials that anatomically converge on fossorial

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 ...

mammals, such as extant

golden mole Golden moles are small insectivorous burrowing mammals endemic to Sub-Saharan Africa. They comprise the family Chrysochloridae (the only family in the suborder Chrysochloridea) and as such they are taxonomically distinct from the true moles, f ...

s (Chrysochloridae) and extinct epoicotheres. The species are: * ''

Notoryctes typhlops The southern marsupial mole (''Notoryctes typhlops''), also known as the itjaritjari () or itjari-itjari, is a mole-like marsupial found in the western central deserts of Australia. It is extremely adapted to a burrowing way of life. It has large ...

'' (southern marsupial mole, known as the ''itjaritjari'' by the

Pitjantjatjara The Pitjantjatjara (; or ) are an Aboriginal people of the Central Australian desert near Uluru. They are closely related to the Yankunytjatjara and Ngaanyatjarra and their languages are, to a large extent, mutually intelligible (all are v ...

and

Yankunytjatjara The Yankunytjatjara people, also written Yankuntjatjarra, Jangkundjara, and other variants, are an Aboriginal Australian people of the state of South Australia. Language Yankunytjatjara is a Western Desert language belonging to the Wati lan ...

people in Central Australia) * ''

Notoryctes caurinus The northern marsupial mole or kakarratul (''Notoryctes caurinus'') is a marsupial in the family Notoryctidae, an endemic animal of arid regions of Central Australia. It lives in the loose sand of dunes and river plains in the desert, spending nea ...

'' (northern marsupial mole, also known as the ''kakarratul'')

Characteristics

In an example of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

, notoryctids resemble (and fill the

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of Resource (biology), resources an ...

of) the talpid or true moles from North America and Eurasia and the Chrysochloridae or

s from Southern Africa. Like chrysochlorids and epoicotheres, notoryctids use their forelimbs and enlarged central claws to dig in a parasagittal (i.e., up and down) plane, as opposed to the "lateral scratch" style of digging that characterizes talpid moles. Marsupial moles spend most of their time underground, coming to the surface only occasionally, probably mostly after rains. They are functionally blind, their eyes having become reduced to

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

lenses under the skin that lack a pupil. They have no external ears, just a pair of tiny holes hidden under thick hair. The head is cone-shaped, with a leathery shield over the muzzle, the body is tubular, and the tail is a short, bald stub encased in leathery skin. They are between long, weigh , and are uniformly covered in fairly short, very fine pale cream to white hair with an iridescent golden sheen. Their pouch is small but well developed and has evolved to face backwards so it does not fill with sand. It contains just two

teat A teat is the projection from the mammary glands of mammals from which milk flows or is ejected for the purpose of feeding young. In many mammals, the teat projects from the udder. The number of teats varies by mammalian species and often corr ...

s, so the animal cannot support more than two young at a time. They are the only marsupials with a true

cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

. The limbs are very short, with reduced digits. The forefeet have two greatly enlarged, spade shaped, flat claws on the third and fourth digits, which are used to excavate soil in front of the animal. The hindfeet are flattened, and bear three small claws; these feet are used to push soil behind the animal as it digs.

Epipubic bone Epipubic bones are a pair of bones projecting forward from the pelvic bones of modern marsupials, monotremes and fossil mammals like multituberculates, and even basal eutherians (the ancestors of placentals, who lack them). They first occur i ...

s are present but small and as in some other fossorial mammals (e.g.,

armadillo Armadillos () are New World placental mammals in the order (biology), order Cingulata. They form part of the superorder Xenarthra, along with the anteaters and sloths. 21 extant species of armadillo have been described, some of which are dis ...

s), the last five cervical

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e are fused, giving the head greater rigidity during digging. The animal swims through the soil and does not leave behind a permanent burrow. The teeth of the marsupial moles are degenerate and bear no resemblance to polyprotodont or diprotodont teeth. Their dental formula varies, but is usually somewhere near . The upper molar teeth are triangular and

zalambdodont The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone tooth ...

, i.e., resembling an inverted Greek letter

lambda Lambda (; uppercase , lowercase ; , ''lám(b)da'') is the eleventh letter of the Greek alphabet, representing the voiced alveolar lateral approximant . In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoen ...

in occlusal view, and the lower molars appear to have lost their talonid basins. Marsupial moles are the only marsupials that are testicond.

Fossil record

Notoryctids are represented by early

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

fossils of ''

Naraboryctes ''Naraboryctes philcreaseri'' is a fossil species of marsupial found at early Miocene deposits of Boodjamulla National Park of Riversleigh area, northwestern Queensland, Australia. Taxonomy It was first named by Michael Archer, Robin Beck, Mi ...

'' from Riversleigh in Queensland, Australia, which show the

mosaic A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...

acquisition of dental and skeletal features of the living ''Notoryctes'' from a more surface-dwelling ancestor. The notoryctid fossil record demonstrates that the primary cusp of the molars is the metacone, distinct from the paracone characteristic of zalambdodont tenrecs, golden moles, and ''Solenodon''. Regarding the number of teeth in each dental quadrant (or

dental formula Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology ...

), the fossil record demonstrates polymorphism of tooth number, both between specimens and within the same specimen. Nonetheless, older studies concluded there are four molars (typical for marsupials) in each quadrant both in living ''Notoryctes'' and the fossil notoryctid ''Naraboryctes''.

Evolutionary affinities

American paleontologist

William King Gregory William King Gregory (May 19, 1876 – December 29, 1970) was an American zoologist, primatologist, paleontologist, and functional and comparative anatomist. He was an expert on mammalian dentition, and a contributor to theories of evolution. H ...

wrote that "''Notoryctes'' is a true marsupial" and this view has been repeatedly verified by phylogenetic analyses of comparative anatomy,

mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

, nuclear DNA, rare genomic events, and combined datasets of nuclear and mitochondrial DNA and morphology and DNA. The largest phylogenetic datasets strongly support the placement of ''Notoryctes'' as the sister taxon to a

dasyuromorph Dasyuromorphia (, meaning "hairy tail" in Greek) is an order comprising most of the Australian carnivorous marsupials, including quolls, dunnarts, the numbat, the Tasmanian devil, and the extinct thylacine. In Australia, the exceptions include t ...

- peramelian clade, within the

Australidelphia Australidelphia is a superorder of marsupials encompassing about three-quarters of all living marsupial species, including all those native to Australasia and one South American species, the monito del monte. Unlike other American marsupials, wh ...

n radiation.

References

External links

*ARKive
images and movies of the marsupial mole ''(Notoryctes typhlops)''
*Australian Geographic

{{DEFAULTSORT:Marsupial Mole Notoryctidae Mammals of Western Australia Extant Burdigalian first appearances Taxa named by Edward Charles Stirling

Characteristics

Fossil record

Evolutionary affinities

References

Further reading

External links