| Ausktribosphenidae Temporal range: Early Cretaceous | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Infraclass: | Australosphenida |
| Family: | † Ausktribosphenidae Rich et al., 1997 [1] |
| Genera | |
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Ausktribosphenidae is an extinct family of australosphenidan mammals from the Early Cretaceous of Australia and mid Cretaceous of South America.
Ausktribosphenidae is closely related to monotremes and hence the two form the yinotherian clade Australosphenida. It includes two species, Ausktribosphenos nyktos and Bishops whitmorei , both of which are known only from skull and jaw fragments. [3]
Like other Australosphenida, ausktribosphenids have tribosphenic molars.
Given that Ausktribosphenidae has been found in Early Cretaceous deposits in Australia, its occurrence has ramifications for knowledge of early monotreme paleobiogeography because Australia was connected only to Antarctica, and placentals originated in the northern hemisphere and were confined to it until continental drift formed land connections from North America to South America, from Asia to Africa and from Asia to India. The late Cretaceous map [4] shows how the southern continents are separated. However, the cladistic analysis of Cifelliodon recovers Fruitafossor as a monotreme relative, suggesting that yinotherians may have originated in the Northern Hemisphere. [5] Remains similar to Bishops are known from the mid Cretaceous Mata Amarilla Formation of Argentina, suggesting faunal interchange. [6]
The Ornithorhynchidae are one of the two extant families in the order Monotremata, and contain the platypus and its extinct relatives. The other family is the Tachyglossidae, or echidnas. Within the Ornithorhynchidae are the genera Monotrematum, Obdurodon, and Ornithorhynchus:
Theria is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians and the metatherians but excludes the egg-laying monotremes and various extinct mammals evolving prior to the common ancestor of placentals and marsupials.
Steropodon is a genus of prehistoric monotreme, or egg-laying mammal. It contains a single species, Steropodon galmani, that lived about 105 to 93.3 million years ago (mya) in the Early to Late Cretaceous period. It is one of the oldest monotremes discovered, and is one of the oldest Australian mammal discoveries.
Teinolophos is a prehistoric species of monotreme, or egg-laying mammal, from the Teinolophidae. It is known from four specimens, each consisting of a partial lower jawbone collected from the Wonthaggi Formation at Flat Rocks, Victoria, Australia. It lived during the late Barremian age of the Lower Cretaceous.
Tribosphenida is a group (infralegion) of mammals that includes the ancestor of Hypomylos, Aegialodontia and Theria. Its current definition is more or less synonymous with Boreosphenida.
The Australosphenida are a clade of mammals, containing mammals with tribosphenic molars, known from the Jurassic to Mid-Cretaceous of Gondwana. They are thought to have acquired their tribosphenic molars independently from those of Tribosphenida. Fossils of australosphenidans have been found from the Jurassic of Madagascar and Argentina, and Cretaceous of Australia and Argentina. Monotremes have also been considered a part of this group in some studies, but this is disputed.
Pseudotribos is an extinct genus of mammal that lived in Northern China during the Middle Jurassic some 165 million years ago, possibly more closely related to monotremes than to theria, although other studies indicate that these shuotheres are closer to therians than to monotremes. The only known specimen was found in the Daohugou Bed in Inner Mongolia.
Vincelestes is an extinct genus of actively mobile mammal, that lived in what would be South America during the Early Cretaceous from 130 to 112 mya, existing for approximately 18 million years.
Shuotherium is a fossil mammal known from Middle-Late Jurassic of the Forest Marble Formation of England, and the Shaximiao Formation of Sichuan, China.
Shuotheriidae is a small family of Jurassic mammals whose remains are found in China, England and possibly Russia. They have been proposed to be close relatives of Australosphenida, the group that contains living monotremes, together forming the clade Yinotheria. However, some studies suggest shuotheres are closer to therians than to monotremes. The Shuotheriidae have been proposed as the sister group of the Gondwanian clade Henosferida and the Monotremata, which are the monotremes.
Monotremes are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals (Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts, compared to the more common mammalian types. In addition, they lay eggs rather than bearing live young, but, like all mammals, the female monotremes nurse their young with milk.
Ausktribosphenos is an extinct genus of mammals from Early Cretaceous of Australia. The only recorded species, Ausktribosphenos nyktos, was found on Flat Rocks, Victoria.
Ambondro mahabo is a mammal from the Middle Jurassic (Bathonian) Isalo III Formation of Madagascar. The only described species of the genus Ambondro, it is known from a fragmentary lower jaw with three teeth, interpreted as the last premolar and the first two molars. The premolar consists of a central cusp with one or two smaller cusps and a cingulum (shelf) on the inner, or lingual, side of the tooth. The molars also have such a lingual cingulum. They consist of two groups of cusps: a trigonid of three cusps at the front and a talonid with a main cusp, a smaller cusp, and a crest at the back. Features of the talonid suggest that Ambondro had tribosphenic molars, the basic arrangement of molar features also present in marsupial and placental mammals. It is the oldest known mammal with putatively tribosphenic teeth; at the time of its discovery it antedated the second oldest example by about 25 million years.
UA 8699 is a fossil mammalian tooth from the Cretaceous of Madagascar. A broken lower molar about 3.5 mm (0.14 in) long, it is from the Maastrichtian of the Maevarano Formation in northwestern Madagascar. Details of its crown morphology indicate that it is a boreosphenidan, a member of the group that includes living marsupials and placental mammals. David W. Krause, who first described the tooth in 2001, interpreted it as a marsupial on the basis of five shared characters, but in 2003 Averianov and others noted that all those are shared by zhelestid placentals and favored a close relationship between UA 8699 and the Spanish zhelestid Lainodon. Krause used the tooth as evidence that marsupials were present on the southern continents (Gondwana) as early as the late Cretaceous and Averianov and colleagues proposed that the tooth represented another example of faunal exchange between Africa and Europe at the time.
Several mammals are known from the Mesozoic of Madagascar. The Bathonian Ambondro, known from a piece of jaw with three teeth, is the earliest known mammal with molars showing the modern, tribosphenic pattern that is characteristic of marsupial and placental mammals. Interpretations of its affinities have differed; one proposal places it in a group known as Australosphenida with other Mesozoic tribosphenic mammals from the southern continents (Gondwana) as well as the monotremes, while others favor closer affinities with northern (Laurasian) tribosphenic mammals or specifically with placentals. At least five species are known from the Maastrichtian, including a yet undescribed species known from a nearly complete skeleton that may represent a completely new group of mammals. The gondwanathere Lavanify, known from two teeth, is most closely related to other gondwanatheres found in India and Argentina. Two other teeth may represent another gondwanathere or a different kind of mammal. One molar fragment is one of the few known remains of a multituberculate mammal from Gondwana and another has been interpreted as either a marsupial or a placental.
Palaeoechinastacus australianus is a species of freshwater crayfish known from Early Cretaceous fossils from Victoria, Australia.
Yinotheria is a proposed basal subclass clade of crown mammals uniting the Shuotheriidae, an extinct group of mammals from the Jurassic of Eurasia, with Australosphenida, a group of mammals known from the Jurassic to Cretaceous of Gondwana, which possibly include living monotremes. Today, there are only five surviving species of monotremes which live in Australia and New Guinea, consisting of the platypus and four species of echidna. Fossils of yinotheres have been found in England, China, Russia, Madagascar and Argentina. Contrary to other known crown mammals, they retained postdentary bones as shown by the presence of a postdentary trough. The extant members (monotremes) developed the mammalian middle ear independently.
Meridiolestida is an extinct clade of mammals known from the Cretaceous and Cenozoic of South America and possibly Antarctica. They represented the dominant group of mammals in South America during the Late Cretaceous. Meridiolestidans were morphologically diverse, containing both small insectivores such as the "sabretooth-squirrel" Cronopio, as well as the clade Mesungulatoidea/Mesungulatomorpha, which ranged in size from the shrew-sized Reigitherium to the dog-sized Peligrotherium. Mesungulatoideans had highly modified dentition with bunodont teeth, and were likely herbivores/omnivores.
Teinolophidae is an extinct family of small, carnivorous mammals that were the earliest known monotremes and were endemic to what would become Australia. Two genera are known: Teinolophos, and possibly also Stirtodon.
Patagorhynchus is a genus of prehistoric monotreme mammal from the Late Cretaceous Early Maastrichtian age of Santa Cruz province, Argentina. It is known from a single species: Patagorhynchus pascuali. The holotype, MPM-PV-23087, consists of a lower right molar attached to a fragment of dentary. It was collected in the Chorillo Formation of Rio Gallegos, Santa Cruz, Argentina in 2022 and is housed in the Museo Padre Molina.
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