|
Australosphenida
The Australosphenida are a clade of mammals, containing mammals with tribosphenic molars, known from the Jurassic to Mid-Cretaceous of Gondwana. Although they have often been suggested to have acquired tribosphenic molars independently from those of Tribosphenida, this has been disputed. 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 its original definition and in many subsequent studies, but its relationship with other members has been disputed by some scholars. Taxonomy This grouping includes the following taxa: *† Henosferidae, including the genera '' Ambondro'', '' Asfaltomylos'', and '' Henosferus'' from the Jurassic of Argentina and Madagascar. *† Ausktribosphenidae known from the Early Cretaceous of Australia *† Bishopidae including ''Bishops'' from the Lower Cretaceous of Australia and an unnamed genus from the Mid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ambondro (genus)
''Ambondro mahabo'' is a mammal from the Middle Jurassic (Bathonian) Isalo III Formation (about 167 million years ago) 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. Upon its description in 1999 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tribosphenida
Tribosphenida is a clade of mammals that includes the ancestor of ''Hypomylos'', Aegialodontia and Theria (the last common ancestor of marsupials and placentals plus all of its descendants). It belongs to the group Zatheria. The current definition of Tribosphenida is more or less synonymous with Boreosphenida. Characteristics Tribosphenid mammals were originally grouped on the basis of triangular or V-shaped (Molar (tooth)#Tribosphenic, tribosphenic) molars. The relationship of the also tribosphenic australosphenidans, a group of mammals from the Jurassic-Cretaceous of the Southern Hemisphere often suggested to be close relatives of living Monotreme, monotremes, has been questioned, and it has been argued that they developed tribosphenic molars independently from those of "true" tribosphenidans. Some authors have alternatively continued to argue that non-monotreme australosphenidans are in fact true tribosphenidans unrelated to monotremes. "True" unambiguous members of Tribospheni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ausktribosphenidae
Ausktribosphenidae is an extinct family of australosphenidan mammals from the Early Cretaceous of Australia and mid Cretaceous of South America. Classification and taxonomy 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. Morphology Like other Australosphenida, ausktribosphenids have tribosphenic molars. Distribution 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 Continental drift is a highly supported scientific theory, originating in the early 20th century, that Earth's continents move or drif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asfaltomylos
''Asfaltomylos'' is an extinct genus of the primitive mammal subclass Australosphenida from the Jurassic of Argentina. The type and only species is ''Asfaltomylos patagonicus'', recovered from and named after the Cañadón Asfalto Formation, Cañadón Asfalto Basin of Chubut Province, Patagonia. See also * ''Argentoconodon'' * '' Condorodon'' * ''Henosferus ''Henosferus'' is an extinct genus of australosphenidan mammal from Lower Jurassic of Argentina. The only recorded species, ''Henosferus molus'', was found in the Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Chubut Province ...'' References Further reading * G. W. Rougier, A. G. Martinelli, A. M. Forasiepi and M. J. Novacek. 2007. "New Jurassic Mammals from Patagonia, Argentina: A Reappraisal of Australosphenidan Morphology and Interrelationships". ''American Museum Novitates'' (3566) 1-54 * Martin, T. & Rauhut, O. W. M. 2005. "Mandible and dentition of ''Asfaltomylos patagonicus'' (Australo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monotremes
Monotremes () are mammals of the order Monotremata. They are the only group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. 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. Although they are different from other living mammals in that they lay eggs, female monotremes are like other mammals in that they nurse their young with milk. Monotremes have been considered by some authors to be members of Australosphenida, a clade that contains extinct mammals from the Jurassic and Cretaceous of Madagascar, South America, and Australia, but this categorization is disputed and their taxonomy is under debate. All extant species of monotremes are indigenous to Australia and New Guinea, although they were also present during the Late Cretaceous and Paleocene epochs in sou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prototheria
Prototheria (, ; from Ancient Greek "first" and "wild animal") is an obsolete subclass of mammals which includes the living Monotremata and to which a variety of extinct groups, including Morganucodonta, Docodonta, Triconodonta and Multituberculata, have also been assigned. It is today no longer considered a valid grouping, but rather a paraphyletic evolutionary grade of basal mammals and mammaliaform cynodonts. Most of the animals in this group are extinct. The egg-laying monotremes are known from fossils of the Cretaceous and Cenozoic periods; they are represented today by the platypus and four species of echidna. The names Prototheria, Metatheria, and Eutheria (loosely meaning "first beasts", "changed beasts", and "true beasts", respectively) refer to the three mammalian groupings of which we have living representatives. Each of the three may be defined as a total clade containing a living crown-group (respectively the Monotremata, Marsupialia and Placentalia) plus a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henosferidae
Henosferidae (also spelled "Henospheridae") is an extinct family of Australosphenida, native to Gondwana during the Early-Middle Jurassic. It is defined as a clade including the most recent common ancestor of ''Henosferus'' and ''Asfaltomylos ''Asfaltomylos'' is an extinct genus of the primitive mammal subclass Australosphenida from the Jurassic of Argentina. The type and only species is ''Asfaltomylos patagonicus'', recovered from and named after the Cañadón Asfalto Formation, Ca ...'' and all its descendants. References * Averianov, A. O. & Lopatin, A. V., '"Phylogeny of truconodonts and symmetrodonts and the origin of extinct mammals"', Dokl Biol Sci 436:32-35. * Rougier, G. W., Martinelli, A. G., Forasiepi, A. M. & Novacek, M. J. 2007. New Jurassic mammals from Patagonia, Argentina: A reappraisal of australosphenidan morphology and interrelationships. ''American Museum Novitates'' 3566: 1-54. Australosphenida Jurassic mammals Prehistoric mammal families ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tribosphenic Molar
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", from ''mola'', millstone and ''dens'', tooth. Molars show a great deal of diversity in size and shape across the mammal groups. The third molar of humans is sometimes vestigial. Human anatomy In humans, the molar teeth have either four or five cusps. Adult humans have 12 molars, in four groups of three at the back of the mouth. The third, rearmost molar in each group is called a wisdom tooth. It is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies among individuals and populations, and in many cases the tooth is missing. The human mouth contains upper (maxillary) and lower (mandibular) molars. They are: maxillary first molar, maxillary second molar, maxillary third mola ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar (tooth)
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", from ''mola'', millstone and ''dens'', tooth. Molars show a great deal of diversity in size and shape across the mammal groups. The third molar of humans is sometimes vestigial. Human anatomy In humans, the molar teeth have either four or five cusps. Adult humans have 12 molars, in four groups of three at the back of the mouth. The third, rearmost molar in each group is called a wisdom tooth. It is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies among individuals and populations, and in many cases the tooth is missing. The human mouth contains upper (maxillary) and lower (mandibular) molars. They are: maxillary first molar, maxillary second molar, maxillary third mol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bishops (mammal)
''Bishops'' is an extinct genus of mammals from Early Cretaceous of Australia. The only recorded species, ''Bishops whitmorei'', was found on Flat Rocks, Wonthaggi Formation, Victoria. The genus was named in honour of Dr Barry Bishop, the former chairman of the Committee for Research and Exploration, National Geographic Society The National Geographic Society, headquartered in Washington, D.C., United States, is one of the largest nonprofit scientific and educational organizations in the world. Founded in 1888, its interests include geography, archaeology, natural sc .... References Further reading * Rich, T. H.; Flannery, T. F.; Trusler, P.; Kool, L.; van Klaveren, N. A. & Vickers-Rich, P. 2001. "A second tribosphenic mammal from the Mesozoic of Australia." ''Records of the Queen Victoria Museum'' 110: 1–9. Cretaceous mammals of Australia Australosphenida Extinct mammals of Australia {{cretaceous-mammal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammalia
A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, from which their ancestors diverged in the Carboniferous Period over 300 million years ago. Around 6,640 extant species of mammals have been described and divided into 27 orders. The study of mammals is called mammalogy. The largest orders of mammals, by number of species, are the rodents, bats, and eulipotyphlans (including hedgehogs, moles and shrews). The next three are the primates (including humans, monkeys and lemurs), the even-toed ungulates (including pigs, camels, and whales), and the Carnivora (including cats, dogs, and seals). Mammals are the only living members of Synapsida; this clade, together with Sauropsida (reptiles and birds), constitut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
