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Eutheria
Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic traits of the feet, ankles, jaws and teeth. All extant eutherians lack epipubic bones, which are present in all other living mammals (marsupials and monotremes). This allows for expansion of the abdomen during pregnancy. The oldest-known eutherian species is '' Juramaia sinensis'', dated at from the early Late Jurassic ( Oxfordian) of China. Eutheria was named in 1872 by Theodore Gill; in 1880 Thomas Henry Huxley defined it to encompass a more broadly defined group than Placentalia. Characteristics Distinguishing features are: *an enlarged malleolus ("little hammer") at the bottom of the tibia, the larger of the two shin bones *the joint between the first metatarsal bone and the entocuneiform bone (the innermost of the three cuneiform ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placentalia
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 from monotremes and marsupials in that the fetus (biology), fetus is carried in the uterus of its mother to a relatively late stage of development. The name is something of a misnomer considering that marsupials also nourish their fetuses via a placenta, though for a relatively briefer period, giving birth to less developed young which are then nurtured for a period inside the mother's pouch (marsupial), pouch. Anatomical features Placental mammals are anatomically distinguished from other mammals by: * a sufficiently wide opening at the bottom of the pelvis to allow the birth of a large baby relative to the size of the mother. * the absence of epipubic bones extending forward from the pelvis, which are found in all other mammals. (Their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marsupial
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 pouch. Marsupials include opossums, Tasmanian devils, kangaroos, koalas, wombats, wallabies, bandicoots, and the extinct thylacine. Marsupials represent the clade originating from the last common ancestor of extant metatherians, the group containing all mammals more closely related to marsupials than to placentals. They give birth to relatively undeveloped young that often reside in a pouch located on their mothers' abdomen for a certain amount of time. Close to 70% of the 334 extant species occur on the Australian continent (the mainland, Tasmania, New Guinea and nearby islands). The remaining 30% are found in the Americas—primarily in South America, thirteen in Central America, and one species, the Virginia opossum, in North America, n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zhelestidae
Zhelestidae is a lineage of extinct eutherian mammals. Occurring in the Late Cretaceous from the Turonian to the Maastrichtian, they were an extremely successful group, with representatives present in Europe, Asia, India (and subsequently in Madagascar), Africa and North America, ostensibly rendering them a cosmopolitan clade. They were specialised towards an herbivorous lifestyle and were in fact initially considered stem-ungulates, but the presence of epipubics and "archaic" dental characters render them as non-placental eutherians. Range The earliest zhelestid remains occur in the of . By the |
Asioryctitheria
Asioryctitheria ("Asian digging beasts") is an extinct order of early eutherians. Skull structure With the exception of '' Prokennalestes'', these advanced forms lacked a Meckelian groove. Furthermore, they were equipped with double-rooted canines, a lower premolar with a reduced or absent metaconid and a more elongated lower premolar than their predecessors. In addition, the entoconid and hypoconulid on the lower molars are untwinned, the entotympanic is non-existent, the alisphenoid is enlarged, a Vidian foramen is present as well as a promontorium linked to the paroccipital process via the crista interfenestralis. Classification Asioryctitheria contains at least four genera and two families.Mikko's Phylogeny ArchivPaleofile.com (net, info) . * '' Sasayamamylos kawaii'' Kusuhashi et al. 2013 * Kennalestidae ''Kennalestes'' is an extinct genus of insectivorous mammal resembling a shrew that was described in 1968.Z. Kielan-Jaworowska. 1968. New Upper Cretaceous multi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leptictida
Leptictida (''leptos iktis'' "small/slender weasel") is a possibly paraphyletic extinct order of eutherian mammals. Their classification is contentious: according to cladistic studies, they may be (distantly) related to Euarchontoglires (rodents, primates and their relatives), although they are more recently regarded as the first branch to split from basal eutherians. One recent large-scale cladistic analysis of eutherian mammals favored lepictidans as close to the placental crown-clade; and several other recent analyses that included data from Cretaceous non-eutherian mammals found ''Leptictis'' to belong to the superorder Afrotheria. The most recent phylogenetic studies recover it as actually a paraphyletic assemblage leading to Placentalia. Description The leptictids are a characteristic example of the non-specialized placental mammals that took part in the late Cretaceous-Paleocene evolutionary radiation, originally bunched together in the order Insectivora. The leptictids ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Juramaia
''Juramaia'' is an extinct genus of very basal eutherian mammal known from the Late Jurassic ( Oxfordian stage) deposits of western Liaoning, China. It is a small shrew-like mammal with a body length of approximately 70–100 mm, making it similar in size to the modern De Winton's shrew. ''Juramaia'' is known from the holotype BMNH PM1343, an articulated and nearly complete skeleton including incomplete skull preserved with full dentition. Discovery It was collected in the Daxigou site, Jianchang, from the Tiaojishan Formation dated at about . It was first named by Zhe-Xi Luo, Chong-Xi Yuan, Qing-Jin Meng and Qiang Ji in 2011 and the type species is ''Juramaia sinensis''. Evolution The discovery of ''Juramaia'' provides new insight into the evolution of placental mammals by showing that their lineage diverged from that of the marsupials 35 million years earlier than previously thought. Furthermore, its discovery fills gaps in the fossil record and helps to calibrate mod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Montanalestes
''Montanalestes'' is an extinct mammal known from the Cretaceous in North America. Classification Known from only six fossil teeth, ''Montanalestes'' is an example of the less well-preserved early eutherian Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic tra ...s found on the northern hemisphere, apparently more closely related to later eutherians than '' Prokennalestes'', and '' Murtoilestes''. References Prehistoric eutherians Cretaceous mammals of North America Cloverly fauna Fossil taxa described in 1999 Prehistoric mammal genera {{cretaceous-mammal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adapisoriculidae
Adapisoriculidae is an extinct family of non-placental eutherian mammals present during the Paleogene and possibly the Late Cretaceous. They were once thought to be members of the order Erinaceomorpha, closely related to the hedgehog family (Erinaceidae), because of their similar dentition, or to be basal Euarchontans. They were also thought to be marsupials at one point. Most recent studies show them to be non-placental eutherians, however.Carly L. Manz, Stephen G. B. Chester, Jonathan I. Bloch, Mary T. Silcox, Eric J. Sargis, New partial skeletons of Palaeocene Nyctitheriidae and evaluation of proposed euarchontan affinities, Published 14 January 2015.DOI: 10.1098/rsbl.2014.0911 They were small mammals of about 15 cm long, with a tail of equal length. They were probably nocturnal, eating insects and fruits. '' Deccanolestes'' and '' Sahnitherium'' from the Late Cretaceous of India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 placental mammals, who lack them). They first occur in non-mammalian cynodonts such as tritylodontids, suggesting that they are a synapomorphy between them and Mammaliformes. They were first described as early as 1698, but to date, their function(s) remain unresolved. Epipubic bones are often called ''marsupial bones'' because they support the mother's pouch in modern marsupials ("''marsupium''" is Latin for "pouch"). Function Some writers have suggested that the epipubic bones are a part of a kinetic link stretching from the femur on one side, to the ribs on the opposite side. This linkage is formed by a series of muscles: Each epipubic bone is connected to the femur by the pectineus muscle, and to the ribs and vertebrae by the pyramidalis, rectus abdominis, and external and inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acristatherium
''Acristatherium yanensis'' is an extinct basal eutherian from the Early Cretaceous (early Aptian, about ) Lujiatun Bed of the Yixian Formation. It was described on the basis of a single specimen (holotype) from Beipiao, Liaoning, China, by Yaoming Hu, Jin Meng, Chuankui Li, and Yuanqing Wang in 2010. The specimen comprises a partial skull, long. It appears to possess a vestige of a septomaxilla, a feature only otherwise seen in nonmammalian therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...s. References Prehistoric eutherians Early Cretaceous mammals of Asia Fossil taxa described in 2010 Prehistoric mammal genera {{cretaceous-mammal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zalambdalestidae
Zalambdalestidae is a clade of Asian eutherians occurring during the Late Cretaceous. Once classified as Glires, features like epipubic bones and various cranial elements have identified these animals as outside of Placentalia, representing thus a specialised clade of non-placental eutherians without any living descendants, and potentially rather different from modern placentals in at least reproductive anatomy. Taxonomy The exact position of Zalambdalestidae within Eutheria varies, though they are generally agreed to be more basal than zhelestids. Currently, the clade includes the genera ''Zalambdalestes'', '' Alymlestes'', '' Anchilestes'', '' Barunlestes'', '' Kulbeckia'', '' Zhangolestes'' and '' Zofialestes''. Palaeobiology Zalambdaltestids were insectivores, having zalambdodont molars much as various modern insectivorous species. They are uniquely suited to a saltatorial, cursorial lifestyle, bearing long, semi-digitigrade limbs and a spinal column similar to that of mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Durlstotherium
''Durlstotherium'' is an extinct genus of mammal from the Early Cretaceous. It contains a single species, ''Durlstotherium newmani''. The type specimen was found in Durlston Bay, Dorset, after which the genus was named. ''D. newmani'' was named after a British pub landlord, Charlie Newman. ''Durlstotherium'' and two of its contemporaries, '' Tribactonodon'' and '' Durlstodon'', had tribosphenidan (three-cusped) molars, which are an advanced characteristic among eutheria Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic tra ...n mammals and suggest that the group emerged earlier than the Early Cretaceous. References {{Taxonbar, from=Q42898185 Prehistoric eutherians Fossil taxa described in 2017 Berriasian genera Early Cretaceous mammals of Europe Prehistoric mammal genera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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