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Placentals
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 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. Placentalia represents the only living group within Eutheria, which contains all mammals that are more closely related to placentals than they are to marsupials. 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 ... [...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] |
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ninth and longest geological period of the entire Phanerozoic. The name is derived from the Latin , 'chalk', which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation . The Cretaceous was a period with a relatively warm climate, resulting in high Sea level#Local and eustatic, eustatic sea levels that created numerous shallow Inland sea (geology), inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites, and rudists, while dinosaurs continued to dominate on land. The world was largely ice-free, although there is some evidence of brief periods of glaciation during the cooler first half, and forests extended to the poles. Many of the dominant taxonomic gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boreoeutheria
Boreoeutheria (, "northern eutherians") is a magnorder of Placentalia, placental mammals that groups together superorders Euarchontoglires and Laurasiatheria. The clade includes groups as diverse as giraffes, Sus (genus), pigs, zebras, Rhinoceros, rhinos, canidae, dogs, felidae, cats, rabbits, mouse, mice, squirrels, bats, whales, dolphins, lemurs, and Simian, simians (Monkey, monkeys and apes). With a few exceptions,Exceptional clades whose males lack the usual boreoeutherian scrotum are Mole (animal), moles, hedgehogs, pangolins, some pinnipeds, rhinoceroses, tapirs, hippopotamuses, and cetaceans. male boreoeutherians have a scrotum, an ancestral feature of the clade. The sub-clade Scrotifera was named after this feature. Etymology The name of this magnorder comes from Ancient Greek words: * () meaning 'Boreas (god), north wind' or 'the North', * () meaning 'good', 'right', or 'true', * and () meaning 'beast'. Boreoeutherian ancestor The majority of earliest known fossi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maastrichtian
The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (stratigraphy), Series, the Cretaceous geologic period, Period or system (stratigraphy), System, and of the Mesozoic geologic era, Era or Erathem. It spanned the interval from . The Maastrichtian was preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene). It is named after the city of Maastricht, the capital and largest city of the Limburg (Netherlands), Limburg province in the Netherlands. The Cretaceous–Paleogene extinction event (formerly known as the Cretaceous–Tertiary period, Tertiary extinction event) occurred at the end of this age. In this extinction event, mass extinction, many commonly recognized groups such as non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-kn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reindeer
The reindeer or caribou (''Rangifer tarandus'') is a species of deer with circumpolar distribution, native to Arctic, subarctic, tundra, taiga, boreal, and mountainous regions of Northern Europe, Siberia, and North America. It is the only representative of the genus ''Rangifer''. More recent studies suggest the splitting of reindeer and caribou into six distinct species over their range. Reindeer occur in both Animal migration, migratory and wiktionary:sedentary#Adjective, sedentary populations, and their herd sizes vary greatly in different regions. The tundra subspecies are adapted for extreme cold, and some are adapted for long-distance migration. Reindeer vary greatly in size and color from the smallest, the Svalbard reindeer (''R.'' (''t.'') ''platyrhynchus''), to the largest, Osborn's caribou (''R. t. osborni''). Although reindeer are quite numerous, some species and subspecies are in decline and considered Vulnerable species, vulnerable. They are unique among deer (Ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infraclass
In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of organisms (a ''taxon'') in a hierarchy that reflects evolutionary relationships. Thus, the most inclusive clades (such as Eukarya and Animalia) have the highest ranks, whereas the least inclusive ones (such as ''Homo sapiens'' or ''Bufo bufo'') have the lowest ranks. Ranks can be either relative and be denoted by an indented taxonomy in which the level of indentation reflects the rank, or absolute, in which various terms, such as species, genus, family, order, class, phylum, kingdom, and domain designate rank. This page emphasizes absolute ranks and the rank-based codes (the Zoological Code, the Botanical Code, the Code for Cultivated Plants, the Prokaryotic Code, and thCode for Viruses require them. However, absolute ranks are not req ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taeniodonta
Taeniodonta ("banded teeth") is an extinct order of eutherian mammals, that lived in North America and Europe from the late Cretaceous (Maastrichtian) to the middle Eocene. Taeniodonts evolved quickly into highly specialized digging animals, and varied greatly in size, from rat-sized to species as large as a bear. Later species developed prominent front teeth and huge claws for digging and rooting. Some genera, like '' Stylinodon'', had ever-growing teeth. The scarcity of taeniodont fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...s can be explained by the fact that these animals probably lived in dry or arid climates unconductive to fossilization. According to 2022 studies of Bertrand, O. C. and Sarah L. Shelley, taeniodonts are identified to be a basal placental ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palaeoryctidae
Palaeoryctidae ("ancient diggers") is an extinct family of non-specialized eutherian mammals from extinct order Palaeoryctida, that lived in North America, Europe, Asia and Africa from the late Cretaceous to the middle Eocene.Gregg F. Gunnell, Thomas Bown, Jonathan Ivan Bloch, Doug M. Boyer (2008."Proteutheria" pp. 63–81 in C. M. Janis, G. F. Gunnell, and M. Uhen (eds.), "Evolution of Tertiary Mammals of North America. Volume 2: Small Mammals, Xenarthrans, and Marine Mammals." Cambridge University Press, Cambridge, U.K. Description From a near-complete skull of the genus '' Palaeoryctes'' found in New Mexico, it is known that palaeoryctids were small, shrew-like insectivores with an elongated snout similar to that of the leptictids. However, in contrast to the latter, little is known about palaeoryctids' postcranial anatomy (the skeleton without the skull). A 2024 study found shared cranial details between palaeoryctids and leptictids, suggesting a possible close relationshi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlantogenata
Atlantogenata ("born around the Atlantic Ocean") is a proposed magnorder of placental mammals containing the cohorts or superorders Xenarthra and Afrotheria. These groups originated and radiated in the South American and African continents, respectively, presumably in the Cretaceous. Together with Boreoeutheria, they make up Placentalia. The monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ... of this grouping is supported by some genetic evidence. Alternative hypotheses are that Boreoeutheria and Afrotheria combine to form Epitheria (as generally supported by anatomical and other physiological evidence) or that Boreoeutheria and Xenarthra combine to form Exafroplacentalia or Notolegia. Updated analysis of transposable element insertions around the time of diverg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
