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Mesonychids
Mesonychia ("middle claws") is an extinct taxon of small- to large-sized carnivorous ungulates related to artiodactyls. Mesonychids first appeared in the early Paleocene, went into a sharp decline at the end of the Eocene, and died out entirely when the last genus, ''Mongolestes'', became extinct in the early Oligocene. In Asia, the record of their history suggests they grew gradually larger and more predatory over time, then shifted to scavenging and bone-crushing lifestyles before the group became extinct. Mesonychids probably originated in China, where the most primitive mesonychid, '' Yangtanglestes'', is known from the early Paleocene. They were also most diverse in Asia, where they occur in all major Paleocene faunas. Since other predators, such as creodonts and Carnivora, were either rare or absent in these animal communities, mesonychids most likely dominated the large predator niche in the Paleocene of eastern Asia. One genus, '' Dissacus'', had successfully spread to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesonychidae
Mesonychidae (meaning "middle claws") is an extinct family of small to large-sized omnivorous-carnivorous mammals. They were endemic to North America and Eurasia during the Early Paleocene to the Early Oligocene, and were the earliest group of large carnivorous mammals in Asia. They are not closely related to any living mammals. Mesonychid taxonomy has long been disputed and they have captured popular imagination as "wolves on hooves," animals that combine features of both ungulates and carnivores. Skulls and teeth have similar features to early whales, and the family was long thought to be the ancestors of cetaceans. Recent fossil discoveries have overturned this idea; the consensus is that whales are highly derived artiodactyls. Some researchers now consider the family a sister group either to whales or to artiodactyls, close relatives rather than direct ancestors. Other studies define Mesonychia as basal to all ungulates, occupying a position between Perissodactyla and Ferae ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mongolestes
''Mongolestes'' ("Mongolian robber") is an extinct genus of mesonychid known from the 'Ulan Gochu' formation of Inner Mongolia, and likely originated in Asia. It was the last surviving representative of Mesonychia and became extinct in the early Oligocene. ''Mongolestes'' is distinct from other mesonychids in several dental features, including very large teeth and the loss of the third molar, and a mandibular symphysis In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halve ... that is steeper. Notes References * * Mesonychids Rupelian extinctions Eocene mammals of Asia Oligocene mammals of Asia Prehistoric placental genera {{paleo-mammal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triisodontidae
Triisodontidae is an extinct, probably paraphyletic, or possibly invalid family of mesonychian placental mammals. Most triisodontid genera lived during the Paleocene in North America, but the genus '' Andrewsarchus'' (if it is a mesonychian, and not an artiodactyl) is known from the middle Eocene of Asia. Triisodontids were the first relatively large predatory mammals to appear in North America following the extinction of the non-bird dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...s. They differ from other mesonychian families in having less highly modified teeth. Because of their comparatively simpler teeth, the Triisodontids are regarded as basal mesonychids. A recent study found them to be a paraphyletic assemblage of stem-mesonychians.Sarah L. Shelley, Thomas E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hapalodectidae
Hapalodectidae (literal translation 'soft biters': ('soft, tender'), ('biter')) is an extinct family of relatively small-bodied () mesonychian placental mammals from the Paleocene and Eocene of North America and Asia. Hapalodectids differ from the larger and better-known mesonychids by having teeth specialized for cutting (presumably meat), while the teeth of other mesonychids, such as ''Mesonyx'' or '' Sinonyx'', are more specialized for crushing bones. Hapalodectids were once considered a subfamily of the Mesonychidae, but the discovery of a skull of '' Hapalodectes hetangensis'' showed additional differences justifying placement in a distinct family. In particular, ''H. hetangensis'' has a postorbital bar closing the back of the orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ungulate
Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses. Cetaceans such as whales, dolphins, and porpoises are also classified as even-toed ungulates, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving. The term means, roughly, "being hoofed" or "hoofed animal". As a descriptive term, "ungulate" normally excludes cetaceans as they do not possess most of the typical morphological characteristics of other ungulates, but recent discoveries indicate that they were also descended from early artiodactyls. Ungulates are typically herbivorous and many employ specialized gut bacteria to allow them to digest cellulose. Some modern species, such as pigs, are omnivor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ankalagon
''Ankalagon saurognathus'' is an extinct carnivorous mammal of the family Mesonychidae, endemic to North America during the Paleocene epoch (63.3—60.2 mya), existing for approximately . Known from the Paleocene Nacimiento Formation of New Mexico, ''Ankalagon'' is the largest mesonychid known from the Paleocene of North America, and it provides the best evidence for sexual dimorphism in mesonychids. Description The main feature that distinguishes ''A. saurognathus'' from the ancestral '' Dissacus'' species is its size: ''Ankalagon'' grew to be as large as a bear,Paleocene mammals of the world "Carnivores, creodonts and carnivorous ungulates: Mammals become predators" as compared to the coyote or jackal-sized species of ''Dissacus''. In fact, the only North American mesonychids that surpassed '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digitigrade
In terrestrial vertebrates, digitigrade () locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (metatarsals) touching the ground, and the rest of its foot lifted. Digitigrades include walking birds (what many assume to be bird knees are actually ankles), cats, dogs, and many other mammals, but not plantigrades or unguligrades. Digitigrades generally move more quickly and quietly than other animals. There are anatomical differences between the limbs of plantigrades, like humans, and both unguligrade and digitigrade limbs. Digitigrade and unguligrade animals have relatively long carpals and tarsals, and the bones which would correspond to the human ankle are thus set much higher in the limb than in a human. In a digitigrade animal, this effectively lengthens the foot, so much so that what are often thought of as a digitigrade animal's "hands" and "feet" corres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissacus
''Dissacus'' is a genus of extinct carnivorous jackal to coyote-sized mammals within the family Mesonychidae, an early group of hoofed mammals that evolved into hunters and omnivores. Their fossils are found in Paleocene to Early Eocene aged strata in France, Asia and southwest North America, from 66 to 50.3 mya, existing for approximately . Orientation patch analysis of the molar teeth of the North American ''D. praenuntius'' suggests it was an omnivore that ate a lot of meat, not an exclusive meat-eater like a cat or weasel. It shared its environment with more omnivorous mammals of a similar body size. Though they are not ancestral to Carnivora, ''Dissacus'' species may have had similar roles in Paleocene-early Eocene environments as the foxes and other small canids that evolved later: generalized hunters who also ate fruit or other foods, and caught small animals that lived on the ground. The bear-sized ''Ankalagon'' is closely related to ''Dissacus''. Some paleontologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pachyaena
''Pachyaena'' (literally, "thick hyena") was a genus of heavily built, relatively short-legged mesonychids, early Cenozoic mammals that evolved before the origin of either modern hoofed animals or carnivores, and combined characteristics similar to both. The genus likely originated from Asia and spread to Europe, and from there to North America across a land bridge in what is now the North Atlantic ocean. Various described species of ''Pachyaena'' ranged in size from a coyote to a bear. However, recent work indicates that ''Pachyaena'' is paraphyletic, with ''P. ossifraga'' being closer to '' Synoplotherium'', '' Harpagolestes'' and ''Mesonyx'' than to ''P. gigantea''. Unlike many mesonychids, ''Pachyaena'' is known from skeletal material in addition to skulls and jaws. Analysis of three wolf- to bear-sized species from the early Eocene of Wyoming (Willwood formation) indicates they all had many adaptations for running, including paraxonic compressed feet with a vestigial fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yangtanglestes
''Yantanglestes'' is a genus of small, Chinese mesonychid with slender jaws that first appeared during the Early Paleocene in the Thanetian stage. It was found throughout Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are .... It is the oldest known mesonychid. ''Yantanglestes'' became extinct during the Nongshanian division of the Late Paleocene,Missiaen, Pieter. "亚洲早古近纪哺乳动物生物年代学与生物地理学的新认识."古脊椎动物学报 49.1 (2011)paper/ref> and lived sympatrically with its descendant genera, including '' Dissacus'', '' Sinonyx'' and '' Jiangxia''. References External linksScience Mesonychids Paleocene mammals Thanetian life Paleocene mammals of Asia Paleogene China Prehistoric animals of China Fossil taxa described in 1980 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leigh Van Valen
Leigh Van Valen (August 12, 1935 – October 16, 2010) was a U.S. evolutionary biologist. At the time of his death, he was professor emeritus in the Department of Ecology and Evolution at the University of Chicago. Research and interests Amongst other work, Van Valen's proposed "Law of Extinction", known as Van Valen's law, drew upon the apparent constant probability (as opposed to rate) of extinction in families of related organisms, based on data compiled from existing literature on the duration of tens of thousands of genera throughout the fossil record. Van Valen proposed the Red Queen Hypothesis (1973), as an explanatory tangent to the Law of Extinction. The Red Queen Hypothesis captures the idea that there is a constant 'arms race' between co-evolving species. Its name is a reference to the Red Queen's race in Lewis Carroll's ''Through the Looking-Glass'', in which the chess board moves such that Alice must continue running just to stay in the same place. Van Valen als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
New Mexico
) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Keres, Zuni , Governor = , Lieutenant Governor = , Legislature = New Mexico Legislature , Upperhouse = Senate , Lowerhouse = House of Representatives , Judiciary = New Mexico Supreme Court , Senators = * * , Representative = * * * , postal_code = NM , TradAbbreviation = N.M., N.Mex. , area_rank = 5th , area_total_sq_mi = 121,591 , area_total_km2 = 314,915 , area_land_sq_mi = 121,298 , area_land_km2 = 314,161 , area_water_sq_mi = 292 , area_water_km2 = 757 , area_water_percent = 0.24 , population_as_of = 2020 , population_rank = 36th , 2010Pop = 2,117,522 , population_density_rank = 45th , 2000DensityUS = 17.2 , 2000Density = 6.62 , MedianHouseholdIncome = $51,945 , IncomeRank = 45th , AdmittanceOrder ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
