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Plagiaulacoid
A plagiaulacoid is a type of blade-like, most often serrated, tooth present in various mammal groups, usually a premolar. Among modern species it is present chiefly on diprotodontian marsupials (specifically, Potoroidae, ''Bettongia'' and ''Burramys''), which have both the upper and lower first premolars converted into serrated blades. However, various other extinct groups also possessed plagiaulacoids. These would be multituberculates, some "Plesiadapiformes" such as ''Carpolestes'' and various metatherians such as '' Epidolops'' and various early diprotodontians. In many of these only a lower premolar became converted into a blade, while the upper premolars showed less specialisation. The various independent development of these teeth is considered a good example of convergent evolution. Multituberculates in particular probably own the most specialised of all plagiaulacoids. In early taxa, all lower premolars became plagiaulacoids, forming a "saw"-like arrangement. However, in Cim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plagiaulacoid Premolars
A plagiaulacoid is a type of blade-like, most often serrated, tooth present in various mammal groups, usually a premolar. Among modern species it is present chiefly on diprotodontian marsupials (specifically, Potoroidae, ''Bettongia'' and ''Burramys''), which have both the upper and lower first premolars converted into serrated blades. However, various other extinct groups also possessed plagiaulacoids. These would be multituberculates, some "Plesiadapiformes" such as ''Carpolestes'' and various metatherians such as '' Epidolops'' and various early diprotodontians. In many of these only a lower premolar became converted into a blade, while the upper premolars showed less specialisation. The various independent development of these teeth is considered a good example of convergent evolution. Multituberculates in particular probably own the most specialised of all plagiaulacoids. In early taxa, all lower premolars became plagiaulacoids, forming a "saw"-like arrangement. However, in Cim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multituberculates
Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, and reached a peak diversity during the Late Cretaceous and Paleocene. They eventually declined from the mid Paleocene onwards, disappearing from the known fossil record in the late Eocene. They are the most diverse order of Mesozoic mammals with more than 200 species known, ranging from mouse-sized to beaver-sized. These species occupied a diversity of ecological niches, ranging from burrow-dwelling to squirrel-like arborealism to jerboa-like hoppers. Multituberculates are usually placed as crown mammals outside either of the two main groups of living mammals—Theria, including placentals and marsupials, and MonotremataAgustí-Antón 2002, pp 3-4—but usually as closer to Theria than to monotremes. They are considered to be clo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multituberculates
Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, and reached a peak diversity during the Late Cretaceous and Paleocene. They eventually declined from the mid Paleocene onwards, disappearing from the known fossil record in the late Eocene. They are the most diverse order of Mesozoic mammals with more than 200 species known, ranging from mouse-sized to beaver-sized. These species occupied a diversity of ecological niches, ranging from burrow-dwelling to squirrel-like arborealism to jerboa-like hoppers. Multituberculates are usually placed as crown mammals outside either of the two main groups of living mammals—Theria, including placentals and marsupials, and MonotremataAgustí-Antón 2002, pp 3-4—but usually as closer to Theria than to monotremes. They are considered to be clo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tooth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the embryonic germ layer, the ectoderm. The general structure of teeth is similar across the vertebrates, although there is considerable variation in their form and position. The teeth of mammals have deep roots, and this pattern is also found in some fish, and in crocodilians. In most teleost fish, however, the teeth are attached to the outer surface of the bone, while in lizards they are attached to the inner surface of the jaw by one side. In cartilaginous fish, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teeth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the embryonic germ layer, the ectoderm. The general structure of teeth is similar across the vertebrates, although there is considerable variation in their form and position. The teeth of mammals have deep roots, and this pattern is also found in some fish, and in crocodilians. In most teleost fish, however, the teeth are attached to the outer surface of the bone, while in lizards they are attached to the inner surface of the jaw by one side. In cartilaginous fish, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kangaroo
Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern grey kangaroo, and western grey kangaroo. Kangaroos are indigenous to Australia and New Guinea. The Australian government estimates that 42.8 million kangaroos lived within the commercial harvest areas of Australia in 2019, down from 53.2 million in 2013. As with the terms "wallaroo" and "wallaby", "kangaroo" refers to a paraphyletic grouping of species. All three terms refer to members of the same taxonomic family, Macropodidae, and are distinguished according to size. The largest species in the family are called "kangaroos" and the smallest are generally called "wallabies". The term "wallaroos" refers to species of an intermediate size. There are also the tree-kangaroos, another type of macropod, which inhabit the tropical ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gondwanathere
Gondwanatheria is an extinct group of mammaliaforms that lived in parts of Gondwana, including Madagascar, India, South America, Africa and Antarctica during the Upper Cretaceous through the Paleogene (and possibly much earlier, if '' Allostaffia'' is a member of this group). Until recently, they were known only from isolated teeth, a few lower jaws, two partial skulls and one complete cranium. They are generally considered to be closely related to the multituberculates and likely the euharamiyidians, well known from the Northern Hemisphere, with which they form the clade Allotheria. Classification For several decades the affinities of the group were not clear, being first interpreted as early xenarthrans, or "toothless" mammals similar to the modern anteater. A variety of studies have placed them as allotheres related to multituberculates, possibly even true multituberculates, closer to cimolodonts than "plagiaulacidans" are. However, a more recent study recovered them as ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taeniolabidoids
Taeniolabidoidea is a group of extinct mammals known from North America and Asia. They were the largest members of the extinct order Multituberculata, as well as the largest non-therian mammals. '' Lambdopsalis'' even provides direct fossil evidence of mammalian fur in a fairly good state of preservation for a 60-million-year-old animal. Some of these animals were large for their time; '' Taeniolabis taoensis'' is the largest known multituberculate and though smaller, '' Yubaatar'' is the largest known Mesozoic Asian multituberculate.L. Xu, X. Zhang, H. Pu, S. Jia, and J. Zhang, J., and J. Meng. 2015. Largest known Mesozoic multituberculate from Eurasia and implications for multituberculate evolution and biology. Scientific Reports 5(14950):1-11 Average members of the Taeniolaboidea were about beaver-sized and the largest even reached sizes comparable to the largest beavers like ''Castoroides'', up to about 100 kilograms. The group was initially established as a suborder, before b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carnassial
Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified fourth upper premolar and the first lower molar, however this may vary in family. These teeth are also referred to as sectorial teeth. Taxonomy The name carnivoran is applied to a member of the order Carnivora. Carnivorans possess a common arrangement of teeth called carnassials, in which the first lower molar and the last upper premolar possess blade-like enamel crowns that act similar to a pair of shears for cutting meat. This dental arrangement has been modified by adaptation over the past 60 million years for diets composed of meat, for crushing vegetation, or for the loss of the carnassial function altogether as in seals, sea lions, and walruses. Carnassial dentition Carnassial teeth are modified molars (and in the case of carn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thylacoleonidae
Thylacoleonidae is a family of extinct meat-eating marsupials from Australia, referred to as marsupial lions. The best known is ''Thylacoleo carnifex'', also called the marsupial lion. The clade ranged from the Late Oligocene to the Pleistocene, with some species the size of a possum and others as large as that of a leopard. As a whole, they were largely arboreal, in contrast to the mostly terrestrial dasyuromorphs (quolls only recently took the niches vacated by small thylacoleonids), monitor lizards and mekosuchines. Hypercarnivory was also found in another order of marsupials, the dasyuromorph family Thylacinidae that included the Tasmanian tiger ''Thylacinus cynocephalus'' that became extinct in the twentieth century. Description A diprotodontian family allied to the Vombatiformes, mammals that radiated and diversified in the Oligocene to Miocene. The thylacoleonid genera exhibit specialised dentition that allowed them to kill prey larger than themselves. The earliest d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Champsosaurus
''Champsosaurus'' is an extinct genus of crocodile-like choristodere reptile, known from the Late Cretaceous and early Paleogene periods of North America and Europe (Campanian-Paleocene). The name ''Champsosaurus'' is thought to come from , () said in an Ancient Greek source to be an Egyptian word for "crocodiles", and , () Greek for "lizard". The morphology of ''Champsosaurus'' resembles that of gharials, with a long, elongated snout. It was native to freshwater environments where it likely preyed on fish, similar to living gharials. History of research ''Champsosaurus'' was the first member of the Choristodera to be described. ''Champsosaurus'' was named by Edward Drinker Cope in 1876, from isolated vertebrae found in Late Cretaceous strata of the Judith River Formation on the banks of the Judith River in Fergus County, Montana. Cope designated ''C. annectens'' as the type species rather than the first named ''C. profundus'' due to the larger number of vertebrae he attributed t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. Their blood is not totally contained in vessels; some circulates in an open cavity known as the haemocoel. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms. The total number of extant species is estimated at between six and ten million; In: potentially over 90% of the animal life forms on Earth are insects. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, which are dominated by another arthropod group, crustaceans, which recent research has indicated insects are nested within. Nearly all insects hatch from eggs. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
