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Hunter-Schreger Band
Hunter-Schreger bands, commonly abbreviated as HSB, are features of the enamel of the teeth in mammals, mostly placentals.Line and Bergqvist, 2005, p. 924 In HSB, enamel prisms are arranged in layers of varying thickness at about right angles to each other. HSB strengthen the enamel and prevent cracks from propagating through the tooth.Martin, 1994, p. 121 HSB are first observed in early Paleocene mammals, but at this time the HSB occupy only a small portion of the incisor and the angle between the bands is low. By the late Paleocene, HSB is seen to extend throughout the enamel and the bands are located at nearly right angles to each other. Under oblique reflected light HSB can be seen as dark and light strips of variable width. Among Glires, the group containing rodents, lagomorphs, and their primitive relatives, the absence of HSB from the incisors has been considered primitive.Martin, 2004, p. 411 Some early representatives, including '' Eurymylus'', lack HSB, b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tooth Enamel
Tooth enamel is one of the four major Tissue (biology), tissues that make up the tooth in humans and many other animals, including some species of fish. It makes up the normally visible part of the tooth, covering the Crown (tooth), crown. The other major tissues are dentin, cementum, and Pulp (tooth), dental pulp. It is a very hard, white to off-white, highly mineralised substance that acts as a barrier to protect the tooth but can become susceptible to degradation, especially by acids from food and drink. Calcium hardens the tooth enamel. In rare circumstances enamel fails to form, leaving the underlying dentin exposed on the surface. Features Enamel is the hardest substance in the human body and contains the highest percentage of minerals (at 96%),Ross ''et al.'', p. 485 with water and organic material composing the rest.Ten Cate's Oral Histology, Nancy, Elsevier, pp. 70–94 The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate. Enamel is formed o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leporidae
Leporidae is the family of rabbits and hares, containing over 60 species of extant mammals in all. The Latin word ''Leporidae'' means "those that resemble ''lepus''" (hare). Together with the pikas, the Leporidae constitute the mammalian order Lagomorpha. Leporidae differ from pikas in that they have short, furry tails and elongated ears and hind legs. The common name "rabbit" usually applies to all genera in the family except ''Lepus'', while members of ''Lepus'' (almost half the species) usually are called hares. Like most common names, however, the distinction does not match current taxonomy completely; jackrabbits are members of ''Lepus'', and members of the genera ''Pronolagus'' and ''Caprolagus'' sometimes are called hares. Various countries across all continents except Antarctica and Australia have indigenous species of Leporidae. Furthermore, rabbits, most significantly the European rabbit, ''Oryctolagus cuniculus'', also have been introduced to most of Oceania and to m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carnivora
Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are formally referred to as carnivorans, and have evolved to specialize in eating flesh. The order is the fifth largest order of mammals, comprising at least 279 species. Carnivorans live on every major landmass and in a variety of habitats, ranging from the cold polar regions to the hyper-arid region of the Sahara Desert to the open seas. They come in a very large array of different body plans in contrasting shapes and sizes. Carnivora can be divided into two subclades: the cat-like Feliformia and the dog-like Caniformia, which are differentiated based on the structure of their ear bones and cranial features. The feliforms include families such as the felidae, cats, the hyenas, the mongooses and the viverridae, civets. The majority of felifor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Octodontoidea
Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now accepted as a genuine part of the rodents. Caviomorphs include the extinct Heptaxodontidae (giant hutias) and extant families of chinchilla rats, hutias, guinea pigs and the capybara, chinchillas and viscachas, tuco-tucos, agoutis, pacas, pacaranas, spiny rats, New World porcupines, coypu and octodonts (Vassallo and Antenucci, 2015). Origin The first known rodent fossils in South America are represented by the three taxa ''Cachiyacuy contamanensis'', ''C. kummeli'', and ''Canaanimys maquiensis'', as well as teeth from ''Eobranisamys'' sp. (Dasyproctidae) and ''Eospina'' sp., the latter two found also in the Santa Rosa fauna from the late Eocene or early Oligocene. By the late Oligocene, all superfamilies and most families of ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Springhare
''Pedetes'' is a genus of rodent, the springhares, in the family Pedetidae. Members of the genus are distributed across southern and Eastern Africa. Species A number of species both extant and extinct are classified in the genus ''Pedetes''. They include: * South African springhare or ''springhaas'' (''Pedetes capensis'') * East African springhare (''Pedetes surdaster'') * ''Pedetes laetoliensis'' (Davies, 1987) (Pliocene fossil) Throughout the 20th century, the living species (and occasionally the prehistoric one) were merged into ''P. capensis'', making the genus monotypic. Ecology These rodents are generally nocturnal and sleep through the day in burrows they dig. They feed on foliage, roots and other vegetable matter, and occasionally arthropods. Outside the burrow they usually move around by hopping on their hind legs. When only one springhare species was recognized, it was listed as vulnerable by the IUCN in 1996 due to an approximately 20% decrease in the population o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gundi
Gundis or comb rats (family Ctenodactylidae) are a group of small, stocky rodents found in Africa. They live in rocky deserts across the northern parts of the continent. The family comprises four living genera and five species ( Speke's gundi, Felou gundi, Val's or desert gundi, common or North African gundi and Mzab gundi), as well as numerous extinct genera and species. They are in the superfamily Ctenodactyloidea. Local people in northern Africa have always known about gundis, however they first came to the notice of western naturalists in Tripoli in 1774, and were given the name ''gundi mice''. While they are not regarded as pests, some people hunt gundis for food. Description Gundis are from 17 to 18 cm in body length, with compact bodies covered in soft fur, short legs, and large eyes. They have only four toes on all feet and the middle toes of the hind feet carry comb-like bristles, which earned them the name "comb rat". Gundis have short tails, which in some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hystricognathi
The Hystricognathi are an infraorder of rodents, distinguished from other rodents by the bone structure of their skulls. The masseter medialis (a jaw muscle) passes partially through a hole below each eye socket (called the infraorbital foramen) and connects to the bone on the opposite side. This, together with their lack of an infraorbital plate and the relative size of the infraorbital foramen, distinguishes hystricognaths from other rodent groups. The 18 families within the Hystricognathi are divided into two parvorders, the Phiomorpha and the Caviomorpha. The Caviomorpha are mostly native to South America, with a few species in the Caribbean and North America, while the Phiomorpha occur in the Old World. Behavior Play behavior has been observed in seven hystricognath families. The caviomorphs chase each other, play-wrestle, and gallop. The longer-legged species chase more often than the shorter-legged species. They also rotate their heads and body muscles as a form of pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (annum, Mya) to the beginning of the Neogene Period Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon. The earlier term Tertiary Period was used to define the span of time now covered by the Paleogene Period and subsequent Neogene Period; despite no longer being recognised as a formal stratigraphy, stratigraphic term, 'Tertiary' is still widely found in earth science literature and remains in informal use. Paleogene is often abbreviated "Pg" (but the United States Geological Survey uses the abbreviation PE for the Paleogene on the Survey's geologic maps). During the Paleogene, evolution of mammals, mammals diversified from relatively small, simple forms into a large group of diverse animals in the wake of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "dawn") and (''kainós'', "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope Carbon-13, 13C in the atmosphere was exceptionally low in comparison with the more common isotope Carbon-12, 12C. The end is set at a major extinction event called the ''Grande Coupure'' (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Popigai impact structure, Siberia and in what is now ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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