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Astrochelys Rogerbouri
''Astrochelys rogerbouri'' is an extinct tortoise species in the family Testudinidae which formerly lived in Madagascar. Discovery and naming The type specimen, MNHN.F.MAD480, is a nearly complete tibia and was collected in June 1900 in Ambolisatra, Madagascar by Guillaume Grandidier. It is kept at the Muséum national d’histoire naturelle. This material was originally assigned as a juvenile specimen of '' Aldabrachelys abrupta'', likely as the two share a type locality, and it was only found to represent a new species after DNA analysis. The specific name honors Roger Bour, a herpetologist and expert on western Indian Ocean giant tortoises who helped in the investigation describing this species. Description ''Astrochelys rogerbouri'' was a large tortoise species, with an estimated straight carapace length of 50 cm. This matches the size of its congeneric relative, the angonoka tortoise, which has a maximum straight carapace length of 51.9 cm. Though it is only known f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tortoise
Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like other members of the suborder Cryptodira, they retract their necks and heads directly backward into the shell to protect them. Tortoises can vary in size with some species, such as the Galápagos giant tortoise, growing to more than in length, whereas others like the Speckled cape tortoise have shells that measure only long. Several lineages of tortoises have independently evolved very large body sizes in excess of 100 kg, including the Galapagos giant tortoise and the Aldabra giant tortoise. They are usually diurnal animals with tendencies to be crepuscular depending on the ambient temperatures. They are generally reclusive animals. Tortoises are the longest-living land animals in the world, although the longest-living specie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Divergence
Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time, often leading to reproductive isolation and continued mutation even after the populations have become reproductively isolated for some period of time, as there isn’t genetic exchange anymore. In some cases, subpopulations living in ecologically distinct peripheral environments can exhibit genetic divergence from the remainder of a population, especially where the range of a population is very large (see parapatric speciation). The genetic differences among divergent populations can involve silent mutations (that have no effect on the phenotype) or give rise to significant morphological and/or physiological changes. Genetic divergence will always accompany reproductive isolation, either due to novel adaptations via selection and/or due to genetic drift, and is the principal mechanism underlying speciation. On a molecular gene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocene Extinctions
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch, called the Flandrian interglacial.Oxford University Press – Why Geography Matters: More Than Ever (book) – "Holocene Humanity" section https://books.google.com/books?id=7P0_sWIcBNsC The Holocene corresponds with the rapid proliferation, growth and impacts of the human species worldwide, including all of its written history, technological revolutions, development of major civilizations, and overall significant transition towards urban living in the present. The human impact on modern-era Earth and its ecosystems may be considered of global ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinct Animals Of Madagascar
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence. More than 99% of all species that ever lived on Earth, amounting to over five billion species, are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryote globally, and possibly many times more if microorganisms, like bacteria, are included. Notable extinct animal species include non-avian dinosaurs, saber-toothed cats, dodos, m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrochelys
''Astrochelys'' is a genus of tortoises in the family Testudinidae. The two species are both found in Madagascar, and both classified as critically endangered on the IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol .... Species References ;Bibliography * {{Taxonbar, from=Q779267 Turtles of Africa Reptiles of Madagascar Endemic fauna of Madagascar Turtle genera Taxa named by John Edward Gray ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Before Present
Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date ( epoch) of the age scale. The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must now account for. In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation RCYBP stands for the explicit "radio carbon years before present". Usage The BP scale is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy. This usage differs from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiated Tortoise
The radiated tortoise (''Astrochelys radiata'') is a tortoise species in the family Testudinidae. Although this species is native to and most abundant in southern Madagascar, it can also be found in the rest of this island, and has been introduced to the islands of Réunion and Mauritius. It is a very long-lived species, with recorded lifespans of up to 188 years. These tortoises are classified as critically endangered by the IUCN, mainly because of the destruction of their habitat and because of poaching. Description Growing to a carapace length of up to 16 in (41 cm) and weighing up to 35 lb (16 kg), the radiated tortoise is considered to be one of the world's most beautiful tortoises. This tortoise has the basic "tortoise" body shape, which consists of the high-domed carapace, a blunt head, and elephantine feet. The legs, feet, and head are yellow except for a variably sized black patch on top of the head. The carapace of the radiated tortoise is br ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sympatry
In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation. Such speciation may be a product of reproductive isolation – which prevents hybrid offspring from being viable or able to reproduce, thereby reducing gene flow – that results in genetic divergence. Sympatric speciation may, but need not, arise through secondary contact, which refers to speciation or divergence in allopatry followed by range expansions leading to an area of sympatry. Sympatric species or taxa in secondary contact may or may not interbreed. Types of populations Four main types of population pairs exist in nature. Sympatric populations (or species) contrast with parapatric populations, which contact one another in adjacent but not shared ranges and do n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spider Tortoise
The spider tortoise (''Pyxis arachnoides'') is a species of tortoise in the family Testudinidae that is endemic to Madagascar and is one of only two species in the genus ''Pyxis''. Habitat The remaining tortoises are found only in south western Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ..., where they inhabit the spiny vegetation of the sandy coastal areas. Life cycle and breeding Very little is known about the life cycle of this endangered tortoise, which is believed to live for up to 70 years. Here they feed on young leaves, insect larvae, and even the droppings of larger animals. When the wet season arrives, the dormancy period ends and the tortoises begin to mate. Females only lay one egg when they reproduce, and the egg is incubated for about 220–250 days. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrochelys Radiata
The radiated tortoise (''Astrochelys radiata'') is a tortoise species in the family Testudinidae. Although this species is native to and most abundant in southern Madagascar, it can also be found in the rest of this island, and has been introduced to the islands of Réunion and Mauritius. It is a very long-lived species, with recorded lifespans of up to 188 years. These tortoises are classified as critically endangered by the IUCN, mainly because of the destruction of their habitat and because of poaching. Description Growing to a carapace length of up to 16 in (41 cm) and weighing up to 35 lb (16 kg), the radiated tortoise is considered to be one of the world's most beautiful tortoises. This tortoise has the basic "tortoise" body shape, which consists of the high-domed carapace, a blunt head, and elephantine feet. The legs, feet, and head are yellow except for a variably sized black patch on top of the head. The carapace of the radiated tortoise i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldabrachelys Grandidieri
''Aldabrachelys grandidieri'', or Grandidier's giant tortoise, is an extinct species of tortoise that was endemic to Madagascar. Mitochondrial DNA extracted from subfossil bone confirm that it is a distinct species. Description ''Aldabrachelys grandidieri'' was a giant tortoise, one of the largest in the world, measuring about in carapace length. It was originally one of the six endemic tortoise species of Madagascar (two large '' Aldabrachelys''; two medium '' Astrochelys''; two small '' Pyxis''). It is distinguished from all other '' Aldabrachelys'' by a massive, flattened or depressed carapace, bulging sides of the carapace, short gulars, top of the nasal aperture is higher than the top of orbits, diverging quadrates, broad postorbitals, and a very large processus vomerinus dorsalis. It also had an unusually thick, strong carapace, possibly an adaptation to heavy predation. It seems to have been predominantly a grazer of meadows and wetlands. Extinction Material of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitochondrial Genome
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of the DNA can be found in the cell nucleus and, in plants and algae, also in plastids such as chloroplasts. Human mitochondrial DNA was the first significant part of the human genome to be sequenced. This sequencing revealed that the human mtDNA includes 16,569 base pairs and encodes 13 proteins. Since animal mtDNA evolves faster than nuclear genetic markers, it represents a mainstay of phylogenetics and evolutionary biology. It also permits an examination of the relatedness of populations, and so has become important in anthropology and biogeography. Origin Nuclear and mitochondrial DNA are thought to be of separate evolutionary origin, with the mtDNA being deri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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