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Labyrinthodont
"Labyrinthodontia" (Greek, 'maze-toothed') is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras (about 390 to 150 million years ago). Traditionally considered a subclass of the class Amphibia, modern classification systems recognize that labyrinthodonts are not a formal natural group (clade) exclusive of other tetrapods. Instead, they consistute an evolutionary grade (a paraphyletic group), ancestral to living tetrapods such as lissamphibians (modern amphibians) and amniotes (reptiles, mammals, and kin). "Labyrinthodont"-grade vertebrates evolved from lobe-finned fishes in the Devonian, though a formal boundary between fish and amphibian is difficult to define at this point in time. "Labyrinthodont" generally refers to extinct four-limbed tetrapods with a large body size and a crocodile-like lifestyle. The name describes the pattern of infolding of the dentin and enamel of the teeth, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temnospondyli
Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian and Triassic periods, with fossils being found on every continent. A few species continued into the Jurassic and Early Cretaceous periods, but all had gone extinct by the Late Cretaceous. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including freshwater, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are amph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Grade
A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Phylogenetics The concept of evolutionary grades arises in the context of phylogenetics: the study of the evolutionary history and relationships among or within groups of organisms. These relationships are determined by phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, protein amino acid sequences, or morphology. The result of such an analysis is a phylogenetic tree—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of organisms. Definition of an evolutionary grade An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that has major differences from the ancestral group's condition, and is thus not considered p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ichthyostegalia
Ichthyostegalia is an obsolete order of early amphibians, representing the earliest landliving vertebrates. The group is thus an evolutionary grade rather than a clade. While the group are recognized as having feet rather than fins, most, if not all, had internal gills in adulthood and lived primarily as shallow water fish and spent minimal time on land. The group evolved from elpistostegalian fish in the late Devonian, or possibly in the middle Devonian. They continued to thrive as denizens of swampland and tidal channels throughout the period. They gave rise to the Temnospondyli and then disappeared during the transition to the Carboniferous. Classification *Ichthyostegalia ** Acanthostegidae ***'' Acanthostega'' ** Crassigyrinidae ***'' Crassigyrinus'' ** Densignathidae ***'' Densignathus'' ** Elginerpetontidae ***'' Elginerpeton'' ***'' Obruchevichthys'' ** Ichthyostegidae ***'' Hynerpeton'' ***'' Ichthyostega'' ** Jakubsonidae ***'' Jakubsonia'' ** Metaxygnathidae * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Grade
A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Phylogenetics The concept of evolutionary grades arises in the context of phylogenetics: the study of the evolutionary history and relationships among or within groups of organisms. These relationships are determined by phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, protein amino acid sequences, or morphology. The result of such an analysis is a phylogenetic tree—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of organisms. Definition of an evolutionary grade An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that has major differences from the ancestral group's condition, and is thus not considered p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amniota
Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the Carboniferous period. Amniota is defined as the smallest crown clade containing humans, the Greek tortoise, and the Nile crocodile. Amniotes are distinguished from the other living tetrapod clade — the non-amniote lissamphibians (frogs/ toads, salamanders/newts and caecilians) — by: the development of three extraembryonic membranes ( amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage); thicker and keratinized skin; costal respiration (breathing by expanding/constricting the rib cage); the presence of adrenocortical and chromaffin tissues as a discrete pair of glands near their kidneys; more complex kidneys; the presence of an astragalus for better extremity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amniotes
Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the Carboniferous period. Amniota is defined as the smallest crown clade containing humans, the Greek tortoise, and the Nile crocodile. Amniotes are distinguished from the other living tetrapod clade — the non-amniote lissamphibians (frogs/ toads, salamanders/ newts and caecilians) — by: the development of three extraembryonic membranes ( amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage); thicker and keratinized skin; costal respiration (breathing by expanding/constricting the rib cage); the presence of adrenocortical and chromaffin tissues as a discrete pair of glands near their kidneys; more complex kidneys; the presence of an astragalus for better ext ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphibian
Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excluding the amniotes (tetrapods with an amniotic membrane, such as modern reptiles, birds and mammals). All extant taxon, extant (living) amphibians belong to the monophyletic subclass (biology), subclass Lissamphibia, with three living order (biology), orders: Anura (frogs and toads), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater ecosystem, freshwater, wetland or terrestrial ecosystems (such as riparian woodland, fossorial and even arboreal habitats). Their biological life cycle, life cycle typically starts out as aquatic animal, aquatic larvae with gills known as tadpoles, but some species have devel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amniote
Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tetrapoda, stem tetrapod ancestors during the Carboniferous geologic period, period. Amniota is defined as the smallest crown clade containing humans, the Greek tortoise, and the Nile crocodile. Amniotes are distinguished from the other living tetrapod clade — the anamniote, non-amniote lissamphibians (frogs/toads, salamanders/newts and caecilians) — by: the development of three fetal membranes, extraembryonic membranes (amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage); thicker and keratinized skin; rib, costal respiration (breathing by expanding/constricting the rib cage); the presence of adrenal cortex, adrenocortical and chromaffin cell, chromaffin tissues as adrenal g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amniotes
Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the Carboniferous period. Amniota is defined as the smallest crown clade containing humans, the Greek tortoise, and the Nile crocodile. Amniotes are distinguished from the other living tetrapod clade — the non-amniote lissamphibians (frogs/ toads, salamanders/ newts and caecilians) — by: the development of three extraembryonic membranes ( amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage); thicker and keratinized skin; costal respiration (breathing by expanding/constricting the rib cage); the presence of adrenocortical and chromaffin tissues as a discrete pair of glands near their kidneys; more complex kidneys; the presence of an astragalus for better ext ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lepospondyli
Lepospondyli is a diverse clade of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ('' Diplocaulus minimus''), lepospondyls lived from the Visean stage of the Early Carboniferous to the Early Permian and were geographically restricted to what is now Europe and North America. Five major groups of lepospondyls are known: Adelospondyli; Aïstopoda; Lysorophia; Microsauria; and Nectridea. Lepospondyls have a diverse range of body forms and include species with newt-like, eel- or snake-like, and lizard-like forms. Various species were aquatic, semiaquatic, or terrestrial. None were large (the biggest genus, the diplocaulid '' Diplocaulus'', reached a meter in length, but most were much smaller), and they are assumed to have lived in specialized ecological niches not taken by the more numerous temnospondyl amphibians that coexisted with them in the Paleozoic. Lepospondyli was named in 1888 by Karl Alfred von Zittel, who coi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrapod
A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all Neontology#Extant taxa versus extinct taxa, extant and Extinction, extinct amphibians and amniotes, with the latter in turn Evolution, evolving into two major clades, the Sauropsida, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (extinct pelycosaur, "pelycosaurs", therapsids and all extant mammals, including Homo sapiens, humans). Hox gene mutations have resulted in some tetrapods becoming Limbless vertebrate, limbless (snakes, legless lizards, and caecilians) or two-limbed (cetaceans, sirenians, Bipedidae, some lizards, kiwi (bird), kiwis, and the extinct moa and elephant birds). Nevertheless, they still qualify as tetrapods through their ancestry, and some retain a pair of ves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lissamphibia
The Lissamphibia (from Greek λισσός (lissós, "smooth") + ἀμφίβια (amphíbia), meaning "smooth amphibians") is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs and their extinct relatives), the Caudata (salamanders and their extinct relatives), and the Gymnophiona (the limbless caecilians and their extinct relatives). Salientians and caudatans are likely more closely related to each other than to caecilians. The name Batrachia is commonly used for the clade combining salientians and caudatans. A fourth group, the Allocaudata (also known as Albanerpetontidae) is also known, spanning 160 million years from the Middle Jurassic to the Early Pleistocene, but became extinct two million years ago. For several decades, this name has been used for a group that includes all living amphibians, but excludes all the main groups of Paleozoic tetrapods, such as Temnospondyli, Lepospondyli, Embolome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
