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Polydactyly In Early Tetrapods
Polydactyly in stem-tetrapods should here be understood as having more than five digits to the finger or foot, a condition that was the natural state of affairs in the earliest stegocephalians during the evolution of terrestriality. The polydactyly in these largely aquatic animals is not to be confused with polydactyly in the medical sense, i.e. it was not an anomaly in the sense it was not a congenital condition of having more than the typical number of digits for a given taxon. Rather, it appears to be a result of the early evolution from a limb with a fin rather than digits. "Living tetrapods, such as the frogs, turtles, birds and mammals, are a subgroup of the tetrapod lineage. The lineage also includes finned and limbed tetrapods that are more closely related to living tetrapods than to living lungfishes." Tetrapods evolved from animals with fins such as found in lobe-finned fishes. From this condition a new pattern of limb formation evolved, where the development axis of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fins To Hands
A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fins are also used to increase surface areas for heat transfer purposes, or simply as ornamentation. Fins first evolved on fish as a means of locomotion. Fish fins are used to generate thrust and control the subsequent motion. Fish and other aquatic animals, such as cetaceans, actively propel and steer themselves with pectoral and tail fins. As they swim, they use other fins, such as dorsal and anal fins, to achieve stability and refine their maneuvering.Helfman G, Collette BB, Facey DE and Bowen BW (2009"Functional morphology of locomotion and feeding" Chapter 8, pp. 101–116. In:''The Diversity of Fishes: Biology'', John Wiley & Sons. . The fins on the tails of cetaceans, ichthyosaurs, metriorhynchids, mosasaurs and plesiosaurs are call ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian
The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago (Megaannum, Ma), to the beginning of the succeeding Carboniferous period at Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. It is named after Devon, South West England, where rocks from this period were first studied. The first significant evolutionary radiation of history of life#Colonization of land, life on land occurred during the Devonian, as free-spore, sporing land plants (pteridophytes) began to spread across dry land, forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaf, leaves and true roots, and by the end of the period the first seed-bearing plants (Pteridospermatophyta, pteridospermatophyt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentadactyly
In biology, dactyly is the arrangement of wikt:digit, digits (fingers and toes) on the hands, feet, or sometimes wings of a tetrapod animal. The term is derived from the Greek (language), Greek word () meaning "finger." Sometimes the suffix "-dactylia" is used. The derived adjectives end with "-dactyl" or "-dactylous." As a normal feature Pentadactyly Pentadactyly (from Ancient Greek, Greek "five") is the condition of having five digits on each limb. It is traditionally believed that all living tetrapods are descended from an ancestor with a pentadactyl limb, although many species have now lost or transformed some or all of their digits by the process of evolution. However, this viewpoint was challenged by Stephen Jay Gould in his 1991 essay "Eight (or Fewer) Little Piggies," where he pointed out polydactyly in early tetrapods and described the specializations of digit reduction. Despite the individual variations listed below, the relationship is to the original five-digit m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrate Palaeontology (Benton)
''Vertebrate Palaeontology'' is a basic textbook on vertebrate paleontology by Michael J. Benton, published by Blackwell's. It has so far appeared in five editions, published in 1990, 1997, 2005, 2014, and 2024. It is designed for paleontology graduate courses in biology and geology as well as for the interested layman. The book is widely used, and has received excellent reviews: *"This book is a ′must′ for a biology or geology student and researcher concerned by palaeontology. It perfectly succeeds in showing how palaeobiological information is obtained". Review of 3rd edition, ''Zentrallblatt fur Geologie und Palaontologie'', 2007. *"One anticipates that Benton's ''Vertebrate Palaeontology'' will become the 'industry standard', and as such it should occupy space on the shelves of all involved in undergraduate teaching". Ivan Sansom, School of Earth Sciences, University of Birmingham. Review of the 2nd edition for the Micropalaeontological Society. *"... his expertise i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Michael Benton
Michael James Benton (born 8 April 1956) is a British palaeontologist, and professor of vertebrate paleontology, vertebrate palaeontology in the School of Earth Sciences at the University of Bristol. His published work has mostly concentrated on the evolution of Triassic reptiles but he has also worked on extinction events and faunal changes in the fossil record. Education Benton was educated at Robert Gordon's College, the University of Aberdeen and Newcastle University where he was awarded a PhD in 1981. Research and career Benton's research investigates palaeobiology, palaeontology, and macroevolution. His research interests include: diversification of life, quality of the fossil record, shapes of phylogenies, age-clade congruence, mass extinctions, Triassic ecosystem evolution, basal diapsid phylogeny, basal archosaurs, and the origin of the dinosaurs. He has made fundamental contributions to understanding the history of life, particularly concerning how biodiversity chang ... [...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] |
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] |
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] |
Anthracosauria
Anthracosauria is a paraphyletic order of extinct reptile-like amphibians (in the broad sense) that flourished during the Carboniferous and early Permian periods, although precisely which species are included depends on one's definition of the taxon. "Anthracosauria" is sometimes used to refer to all tetrapods more closely related to amniotes such as reptiles, mammals, and birds, than to lissamphibians such as frogs and salamanders. An equivalent term to this definition would be Reptiliomorpha. Anthracosauria has also been used to refer to a smaller group of large, crocodilian-like aquatic tetrapods also known as embolomeres. Various definitions As originally defined by Säve-Söderbergh in 1934, the anthracosaurs are a group of usually large aquatic Amphibia from the Carboniferous and lower Permian. As defined by Alfred Sherwood Romer however, the anthracosaurs include all non-amniote " labyrinthodont" reptile-like amphibians, and Säve-Söderbergh's definition is more equ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Romer's Gap
Romer's gap is an apparent gap in the Paleozoic tetrapod fossil record noted in the studies of paleontology and evolutionary biology, which represent periods in the Early Carboniferous from which excavators have not yet found relevant transitional fossils. It is named after American paleontologist Alfred Romer, who first recognised it in 1956. Recent discoveries in Scotland and Australia are beginning to close this gap in palaeontological knowledge. Age Romer's gap runs from approximately 360 to 345 million years ago, corresponding to the first 15 million years of the Carboniferous, the early Mississippian (starting with the Tournaisian and moving into the Visean). The gap forms a discontinuity between the primitive forests and high diversity of fishes at the end Devonian and more modern aquatic and terrestrial assemblages of the early Carboniferous. Mechanism behind the gap There has been long debate as to why there are so few fossils from this time period. Some have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crassigyrinus
''Crassigyrinus'' (from , 'thick' and , 'tadpole') is an extinct genus of carnivorous stem tetrapod from the Early Carboniferous Clackmannan Group of Scotland and possibly Greer, West Virginia. Discovery The type specimen was originally described as ''Macromerium scoticum'' and lacked a complete skull. With subsequent discoveries, ''Crassigyrinus'' is now known from three skulls, one of which is in articulation with a fairly complete skeleton, and two incomplete lower jaws. ''Crassigyrinus'' grew up to 2 meters in length, coupled with tiny limbs and unusually large jaws. ''Crassigyrinus'' is taxonomically enigmatic, having confused paleontologists for decades with its apparent fish-like and tetrapod features.Chapter on ''Crassigyrinus'' from ''Gaining ground: the origin and evolution of te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous
The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the Permian Period, Ma. It is the fifth and penultimate period of the Paleozoic era and the fifth period of the Phanerozoic eon (geology), eon. In North America, the Carboniferous is often treated as two separate geological periods, the earlier Mississippian (geology), Mississippian and the later Pennsylvanian (geology), Pennsylvanian. The name ''Carboniferous'' means "coal-bearing", from the Latin ("coal") and ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern "system" names, it was coined by geologists William Conybeare (geologist), William Conybeare and William Phillips (geologist), William Phillips in 1822, based on a study of the British rock succession. Carboniferous is the per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
