Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago. Reverse genetic engineering and the fossil record both demonstrate that birds are modern feathered dinosaurs, having evolved from earlier theropods during the late Jurassic Period; as such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago. Dinosaurs can therefore be divided into birds; this article deals with non-avian dinosaurs. Dinosaurs are a varied group of animals from taxonomic and ecological standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides perciform fish. Using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs.
Dinosaurs are represented on every continent by fossil remains. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded. Most research conducted since the 1970s, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction; some were herbivorous, others carnivorous. Evidence suggests that egg-laying and nest-building are additional traits shared by all dinosaurs and non-avian alike. While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, some extinct groups developed skeletal modifications such as bony armor and spines. While the dinosaurs' modern-day surviving avian lineage are small due to the constraints of flight, many prehistoric dinosaurs were large-bodied—the largest sauropod dinosaurs are estimated to have reached lengths of 39.7 meters and heights of 18 meters and were the largest land animals of all time.
Still, the idea that non-avian dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large, sturdy bones are more to last until they are fossilized. Many dinosaurs were quite small: Xixianykus, for example, was only about 50 cm long. Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons have been major attractions at museums around the world, dinosaurs have become an enduring part of world culture; the large sizes of some dinosaur groups, as well as their monstrous and fantastic nature, have ensured dinosaurs' regular appearance in best-selling books and films, such as Jurassic Park. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, new discoveries are covered by the media; the taxon'Dinosauria' was formally named in 1841 by paleontologist Sir Richard Owen, who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were being recognized in England and around the world.
The term is derived from Ancient Greek δεινός, meaning'terrible, potent or fearfully great', σαῦρος, meaning'lizard or reptile'. Though the taxonomic name has been interpreted as a reference to dinosaurs' teeth and other fearsome characteristics, Owen intended it to evoke their size and majesty. Other prehistoric animals, including pterosaurs, ichthyosaurs and Dimetrodon, while popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs. Pterosaurs are distantly related to dinosaurs; the other groups mentioned are, like dinosaurs and pterosaurs, members of Sauropsida, except Dimetrodon. Under phylogenetic nomenclature, dinosaurs are defined as the group consisting of the most recent common ancestor of Triceratops and Neornithes, all its descendants, it has been suggested that Dinosauria be defined with respect to the MRCA of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia", encompassing ankylosaurians, ceratopsians, ornithopods and sauropodomorphs.
Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder. However, a majority of contemporary paleontologists concerned with dinosaurs reject the traditional style of classification in favor of phylogenetic taxonomy. Birds are thus considered to be dinosaurs and dinosaurs are, not extinct. Birds are classified as belonging to the subgroup M
The Oxfordian is, in the ICS' geologic timescale, the earliest age of the Late Jurassic epoch, or the lowest stage of the Upper Jurassic series. It spans the time between 163.5 ± 4 Ma and 157.3 ± 4 Ma. The Oxfordian is followed by the Kimmeridgian; the Oxfordian stage was called "Clunch Shale" by William Smith. The term Oxfordian was introduced by Alcide d'Orbigny in 1844; the name is derived from the English county of Oxford, where the beds are well developed, but they crop out continuously from Dorset to the coast of Yorkshire forming low, broad valleys. They are well exposed at Weymouth, Bedford, in the cliffs at Scarborough, Red Cliff and Gristhorpe Bay. Rocks of this age are found in Uig and Skye; the base of the Oxfordian stage is defined as the point in the stratigraphic record where the ammonite species Brightia thuouxensis first appears. A global reference profile for the base had in 2009 not yet been assigned; the top of the Oxfordian stage is at the first appearance of ammonite species Pictonia baylei.
In the Tethys domain, the Oxfordian contains six ammonite biozones: zone of Epipeltoceras bimammatum zone of Perishinctes bifurcatus zone of Gregoryceras transversarium zone of Perisphinctes plicatilis zone of Cardioceras cordatum zone of Quenstedtoceras mariae Brongniart, A.. Gradstein, F. M.. G. & Smith, A. G.. GeoWhen Database - Oxfordian Jurassic-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS Stratigraphic chart of the Upper Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy
Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, snakes, lizards and their extinct relatives. The study of these traditional reptile orders combined with that of modern amphibians, is called herpetology; because some reptiles are more related to birds than they are to other reptiles, the traditional groups of "reptiles" listed above do not together constitute a monophyletic grouping or clade. For this reason, many modern scientists prefer to consider the birds part of Reptilia as well, thereby making Reptilia a monophyletic class, including all living Diapsids; the earliest known proto-reptiles originated around 312 million years ago during the Carboniferous period, having evolved from advanced reptiliomorph tetrapods that became adapted to life on dry land. Some early examples include Casineria. In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the Cretaceous–Paleogene extinction event wiped out the pterosaurs, plesiosaurs and sauropods, as well as many species of theropods, including troodontids, dromaeosaurids and abelisaurids, along with many Crocodyliformes, squamates.
Modern non-avian reptiles inhabit all the continents except Antarctica, although some birds are found on the periphery of Antarctica. Several living subgroups are recognized: Testudines, 350 species. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Unlike amphibians, reptiles do not have an aquatic larval stage. Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades – the fetus develops within the mother, contained in a placenta rather than an eggshell; as amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae, which can grow up to 17 mm to the saltwater crocodile, Crocodylus porosus, which can reach 6 m in length and weigh over 1,000 kg.
In the 13th century the category of reptile was recognized in Europe as consisting of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, assorted amphibians, worms", as recorded by Vincent of Beauvais in his Mirror of Nature. In the 18th century, the reptiles were, from the outset of classification, grouped with the amphibians. Linnaeus, working from species-poor Sweden, where the common adder and grass snake are found hunting in water, included all reptiles and amphibians in class "III – Amphibia" in his Systema Naturæ; the terms "reptile" and "amphibian" were interchangeable, "reptile" being preferred by the French. Josephus Nicolaus Laurenti was the first to formally use the term "Reptilia" for an expanded selection of reptiles and amphibians similar to that of Linnaeus. Today, the two groups are still treated under the same heading as herptiles, it was not until the beginning of the 19th century that it became clear that reptiles and amphibians are, in fact, quite different animals, Pierre André Latreille erected the class Batracia for the latter, dividing the tetrapods into the four familiar classes of reptiles, amphibians and mammals.
The British anatomist Thomas Henry Huxley made Latreille's definition popular and, together with Richard Owen, expanded Reptilia to include the various fossil "antediluvian monsters", including dinosaurs and the mammal-like Dicynodon he helped describe. This was not the only possible classification scheme: In the Hunterian lectures delivered at the Royal College of Surgeons in 1863, Huxley grouped the vertebrates into mammals and ichthyoids, he subsequently proposed the names of Ichthyopsida for the latter two groups. In 1866, Haeckel demonstrated that vertebrates could be divided based on their reproductive strategies, that reptiles and mammals were united by the amniotic egg; the terms "Sauropsida" and "Theropsida" were used again in 1916 by E. S. Goodrich to distinguish between lizards and their relatives on the one hand and mammals and their extinct relatives on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, other features, such as the structure of the forebrain.
According to Goodrich, both lineages evolved from an earlier stem group, Protosauria in which he included some animals today considered reptile-like amphibians, as well as early reptiles. In 1956, D. M. S. Watson observed that the first two groups diverged early in reptilian history, so he divided Goodrich's Protosauria between them, he reinterpreted Sauropsida and Theropsida to exclude birds and mammals, respectively. Thus his Sauropsida included Procolophonia, Millerosauria, Squamata, Rhynchocephalia
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype. Under the International Code of Zoological Nomenclature, a holotype is one of several kinds of name-bearing types. In the International Code of Nomenclature for algae and plants and ICZN the definitions of types are similar in intent but not identical in terminology or underlying concept. For example, the holotype for the butterfly Lycaeides idas longinus is a preserved specimen of that species, held by the Museum of Comparative Zoology at Harvard University. An isotype is a duplicate of the holotype and is made for plants, where holotype and isotypes are pieces from the same individual plant or samples from the same gathering. A holotype is not "typical" of that taxon, although ideally it should be. Sometimes just a fragment of an organism is the holotype in the case of a fossil.
For example, the holotype of Pelorosaurus humerocristatus, a large herbivorous dinosaur from the early Jurassic period, is a fossil leg bone stored at the Natural History Museum in London. If a better specimen is subsequently found, the holotype is not superseded. Under the ICN, an additional and clarifying type could be designated an epitype under Article 9.8, where the original material is demonstrably ambiguous or insufficient. A conserved type is sometimes used to correct a problem with a name, misapplied. In the absence of a holotype, another type may be selected, out of a range of different kinds of type, depending on the case, a lectotype or a neotype. For example, in both the ICN and the ICZN a neotype is a type, appointed in the absence of the original holotype. Additionally, under the ICZN the Commission is empowered to replace a holotype with a neotype, when the holotype turns out to lack important diagnostic features needed to distinguish the species from its close relatives. For example, the crocodile-like archosaurian reptile Parasuchus hislopi Lydekker, 1885 was described based on a premaxillary rostrum, but this is no longer sufficient to distinguish Parasuchus from its close relatives.
This made. Texan paleontologist Sankar Chatterjee proposed that a new type specimen, a complete skeleton, be designated; the International Commission on Zoological Nomenclature considered the case and agreed to replace the original type specimen with the proposed neotype. The procedures for the designation of a new type specimen when the original is lost come into play for some recent, high-profile species descriptions in which the specimen designated as the holotype was a living individual, allowed to remain in the wild. In such a case, there is no actual type specimen available for study, the possibility exists that—should there be any perceived ambiguity in the identity of the species—subsequent authors can invoke various clauses in the ICZN Code that allow for the designation of a neotype. Article 75.3.7 of the ICZN requires that the designation of a neotype must be accompanied by "a statement that the neotype is, or upon publication has become, the property of a recognized scientific or educational institution, cited by name, that maintains a research collection, with proper facilities for preserving name-bearing types, that makes them accessible for study", but there is no such requirement for a holotype.
Type Allotype Paratype Type species Genetypes- genetic sequence data from type specimens. BOA Photographs of type specimens of Neotropical Rhopalocera
Friedrich von Huene
Friedrich von Huene, full name Friedrich Richard von Hoinigen was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He made key contributions about various Permo-Carboniferous limbed vertebrates. Huene was born in Kingdom of Württemberg, his discoveries include the skeletons of more than 35 individuals of Plateosaurus in the famous Trossingen quarry, the early proto-dinosaur Saltopus in 1910, Proceratosaurus in 1926, the giant Antarctosaurus in 1929, numerous other dinosaurs and fossilized animals like pterosaurs. He was the first to naming several higher taxa, including Prosauropoda and Sauropodomorpha, he visited the Geopark of Paleorrota in 1928, there collected the Prestosuchus chiniquensis in 1938. He studied several Permo-Carboniferous and Triassic limbed vertebrates, including members of several large clades, such as Temnospondyli and Sauropsida. In his work on mesosaurs, Huene indicated that a lower temporal fenestra was present, an interpretation rejected by many subsequent workers, but more upheld.
A new species of basal sauropodomorph, Lufengosaurus huenei, was named after von Huene in 1941. Liassaurus huenei, an early carnivorous theropod, was named for him in 1995, though this name is invalid. Category:Taxa named by Friedrich von Huene Westphal, Frank "Huene, Friedrich von" In Neue Deutsche Biographie, Duncker & Humblot, pages 740–741 Isaia, Antônio. Os Fascinantes Caminhos da Paleontologia. Porto Alegre, Brazil: Grafica Editora Pallotti. Length: 60 pages. Beltrão, Romeu. Cronologia Histórica de Santa Maria e do extinto município de São Martinho: 1787-1930. Grafica Editora Pallotti. OCLC 10022858. Length: 582 pages
Sauropoda, or the sauropods, are a clade of saurischian dinosaurs. They had long necks, long tails, small heads, four thick, pillar-like legs, they are notable for the enormous sizes attained by some species, the group includes the largest animals to have lived on land. Well-known genera include Brachiosaurus, Diplodocus and Brontosaurus. Sauropods first appeared in the late Triassic Period, where they somewhat resembled the related group "Prosauropoda". By the Late Jurassic, sauropods had become widespread. By the Late Cretaceous, those groups had been replaced by the titanosaurs, which had a near-global distribution. However, as with all other non-avian dinosaurs alive at the time, the titanosaurs died out in the Cretaceous–Paleogene extinction event. Fossilised remains of sauropods have been found on every continent, including Antarctica; the name Sauropoda was coined by O. C. Marsh in 1878, is derived from Greek, meaning "lizard foot". Sauropods are one of the most recognizable groups of dinosaurs, have become a fixture in popular culture due to their large sizes.
Complete sauropod fossil finds are rare. Many species the largest, are known only from isolated and disarticulated bones. Many near-complete specimens lack tail tips and limbs. Sauropods were herbivorous quite long-necked quadrupeds with spatulate teeth, they had tiny heads, massive bodies, most had long tails. Their hind legs were thick and powerful, ending in club-like feet with five toes, though only the inner three bore claws, their forelimbs were rather more slender and ended in pillar-like hands built for supporting weight. Many illustrations of sauropods in the flesh miss these facts, inaccurately depicting sauropods with hooves capping the claw-less digits of the feet, or more than three claws or hooves on the hands; the proximal caudal vertebrae are diagnostic for sauropods. The sauropods' most defining characteristic was their size; the dwarf sauropods were counted among the largest animals in their ecosystem. Their only real competitors in terms of size are the rorquals, such as the blue whale.
But, unlike whales, sauropods were terrestrial animals. Their body structure did not vary as much as other dinosaurs due to size constraints, but they displayed ample variety. Some, like the diplodocids, possessed tremendously long tails, which they may have been able to crack like a whip as a signal or to deter or injure predators, or to make sonic booms. Supersaurus, at 33 to 34 metres long, was the longest sauropod known from reasonably complete remains, but others, like the old record holder, were extremely long; the holotype vertebra of Amphicoelias fragillimus may have come from an animal 58 metres long. However, a research published in 2015 speculated that the size estimates of A. fragillimus may have been exaggerated. The longest dinosaur known from reasonable fossils material is Argentinosaurus huinculensis with length estimates of 25 metres to 39.7 metres. The longest terrestrial animal alive today, the reticulated python, only reaches lengths of 6.95 metres. Others, like the brachiosaurids, were tall, with high shoulders and long necks.
Sauroposeidon was the tallest, reaching about 18 metres high, with the previous record for longest neck being held by Mamenchisaurus. By comparison, the giraffe, the tallest of all living land animals, is only 4.8 to 5.5 metres tall. The best evidence indicates that the most massive were Argentinosaurus, Alamosaurus, Antarctosaurus. There was poor evidence that so-called Bruhathkayosaurus, might have weighed over 175 metric tons but this has been questioned; the weight of Amphicoelias fragillimus was estimated at 122.4 metric tons but 2015 research argued that these estimates may have been exaggerated. The largest land animal alive today, the Savannah elephant, weighs no more than 10.4 metric tons. Among the smallest sauropods were the primitive Ohmdenosaurus, the dwarf titanosaur Magyarosaurus, the dwarf brachiosaurid Europasaurus, 6.2 meters long as a fully-grown adult. Its small stature was the result of insular dwarfism occurring in a population of sauropods isolated on an island of the late Jurassic in what is now the Langenberg area of northern Germany.
The diplodocoid sauropod Brachytrachelopan was the shortest member of its group because of its unusually short neck. Unlike other sauropods, whose necks could grow to up to four times the length of their backs, the neck of Brachytrachelopan was shorter than its backbone. On or shortly before 29 March 2017 a sauropod footprint about 5.6 feet long was found at Walmadany in the Kimberley Region of Western Australia. The report said; as massive quadrupeds, sauropods developed specialized graviportal limbs. The hind feet were broad, retained three claws in most species. Unusual compared with other animals were the modified front feet; the front feet of sauropods were dissimilar from those of modern
Stegosauridae is a clade of thyreophoran dinosaurs within the suborder Stegosauria. The clade is defined as all species of dinosaurs more related to Stegosaurus than Huayangosaurus; the name ‘Stegosauridae’ is thus a stem-based name taken from the well-represented genus – Stegosaurus. Fossil evidence of stegosaurids, dating from the Middle Jurassic through the Early Cretaceous, have been recovered from North America and Africa. On the other hand, Stegosauridae's sister clade, can be traced only to the Middle Jurassic; the clade Stegosauridae is composed of the genera Stegosaurus, Miragaia and Kentrosaurus, with the last considered to be at the base of the clade. The stegosaurids like all other stegosaurians were quadrupedal herbivores that exhibited the characteristic stegosaurian dorsal dermal plates; these large, erect plates are thought to be aligned parasagittally from the neck to near the end of the tail, where they give way to paired of spikes. Although defense, thermo-regulation and display have been theorized to be the possible functions of these dorsal plates, a study of the ontogenetic histology of the plates and spikes suggests that the plates serve different functions at different stages of the stegosaurids’ life histories.
The terminal spikes in the tail are thought to have been used in old adults, at least, as a weapon for defence. However, the function of stegosaurid plates and spikes, at different life stages, still remains a matter of great debate. Stegosaurids are distinguished from huayangosaurids in that the former have lost the plesiomorphic pre-maxillary teeth and lateral scute rows along the trunk. Furthermore, stegosaurids as opposed to huayangosaurids have long narrow skulls and longer hindlimbs compared to their forelimbs. However, these two features are not diagnostic of Stegosauridae because they may be present in non-stegosaurids other than huayangosaurids; the cranial remains of stegosaurids, like all stegosaurians, are discovered. Hence, a significant portion of the knowledge of their skull morphology comes from few complete skulls discovered of Stegosaurus and fragmentary remains of other stegosaurids. In general, stegosaurids have proportionally long and narrow snouts with a deep mandible, compared to that of Huayangosaurus.
Stegosaurids lack premaxillary teeth. Among stegosaurids, only Kentrosaurus has been found with parascapular spines, which project posteriorly out of the lower part of the shoulder plates; these spines are long and comma-shaped in lateral view and have an enlarged base. Loricatosaurus was believed to have a parascapular spine, but Maidment et al. observed that the discovered specimen, from which the spine is described, has a different morphology than the parascapular spine specimens of other stegosaurs. They suggest; the genuine absence of parascapular spines in other stegosaurids is considered a secondary loss since many basal stegosaurs like Gigantspinosaurus and Huayangosaurus have been discovered with them. Stegosaurids lack lateral scute rows that run longitudinally on either side of the trunk in huayangosaurids and ankylosaurs, indicating yet another secondary loss of a plesiomorphic characters. However, the absence of lateral scutes as well as pre-maxillary teeth mentioned above are not diagnostic of stegosaurids, since these features are present in other non-huayangosaurid stegosaurs, whose phylogenetic relations within Stegosauria are unclear.
Stegosaurids exhibit the characteristic dorsal osteoderms, found in all stegosaurs, in the form of erect plates and spines. Stegosaurid plates have a thick base and central portion, but are transversely thin elsewhere; the plates become remarkably thin in Stegosaurus. They are found in varying sizes along the dorsum, with the central region of the back having the largest and tallest plates; the arrangement of these parasagittal dorsal plates has been intensely debated in the past. Marsh suggested a single median row of plates running post-cranially along the longitudinal axis and Lull argued in favour of bilaterally paired arrangement throughout the series. Current scientific consensus lies in the arrangement proposed by Gilmore - two parasagittal rows of staggered alternates, after the discovery of an complete skeleton preserved in this manner in rock. Furthermore, no two plates share the same size and shape, making the possibility of bilaterally paired rows less likely. Plates are found with distinct vascular grooves on their lateral surfaces, suggesting the presence of a circulatory network.
Stegosaurids have osteoderms on the throat in the form of small depressed ossicles and two pairs of elongated spike-like tail-spines. In an ontogenetic histological analysis of Stegosaurus plates and spikes, Hayashi et al. examined their structure and function through juveniles to old adults. They found that throughout the ontogeny, the dorsal osteoderms are composed of dense ossified collagen fibres in both the cortical and cancellous sections of the bone, suggesting that plates and spikes are formed from the direct mineralization of existing fibrous networks in the skin. However, the many structural features, seen in the spikes and plates of old adults specimens, are acquired at different stages of development. Extensive vascular networks form in the plates during the change from juveniles to young adults and persist in old adults but spikes acquire a thick cortex with a large axial vascular channel only in old adults. Hayashi et al. argue that the formation of nourishing vascular networks in young adults supported the growth of large plates.
This would have enhanced the size of the animal, which may have he