Forty-seven species of snake have been recorded in Trinidad and Tobago, making the snake population of this area the most diverse in the Caribbean. Forty-four of these snake species are found in Trinidad and twenty-one in Tobago. Many of these species are South American, most of which are present in Venezuela. Trinidad and Tobago consists of two main islands, Trinidad and Tobago, and several smaller islands. The Bocas Islands, which lie between Trinidad and Venezuela, in the Bocas del Dragón (Dragon's Mouths), consist of Chacachacare, Monos, Huevos and Gaspar Grande. Several smaller islands lie off Trinidad, but snakes have been recorded on only one of them, Caledonia Island. Snakes have been recorded on one island off Tobago, Little Tobago. Four species are venomous: two coral snake species (Micrurus spp.), the fer-de-lance (Bothrops atrox) and the South American bushmaster (Lachesis muta). The common coral (Micrurus fulvius) is found on at least two of the Bocas Islands: Gaspar Grande and Monos. No venomous snakes inhabit Tobago.(see more...)
The list of dinosaurs is a comprehensive listing of all genera that have ever been included in the superorder Dinosauria, excluding class Aves (birds, both living and those known only from fossils) and purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered dinosaurs. Many listed names have been reclassified as everything from birds to crocodilians to petrified wood. The list contains more than 1,000 names considered either valid dinosaur genera or nomina dubia. (see more...)
Acrocanthosaurus was a bipedalpredator. As the name suggests, it is best known for the high neural spines on many of its vertebrae, which most likely supported a ridge of muscle over the animal's neck, back and hips. Acrocanthosaurus was one of the largest theropods, approaching 12 meters (40 ft) in length, and weighing up to 6.2 tonnes (6.8 short tons). Large theropod footprints discovered in Texas may have been made by Acrocanthosaurus, although there is no direct association with skeletal remains.
Recent discoveries have elucidated many details of its anatomy, allowing for specialized studies focusing on its brain structure and forelimb function. Acrocanthosaurus was the largest theropod in its ecosystem and likely an apex predator which possibly preyed on large sauropods and ornithopods. (see more...)
As a tyrannosaurid, Albertosaurus was a bipedalpredator with tiny, two-fingered hands and a massive head with dozens of large, sharp teeth. It may have been at the top of the food chain in its local ecosystem. Although relatively large for a theropod, Albertosaurus was much smaller than its more famous relative Tyrannosaurus, probably weighing less than 2 metric tons.
Since the first discovery in 1884, fossils of more than thirty individuals have been recovered, providing scientists with a more detailed knowledge of Albertosaurus anatomy than is available for most other tyrannosaurids. The discovery of 26 individuals at one site provides evidence of pack behaviour and allows studies of ontogeny and population biology which are impossible with lesser-known dinosaurs. (see more...)
Allosaurus is a genus of large theropoddinosaur that lived 155 to 150 million years ago during the late Jurassicperiod (Kimmeridgian to early Tithonian). The name "Allosaurus" means "different lizard". The first fossil remains that can definitely be ascribed to this genus were described in 1877 by paleontologist Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.
Allosaurus was a large bipedalpredator. Its skull was large and equipped with dozens of large, sharp teeth. It averaged 8.5 m (28 ft) in length, though fragmentary remains suggest it could have reached over 12 m (39 ft). It is classified as an allosaurid, a type of carnosaurian theropod dinosaur. The genus has a complicated taxonomy, and includes an uncertain number of valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North America's Morrison Formation, with material also known from Portugal and possibly Tanzania.
As the most abundant large predator in the Morrison Formation, Allosaurus was at the top of the food chain, probably preying on contemporaneous large herbivorous dinosaurs and perhaps even other predators. Potential prey included ornithopods, stegosaurids, and sauropods. Some paleontologists interpret Allosaurus as having had cooperative social behavior, and hunting in packs, while others believe individuals may have been aggressive toward each other. It may have attacked large prey by ambush, using its upper jaw like a hatchet. (see more...)
Archaeopteryx is a genus of early bird that is transitional between feathered dinosaurs and modern birds. Since the late nineteenth century, it had been generally accepted by palaeontologists, and celebrated in lay reference works, as being the oldest known bird. Archaeopteryx lived in the Late Jurassicperiod around 150 million years ago, in what is now southern Germany during a time when Europe was an archipelago of islands in a shallow tropical sea. Similar in shape to a European Magpie, with the largest individuals possibly attaining the size of a raven, Archaeopteryx could grow to about 0.5 m (1 ft 8 in) in length. Despite its small size, broad wings, and inferred ability to fly or glide, Archaeopteryx has more in common with other small Mesozoic dinosaurs than it does with modern birds. In particular, it shares the following features with the deinonychosaurs (dromaeosaurs and troodontids): jaws with sharp teeth, three fingers with claws, a long bony tail, hyperextensible second toes ("killing claw"), feathers (which also suggest homeothermy), and various skeletal features.
These features make Archaeopteryx a clear candidate for a transitional fossil between dinosaurs and birds. The type specimen of Archaeopteryx was discovered just two years after Charles Darwin published On the Origin of Species. Archaeopteryx seemed to confirm Darwin's theories and has since become a key piece of evidence for the origin of birds, the transitional fossils debate, and confirmation of evolution. (see more...)
Carnotaurus is a genus of large theropoddinosaur that lived in South America during the Late Cretaceous period, between about 72 and 70 million years ago. The only species is Carnotaurus sastrei. Known from a single well-preserved skeleton, it is one of the best-understood theropods from the Southern Hemisphere. The skeleton, found in 1984, was uncovered in the Chubut Province of Argentina from rocks of the La Colonia Formation. Carnotaurus is a derived member of the Abelisauridae, a group of large theropods that occupied the large predatorialniche in the southern Landmasses of Gondwana during the late Cretaceous.
Carnotaurus was a lightly built, bipedal predator, measuring 8 to 9 m (26 to 30 ft) in length and weighing at least 1 metric ton (0.98 long tons; 1.1 short tons). The skeleton is preserved with extensive skin impressions, showing a mosaic of small, non-overlapping scales. The mosaic was interrupted by large bumps that lined the sides of the animal, and there are no hints of feathers. The distinctive horns and the muscular neck may have been used in fighting conspecifics. The feeding habits of Carnotaurus remain unclear: some studies suggest the animal was able to hunt down very large prey such as sauropods, while other studies find it preyed mainly on relatively small animals. Carnotaurus was well adapted for running and was possibly one of the fastest large theropods. (see more...)
Compsognathus is a genus of small, bipedal, carnivoroustheropoddinosaurs. Members of its single speciesCompsognathus longipes could grow to the size of a turkey. They lived around 150 million years ago, the latest Kimmeridgianage of the late Jurassicperiod, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany in the 1850s and the second in France more than a century later. Today, C. longipes is the only recognized species, although the larger specimen discovered in France in the 1970s was once thought to belong to a separate species and named C. corallestris.
Many presentations still describe Compsognathus as "chicken-sized" dinosaurs because of the small size of the German specimen, which is now believed to be a juvenile. Compsognathus longipes is one of the few dinosaur species for which diet is known with certainty: the remains of small, agile lizards are preserved in the bellies of both specimens. Teeth discovered in Portugal may be further fossil remains of the genus.
Although not recognized as such at the time of its discovery, Compsognathus is the first theropod dinosaur known from a reasonably complete fossil skeleton. Until the 1990s, it was the smallest known non-avialan dinosaur; earlier it was the closest supposed relative of the early bird Archaeopteryx. (see more...)
Daspletosaurus is closely related to the much larger and more recent Tyrannosaurus. Like most known tyrannosaurids, it was a multi-tonne bipedalpredator equipped with dozens of large, sharp teeth. Daspletosaurus had the small forelimbs typical of tyrannosaurids, although they were proportionately longer than in other genera.
As an apex predator, Daspletosaurus was at the top of the food chain, probably preying on large dinosaurs like the ceratopsidCentrosaurus and the hadrosaurHypacrosaurus. In some areas, Daspletosaurus coexisted with another tyrannosaurid, Gorgosaurus, though there is some evidence of niche differentiation between the two. While Daspletosaurus fossils are rarer than other tyrannosaurids, the available specimens allow some analysis of the biology of these animals, including social behavior, diet, and life history. (see more...)
PaleontologistJohn Ostrom's study of Deinonychus in the late 1960s revolutionized the way scientists thought about dinosaurs, leading to the "dinosaur renaissance" and igniting the debate on whether dinosaurs were warm-blooded or cold blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted the small body, sleek, horizontal posture, ratite-like spine, and especially the enlarged raptorial claws on the feet, which suggested an active, agile predator. The etymology "terrible claw" refers to the unusually large, sickle-shaped talon on the second toe of each hind foot. The fossil YPM 5205 preserves a large, strongly curved ungual. Ostrom looked at crocodile and bird claws and reconstructed the claw for YPM 5205 as over 150 millimetres (5.9 in) long.
In both the Cloverly and Antlers formations, Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply they were hunted, or at least scavenged upon, by Deinonychus. (see more...)
Dinosaurs are a diverse group of animals that first appeared during the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic until the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups. The fossil record indicates that birds evolved from theropod dinosaurs and, consequently, they are considered a subgroup of dinosaurs by many paleontologists. Some birds survived the extinction event and their descendants continue the dinosaur lineage to the present day.
Using fossil evidence, paleontologists have identified over 500 distinct genera of non-avian dinosaurs. Dinosaurs are represented on every continent. Some are herbivorous, others carnivorous. While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species. Elaborate display structures such as horns or crests are common to all dinosaur groups, and some extinct groups developed skeletal modifications such as bony armor and spines. Evidence suggests that egg laying and nest building are additional traits shared by all dinosaurs. While modern birds are generally small due to the constraints of flight, many prehistoric dinosaurs were large-bodied—the largest sauropod dinosaurs may have achieved lengths of 58 meters (190 feet). Many dinosaurs were quite small: Xixianykus, for example, was only about 50 cm (20 in) long. (see more...)
Diplodocus is an extinct genus of diplodocidsauropoddinosaur whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a Neo-Latin term derived from Greek διπλός (diplos) "double" and δοκός (dokos) "beam", in reference to its double-beamed chevron bones located in the underside of the tail. These bones were initially believed to be unique to Diplodocus; however, they have since then been discovered in other members of the diplodocid family and in non-diplodocid sauropods such as Mamenchisaurus.
This genus of dinosaurs lived in what is now western North America at the end of the JurassicPeriod. Diplodocus is one of the more common dinosaur fossils found in the Upper Morrison Formation, a sequence of shallow marine and alluvial sediments deposited about 155 to 148 million years ago, in what is now termed the Kimmeridgian and Tithonianstages (Diplodocus itself ranged from about 154 to 150 million years ago). The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Barosaurus, Apatosaurus and Brachiosaurus.
Diplodocus is among the most easily identifiable dinosaurs, with its classic dinosaur shape, long neck and tail and four sturdy legs. For many years, it was the longest dinosaur known. Its great size may have been a deterrent to the predators Allosaurus and Ceratosaurus: their remains have been found in the same strata, which suggests they coexisted with Diplodocus. (see more...)
Dromaeosauroides is a genus of dromaeosauridtheropoddinosaur from the Early Cretaceous of what is now Denmark. It is known from two teeth, the first of which was found in 2000. Based on the first tooth, the genus and species Dromaeosauroides bornholmensis was named in 2003. The genus name means "Dromaeosaurus-like", due to the similarity to the teeth of that genus, and the species name means "from Bornholm". The holotype tooth is 21.7 millimetres (0.85 in) long, and the second tooth is 15 millimetres (0.59 in). They are curved and finely serrated. In life, Dromaeosauroides would have been 3 to 4 metres (10 to 10 ft) in length, and weighed about 40 kilograms (88 lb). As a dromaeosaur it would have been feathered, and had a large sickle claw on its feet like its relatives Dromaeosaurus and Deinonychus. Some teeth from Britain that have been referred to the genus Nuthetes may also belong to Dromaeosauroides. Coprolites containing fish remains found in the Jydegaard Formation may belong to this animal.
Dromaeosauroides was discovered in the Jydegaard Formation in Robbedale, on the island of Bornholm in the Baltic Sea. It is one of the oldest known dromaeosaurs in the world, and the first known uncontested dromaeosaur from the Early Cretaceous of Europe. It lived in a coastal lagoon environment with sauropods, as evidenced by a possible titanosaur tooth. Remains and tracks of other dinosaurs have been found in several formations on Bornholm. (see more...)
Edmontosaurus is a genus of crestless duck-billed dinosaur. The fossils of this animal have been found in rocks of western North America that date from the late Campanianstage to the end of the Maastrichtian stage of the CretaceousPeriod, between 73 and 65.5 million years ago. It was one of the last non-avian dinosaurs, and lived shortly before the Cretaceous–Paleogene extinction event. Edmontosaurus was one of the largest hadrosaurids, measuring up to 13 meters (43 ft) long and weighing around 4.0 metric tons (4.4 short tons). It is known from several well-preserved specimens that include not only bones, but in some cases extensive skin impressions and possible gut contents.
Edmontosaurus has a lengthy and complicated taxonomic history dating to the late 19th century. The type species, E. regalis, was named by Lawrence Lambe in 1917, although several other species that are now classified in Edmontosaurus were named earlier. The best known of these is E. annectens, originally named by Othniel Charles Marsh in 1892.
Edmontosaurus was widely distributed across western North America. The distribution of Edmontosaurus fossils suggests that it preferred coasts and coastal plains. It was an herbivore that could move on both two legs and four. Because it is known from several bone beds, Edmontosaurus is thought to have lived in groups, and may have been migratory as well.
Like most known tyrannosaurids, Gorgosaurus was a bipedalpredator weighing more than two metric tons as an adult; dozens of large, sharp teeth lined its jaws, while its two-fingered forelimbs were comparatively small. Gorgosaurus was most closely related to Albertosaurus, and more distantly related to the larger Tyrannosaurus. Some experts consider G. libratus to be a species of Albertosaurus; this would make Gorgosaurus a junior synonym of that genus.
Gorgosaurus lived in a lush floodplain environment along the edge of an inland sea. It was an apex predator (meaning that it was at the top of its food chain), preying upon abundant ceratopsids and hadrosaurs. In some areas, Gorgosaurus coexisted with another tyrannosaurid, Daspletosaurus. Although these animals were roughly the same size, there is some evidence of niche differentiation between the two. Gorgosaurus is the best-represented tyrannosaurid in the fossil record, known from dozens of specimens. These plentiful remains have allowed scientists to investigate its ontogeny, life history and other aspects of its biology. (see more...)
Herrerasaurus was one of the earliest dinosaurs. Its name means "Herrera's lizard", after the rancher who discovered the first specimen. All known fossils of this carnivore have been discovered in rocks of Carnian age (late Triassic according to the ICS, dated to 231.4 million years ago) in northwestern Argentina. The type species, Herrerasaurus ischigualastensis, was described by Osvaldo Reig in 1963 and is the only species assigned to the genus. Ischisaurus and Frenguellisaurus are synonyms.
For many years, the classification of Herrerasaurus was unclear because it was known from very fragmentary remains. It was hypothesized to be a basaltheropod, a basal sauropodomorph, a basal saurischian, or not a dinosaur at all but another type of archosaur. However, with the discovery of an almost complete skeleton and skull in 1988, Herrerasaurus has been classified as either an early theropod or an early saurischian in at least five recent reviews of theropod evolution, with many researchers treating it at least tentatively as the most primitive member of Theropoda.
Iguanodon is a genus of ornithopoddinosaur that existed roughly halfway between the first of the swift bipedalhypsilophodontids of the mid-Jurassic and the duck-billed dinosaurs of the late Cretaceous. The genus was named in 1825 by EnglishgeologistGideon Mantell, based on fossil specimens that are now assigned to different genera and species. Iguanodon was the second type of dinosaur formally named based on fossil specimens, after Megalosaurus. Together with Megalosaurus and Hylaeosaurus, it was one of the three genera originally used to define Dinosauria. The genus Iguanodon belongs to the larger group Iguanodontia, along with the duck-billed hadrosaurs. The taxonomy of this genus continues to be a topic of study as new species are named or long-standing ones reassigned to other genera.
Scientific understanding of Iguanodon has evolved over time as new information has been obtained from fossils. The numerous specimens of this genus, including nearly complete skeletons from two well-known bonebeds, have allowed researchers to make informed hypotheses regarding many aspects of the living animal, including feeding, movement, and social behaviour. As one of the first scientifically well-known dinosaurs, Iguanodon has occupied a small but notable place in the public's perception of dinosaurs, its artistic representation changing significantly in response to new interpretations of its remains. (see more...)
Lambeosaurus (/ˌlæmbi.oʊˈsɔːrəs/LAM-bee-ə-SOR-əs; meaning "Lambe's lizard") is a genus of hadrosauriddinosaur that lived about 76 to 75 million years ago, in the Late Cretaceousperiod (Campanian) of North America. This bipedal/quadrupedal, herbivorous dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a hatchet. Several possible species have been named, from Canada, the United States, and Mexico, but only the two Canadian species are currently recognized as valid.
Lambeosaurus was belatedly described in 1923 by William Parks, over twenty years after the first material was studied by Lawrence Lambe. The genus has had a complicated taxonomic history, in part because small-bodied crested hadrosaurids now recognized as juveniles were once thought to belong to their own genera and species. Currently, the various skulls assigned to the type speciesL. lambei are interpreted as showing age differences and sexual dimorphism. Lambeosaurus was closely related to the better known Corythosaurus, which is found in slightly older rocks, as well as the less well-known genera Hypacrosaurus and Olorotitan. All had unusual crests, which are now generally assumed to have served social functions like noisemaking and recognition. (see more...)
Like other abelisaurids, Majungasaurus was a bipedalpredator with a short snout. Although the forelimbs are not completely known, they were very short, while the hindlimbs were longer and very stocky. It can be distinguished from other abelisaurids by its wider skull, the very rough texture and thickened bone on the top of its snout, and the single rounded horn on the roof of its skull, which was originally mistaken for the dome of a pachycephalosaur. It also had more teeth in both upper and lower jaws than most abelisaurids.
Known from several well-preserved skulls and abundant skeletal material, Majungasaurus has recently become one of the best-studied theropod dinosaurs from the Southern Hemisphere. It appears to be most closely related to abelisaurids from India rather than South America or continentalAfrica, a fact which has important biogeographical implications. Majungasaurus was the apex predator in its ecosystem, mainly preying on sauropods like Rapetosaurus, and is also one of the few dinosaurs for which there is direct evidence of cannibalism. (see more...)
The type species is M. carinatus; seven other species have been named during the past 150 years, but only M. kaalae among these is still considered valid. Prosauropod systematics have undergone numerous revisions during the last several years, and many scientists disagree where exactly Massospondylus lies on the dinosaur evolutionary tree. The family name Massospondylidae was once coined for the genus, but because knowledge of prosauropod relationships is in a state of flux, it is unclear which other dinosaurs—if any—belong in a natural grouping of massospondylids.
Although Massospondylus was long depicted as quadrupedal, a 2007 study found it to be bipedal. It was probably a plant eater (herbivore), although it is speculated that the prosauropods may have been omnivorous. This animal, 4–6 metres (13–20 ft) long, had a long neck and tail, with a small head and slender body. On each of its forefeet, it bore a sharp thumb claw that was used in defense or feeding. Recent studies indicate Massospondylus grew steadily throughout its lifespan, possessed air sacs similar to those of birds, and may have cared for its young. (see more...)
Nigersaurus (meaning "Niger reptile") is a genus of rebbachisauridsauropod dinosaur that lived during the middle Cretaceous period, about 115 to 105 million years ago. It was discovered in the Elrhaz Formation in an area called Gadoufaoua, in the Republic of Niger. Fossils of this dinosaur were first described in 1976, but it was only named in 1999 after further and more complete remains were found and described. The genus contains a single species, Nigersaurus taqueti.
Nigersaurus was 9 m (30 ft) long, which is small for a sauropod, and had a short neck. It weighed around four tonnes, comparable to a modern elephant. Its skeleton was filled with air spaces connected to air sacs, but the limbs were robustly built. Its skull was very specialised for feeding, with a wide muzzle filled with more than 500 teeth. The jaws may have borne a keratinous sheath. Unlike other tetrapods, the tooth-bearing bones of its jaws were rotated transversely relative to the rest of the skull, so that all of its teeth were located far to the front.
Nigersaurus was probably a browser, and fed with its head close to the ground. It lived in a riparian habitat, and its diet probably consisted of soft plants, such as ferns, horsetails, and angiosperms. It is one of the most common fossil vertebrates found in the area, and shared its habitat with other dinosaurian megaherbivores, as well as large theropods and crocodylomorphs. (see more...)
Parasaurolophus (/ˌpærəsɔːˈrɒləfəs/PARR-ə-saw-ROL-ə-fəs or /ˌpærəˌsɔːrəˈloʊfəs/PARR-ə-SAWR-ə-LOH-fəs; meaning "near crested lizard" in reference to Saurolophus) is a genus of ornithopoddinosaur that lived in what is now North America during the Late CretaceousPeriod, about 76.5–73 million years ago. It was a herbivore that walked both as a biped and a quadruped. Three species are recognized: P. walkeri (the type species), P. tubicen, and the short-crested P. cyrtocristatus. Remains are known from Alberta (Canada), and New Mexico and Utah (United States). The genus was first described in 1922 by William Parks from a skull and partial skeleton found in Alberta.
Parasaurolophus was a hadrosaurid, part of a diverse family of Cretaceous dinosaurs known for their range of bizarre head adornments. This genus is known for its large, elaborate cranial crest, which at its largest forms a long curved tube projecting upwards and back from the skull. Charonosaurus from China, which may have been its closest relative, had a similar skull and potentially a similar crest. The crest has been much discussed by scientists; the consensus is that major functions included visual recognition of both species and sex, acoustic resonance, and thermoregulation. It is one of the rarer hadrosaurids, known from only a handful of good specimens. (see more...)
Discovered in 1834 by Johann Friedrich Engelhardt and described three years later by Hermann von Meyer, Plateosaurus was the fifth named dinosaur genus that is still considered valid. It is now among the dinosaurs best known to science: over 100 skeletons have been found, some of them nearly complete.
Plateosaurus was a bipedalherbivore with a small skull on a long, mobile neck, sharp but plump plant-crushing teeth, powerful hind limbs, short but muscular arms and grasping hands with large claws on three fingers, possibly used for defence and feeding. Unusually for a dinosaur, Plateosaurus showed strong developmental plasticity: instead of having a fairly uniform adult size, fully grown individuals were between 4.8 and 10 metres (16 and 33 ft) long and weighed between 600 and 4,000 kilograms (1,300 and 8,800 lb). Commonly, the animals lived for at least 12 to 20 years, but the maximum life span is not known. (see more...)
All species of Psittacosaurus were gazelle-sized bipedalherbivores characterized by a high, powerful beak on the upper jaw. At least one species had long, quill-like structures on its tail and lower back, possibly serving a display function. Psittacosaurs were extremely early ceratopsians. Although they developed many novel adaptations, they shared many anatomical features with later ceratopsians such as Protoceratops and Triceratops.
Psittacosaurus is not as familiar to the general public as its distant relative Triceratops but it is one of the most completely known dinosaur genera. Fossils of over 400 individuals have been collected so far, including many complete skeletons. Most different age classes are represented, from hatchling through to adult, which has allowed several detailed studies of Psittacosaurus growth rates and reproductivebiology. The abundance of this dinosaur in the fossil record has led to the creation of the Psittacosaurusbiochron for Lower Cretaceous sediments of east Asia. (see more...)
Stegosaurus (/ˌstɛɡoʊˈsɔːrəs/, meaning "roof lizard" or "covered lizard" in reference to its bony plates) is a genus of armoredstegosauriddinosaur. They lived during the Late Jurassicperiod (Kimmeridgian to early Tithonian), some 155 to 150 million years ago in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well. Due to its distinctive tail spikes and plates, Stegosaurus is one of the most recognizable dinosaurs. At least three species have been identified in the upper Morrison Formation and are known from the remains of about 80 individuals.
A large, heavily built, herbivorousquadruped, Stegosaurus had a distinctive and unusual posture, with a heavily rounded back, short forelimbs, head held low to the ground and a stiffened tail held high in the air. Its array of plates and spikes has been the subject of much speculation. The spikes were most likely used for defense, while the plates have also been proposed as a defensive mechanism, as well as having display and thermoregulatory functions. Stegosaurus had a relatively low brain-to-body mass ratio. It had a short neck and small head, meaning it most likely ate low-lying bushes and shrubs. It was the largest of all the stegosaurians (bigger than genera such as Kentrosaurus and Huayangosaurus) and, although roughly bus-sized, it nonetheless shared many anatomical features (including the tail spines and plates) with the other stegosaurian genera. (see more...)
Artist's restoration of Styracosaurus albertensis.
Styracosaurus (/stɪˌrækəˈsɔːrəs/stə-RAK-ə-SOR-əs; meaning "spiked lizard" from the Ancient Greekstyrax/στύραξ "spike at the butt-end of a spear-shaft" and sauros/σαῦρος "lizard") was a genus of herbivorousceratopsiandinosaur from the CretaceousPeriod (Campanianstage), about 75.5 to 75 million years ago. It had four to six long horns extending from its neck frill, a smaller horn on each of its cheeks, and a single horn protruding from its nose, which may have been up to 60 centimetres (2 ft) long and 15 centimetres (6 in) wide. The function or functions of the horns and frills have been debated for many years.
Styracosaurus was a relatively large dinosaur, reaching lengths of 5.5 metres (18 ft) and weighing nearly 3 tons. It stood about 1.8 meters (6 ft) tall. Styracosaurus possessed four short legs and a bulky body. Its tail was rather short. The skull had a beak and shearing cheek teeth arranged in continuous dental batteries, suggesting that the animal sliced up plants. Like other ceratopsians, this dinosaur may have been a herd animal, traveling in large groups, as suggested by bonebeds.
Named by Lawrence Lambe in 1913, Styracosaurus is a member of the Centrosaurinae. One species, S. albertensis, is currently assigned to Styracosaurus. Other species assigned to the genus have since been reassigned elsewhere. (see more...)
Although many species have been named, modern paleontologists recognize only one, T. bataar, as valid. Some experts see this species as an Asian representative of the North American genus Tyrannosaurus; this would make the genus Tarbosaurus redundant. Tarbosaurus and Tyrannosaurus, if not synonymous, are considered to be at least closely related genera.
Like most known tyrannosaurids, Tarbosaurus was a large bipedalpredator, weighing up to six tonnes and equipped with about sixty large teeth. It had a unique locking mechanism in its lower jaw and the smallest forelimbs relative to body size of all tyrannosaurids, renowned for their disproportionately tiny, two-fingered forelimbs.
Tarbosaurus lived in a humid floodplain criss-crossed by river channels. In this environment, it was an apex predator at the top of the food chain, probably preying on other large dinosaurs like the hadrosaurSaurolophus or the sauropodNemegtosaurus. Tarbosaurus is very well represented in the fossil record, known from dozens of specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure. (see more...)
This bipedal ornithopod is known from several partial skeletons and skulls that indicate it grew to between 2.5 and 4.0 meters (8.2 to 13.1 ft) in length on average. It had sturdy hind limbs, small wide hands, and a head with an elongate pointed snout. The form of the teeth and jaws suggest a primarily herbivorous animal. This genus of dinosaur is regarded as a specialized basal ornithopod, traditionally described as a hypsilophodont, but more recently recognized as distinct from Hypsilophodon. Several species have been suggested for this genus. Three currently are recognized as valid: the type speciesT. neglectus, as well as T. garbanii and T. assiniboiensis.
The genus attracted media attention in 2000, when a specimen unearthed in 1993 in South Dakota, United States, was interpreted as including a fossilized heart. There was much discussion over whether the remains were of a heart. Many scientists now doubt the identification of the object and the implications of such an identification. (see more...)
The exact placement of the Triceratops genus within the ceratopsid group has been debated by paleontologists. Two species, T. horridus and T. prorsus, are considered valid. Research published in 2010 suggests that the contemporaneous Torosaurus, a ceratopsid long regarded as a separate genus, represents Triceratops in its mature form, a view not accepted by all researchers. Triceratops has been documented by numerous remains collected since the genus was first described in 1889, including at least one complete individual skeleton. Specimens representing life stages from hatchling to adult have been found.
The function of the frills and three distinctive facial horns has long inspired debate. Traditionally these have been viewed as defensive weapons against predators. More recent theories, noting the presence of blood vessels in the skull bones of ceratopsids, find it more probable that these features were primarily used in identification, courtship and dominance displays, much like the antlers and horns of modern reindeer, mountain goats, or rhinoceros beetles. (see more...)
Like other tyrannosaurids, Tyrannosaurus was a bipedalcarnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hindlimbs, Tyrannosaurus forelimbs were short and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size it is one of the largest known land predators in history. The most complete specimen measures up to 12.3 m (40 ft) in length, up to 4 metres (13 ft) tall at the hips, and up to 6.8 metric tons (7.5 short tons) in weight. Tyrannosaurus rex would have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly sauropods.
More than 50 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology. Its taxonomy is also controversial: some scientists consider Tarbosaurus bataar from Asia to be a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. (see more...)
Like other dromaeosaurids like Deinonychus and Achillobator, Velociraptor was a bipedal, featheredcarnivore with a long tail and an enlarged sickle-shaped claw on each hindfoot, which is thought to have been used to tackle prey. Velociraptor can be distinguished from other dromaeosaurids by its long and low skull, with an upturned snout.
Velociraptor (commonly shortened to "raptor") is one of the dinosaur genera most familiar to the general public due to its prominent role in the Jurassic Park motion picture series. In the films it was shown with anatomical inaccuracies, including being much larger than it was in reality and without feathers. Some of these inaccuracies, along with the head's larger dome in the movies may suggest that the dinosaurs in the movies were actually modeled on Deinonychus. Velociraptor is also well known to paleontologists, with over a dozen described fossil skeletons, the most of any dromaeosaurid. One particularly famous specimen preserves a Velociraptor locked in combat with a Protoceratops. (see more...)
Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosauriantheropoddinosaurs. Abelisaurids thrived during the CretaceousPeriod, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indiansubcontinent and the island of Madagascar. Abelisaurids first appear in the fossil record of the early middle Jurassic period, and at least one species (Majungasaurus crenatissimus) survived until the end of the Mesozoic era 66 million years ago.
Like most theropods, abelisaurids were carnivorousbipeds. They were characterized by stocky hindlimbs and extensive ornamentation of the skull bones, with grooves and pits. In many abelisaurids, like Carnotaurus, the forelimbs are vestigial, the skull is shorter and bony crests grows above the eyes. Most of the known abelisaurids would have been between 5 to 9 meters (17 to 30 ft) in length, from snout to tip of tail, with a new and as yet unnamed specimen from northwestern Turkana in Kenya, Africa reaching a possible length of 11–12 meters (36 to 39 feet). Before becoming well known, fragmentary abelisaurid remains were occasionally misidentified as possible South American tyrannosaurids. (see more...)
Ampelosaurus is a titanosauriansauropoddinosaur hailing from the Late CretaceousPeriod of what is now Europe. Its type species is A. atacis, named by Le Loeuff in 1995. A possible unnamed species has given Ampelosaurus an age reaching to the latest Cretaceous, from about 70 to 66 million years ago.
Like most sauropods, it would have had a long neck and tail but it also carried armor in the form of osteoderms. The blade of the scapula, contrary to most titanosaurs, is triangular. The blade narrows at one end instead of showing an expansion like most other genera. Titanosaurians were a flourishing group of sauropod dinosaurs during Cretaceous times. The Spanish locality from the latest Cretaceous of “Lo Hueco” yielded a relatively well preserved, titanosaurian braincase, which shares a number of unique features with A. atacis from France. However, it appeared to differ from A. atacis in some traits also. The specimen has been provisionally identified as Ampelosaurus sp..
Ampelosaurus lived alongside many other animals. Over 8500 specimens have been found alongside it, including gastropods, bivalves, crocodiles, other sauropods, plants and invertebrates in the Villalba de la Sierra, Gres de Saint-Chinian, Marnes Rouges Inférieures and Gres de Labarre formations. Recent attention has made Ampelosaurus one of the most well-known dinosaurs known from France. (see more...)
Amphicoelias (/ˌæmfɪˈsiːliəs/, meaning "biconcave", from the Greek αμφι, amphi: "on both sides", and κοιλος, koilos: "hollow, concave") is a genus of herbivorous sauropoddinosaur that includes what may be the largest dinosaur ever discovered, A. fragillimus. Based on surviving descriptions of a single fossil bone, A. fragillimus may have been the longest known vertebrate at 40 to 60 metres (130 to 200 ft) in length, and may have had a mass of up to 122 tonnes (135 short tons). However, because the only fossil remains were lost at some point after being studied and described in the 1870s, evidence survives only in drawings and field notes. The fossil was found in the Morrison Formation. (see more...)
Balaur bondoc is a species of theropoddinosaurs which lived in what is now Romania during the late Cretaceous period. It is the type species of the monotypicgenusBalaur which was described by scientists in August 2010, and was named after the balaur (Romanian pronunciation:[baˈla.ur]), a dragon of Romanian folklore. The specific name bondoc means "stocky", so Balaur bondoc means "Stocky dragon" in Romanian. This name refers to the greater musculature that Balaur had compared to its relatives. The genus is known from two partial skeletons including the type specimen.
Seventy million years ago, world sea levels were higher, and the location where its fossils are found was a part of the European Archipelago called Hațeg Island which is also referred to as the "Island of the Dwarf Dinosaurs". Unlike other early members of the group Paraves, which includes Velociraptor, Troodon, and Archaeopteryx, this theropod had not just one but two large, retractable, sickle-shaped claws on each foot, and its limbs were proportionally shorter and heavier than those of its relatives. As with other dinosaurs from Hațeg, such as Magyarosaurus, a dwarf sauropod, its strange features have been argued to show the effects of its island habitat on its evolution. (see more...)
Amargasaurus is a genus of sauropoddinosaur from the Early Cretaceous epoch (129.4–122.46 mya) of what is now Argentina. The only known skeleton was discovered in 1984 and described in 1991, forming the holotype specimen of the single species Amargasaurus cazaui. The skeleton is nearly complete, including a fragmentary skull, making Amargasaurus one of the best-known sauropods from the Early Cretaceous. Amargasaurus was small for a sauropod, reaching 9 to 10 meters (30 to 33 feet) in length. It sported two parallel rows of tall spines down its neck and back, taller than in any other known sauropod. It is unclear how these spines appeared in life—they could have supported skin sails or stuck out of the body as solitary structures supporting a keratinous sheath. They might have been used for display, combat, or defense.
Amargasaurus was discovered in sedimentary rocks of the La Amarga Formation, which dates back to the Barremian and late Aptian of the Early Cretaceous epoch. Amargasaurus probably fed at mid-height, as shown by the orientation of its inner ear and the articulation of its neck vertebrae, which suggest a habitual position of the snout some 80 centimeters (31 inches) above the ground and a maximum height of 2.7 meters (8.9 feet). Within the Sauropoda, Amargasaurus was a member of the family Dicraeosauridae. (see more...)
Apatosaurus is a genus of extinct sauropoddinosaurs that lived in North America during the Late Jurassicperiod. Othniel Charles Marsh described and named the first-known species, A. ajax in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 1916. Fossils are known from the Morrison Formation of modern-day Colorado, Oklahoma, and Utah, in the United States. Apatosaurus had an average length of 22.8 m (75 ft), and an average mass of at least 16.4 metric tons (18.1 short tons).
The cervical vertebrae of Apatosaurus are less elongated and more heavily constructed than those of Diplodocus, and the bones of the leg are much stockier despite being longer, implying that Apatosaurus was a more robust animal. The tail was held above the ground during normal locomotion. Apatosaurus had a single claw on each forelimb and three on each hindlimb. Apatosaurus was a generalized browser that likely held its head elevated. To lighten its vertebrae, Apatosaurus had air sacs that made the bones internally full of holes. Like that of other diplodocids, its tail may have been used as a whip to create loud noises.
Apatosaurus is a genus in the family Diplodocidae. It is one of the more basal genera. Brontosaurus has long been considered a junior synonym of Apatosaurus; its only species was reclassified as A. excelsus in 1903. However, the 2015 study concluded that Brontosaurus was a valid genus of sauropod distinct from Apatosaurus. (see more...)
Opisthocoelicaudia/ɒˈpɪsθoʊsɪlɪˈkɔːdiə/ was a genus of sauropoddinosaur of the Late Cretaceous Period discovered in the Gobi Desert of Mongolia. The only species is Opisthocoelicaudia skarzynskii. A well-preserved skeleton lacking only the head and neck was unearthed in 1965 by Polish and Mongolian scientists, making Opisthocoelicaudia one of the best known sauropods from the Late Cretaceous. Tooth marks on this skeleton indicate that large carnivorous dinosaurs had fed on the carcass and possibly had carried away the now-missing parts. A relatively small sauropod, Opisthocoelicaudia measured approximately 11 metres (36 ft) in length. The name Opisthocoelicaudia means "posterior cavity tail", alluding to the unusual, opisthocoel condition of the anterior tail vertebrae that were concave on their posterior sides. This and other skeletal features lead researchers to propose that Opisthocoelicaudia was able to rear on its hindlegs.
Named and described by Polish paleontologist Maria Magdalena Borsuk-Białynicka in 1977, Opisthocoelicaudia was first thought to be a new member of the Camarasauridae, but is currently considered a derived member of the Titanosauria. Its exact relationships within Titanosauria are contentious, but it may have been close to the North American Alamosaurus. All Opisthocoelicaudia fossils stem from the Nemegt Formation. (see more...)
Cryolophosaurus (/ˌkraɪ.oʊˌlɒfoʊˈsɔːrəs/ or /kraɪˌɒloʊfəˈsɔːrəs/; "CRY-oh-loaf-oh-SAWR-us") is a genus of large theropods known from only a single speciesCryolophosaurus ellioti, known from the early Jurassic period of Antarctica. It was about 6 to 7 metres (20 to 23 ft) long and 460 kilograms (1,010 lb) in weight, making it one of the largest theropods of its time. Individuals of this species may have grown even larger, because the only known specimen probably represents a sub-adult.
Cryolophosaurus is known from a skull, a femur and other material, the skull. C. ellioti possessed a distinctive crest on its head that spanned the head from side to side. Based on evidence from related species and studies of bone texture, it is thought that this bizarre crest was used for intra-species recognition. Since its original description, the consensus is that Cryolophosaurus is either a primitive member of the Tetanurae or a close relative of that group.
Cryolophosaurus was first excavated from Antarctica's Early Jurassic, Sinemurian to Pliensbachian aged Hanson Formation, formerly the upper Falla Formation, by paleontologistDr. William Hammer in 1991. It was the first carnivorous dinosaur to be discovered in Antarctica and the first non-avian dinosaur from the continent to be officially named. The sediments in which its fossils were found have been dated at ~194 to 188 million years ago, representing the Early Jurassic Period. (see more...)
Dromaeosauridae is a family of bird-like theropoddinosaurs. They were small- to medium-sized feathered carnivores that flourished in the CretaceousPeriod. The name Dromaeosauridae means 'running lizards', from Greekdromeus (δρομευς) meaning 'runner' and sauros (σαυρος) meaning 'lizard'. In informal usage they are often called raptors (after Velociraptor), a term popularized by the film Jurassic Park; a few types include the term "raptor" directly in their name and have come to emphasize their supposed bird-like habits.
Dromaeosaurid fossils have been found in North America, Europe, Africa, Japan, China, Mongolia, Madagascar, Argentina, and Antarctica. They first appeared in the mid-Jurassic Period (late Bathonian stage, about 164 million years ago) and survived until the end of the Cretaceous (Maastrichtian stage, 66 ma), existing for over 100 million years, up until the Cretaceous–Paleogene extinction event. The presence of dromaeosaurs as early as the Middle Jurassic has been confirmed by the discovery of isolated fossil teeth, though no dromaeosaurid body fossils have been found from this period. (see more...)
Gryposaurus (meaning "hooked-nosed (Greekgrypos) lizard"; sometimes incorrectly translated as "griffin (Latingryphus) lizard") was a genus of duckbilleddinosaur that lived about 83 to 75.5 million years ago, in the Late Cretaceous (late Santonian to late Campanianstages) of North America. Named species of Gryposaurus are known from the Dinosaur Park Formation in Alberta, Canada and the Lower Two Medicine Formation in Montana and the Kaiparowits Formation of Utah in the United States.
Gryposaurus is similar to Kritosaurus, and for many years was regarded as the same genus. It is known from numerous skulls, some skeletons, and even some skin impressions that show it to have had pyramidal scales pointing out along the midline of the back. It is most easily distinguished from other duckbills by its narrow arching nasal hump, sometimes described as similar to a "Roman nose," and which may have been used for species or sexual identification, and/or combat with individuals of the same species. A large bipedal/quadrupedalherbivore around 9 meters long (30 ft), it may have preferred river settings. (see more...)
Heterodontosauridae ("different-toothed lizards") is a family of early ornithischiandinosaurs that were likely among the most basal (primitive) members of the group. Although their fossils are rare, they lived around the globe beginning in the late TriassicPeriod, and a few late-surviving species persisted into the Early Cretaceous.
Heterodontosaurids were fox-sized dinosaurs less than 2 meters (6.6 ft) in length, including a long tail. They are known mainly for their characteristic teeth, including enlarged canine-like tusks and cheek teeth adapted for chewing, analogous to those of Cretaceous hadrosaurids. Their diet was herbivorous or possibly omnivorous. (see more...)
Hypacrosaurus (meaning "near the highest lizard" [Greek υπο-, hypo- = less + ακρος, akros, high], because it was almost but not quite as large as Tyrannosaurus) was a genus of duckbilldinosaur similar in appearance to Corythosaurus. Like Corythosaurus, it had a tall, hollow rounded crest, although not as large and straight. It is known from the remains of two species that spanned 75 to 67 million years ago, in the Late Cretaceous of Alberta, Canada, and Montana, United States, and is the latest hollow-crested duckbill known from good remains in North America. It was an obscure genus until the description of nests, eggs, and hatchlings belonging to H. stebingeri in the 1990s. (see more...)
Hypsibema missouriensis (pronounced /ˌhɪpsɪˈbiːməmɪˌzʊəriˈɛnsɪs/; originally Neosaurus missouriensis, first renamed to Parrosaurus missouriensis, also spelled Hypsibema missouriense) is a species of plant-eatingdinosaur in the genusHypsibema, and the state dinosaur of the U.S. stateMissouri. One of the few official state dinosaurs, bones of the species were discovered in 1942, at what later became known as the Chronister Dinosaur Site near Glen Allen, Missouri. The remains of Hypsibema missouriensis at the site, which marked the first known discovery of dinosaur remains in Missouri, are the only ones to have ever been found. Although first thought to be a sauropod, later study determined that it was a hadrosaur, or "duck-billed" dinosaur, whose snouts bear likeness to ducks' bills. Some of the species' bones found at the Chronister Dinosaur Site are housed in Washington, D.C.'s Smithsonian Institution. (see more...)
Kritosaurus is an incompletely known but historically important genus of hadrosaurid (duck-billed) dinosaur. It lived about 74-70 million years ago, in the Late Cretaceous of North America. The name means "separated lizard" (referring to the arrangement of the cheek bones in an incomplete type skull), but is often mistranslated as "noble lizard" in reference to the presumed "Roman nose" (in the original specimen, the nasal region was fragmented and disarticulated, and was originally restored flat). Despite the dearth of material, this herbivore appeared frequently in dinosaur books until the 1990s, although what was usually represented was the much more completely known Gryposaurus, then thought to be a synonym. (see more...)
Megalosaurus is a genus of large meat-eating theropoddinosaurs of the Middle Jurassicperiod (Bathonian stage, 166 million years ago) of Southern England. Although fossils from other areas have been assigned to the genus, the only certain remains of Megalosaurus come from the late Middle Jurassic of the Oxfordshire.
Megalosaurus was, in 1824, the first genus of dinosaur to be validly named, apart from birds. The type species is Megalosaurus bucklandii, named in 1827. In 1842, Megalosaurus was one of three genera on which Richard Owen based his Dinosauria. On Owen's directions a model was made as one of the Crystal Palace Dinosaurs, which greatly increased the public interest for prehistoric reptiles. Subsequently, over fifty other species would be classified under the genus, originally because dinosaurs were not well known, but even during the 20th century after many dinosaurs had been discovered. Today it is understood these additional species were not directly related to M. bucklandii, which is the only true Megalosaurus species.
Megalosaurus was about seven metres long, weighing roughly 1.5 tonnes. It was bipedal, walking on stout hindlimbs, its horizontal torso balanced by a horizontal tail. Its forelimbs were short, though very robust. Megalosaurus had a rather large head, equipped with long curved teeth. It was generally a robust and heavily muscled animal. (see more...)
Othnielosaurus is a genus of ornithischiandinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age Morrison Formation of the western United States. It is named in honor of famed paleontologistOthniel Charles Marsh, and was formerly assigned to the genus Laosaurus. This genus was coined to hold fossils formerly included in Othnielia, which is based on remains that may be too sparse to hold a name; as such, it is part of decades of research to untangle the taxonomy left behind by Marsh and his rival Edward Drinker Cope from the Bone Wars. Othnielosaurus has usually been classified as a hypsilophodont, a type of generalized small bipedalherbivore or omnivore, although recent research has called this and the existence of a distinct group of hypsilophodonts into question. (see more...)
Like other pachycephalosaurids, Pachycephalosaurus was a bipedalomnivore with an extremely thick skull roof. It possessed long hindlimbs and small forelimbs. Pachycephalosaurus is the largest known pachycephalosaur.
The thick skull domes of Pachycephalosaurus and related genera gave rise to the hypothesis that pachycephalosaurs used their skulls in intraspecific combat. This hypothesis has been disputed in recent years. (see more...)
PaleontologistsPaul Sereno of the University of Chicago, Jeff Wilson of the University of Michigan, and Srivastava worked together as an Indo–American group to study the Narmada River fossils. The fossils represented the partial skeleton of the new species Rajasaurus narmadensis, which means "princely lizard from the Narmada Valley."
The fossilized bones of Rajasaurus have also been found in the upriver region of the Narmada, at Jabalpur, in the state of Madhya Pradesh.(see more...)
Sauropelta (/ˌsɔːroʊˈpɛltə/SAWR-o-PEL-tə; meaning 'lizard shield') is a genus of nodosauriddinosaur that existed in the Early Cretaceous Period of North America. One species (S. edwardsorum) has been named although others may have existed. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of Wyoming, Montana, and possibly Utah. It is also the earliest known genus of nodosaurid; most of its remains are found in the Cloverly Formation, which dates to about 108.05±0.2 Ma (million years ago).
It was a medium-sized nodosaurid, measuring about 5 meters (16.5 ft) long. Sauropelta had a distinctively long tail which made up about half of its body length. Although its body was smaller than a modern black rhinoceros, Sauropelta was about the same mass, weighing in at about 1,500 kilograms (3,300 lb). The extra weight was largely due to its extensive bony body armor, including the characteristically large spines projecting from its neck. (see more...)
Scelidosaurus was about 4 metres (13 ft) long. It was a largely quadrupedal animal, feeding on low scrubby plants, the parts of which were bitten off by the small, elongated, head to be processed in the large gut. Scelidosaurus was lightly armoured, protected by long horizontal rows of keeled oval scutes, that stretched along the neck, back and tail.
One of the oldest known and most "primitive" of the thyreophorans, the exact placement of Scelidosaurus within this group has been the subject of debate for nearly 150 years. This was not helped by the limited additional knowledge about the early evolution of armoured dinosaurs. Today most evidence indicates that Scelidosaurus is a basal member of the Thyreophora, lower placed in the evolutionary tree of life than the Ankylosauridae or the Stegosauridae. (see more...)
Sinoceratops was a medium sized, averagely-built, ground-dwelling, quadrupedalherbivore. It could grow up to an estimated 6 m (19.7 ft) long and 2 metres (6.6 ft) high, and weigh up to 2 tonnes (2.0 long tons; 2.2 short tons). It was the first ceratopsid dinosaur discovered in China, and the only ceratopsid known from Asia. All other centrosaurines, and all chasmosaurines, are known from fossils discovered in North America, except for possibly Turanoceratops. Sinoceratops is also significant because it is one of the largest known centrosaurines, and is much larger than any other known basal members of this group.
Sinoceratops existed in the Xingezhuang Formation during the late Cretaceous. It lived alongside leptoceratopsids, saurolophines, and tyrannosaurines. The most common creature in the formation was Shantungosaurus, to whom most of the material has been assigned to. The animals living alongside Sinoceratops and Shantungosaurus were Zhuchengceratops, Huaxiaosaurus, and Zhuchengtyrannus. (see more...)
Sinosauropteryx is a compsognathiddinosaur. Described in 1996, it was the first dinosaur taxon outside of Avialae (birds and their immediate relatives) to be found with evidence of feathers. It was covered with a coat of very simple filament-like feathers. Structures that indicate colouration have also been preserved for some of the feathers, which makes Sinosauropteryx the first non-avialian dinosaurs where colouration has been determined. Colouration includes a reddish and light banded tail.
Sinosauropteryx was a small theropod with an unusually long tail and short arms. The longest known specimen reaches up to 1.07 m (3.5 ft) in length, with an estimated weight of 0.55 kg (1.2 lb). It was a close relative of the similar but older genus Compsognathus, both genera belonging to the familyCompsognathidae. Only one species of Sinosauropteryx has been named: S. prima, meaning "first" in reference to its status as the first feathered non-avialian dinosaur species discovered.
Sinosauropteryx lived in what is now northeastern China during the early Cretaceousperiod. It was among the first dinosaurs discovered from the Yixian Formation in Liaoning Province, and was a member of Jehol Biota. Well-preserved fossils of this species illustrate many aspects of their biology, such as their diet and reproduction. (see more...)
Spinosaurus is a genus of theropoddinosaur which lived in what is now North Africa, from the lower Albian to lower Cenomanianstages of the Cretaceousperiod, about 112 to 97 million years ago. This genus was first known from Egyptian remains discovered in 1912 and described by GermanpaleontologistErnst Stromer in 1915. The best known species is S. aegyptiacus from Egypt, although a potential second species S. maroccanus has been recovered from Morocco.
Spinosaurus may be the largest of all known carnivorous dinosaurs. Estimates published in 2005 and 2007 suggest that it was 12.6 to 18 metres (41 to 59 ft) in length and 7 to 20.9 tonnes (7.7 to 23.0 short tons) in weight. The skull of Spinosaurus was long and narrow like that of a modern crocodilian. Spinosaurus is known to have eaten fish; evidence suggests that it lived both on land and in water like a modern crocodilian. The distinctive spines of Spinosaurus, which were long extensions of the vertebrae, grew to at least 1.65 meters (5.4 ft) long and were likely to have had skin connecting them, forming a sail-like structure. Multiple functions have been put forward for this structure, including thermoregulation and display. (see more...)
It was originally mentioned by Franz Nopcsa in 1923 as a subfamily of Acanthopholidae, along with the previously defined Acanthopholinae. The family has gone through many taxonomic revisions since it was defined by Nopcsa in 1902. It is now recognized as a junior synonym of the familyNodosauridae. The subfamily now includes the generaAnoplosaurus, Europelta, Hungarosaurus, and Struthiosaurus, designated as the type genus. Because of the instability of Acanthopholis, the generic namesake of Acanthopholinae, and its current identification as a nomen dubium, Struthiosaurinae, the next named group, was decidedly used over the older one.
Struthiosaurinae appeared at about exactly the same time as the North American subfamily Nodosaurinae. Struthiosaurines range all across the cretaceous, the oldest genus being Europelta at an age of 112 Ma and the youngest being Struthiosaurus at about 85–66 Ma. (see more...)
Although descended from smaller ancestors, tyrannosaurids were almost always the largest predators in their respective ecosystems, putting them at the apex of the food chain. The largest species was Tyrannosaurus rex, one of the largest known land predators, which measured up to 12.3 metres (40 ft) in length and up to 6,500 kilograms (7.2 short tons) in weight. Tyrannosaurids were bipedal carnivores with massive skulls filled with large teeth. Despite their large size, their legs were long and proportioned for fast movement. In contrast, their arms were very small, bearing only two functional digits.
Unlike most other groups of dinosaurs, very complete remains have been discovered for most known tyrannosaurids. This has allowed a variety of research into their biology. Scientific studies have focused on their ontogeny, biomechanics and ecology, among other subjects. Soft tissue, both fossilized and intact, has been reported from one specimen of Tyrannosaurus rex. (see more...)
Vulcanodon (meaning "volcanotooth") is an extinctgenus of sauropoddinosaur from the Early Jurassic of southern Africa. The only known species is V. karibaensis. Discovered in 1969 in Rhodesia (now known as Zimbabwe), it was regarded as the earliest known sauropod for decades, and is still one of the most primitive sauropods that has been discovered. As a quadrupedal, ground-dwelling herbivore, Vulcanodon already showed the typical sauropod body plan with column-like legs and a long neck and tail. It was much smaller than most other sauropods, measuring approximately 6.5 metres (20 ft) in length. Vulcanodon is known from a fragmentary skeleton including much of the pelvic girdle, hind limbs, forearms, and tail, but lacking the trunk and neck vertebrae as well as the skull.
Originally, this genus was believed to be a prosauropod because of the knife-shaped teeth found near its fossils, which fit in with the idea that prosauropods were omnivorous. Scientists now know that the teeth belonged to an unidentified theropod that may have scavenged on the Vulcanodoncarcass. Vulcanodon is now known to be a true sauropod. Upon the discovery of the related Tazoudasaurus, both animals were unified in the family Vulcanodontidae, though this has not been universally accepted. (see more...)
Pteranodon (/tɪˈrænədɒn/; from Greek πτερόν ("wing") and ἀνόδων ("toothless")) is a genus of pterosaurs which included some of the largest known flying reptiles, with wingspans over 6 metres (20 ft). It existed during the late Cretaceous geological period of North America in present day Kansas, Alabama, Nebraska, Wyoming, and South Dakota. More fossil specimens of Pteranodon have been found than any other pterosaur, with about 1,200 specimens known to science, many of them well preserved with nearly complete skulls and articulated skeletons. It was an important part of the animal community in the Western Interior Seaway.
Pteranodon was not a dinosaur. By definition, all dinosaurs belong to the groups Saurischia and Ornithischia, which exclude pterosaurs. Nevertheless, Pteranodon is frequently featured in dinosaur books and is strongly associated with dinosaurs by the general public. (see more...)
Pterosaurs were flying reptiles of the clade or orderPterosauria. They existed from the late Triassic to the end of the CretaceousPeriod (228 to 66 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger. Early species had long, fully toothed jaws and long tails, while later forms had a highly reduced tail, and some lacked teeth. Many sported furry coats made up of hair-like filaments known as pycnofibres, which covered their bodies and parts of their wings. Pterosaurs spanned a wide range of adult sizes, from the very small Nemicolopterus to the largest known flying creatures of all time, including Quetzalcoatlus and Hatzegopteryx.
Pterosaurs are often referred to in the popular media and by the general public as flying dinosaurs, but this is incorrect. However, like the dinosaurs, pterosaurs are more closely related to birds than to any living reptile. Pterosaurs are also incorrectly referred to as pterodactyls, particularly by journalists. "Pterodactyl" refers specifically to members of the genus Pterodactylus, and more broadly to members of the suborder Pterodactyloidea of the pterosaurs. (see more...)
Uplift of the Colorado Plateau during the Cretaceous had a profound impact on the geology of the Grand Canyon area.
Deinocheirus is a genus of large ornithomimosaur (ostrich dinosaur) that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Nemegt Formation of Mongolia. In 1970, this specimen became the holotype of the only species within the genus, Deinocheirus mirificus. No further remains were discovered for almost fifty years, and its nature remained a mystery. Two more complete specimens were described in 2014, which shed light on many aspects of the animal.
Deinocheirus was largest ornithomimosaur at 11 m (36 ft) long, and weighing 6.36 t (14,000 lb). The arms were among the largest of any bipedal dinosaurs at 2.4 m (7.9 ft) long, with large, blunt claws on its three-fingered hands. The legs were relatively short, and bore blunt claws. Its vertebrae had tall neural spines that formed a "sail" along its back. The tail ended in pygostyle-like vertebrae, which indicate the presence of a fan of feathers. The skull was 1.024 m (3.36 ft) long, with a wide bill and a deep lower jaw, similar to those of hadrosaurs. Members of this group were not adapted for speed, unlike other ornithomimosaurs. Deinocheirus is thought to have been omnivorous; its skull shape indicate a diet of plants, whereas fish scales were found in association with a specimen. (see more...)
Baryonyx (/ˌbæriˈɒnɪks/) is a genus of theropoddinosaur which lived in the Barremian stage of the early CretaceousPeriod, about 130–125 million years ago. The holotype specimen was discovered in 1983 in Surrey, England, and the animal was named Baryonyx walkeri in 1986. Fragmentary specimens were later discovered in other parts of the United Kingdom and Iberia. Baryonyx was about 7.5 m (25 ft) long and weighed 1.2 t (1.3 short tons). It had a long, low snout and narrow jaws, which have been compared to those of a gharial. Baryonyx had many finely serrated teeth. It had robust forelimbs, with the eponymous first-finger claw measuring about 31 cm (12 in) long.
Now recognised as a member of the family Spinosauridae, Baryonyx's affinities were obscure when it was discovered. Apart from the type species (B. walkeri), some researchers have suggested that Suchomimus tenerensis belongs in the same genus and that Suchosaurus cultridens is a senior synonym; however, subsequent authors have kept them separate. Baryonyx was the first theropod dinosaur demonstrated to have been piscivorous (fish-eating), as evidenced by fish scales in the stomach region of the holotype specimen. It may also have been an active predator of larger prey and a scavenger, since it also contained bones of a juvenile Iguanodon. The creature would have caught and processed its prey primarily with its forelimbs and large claws. Baryonyx lived near bodies of water. (see more...)
The known material includes two cervical vertebrae, nine dorsal vertebrae, a few ribs, a fragment of a pubis, and many gastroliths. Of the material, only the vertebrae are diagnostic, with the ribs and pubis being too fragmentary or general to distinguish Dinheirosaurus. This material was first described as in the genus Lourinhasaurus, but differences were noticed and in 1999 Bonaparte and Mateus redescribed the material under the new binomialDinheirosaurus lourinhanensis. Another specimen, ML 418, thought to be Dinheirosaurus, is now known to be from another Portuguese diplodocid. This means that Dinheirosaurus lived alongside many theropods, sauropods, thyreophorans and ornithopods, as well as at least one other diplodocid.
Early members of the ceratopsian group, such as Psittacosaurus, were small bipedal animals. Later members, including ceratopsids like Centrosaurus and Triceratops, became very large quadrupeds and developed elaborate facial horns and frills extending over the neck. While these frills might have served to protect the vulnerable neck from predators, they may also have been used for display, thermoregulation, the attachment of large neck and chewing muscles or some combination of the above. Ceratopsians ranged in size from 1 meter (3 ft) and 23 kilograms (50 lb) to over 9 meters (30 ft) and 5,400 kg (12,000 lb).
Triceratops are by far the best-known ceratopsians to the general public. It is traditional for ceratopsian genus names to end in "-ceratops", although this is not always the case. One of the first named genera was Ceratops itself, which lent its name to the group, although it is considered a nomen dubium today as its fossil remains have no distinguishing characteristics that are not also found in other ceratopsians. (see more...)
Deinosuchus is an extinctgenus related to the alligator that lived 80 to 73 million years ago (Ma), during the late Cretaceousperiod. The name translates as "terrible crocodile" and is derived from the Greek. Although Deinosuchus was far larger than any modern crocodile or alligator, with the largest adults measuring 10.6 m (35 ft) in total length, its overall appearance was fairly similar to its smaller relatives. It had large, robust teeth built for crushing, and its back was covered with thick hemispherical osteoderms. One study indicated Deinosuchus may have lived for up to 50 years, growing at a rate similar to that of modern crocodilians, but maintaining this growth over a much longer time.
Deinosuchus fossils have been found in 10 US states, including Texas, Montana, and many along the East Coast. Fossils have also been found in northern Mexico. It lived on both sides of the Western Interior Seaway, and was an opportunistic apex predator in the coastal regions of eastern North America. Deinosuchus reached its largest size in its western habitat, but the eastern populations were far more abundant. Deinosuchus was probably capable of killing and eating large dinosaurs. It may have also fed upon sea turtles, fish, and other aquatic and terrestrial prey. (see more...)
Aetosaurs (order name Aetosauria) are an extinctorder of heavily armoured, medium- to large-sized Late Triassicherbivorousarchosaurs. They have small heads, upturned snouts, erect limbs, and a body covered by plate-like scutes. All aetosaurs belong to the familyStagonolepididae. Two distinct subdivisions of aeotosaurs are currently recognized, Desmatosuchinae and Aetosaurinae, based primarily on differences in the morphology of the bony scutes of the two groups. Over 20 genera of aetosaurs have been described.
Aetosaur fossil remains are known from Europe, North and South America, parts of Africa and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassictetrapodindex fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site that they are found in.
Aetosaur remains have been found since the early 19th century, although the very first remains that were described were mistaken for fish scales. Aetosaurs were later recognized as crocodile relatives, with early paleontologists considering them to be semiaquatic scavengers. They are now considered to have been entirely terrestrial animals. Some forms have characteristics that may have been adaptations to digging for food. There is also evidence that some if not all aetosaurs made nests. (see more...)
Batrachotomus/ˌbætrəˈkɒtoʊməs/ is a genus of prehistoric archosaur. Fossils of this animal have been found in southern Germany and dated from the Ladinian stage of the Middle Triassicperiod, around 228 to 231 million years ago. Batrachotomus was described by palaeontologistDavid J. Gower 22 years after its discovery.
The locality where Batrachotomus lived was a swampy region and the name comes from the Greekbatrachos/βάτραχος (frog) and tome/τομή (cutting, slicing), which refers to its preying on the large amphibian Mastodonsaurus. In contrast with sprawling reptiles, like crocodiles, this large carnivore was very agile with locomotor superiority due to its erect stance. A remarkable feature seen on its back was a row of paired, flattened bony plates. Batrachotomus was possibly an early relative of Postosuchus, which lived during the dawn of the dinosaurs. (see more...)
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