The Ediacaran biota were ancient lifeforms representing the earliest known complex multicellular organisms. They appeared soon after the Earth thawed from the Cryogenian period's extensive glaciers, and largely disappeared soon before the rapid appearance of biodiversity known as the Cambrian explosion, which saw the first appearance in the fossil record of the basic patterns and body-plans that would go on to form the basis of modern animals. Little of the diversity of the Ediacaran biota would be incorporated in this new scheme, with a distinct Cambrian biota arising and usurping the organisms that dominated the Ediacaran fossil record.
Some Ediacaran organisms might have been closely related to groups that would rise to prominence later, but most non-microscopic fossils are morphologically distinct from later lifeforms, resembling discs, mud-filled bags, or quilted mattresses. Classification is difficult, and the assignment of some species even at the level of kingdom — animal, fungus, protist or otherwise — is uncertain: one paleontologist has even gained support for a separate kingdom Vendobionta. Their strange form and apparent disconnectedness from later organisms have led some to consider them a "failed experiment" in multicellular life, with later multicellular life independently re-evolving from unrelated single-celled organisms. ( more...)All species of Psittacosaurus were gazelle-sized bipedal herbivores 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 and, while they developed many novel adaptations of their own, they also shared many anatomical features with later ceratopsians, such as Protoceratops and the elephant-sized 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 150 individuals have been collected so far, including many near-complete skeletons. Most different age classes are represented, from nestling through to adult, which has allowed several detailed studies of Psittacosaurus growth rates and reproductive biology. The abundance of this dinosaur in the fossil record has led to its use as an index fossil for Early Cretaceous sediments of central Asia. ( see more...)Although no complete skeleton has been found, Triceratops is well-known from numerous partial specimens collected since the introduction of the genus in 1887. The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, the latest theories explain how these features were probably primarily used in display for courtship and dominance, much like the antlers and horns of modern reindeer, mountain goats or rhinoceros beetles.
Triceratops is the best-known of the ceratopsids, though the genus' exact placement within the group has been a point of contention amongst paleontologists. Two species, T. horridus and T. prorsus, are considered valid, although many other species have been named. ( see more...)Smaller than other dromaeosaurids like Deinonychus and Achillobator, the turkey-sized Velociraptor nevertheless shared many of the same anatomical features. It was a bipedal carnivore with a long, stiffened tail and had an enlarged, sickle-shaped claw on each hindfoot, which is thought to have been used to kill its prey. Velociraptor can be distinguished from other dromaeosaurids by its long and low skull, with an upturned snout.
Due in large part to its prominent role in Michael Crichton's novel Jurassic Park and the subsequent motion picture series, Velociraptor (commonly shortened to 'raptor') is one of the dinosaur genera most familiar to the general public. It is also well-known to paleontologists, with over a dozen recovered fossil skeletons — the most of any dromaeosaurid. One particularly famous specimen shows a Velociraptor locked in combat with a Protoceratops. ( see more...)Discovered in 1822 and described three years later by English geologist Gideon Mantell, Iguanodon was the second dinosaur formally named, after Megalosaurus. Together with Megalosaurus and Hylaeosaurus, it was one of the three genera originally used to define Dinosauria. A large, bulky herbivore, Iguanodon is a member of 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 the 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...)Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small and retained only two digits. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring over 13 metres (43 ft) in length and up to 7.5 tons in weight.
Fossils of some T. rex have been found in North American rock formations dating to the very end of the Cretaceous Period (late Maastrichtian stage, 65 million years ago); it was among the last dinosaurs to exist prior to the Cretaceous–Paleogene extinction event. More than 30 specimens of T. rex have now been identified, some nearly complete, which has allowed significant research into many aspects of its biology, including its life history and biomechanics. The feeding habits and potential speed of T. rex remain controversial. ( 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 feet) in length on average. It had sturdy hind limbs, small wide hands, a head with an elongate pointed snout, and possibly small armor scutes along the midline of the back. This genus of dinosaur is regarded as a specialized hypsilophodont and a herbivore. Several species have been suggested for this genus, but only one, T. neglectus, is currently recognized; the others have been given their own genera, or are believed to be the same as T. neglectus.
The genus attracted media attention in 2000, when a specimen unearthed in 1993 in South Dakota was interpreted as including a fossilized heart. There was much discussion over whether the remains were actually of a heart. Many scientists now doubt the identification of the object and the implications of such an identification. ( see more...)Daspletosaurus is closely related to the much larger and more recent Tyrannosaurus. Like most known tyrannosaurids, it was a multi-ton bipedal predator equipped with dozens of large, sharp teeth. Daspletosaurus had the small forelimbs typical of tyrannosaurids, although they were proportionately longer than in other genera. It was probably similar in weight to a modern white rhinoceros or a small elephant.
As an apex predator, Daspletosaurus was at the top of the food chain, probably preying on large dinosaurs like the ceratopsid Centrosaurus and the hadrosaur Hypacrosaurus. 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...)Its name refers to the unusually large, sickle-shaped talon on the second toe of each hind foot, which was probably held retracted while the dinosaur walked on the third and fourth toes. It was commonly thought that Deinonychus would kick with the sickle claw to slash at its prey but recent tests on reconstructions of similar Velociraptor talons suggest that the claw was used to stab, not slash. As in other dromaeosaurids, the tail was stiffened by a series of elongated bones and bone processes. This might have given Deinonychus greater balance and turning ability. In both the Cloverly and Antlers Formation, Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply it was hunted or at least scavenged upon by Deinonychus.
Paleontologist John Ostrom's study of Deinonychus in the late 1960s revolutionized the way scientists thought about dinosaurs, igniting the debate on whether or not dinosaurs were warm-blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted lightweight bones and stiffened tendons which revealed an active, agile predator. ( see more...)Like other abelisaurids, Majungasaurus was a bipedal predator 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 continental Africa, a fact which has important biogeographical implications. Majungasaurus was the apex predator in its ecosystem, mainly preying on sauropods like Rapetosaurus, and is also the only dinosaur for which direct evidence of cannibalism is known. ( see more...)Non- avian dinosaur fossils are only found below the K–Pg boundary and became extinct immediately before or during the event. A very small number of dinosaur fossils have been found above the K-Pg boundary, but they have been explained as reworked, that is, fossils that have been eroded from their original locations then preserved in later sedimentary layers. Mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates also became extinct. Mammalian and bird clades passed through the boundary with few extinctions, and radiation from those Maastrichtian clades occurred well past the boundary. Rates of extinction and radiation varied across different clades of organisms.
Many scientists theorize that the Cretaceous–Paleogene extinctions were caused by one or more catastrophic geological events such as massive asteroid impacts or increased volcanic activity. Several impact craters and massive volcanic activity in the Deccan traps have been dated to the approximate time of the extinction event. These geological events may have reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology. Other researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate. ( see more...)Acrocanthosaurus was a bipedal predator. 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 about 2.40 metric tons (2.65 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. However, there is still debate over its evolutionary relationships, with some scientists classifying it as an allosaurid, and others as a carcharodontosaurid. Acrocanthosaurus was the largest theropod in its ecosystem and likely an apex predator which possibly preyed on large sauropods and ornithopods. ( see more...)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.
( see more...)Allosaurus was a large bipedal predator with a large skull, equipped with dozens of large, sharp teeth. It averaged 8.5 meters (30 ft) in length, though fragmentary remains suggest it could have reached over 12 meters (39 ft). Relative to the large and powerful hindlimbs, its three-fingered forelimbs were small, and the body was balanced by a long, heavy tail. 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 from Portugal and possibly Tanzania. It was known for over half of the 20th century as Antrodemus, but study of the copious remains from the Cleveland-Lloyd Dinosaur Quarry brought the name Allosaurus back to prominence, and established it as one of the best-known dinosaurs.
As the prominent large predator in the Morrison Formation, Allosaurus was at the top of the food chain, probably preying on contemporaneous large herbivorous dinosaurs. Potential prey included ornithopods, stegosaurids, and sauropods. While it is often thought of as preying on sauropod dinosaurs in groups, there is little evidence for cooperative social behavior in this genus, and individuals may have been aggressive toward each other instead. It may have attacked large prey by ambush, using its upper jaws like a hatchet. ( see more...)The type, and only universally recognized species, is M. carinatus, although six other species have been named during the past 150 years. 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; several 2007 papers support the family's validity.
Although Massospondylus was long depicted as quadrupedal, a 2007 study found it to be bipedal. It was probably a herbivore, although it is speculated that the prosauropods may have been omnivorous. This animal, 4–6 meters (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...)Tarbosaurus (meaning 'terrifying lizard') is a genus of tyrannosaurid theropod dinosaur that flourished in Asia between 70 and 65 million years ago, near the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia with more fragmentary remains found further afield in parts of China. Although many species have been named, modern paleontologists recognize only one, T bataar, as valid. Some experts contend that this species is actually an Asian representative of the North American genus Tyrannosaurus; if true, this would invalidate the genus Tarbosaurus altogether.
Tarbosaurus and Tyrannosaurus are considered closely related genera, even if they are not synonymous. Alioramus, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus. Like most known tyrannosaurids, Tarbosaurus was a large bipedal predator, weighing more than a ton and equipped with dozens of large, sharp 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 hadrosaur Saurolophus or the sauropod Nemegtosaurus. 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...)Gorgosaurus (meaning 'fierce lizard') is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 77 and 74 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus.
Like most known tyrannosaurids, Gorgosaurus was a bipedal predator weighing more than a metric ton 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. Gorgosaurus and Albertosaurus are extremely similar, distinguished mainly by subtle differences in the teeth and skull bones. 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. An apex predator, it was at the top of the food chain, preying upon abundant ceratopsids and hadrosaurs. In some areas, Gorgosaurus coexisted with another tyrannosaurid, Daspletosaurus. Though 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...)Coal balls, despite their name, are calcium-rich masses of permineralised life forms, generally having a round shape. Coal balls were formed roughly 300 million years ago, during the Carboniferous Period. They are exceptional at preserving organic matter, which makes them useful to scientists, who cut and peel the coal balls to research the geological past of the Earth.
In 1855, two English scientists, Joseph Dalton Hooker and Edward William Binney, discovered coal balls in England, and the initial research on coal balls was carried out in Europe. It was not until 1922 that coal balls were discovered and identified in North America. Since then, coal balls have been discovered in other countries and they have led to the discovery of over 300 species and 130 genera.
Coal balls can be found in coal seams across North America and Eurasia. North American coal balls are relatively widespread, both stratigraphically and geologically, as compared to coal balls from Europe. The oldest known coal balls were found in Germany and the former Czechoslovakia.Based on the number of individuals, Waptia fieldensis is the third most abundant arthropod from the Burgess Shale Formation, with thousands of specimens collected. It was among the first fossils found by the American paleontologist Charles D. Walcott in 1909. He described it in 1912 and named it after two mountains near the discovery site – Wapta Mountain and Mount Field.
Waptia fieldensis is the only species classified under the genus Waptia. Although it bears a remarkable resemblance to modern crustaceans, its taxonomic affinities remain unclear. It is currently classified as a stem group crustacean and tentatively included in the clade Crustaceomorpha. ( see more...)Their bizarre form has made classification and ecological reconstruction difficult. Since their discovery in 1931, suggestions of protist, plant, and fungalaffinities have all been entertained. The organisms have been better understood as improvements in microscopy facilitated the study of their fine structure, and there is mounting evidence to suggest that they represent either the eggs or juvenile stage of a marine animal.
The ecology of chitinozoa is also open to speculation; some may have floated in the water column, where others may have attached themselves to other organisms. Most species were particular about their living conditions, and tend to be most common in specific paleoenvironments. Their abundance also varied with the seasons.( see more...)Tiktaalik has a possibility of being a representative of the evolutionary transition from fish to amphibians. It is an example from several lines of ancient sarcopterygian fish developing adaptations to the oxygen-poor shallow-water habitats of its time, environmental conditions which led to the evolution of tetrapods.
It and similar animals may possibly be the common ancestors of the broad swath of all terrestrial fauna: amphibians, reptiles, birds, and mammals. The first well-preserved Tiktaalik fossils were found in 2004 on Ellesmere Island in Nunavut, Canada. ( see more...)For many years, the classification of Herrerasaurus was unclear because it was known from very fragmentary remains. It was hypothesized to be a basal theropod, 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.
It is a member of the Herrerasauridae, a family of similar genera that were among the earliest of the dinosaurian evolutionary radiation. ( see more...)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...)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 bipedal herbivore 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...)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...)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...)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 paleontologist Dr. 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...)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...)Like other pachycephalosaurids, Pachycephalosaurus was a bipedal omnivore 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...)Paleontologists Paul 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...)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, quadrupedal herbivore. 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 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 family Compsognathidae. 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 Cretaceous period. 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...)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 family Nodosauridae. The subfamily now includes the genera Anoplosaurus, 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...)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 Triassic tetrapod index 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...)The species was originally described as a pitcher plant with close affinities to extant members of the family Sarraceniaceae. This would make it the earliest known carnivorous plant and the only known fossil record of pitcher plants (with the possible exception of some palynomorphs of uncertain nepenthacean affinity).Archaeamphora is also one of the three oldest known genera of angiosperms (flowering plants). Li (2005) wrote that "the existence of a so highly derived Angiosperm in the Early Cretaceous suggests that Angiosperms should have originated much earlier, maybe back to 280 mya as the molecular clock studies suggested".
Subsequent authors have questioned the identification of Archaeamphora as a pitcher plant. ( see more...)The taxonomic assignment of C. megalodon has been debated for nearly a century, and is still under dispute. The two major interpretations are Carcharodon megalodon (under family Lamnidae) or Carcharocles megalodon (under the family Otodontidae). Consequently, the scientific name of this species is commonly abbreviated C. megalodon in the literature.
C. megalodon is regarded as one of the largest and most powerful predators in vertebrate history, and likely had a profound impact on the structure of marine communities. Fossil remains suggest that this giant shark reached a maximum length of 18 metres (59 ft), and also affirm that it had a cosmopolitan distribution. Scientists suggest that C. megalodon looked like a stockier version of the great white shark, Carcharodon carcharias. ( see more...)Subfossil lemurs are lemurs from Madagascar that are represented by recent ( subfossil) remains dating from nearly 26,000 years ago (during the late Pleistocene) to approximately 560 years ago. They include both living and extinct species, although the term more frequently refers to the extinct giant lemurs. The diversity of subfossil lemur communities was greater than that of present-day lemur communities, ranging from as high as 20 or more species per location, compared with 10 to 12 species today. Extinct species are estimated to have ranged in size from slightly over 10 kg (22 lb) to roughly 160 kg (350 lb).
Despite their size, the giant lemurs shared many features with living lemurs, including rapid development, poor day vision, relatively small brains, and lack of male dominance. They also had many distinct traits among lemurs, including a tendency to rely on terrestrial locomotion, slow climbing, and suspension instead of leaping, as well as a greater dependence on leaf-eating and seed predation. The giant lemurs likely filled ecological niches now left vacant, particularly seed dispersal for plants with large seeds. There were three distinct families of giant lemur, including the Palaeopropithecidae ( sloth lemurs), Megaladapidae ( koala lemurs), and Archaeolemuridae ( monkey lemurs). Two other types were more closely related and similar in appearance to living lemurs: the giant aye-aye and Pachylemur, a genus of "giant ruffed lemurs".( see more...)Cloudinids had a wide geographic range, reflected in the present distribution of localities in which their fossils are found, and are an abundant component of some deposits. They never appear in the same layers as soft-bodied Ediacaran biota, but the fact that some sequences contain Cloudinids and Ediacaran biota in alternating layers suggests that these groups had different environmental preferences.
Cloudinids are important in the history of animal evolution for two reasons. They are among the earliest and most abundant of the small shelly fossils with mineralized skeletons, and therefore feature in the debate about why such skeletons first appeared in the Late Ediacaran. The most widely supported answer is that their shells are a defense against predators, as some Cloudina specimens from China bear the marks of multiple attacks, which suggests they survived at least a few of them. The evolutionary arms race which this indicates is commonly cited as a cause of the Cambrian explosion of animal diversity and complexity. ( see more...)Specimens were first found in Australia's Ediacara Hills, but recent research has concentrated on the numerous finds near the White Sea in Russia, which cover an interval of time from 555 to 558 million years ago. As with many fossils from this time, its evolutionary relationships to other organisms are hotly debated. Paleontologists initially classified Kimberella as a type of jellyfish, but since 1997 features of its anatomy and its association with scratch marks resembling those made by a radula have been interpreted as signs that it may have been a mollusc. Although some paleontologists dispute its classification as a mollusc, it is generally accepted as being at least a bilaterian.
The classification of Kimberella is important for scientific understanding of the Cambrian explosion: if it was a mollusc or at least a protostome, the protostome and deuterostome lineages must have diverged significantly before 555 million years ago. Even if it was a bilaterian but not a mollusc, its age would indicate that animals were diversifying well before the start of the Cambrian. ( 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 binomial Dinheirosaurus 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.
Dinheirosaurus is a diplodocid, a relative of Apatosaurus, Diplodocus, Barosaurus, Supersaurus, and Tornieria. Among those, the closest relative to Dinheirosaurus is Supersaurus, and together they form a clade of primitive diplodocids. While they were once considered to be diplodocines they are likely more basal than Apatosaurus. ( see more...)The fossil aroused much controversy. Less than ten years after 1891, almost eighty books or articles had been published on Dubois's finds. Despite Dubois' argument, few accepted that Java Man was a transitional form between apes and humans. Some dismissed the fossils as apes and others as modern humans, whereas many scientists considered Java Man as a primitive side branch of evolution not related to modern humans at all.
Eventually, similarities between Pithecanthropus erectus (Java Man) and Sinanthropus pekinensis ( Peking Man) led Ernst Mayr to rename both Homo erectus in 1950, placing them directly in the human evolutionary tree. To distinguish Java Man from other Homo erectus populations, some scientists began to regard it as a subspecies, Homo erectus erectus, in the 1970s. Estimated to be between 700,000 and 1,000,000 years old, at the time of their discovery the fossils of Java Man were the oldest hominin fossils ever found. ( see more...)Overall, Smilodon was more robustly built than any extant (living) cat, with particularly well-developed forelimbs and exceptionally long upper canines. Its jaw had a bigger gape than that of modern cats and its upper canines were slender and fragile, being adapted for precision killing. S. gracilis was the smallest species at 55 to 100 kg (120 to 220 lb) in weight. S. populator from South America is perhaps the largest known felid at 220 to 400 kg (490 to 880 lb) in weight and 120 cm (47 in) in height.
Smilodon probably lived in closed habitats such as forests and bush, which would have provided cover for ambushing prey. Smilodon died out at the same time that most North and South American megafauna disappeared, about 10,000 years ago. Its reliance on large animals has been proposed as the cause of its extinction, along with climate change and competition with other species, but the exact cause is unknown. ( see more...)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...)Reaching 4 m (13 ft) at the shoulders and 8–10 tonnes (18,000–22,000 lb) in weight, the Columbian mammoth was one of the largest species of mammoth. It most likely used its tusks and trunk like modern elephants—for manipulating objects, fighting, and foraging. The Columbian mammoth preferred open areas, such as parkland landscapes, and fed on sedge, grass, and other plants. Genetic evidence suggests that they interbred with wooly mammoths.
Before they went extinct, Columbian mammoths coexisted in North America for a few thousand years with Palaeoamericans, who hunted them for food, used their bones for making tools, and depicted them in ancient art. Columbian mammoth remains have been found in association with Clovis culture artefacts; these remains may have stemmed either from hunting or from scavenging. The Columbian mammoth disappeared at the end of the Pleistocene around 11,000 years ago, most likely as a result of habitat loss caused by climate change, hunting by humans, or a combination of both. ( see more...)The species is characterized by a body mass and stature similar to small-bodied human populations, a smaller endocranial volume similar to Australopithecus, and a skull shape similar to early Homo species. The skeletal anatomy presents ancestral features known from australopithecines with more recent features associated with later hominins. The fossils have not been dated.
The fossils were discovered by recreational cavers Rick Hunter and Steven Tucker in 2013. Homo naledi was formally described in September 2015 by a 47-member international team of authors led by American and South African paleoanthropologist Lee Berger of the University of the Witwatersrand, who proposed the bones represent a new Homo species. Other experts contend more analysis and evidence is needed to support this classification. There are some indications that the individuals may have been deliberately placed in the cave near the time of their death; other experts state more evidence is needed to support this hypothesis. ( see more...)The Ediacaran biota were ancient lifeforms representing the earliest known complex multicellular organisms. They appeared soon after the Earth thawed from the Cryogenian period's extensive glaciers, and largely disappeared soon before the rapid appearance of biodiversity known as the Cambrian explosion, which saw the first appearance in the fossil record of the basic patterns and body-plans that would go on to form the basis of modern animals. Little of the diversity of the Ediacaran biota would be incorporated in this new scheme, with a distinct Cambrian biota arising and usurping the organisms that dominated the Ediacaran fossil record.
Some Ediacaran organisms might have been closely related to groups that would rise to prominence later, but most non-microscopic fossils are morphologically distinct from later lifeforms, resembling discs, mud-filled bags, or quilted mattresses. Classification is difficult, and the assignment of some species even at the level of kingdom — animal, fungus, protist or otherwise — is uncertain: one paleontologist has even gained support for a separate kingdom Vendobionta. Their strange form and apparent disconnectedness from later organisms have led some to consider them a "failed experiment" in multicellular life, with later multicellular life independently re-evolving from unrelated single-celled organisms. ( more...)All species of Psittacosaurus were gazelle-sized bipedal herbivores 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 and, while they developed many novel adaptations of their own, they also shared many anatomical features with later ceratopsians, such as Protoceratops and the elephant-sized 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 150 individuals have been collected so far, including many near-complete skeletons. Most different age classes are represented, from nestling through to adult, which has allowed several detailed studies of Psittacosaurus growth rates and reproductive biology. The abundance of this dinosaur in the fossil record has led to its use as an index fossil for Early Cretaceous sediments of central Asia. ( see more...)Although no complete skeleton has been found, Triceratops is well-known from numerous partial specimens collected since the introduction of the genus in 1887. The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, the latest theories explain how these features were probably primarily used in display for courtship and dominance, much like the antlers and horns of modern reindeer, mountain goats or rhinoceros beetles.
Triceratops is the best-known of the ceratopsids, though the genus' exact placement within the group has been a point of contention amongst paleontologists. Two species, T. horridus and T. prorsus, are considered valid, although many other species have been named. ( see more...)Smaller than other dromaeosaurids like Deinonychus and Achillobator, the turkey-sized Velociraptor nevertheless shared many of the same anatomical features. It was a bipedal carnivore with a long, stiffened tail and had an enlarged, sickle-shaped claw on each hindfoot, which is thought to have been used to kill its prey. Velociraptor can be distinguished from other dromaeosaurids by its long and low skull, with an upturned snout.
Due in large part to its prominent role in Michael Crichton's novel Jurassic Park and the subsequent motion picture series, Velociraptor (commonly shortened to 'raptor') is one of the dinosaur genera most familiar to the general public. It is also well-known to paleontologists, with over a dozen recovered fossil skeletons — the most of any dromaeosaurid. One particularly famous specimen shows a Velociraptor locked in combat with a Protoceratops. ( see more...)Discovered in 1822 and described three years later by English geologist Gideon Mantell, Iguanodon was the second dinosaur formally named, after Megalosaurus. Together with Megalosaurus and Hylaeosaurus, it was one of the three genera originally used to define Dinosauria. A large, bulky herbivore, Iguanodon is a member of 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 the 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...)Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small and retained only two digits. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring over 13 metres (43 ft) in length and up to 7.5 tons in weight.
Fossils of some T. rex have been found in North American rock formations dating to the very end of the Cretaceous Period (late Maastrichtian stage, 65 million years ago); it was among the last dinosaurs to exist prior to the Cretaceous–Paleogene extinction event. More than 30 specimens of T. rex have now been identified, some nearly complete, which has allowed significant research into many aspects of its biology, including its life history and biomechanics. The feeding habits and potential speed of T. rex remain controversial. ( 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 feet) in length on average. It had sturdy hind limbs, small wide hands, a head with an elongate pointed snout, and possibly small armor scutes along the midline of the back. This genus of dinosaur is regarded as a specialized hypsilophodont and a herbivore. Several species have been suggested for this genus, but only one, T. neglectus, is currently recognized; the others have been given their own genera, or are believed to be the same as T. neglectus.
The genus attracted media attention in 2000, when a specimen unearthed in 1993 in South Dakota was interpreted as including a fossilized heart. There was much discussion over whether the remains were actually of a heart. Many scientists now doubt the identification of the object and the implications of such an identification. ( see more...)Daspletosaurus is closely related to the much larger and more recent Tyrannosaurus. Like most known tyrannosaurids, it was a multi-ton bipedal predator equipped with dozens of large, sharp teeth. Daspletosaurus had the small forelimbs typical of tyrannosaurids, although they were proportionately longer than in other genera. It was probably similar in weight to a modern white rhinoceros or a small elephant.
As an apex predator, Daspletosaurus was at the top of the food chain, probably preying on large dinosaurs like the ceratopsid Centrosaurus and the hadrosaur Hypacrosaurus. 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...)Its name refers to the unusually large, sickle-shaped talon on the second toe of each hind foot, which was probably held retracted while the dinosaur walked on the third and fourth toes. It was commonly thought that Deinonychus would kick with the sickle claw to slash at its prey but recent tests on reconstructions of similar Velociraptor talons suggest that the claw was used to stab, not slash. As in other dromaeosaurids, the tail was stiffened by a series of elongated bones and bone processes. This might have given Deinonychus greater balance and turning ability. In both the Cloverly and Antlers Formation, Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply it was hunted or at least scavenged upon by Deinonychus.
Paleontologist John Ostrom's study of Deinonychus in the late 1960s revolutionized the way scientists thought about dinosaurs, igniting the debate on whether or not dinosaurs were warm-blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted lightweight bones and stiffened tendons which revealed an active, agile predator. ( see more...)Like other abelisaurids, Majungasaurus was a bipedal predator 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 continental Africa, a fact which has important biogeographical implications. Majungasaurus was the apex predator in its ecosystem, mainly preying on sauropods like Rapetosaurus, and is also the only dinosaur for which direct evidence of cannibalism is known. ( see more...)Non- avian dinosaur fossils are only found below the K–Pg boundary and became extinct immediately before or during the event. A very small number of dinosaur fossils have been found above the K-Pg boundary, but they have been explained as reworked, that is, fossils that have been eroded from their original locations then preserved in later sedimentary layers. Mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates also became extinct. Mammalian and bird clades passed through the boundary with few extinctions, and radiation from those Maastrichtian clades occurred well past the boundary. Rates of extinction and radiation varied across different clades of organisms.
Many scientists theorize that the Cretaceous–Paleogene extinctions were caused by one or more catastrophic geological events such as massive asteroid impacts or increased volcanic activity. Several impact craters and massive volcanic activity in the Deccan traps have been dated to the approximate time of the extinction event. These geological events may have reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology. Other researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate. ( see more...)Acrocanthosaurus was a bipedal predator. 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 about 2.40 metric tons (2.65 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. However, there is still debate over its evolutionary relationships, with some scientists classifying it as an allosaurid, and others as a carcharodontosaurid. Acrocanthosaurus was the largest theropod in its ecosystem and likely an apex predator which possibly preyed on large sauropods and ornithopods. ( see more...)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.
( see more...)Allosaurus was a large bipedal predator with a large skull, equipped with dozens of large, sharp teeth. It averaged 8.5 meters (30 ft) in length, though fragmentary remains suggest it could have reached over 12 meters (39 ft). Relative to the large and powerful hindlimbs, its three-fingered forelimbs were small, and the body was balanced by a long, heavy tail. 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 from Portugal and possibly Tanzania. It was known for over half of the 20th century as Antrodemus, but study of the copious remains from the Cleveland-Lloyd Dinosaur Quarry brought the name Allosaurus back to prominence, and established it as one of the best-known dinosaurs.
As the prominent large predator in the Morrison Formation, Allosaurus was at the top of the food chain, probably preying on contemporaneous large herbivorous dinosaurs. Potential prey included ornithopods, stegosaurids, and sauropods. While it is often thought of as preying on sauropod dinosaurs in groups, there is little evidence for cooperative social behavior in this genus, and individuals may have been aggressive toward each other instead. It may have attacked large prey by ambush, using its upper jaws like a hatchet. ( see more...)The type, and only universally recognized species, is M. carinatus, although six other species have been named during the past 150 years. 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; several 2007 papers support the family's validity.
Although Massospondylus was long depicted as quadrupedal, a 2007 study found it to be bipedal. It was probably a herbivore, although it is speculated that the prosauropods may have been omnivorous. This animal, 4–6 meters (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...)Tarbosaurus (meaning 'terrifying lizard') is a genus of tyrannosaurid theropod dinosaur that flourished in Asia between 70 and 65 million years ago, near the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia with more fragmentary remains found further afield in parts of China. Although many species have been named, modern paleontologists recognize only one, T bataar, as valid. Some experts contend that this species is actually an Asian representative of the North American genus Tyrannosaurus; if true, this would invalidate the genus Tarbosaurus altogether.
Tarbosaurus and Tyrannosaurus are considered closely related genera, even if they are not synonymous. Alioramus, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus. Like most known tyrannosaurids, Tarbosaurus was a large bipedal predator, weighing more than a ton and equipped with dozens of large, sharp 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 hadrosaur Saurolophus or the sauropod Nemegtosaurus. 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...)Gorgosaurus (meaning 'fierce lizard') is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 77 and 74 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus.
Like most known tyrannosaurids, Gorgosaurus was a bipedal predator weighing more than a metric ton 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. Gorgosaurus and Albertosaurus are extremely similar, distinguished mainly by subtle differences in the teeth and skull bones. 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. An apex predator, it was at the top of the food chain, preying upon abundant ceratopsids and hadrosaurs. In some areas, Gorgosaurus coexisted with another tyrannosaurid, Daspletosaurus. Though 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...)Coal balls, despite their name, are calcium-rich masses of permineralised life forms, generally having a round shape. Coal balls were formed roughly 300 million years ago, during the Carboniferous Period. They are exceptional at preserving organic matter, which makes them useful to scientists, who cut and peel the coal balls to research the geological past of the Earth.
In 1855, two English scientists, Joseph Dalton Hooker and Edward William Binney, discovered coal balls in England, and the initial research on coal balls was carried out in Europe. It was not until 1922 that coal balls were discovered and identified in North America. Since then, coal balls have been discovered in other countries and they have led to the discovery of over 300 species and 130 genera.
Coal balls can be found in coal seams across North America and Eurasia. North American coal balls are relatively widespread, both stratigraphically and geologically, as compared to coal balls from Europe. The oldest known coal balls were found in Germany and the former Czechoslovakia.Based on the number of individuals, Waptia fieldensis is the third most abundant arthropod from the Burgess Shale Formation, with thousands of specimens collected. It was among the first fossils found by the American paleontologist Charles D. Walcott in 1909. He described it in 1912 and named it after two mountains near the discovery site – Wapta Mountain and Mount Field.
Waptia fieldensis is the only species classified under the genus Waptia. Although it bears a remarkable resemblance to modern crustaceans, its taxonomic affinities remain unclear. It is currently classified as a stem group crustacean and tentatively included in the clade Crustaceomorpha. ( see more...)Their bizarre form has made classification and ecological reconstruction difficult. Since their discovery in 1931, suggestions of protist, plant, and fungalaffinities have all been entertained. The organisms have been better understood as improvements in microscopy facilitated the study of their fine structure, and there is mounting evidence to suggest that they represent either the eggs or juvenile stage of a marine animal.
The ecology of chitinozoa is also open to speculation; some may have floated in the water column, where others may have attached themselves to other organisms. Most species were particular about their living conditions, and tend to be most common in specific paleoenvironments. Their abundance also varied with the seasons.( see more...)Tiktaalik has a possibility of being a representative of the evolutionary transition from fish to amphibians. It is an example from several lines of ancient sarcopterygian fish developing adaptations to the oxygen-poor shallow-water habitats of its time, environmental conditions which led to the evolution of tetrapods.
It and similar animals may possibly be the common ancestors of the broad swath of all terrestrial fauna: amphibians, reptiles, birds, and mammals. The first well-preserved Tiktaalik fossils were found in 2004 on Ellesmere Island in Nunavut, Canada. ( see more...)For many years, the classification of Herrerasaurus was unclear because it was known from very fragmentary remains. It was hypothesized to be a basal theropod, 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.
It is a member of the Herrerasauridae, a family of similar genera that were among the earliest of the dinosaurian evolutionary radiation. ( see more...)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...)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 bipedal herbivore 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...)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...)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...)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 paleontologist Dr. 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...)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...)Like other pachycephalosaurids, Pachycephalosaurus was a bipedal omnivore 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...)Paleontologists Paul 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...)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, quadrupedal herbivore. 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 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 family Compsognathidae. 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 Cretaceous period. 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...)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 family Nodosauridae. The subfamily now includes the genera Anoplosaurus, 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...)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 Triassic tetrapod index 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...)The species was originally described as a pitcher plant with close affinities to extant members of the family Sarraceniaceae. This would make it the earliest known carnivorous plant and the only known fossil record of pitcher plants (with the possible exception of some palynomorphs of uncertain nepenthacean affinity).Archaeamphora is also one of the three oldest known genera of angiosperms (flowering plants). Li (2005) wrote that "the existence of a so highly derived Angiosperm in the Early Cretaceous suggests that Angiosperms should have originated much earlier, maybe back to 280 mya as the molecular clock studies suggested".
Subsequent authors have questioned the identification of Archaeamphora as a pitcher plant. ( see more...)The taxonomic assignment of C. megalodon has been debated for nearly a century, and is still under dispute. The two major interpretations are Carcharodon megalodon (under family Lamnidae) or Carcharocles megalodon (under the family Otodontidae). Consequently, the scientific name of this species is commonly abbreviated C. megalodon in the literature.
C. megalodon is regarded as one of the largest and most powerful predators in vertebrate history, and likely had a profound impact on the structure of marine communities. Fossil remains suggest that this giant shark reached a maximum length of 18 metres (59 ft), and also affirm that it had a cosmopolitan distribution. Scientists suggest that C. megalodon looked like a stockier version of the great white shark, Carcharodon carcharias. ( see more...)Subfossil lemurs are lemurs from Madagascar that are represented by recent ( subfossil) remains dating from nearly 26,000 years ago (during the late Pleistocene) to approximately 560 years ago. They include both living and extinct species, although the term more frequently refers to the extinct giant lemurs. The diversity of subfossil lemur communities was greater than that of present-day lemur communities, ranging from as high as 20 or more species per location, compared with 10 to 12 species today. Extinct species are estimated to have ranged in size from slightly over 10 kg (22 lb) to roughly 160 kg (350 lb).
Despite their size, the giant lemurs shared many features with living lemurs, including rapid development, poor day vision, relatively small brains, and lack of male dominance. They also had many distinct traits among lemurs, including a tendency to rely on terrestrial locomotion, slow climbing, and suspension instead of leaping, as well as a greater dependence on leaf-eating and seed predation. The giant lemurs likely filled ecological niches now left vacant, particularly seed dispersal for plants with large seeds. There were three distinct families of giant lemur, including the Palaeopropithecidae ( sloth lemurs), Megaladapidae ( koala lemurs), and Archaeolemuridae ( monkey lemurs). Two other types were more closely related and similar in appearance to living lemurs: the giant aye-aye and Pachylemur, a genus of "giant ruffed lemurs".( see more...)Cloudinids had a wide geographic range, reflected in the present distribution of localities in which their fossils are found, and are an abundant component of some deposits. They never appear in the same layers as soft-bodied Ediacaran biota, but the fact that some sequences contain Cloudinids and Ediacaran biota in alternating layers suggests that these groups had different environmental preferences.
Cloudinids are important in the history of animal evolution for two reasons. They are among the earliest and most abundant of the small shelly fossils with mineralized skeletons, and therefore feature in the debate about why such skeletons first appeared in the Late Ediacaran. The most widely supported answer is that their shells are a defense against predators, as some Cloudina specimens from China bear the marks of multiple attacks, which suggests they survived at least a few of them. The evolutionary arms race which this indicates is commonly cited as a cause of the Cambrian explosion of animal diversity and complexity. ( see more...)Specimens were first found in Australia's Ediacara Hills, but recent research has concentrated on the numerous finds near the White Sea in Russia, which cover an interval of time from 555 to 558 million years ago. As with many fossils from this time, its evolutionary relationships to other organisms are hotly debated. Paleontologists initially classified Kimberella as a type of jellyfish, but since 1997 features of its anatomy and its association with scratch marks resembling those made by a radula have been interpreted as signs that it may have been a mollusc. Although some paleontologists dispute its classification as a mollusc, it is generally accepted as being at least a bilaterian.
The classification of Kimberella is important for scientific understanding of the Cambrian explosion: if it was a mollusc or at least a protostome, the protostome and deuterostome lineages must have diverged significantly before 555 million years ago. Even if it was a bilaterian but not a mollusc, its age would indicate that animals were diversifying well before the start of the Cambrian. ( 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 binomial Dinheirosaurus 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.
Dinheirosaurus is a diplodocid, a relative of Apatosaurus, Diplodocus, Barosaurus, Supersaurus, and Tornieria. Among those, the closest relative to Dinheirosaurus is Supersaurus, and together they form a clade of primitive diplodocids. While they were once considered to be diplodocines they are likely more basal than Apatosaurus. ( see more...)The fossil aroused much controversy. Less than ten years after 1891, almost eighty books or articles had been published on Dubois's finds. Despite Dubois' argument, few accepted that Java Man was a transitional form between apes and humans. Some dismissed the fossils as apes and others as modern humans, whereas many scientists considered Java Man as a primitive side branch of evolution not related to modern humans at all.
Eventually, similarities between Pithecanthropus erectus (Java Man) and Sinanthropus pekinensis ( Peking Man) led Ernst Mayr to rename both Homo erectus in 1950, placing them directly in the human evolutionary tree. To distinguish Java Man from other Homo erectus populations, some scientists began to regard it as a subspecies, Homo erectus erectus, in the 1970s. Estimated to be between 700,000 and 1,000,000 years old, at the time of their discovery the fossils of Java Man were the oldest hominin fossils ever found. ( see more...)Overall, Smilodon was more robustly built than any extant (living) cat, with particularly well-developed forelimbs and exceptionally long upper canines. Its jaw had a bigger gape than that of modern cats and its upper canines were slender and fragile, being adapted for precision killing. S. gracilis was the smallest species at 55 to 100 kg (120 to 220 lb) in weight. S. populator from South America is perhaps the largest known felid at 220 to 400 kg (490 to 880 lb) in weight and 120 cm (47 in) in height.
Smilodon probably lived in closed habitats such as forests and bush, which would have provided cover for ambushing prey. Smilodon died out at the same time that most North and South American megafauna disappeared, about 10,000 years ago. Its reliance on large animals has been proposed as the cause of its extinction, along with climate change and competition with other species, but the exact cause is unknown. ( see more...)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...)Reaching 4 m (13 ft) at the shoulders and 8–10 tonnes (18,000–22,000 lb) in weight, the Columbian mammoth was one of the largest species of mammoth. It most likely used its tusks and trunk like modern elephants—for manipulating objects, fighting, and foraging. The Columbian mammoth preferred open areas, such as parkland landscapes, and fed on sedge, grass, and other plants. Genetic evidence suggests that they interbred with wooly mammoths.
Before they went extinct, Columbian mammoths coexisted in North America for a few thousand years with Palaeoamericans, who hunted them for food, used their bones for making tools, and depicted them in ancient art. Columbian mammoth remains have been found in association with Clovis culture artefacts; these remains may have stemmed either from hunting or from scavenging. The Columbian mammoth disappeared at the end of the Pleistocene around 11,000 years ago, most likely as a result of habitat loss caused by climate change, hunting by humans, or a combination of both. ( see more...)The species is characterized by a body mass and stature similar to small-bodied human populations, a smaller endocranial volume similar to Australopithecus, and a skull shape similar to early Homo species. The skeletal anatomy presents ancestral features known from australopithecines with more recent features associated with later hominins. The fossils have not been dated.
The fossils were discovered by recreational cavers Rick Hunter and Steven Tucker in 2013. Homo naledi was formally described in September 2015 by a 47-member international team of authors led by American and South African paleoanthropologist Lee Berger of the University of the Witwatersrand, who proposed the bones represent a new Homo species. Other experts contend more analysis and evidence is needed to support this classification. There are some indications that the individuals may have been deliberately placed in the cave near the time of their death; other experts state more evidence is needed to support this hypothesis. ( see more...)