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Potholes or tracks? A group of paleontologists visited the northern Arizona wilderness site nicknamed a “dinosaur dance floor” and concluded there were no dinosaur tracks there, only a dense collection of unusual potholes eroded in the sandstone. So the scientist who leads the University of Utah’s geology department says she will team up with the skeptics for a follow-up study.

A group of paleontologists visited the northern Arizona wilderness site nicknamed a “dinosaur dance floor” and concluded there were no dinosaur tracks there, only a dense collection of unusual potholes eroded in the sandstone.

Paleontology may be one of the coolest careers to break into, but it’s far from the easiest.

As Smithsonian Magazine and National Geographic writer Brian Switek laments, while some people develop other interests, quite a few “would-be” paleontologists simply didn’t know where to start.

Luckily, Robert T. Bakker, author of “The Dinosaur Heresies,” “Raptor Red,” and “The Big Golden Book of Dinosaurs,” and curator of paleontology at the Houston Museum of Natural Science and Matthew T. Mossbrucker, director and curator of the Morrison Natural History Museum, and discoverer of the first baby Stegosaurus fossils, shed some light on how to get your start as a paleontologist during a recent Reddit AMA.

First, there are a few myths and misconceptions that need dispelling. The first is that paleontologists spend all their time digging for dinosaurs.

According to the University of California Museum of Paleontology website, “Paleontology is a rich field, imbued with a long and interesting past and an even more intriguing and hopeful future. Many people think paleontology is the study of fossils. In fact, paleontology is much more.”

Paleontology is divided into various sub-disciplines including the study of microscopic fossils, fossil plants, invertebrate animal fossils, vertebrate fossils, and prehistoric human and proto-human fossils.

And as Bakker and Mossbrucker explain, there are many jobs you can hold within the paleontology field.

Bakker says most vertebrate paleontologists make a living teaching geology or anatomy. “A few lucky ones” get full time jobs working in a museum. Fossils are also a hot commodity right now, since scientists can use them to teach basic science literacy, so fossil-sleuth could be a lucrative route.

Generally, though, the pay isn’t as much as you might hope.

“Doc [Bakker] always told me to ‘marry money,’” Mossbrucker jokes. “Seriously though, this is a calling. Most of us live a monastic lifestyle, while some took his sage advice.”

After all this, if pursuing a career in paleontology is still your calling, Bakker and Mossbrucker have a couple tips before you pursue the required higher education:

1. The best way to begin a career in dinosaurology is to start young. Bakker suggests studying living animals at a zoo or in your own backyard, filming them, and then using photo prints to sketch in the bones.

“Find the nearest display of fossils — whether at the natural history museum, science center, or state/national park — and visit,” Mossbrucker suggests. “While visiting, take a guided tour. Ask questions. Then, slow down, put the phone away and bask in the glory of the old dead things. Read the labels. (Seriously, nobody reads the labels…) and soak it all in.”

2. The next step is to volunteer, preferably in a program at your nearest natural history museum with a paleontology department. This will provide a chance to experience various aspects of what paleontology is all about and explore undergraduate programs.

“Get involved with your local museum and get your hands dirty,” Mossbrucker says.

“In museums where I work — one huge, two small — volunteers are essential,” Bakker says. “They find most of the specimens and do most of the tour-guide duties. In exceptional cases, volunteers are so good that we move heaven and earth to get a salary for them. And succeed.”

“This life is a calling and I’m grateful for every moment of it,” Mossbrucker says of his job as a paleontologist. “I’m surrounded by interesting objects, curious people, and a constant stream of weirdness.”

Source: https://uk.finance.yahoo.com

Baryonyx is a genus of theropod dinosaur which lived in the Barremian stage of the early Cretaceous Period, about 130–125 million years ago. The holotype specimen was discovered in 1983 in Surrey, England, and the animal was named B. walkeri in 1986. The genus name, Baryonyx, means “heavy claw” and alludes to the animal’s very large claw on the first finger; the specific name (walkeri) refers to its discoverer, amateur fossil hunter William J. Walker. Fragmentary specimens were later discovered in other parts of the United Kingdom and Iberia. The holotype specimen is one of the most complete theropod skeletons from the UK, and its discovery attracted media attention.

Baryonyx was between 7.5 and 10 m (25 and 33 ft) long and weighed between 1.2 and 1.7 t (1.3 and 1.9 short tons), but the holotype specimen may not have been fully grown. It had a long, low snout and narrow jaws, which have been compared to those of a gharial. The tip of the snout expanded to the sides in the shape of a rosette. Behind this, the upper jaw had a notch which fitted into the lower jaw (which curved upwards in the same area). It had a triangular crest on the top of its nasal bones. Baryonyx had many finely serrated, conical teeth, with the largest teeth in front. The neck was less curved than that of other theropods, and the neural spines of its dorsal vertebrae increased in height from front to back. It had robust forelimbs, with the eponymous first-finger claw measuring about 31 cm (12 in) long.

Now recognised as a member of the family Spinosauridae, Baryonyx‘s affinities were obscure when it was discovered. Apart from the type species (B. walkeri), some researchers have suggested that Suchomimus tenerensis belongs in the same genus and that Suchosaurus cultridens is a senior synonym; subsequent authors have kept them separate. Baryonyx was the first theropod dinosaur demonstrated to have been piscivorous (fish-eating), as evidenced by fish scales in the stomach region of the holotype specimen. It may also have been an active predator of larger prey and a scavenger, since it also contained bones of a juvenile Iguanodon. The creature would have caught and processed its prey primarily with its forelimbs and large claws. Baryonyx lived near water bodies, in areas where other theropod, ornithopod, and sauropod dinosaurs have also been found.

The Weald Clay Formation consists of sediments of Hauterivian (Lower Weald Clay) to Barremian (Upper Weald Clay) age, about 130–125 million years old. The B. walkeri holotype was found in the latter, in clay representing non-marine still water, which has been interpreted as a fluvial or mudflat environment with shallow water, lagoons, and marshes. During the Early Cretaceous, the Weald area of Surrey, Sussex, and Kent was partly covered by the large, fresh-to-brackish water Wealden Lake. Two large rivers drained the northern area (where London now stands), flowing into the lake through a river delta; the Anglo-Paris Basin was in the south. Its climate was sub-tropical, similar to the present Mediterranean region. Since the Smokejacks Pit consists of different stratigraphic levels, fossil taxa found there are not necessarily contemporaneous. Dinosaurs from the locality include the ornithopods Mantellisaurus, Iguanodon, and small sauropods. Other vertebrates from the Weald Clay include crocodiles, pterosaurs, lizards (such as Dorsetisaurus), amphibians, sharks (such as Hybodus), and bony fishes (including Scheenstia). Members of ten orders of insects have been identified, including Valditermes, Archisphex, and Pterinoblattina. Other invertebrates include ostracods, isopods, conchostracans, and bivalves. The plants Weichselia and the aquatic, herbaceous Bevhalstia were common. Other plants found include ferns, horsetails, club mosses, and conifers.

Other dinosaurs from the Wessex Formation of the Isle of Wight include the theropods Neovenator, Aristosuchus, Thecocoelurus, Calamospondylus, and Ornithodesmus; the ornithopods Iguanodon, Hypsilophodon, and Valdosaurus; the sauropods Ornithopsis, Eucamerotus, and Chondrosteosaurus; and the ankylosaur Polacanthus. The Papo Seco Formation of Portugal where Baryonyx has possibly been identified is composed of marl, representing a lagoon environment. Other dinosaur remains from the area include fragments tentatively assigned to Mantellisaurus, a macronarian sauropod, and Megalosaurus.

Source: www.wikipedia.org

Barosaurus was a giant, long-tailed, long-necked, plant-eating dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Dakota (and possibly Africa, as exemplified by the Kadsi Formation). It is present in stratigraphic zones 2-5.

The composite term Barosaurus comes from the Greek words barys (βαρυς) meaning “heavy” and sauros (σαυρος) meaning “lizard”; thus “heavy lizard”.

Visitors to the American Museum of Natural History are greeted by a startling sight. Towering above them is a skeleton of a female Barosaurus protecting its infant from the menacing approach of an Allosaurus. The reconstruction is, of course, based to some extent on guesswrok, but it is a striking depiction of how life might have been 150 million years ago.

Barosaurus is very similar to Diplodocus, to which it is closely related. Both were very long animals with relatively compact bodies that supported long necks and tails. Like Diplodocus, Barosaurus had front legs shorter than the hind ones. As a result, its back sloped gently forward. The neck projected around 30 feet (9 m) in front of the shoulders. It was once thought that sauropods’ long necks allowed them to feed high in tree tops. However, as the neck vertebrae would not have allowed much up-and-down movement, but would have permitted a considerable sweep from side to side, we now think that these dinosaurs fed much close to the ground on ferns and cycads.

Despite more than a century of searching and the recovery of five partial skeletons, some of them almost complete, the head and the tip of the tail of Barosaurus have never been found. The only clues we have about the head are a few bones from the skull collected in Tanzania and comparisons with close relatives such as Diplodocus. These indicate that Barosaurus had a horselike skull with a long snout and teeth restricted to the very front of the mouth.

Feeding

The structure of the cervical vertebrae of Barosaurus allowed for a significant degree of lateral flexibility in the neck, but restricted vertical flexibility. This suggests a different feeding style for this genus when compared to other diplodocids. Barosaurus swept its neck in long arcs at ground level when feeding, which resembled the strategy that was first proposed by John Martin in 1987. The restriction in vertical flexibility suggests that Barosaurus could not feed on vegetation that was high off the ground.

The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Diplodocus, Apatosaurus and Brachiosaurus. Dinosaurs that lived alongside Barosaurus included the herbivorous ornithischians Camptosaurus, Dryosaurus, Stegosaurus and Othnielosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes and Allosaurus accounted for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food web. Other vertebrates that shared this paleoenvironment included bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans, and several species of pterosaur. Early mammals were present such as docodonts, multituberculates, symmetrodonts, and triconodonts. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.

Assistant Curator David Evans mounted the ROM specimen conservatively, with a relatively low head to give the dinosaur moderate blood pressure. The extremely long neck, 10 metres (30 feet) may have developed to enable Barosaurus to feed over a wide area without moving around; it may also have enabled the dinosaurs to radiate excess body heat. Evans suggests that sexual selection might have favoured those with longer necks. (See video "Neck Impossible" at reference.)

Source: www.wikipedia.org

Brachiosaurus is a genus of sauropod dinosaur from the Jurassic Morrison Formation of North America. It was first described by Elmer S. Riggs in 1903 from fossils found in the Grand River Canyon (now Colorado River) of western Colorado, in the United States. Riggs named the dinosaur Brachiosaurus altithorax, declaring it “the largest known dinosaur”. Brachiosaurushad a disproportionately long neck, small skull, and large overall size, all of which are typical for sauropods. However, the proportions of Brachiosaurus are unlike most sauropods: the forelimbs were longer than the hindlimbs, which resulted in a steeply inclined trunk, and its tail was shorter in proportion to its neck than other sauropods of the Jurassic.

Brachiosaurus is the namesake genus of the family Brachiosauridae, which includes a handful of other similar sauropods. Much of what is known by laypeople about Brachiosaurus is in fact based on Giraffatitan brancai, a species of brachiosaurid dinosaur from the Tendaguru Formation of Tanzania that was originally described by German paleontologist Werner Janensch as a species of Brachiosaurus. Recent research shows that the differences between the type species of Brachiosaurusand the Tendaguru material are significant enough that the African material should be placed in a separate genus. Several other potential species of Brachiosaurus have been described from Africa and Europe, but none of them are thought to belong to Brachiosaurus at this time.

Brachiosaurus is one of the rarer sauropods of the Morrison Formation. The type specimen of B. altithorax is still the most complete specimen, and only a relative handful of other specimens are thought to belong to the genus. It is regarded as a high browser, probably cropping or nipping vegetation as high as possibly 9 metres (30 ft) off of the ground. Unlike other sauropods, and its depiction in the film Jurassic Park, it was unsuited for rearing on its hindlimbs. It has been used as an example of a dinosaur that was most likely ectothermic because of its large size and the corresponding need for forage, but more recent research finds it to have been warm-blooded.

Species

Brachiosaurus altithorax

FMNH P 25107, the holotype of both the genus Brachiosaurus and the species B. altithorax, consists of the right humerus (upper arm bone), the right femur (thigh bone), the right ilium (a hip bone), the right coracoid (a shoulder bone), the sacrum (fused vertebrae of the hip), the last seven thoracic (trunk) and two caudal (tail) vertebrae, and a number of ribs. Riggs described the coracoid as from the left side of the body, but restudy has shown it to be a right coracoid.

In 1969, during a study by Kingham, Brachiosaurus altithorax, along with species now assigned to other genera, were moved from the genus. Kingham found “B.” atalaiensis, “B.” brancai, and B. altithorax were referable to Astrodon creating many new species of Astrodon apart from the type. Kingham’s views of brachiosaurid taxonomy have not been accepted by many authors.

Other assigned species

• “B.” atalaiensis: Originally described by de Lapparent and Zbyszewski, this material’s reference to Brachiosaurus was doubted by Upchurch, Barret and Dodson, who listed it as an unnamed brachiosaurid, and placed in its own genus Lusotitan by Antunes and Mateus. De Lapparent and Zbyszewski described a series of remains but did not designate a type specimen. Antunes and Mateus selected a partial postcranial skeleton (MIGM 4978, 4798, 4801–4810, 4938, 4944, 4950, 4952, 4958, 4964–4966, 4981–4982, 4985, 8807, 8793–87934) as a lectotype; this specimen includes 28 vertebrae, chevrons, ribs, a possible shoulder blade, humeri, forearm bones, partial left pelvis, lower leg bones, and part of the right ankle. The low neural spines, the prominent deltopectoral crest of the humerus (a muscle attachment site on the upper arm bone), the elongated humerus (very long and slender), and the long axis of the ilium tilted upward indicate that Lusotitan is a brachiosaurid.
• “B.” brancai: Janensch based his description on “Skelett S” (skeleton S) from Tendaguru, but later realized that it comprised two partial individuals: S I and S II. He at first did not designate them as a syntype series, but in 1935 made S I (MB.R.2180) the lectotype. Taylor in 2009, unaware of this action, proposed the larger and more complete S II (MB.R.2181) as the lectotype. It includes, among other bones, several dorsal (trunk) vertebrae, the left scapula, both coracoids, both sternals (breastbones), both humeri, both ulna and radii (lower arm bones), a right hand, a partial left hand, both pubes (a hip bone) and the right femur, tibia and fibula (shank bones). Later Taylor realised that Janensch had in 1935 designated the smaller skeleton S I as the lectotype. A re-assessment of the relation between the African and American brachiosaur material indicates that a separate generic name is warranted for the Tendaguru material, so “B.” brancai has been moved to its own genus: Giraffatitan.
• “B.” fraasi: erected by Janensch in 1914, but later synonymized with “B.” brancai; this material now belongs to Giraffatitan.
• “B.” nougaredi: This species is known from fragmentary remains discovered in eastern Algeria, in the Sahara Desert. The present type material consists of a sacrum and some of the left metacarpals and phalanges. Found at the discovery site but not collected were partial bones of the left forearm, wrist bones, a right shin bone, and fragments that may have come from metatarsals. de Lapparent, who described and named the material in 1960, reported the discovery locality as being in the Late Jurassic–age Taouratine Series (he assigned the rocks this age in part because of the presumed presence of Brachiosaurus). This material was found disjointed over an area of several hundred meters, and probably does not represent a single species.

Classification

Brachiosaurus is the namesake genus of Brachiosauridae. Over the years, a number of sauropods have been assigned to Brachiosauridae, such as Astrodon, Bothriospondylus, Dinodocus, Pelorosaurus, Pleurocoelus, and Ultrasaurus, but most of these are currently regarded as dubious or of uncertain placement. A phylogenetic analysis of sauropods published in the description of Abydosaurus found that genus to form a clade with Brachiosaurus and Giraffatitan (included in Brachiosaurus). A more recent analysis focused on possible Asian brachiosaurid material found a clade including Abydosaurus, Brachiosaurus, Cedarosaurus, Giraffatitan, and Paluxysaurus, but not Qiaowanlong, the putative Asian brachiosaurid. Related genera include Lusotitan and Sauroposeidon. Brachiosauridae is situated at the base of Titanosauriformes, a group of sauropods that also includes the titanosaurs.

According to the revised diagnosis by Taylor, Brachiosaurus altithorax is diagnosed by a plethora of characters, many to be found on the dorsal (back) vertebrae. Among the characters placing it in the family Brachiosauridae are a ratio of humerus length to femur length of at least 0.9 (i.e. the upper arm bone is at least nearly as long as the thigh bone), and a very flattened femur shaft (ratio ≥1.85).

Camarasaurus was a genus of quadrupedal, herbivorous dinosaurs. It was the most common of the giant sauropods to be found in North America. Its fossil remains have been found in the Morrison Formation of Colorado and Utah, dating to the Late Jurassic epoch (Kimmeridgian to Tithonian stages), between 155 and 145 million years ago.

Camarasaurus presented a distinctive cranial profile of a blunt snout and an arched skull that was remarkably square. It likely travelled in herds, or at least in family groups.

The name means “chambered lizard”, referring to the hollow chambers in its vertebrae (Greek καμαρα/kamara meaning “vaulted chamber”, or anything with an arched cover, and σαυρος/sauros meaning “lizard”).

When the noted American paleontologist Edward Drinker Cope described Camarasaurus in 1877, he was obviously impressed by the hollow, box-like vertebrae in the neck. This feature made the neck much lighter and easier for the animal to carry, and it is this characteristic that gave the animal its name: “Chambered lizard.”

Camarasaurus was a stout, compact sauropod with a relatively short neck and short tail. The front legs were slightly shorter than the back legs. The head can be described as a bubble of air encased by thin struts of bone. Huge holes for the nostrils, eye sockets, and other skull cavities made the skull as light as possible but strong enough to withstand the bite forces from the doglike snout.

Herding

A fossil record exists of two adults and a 12.2-m-long (40 ft) juvenile that died together in the Late Jurassic epoch, around 150 million years ago (in northeast Wyoming, United States). Their bodies were assumed to be washed by a river in spate (flood) to their final resting place in alluvial mud. The scenario suggests that Camarasaurus traveled in herds or at least in family groups. At other sites, fossil camarasaur eggs have been found in lines, rather than in neatly arranged nests as with some other dinosaurs, which suggests that, like most sauropods, Camarasaurus did not tend its young.

Feeding

Previously, scientists have suggested that Camarasaurus and other sauropods may have swallowed gastroliths (stones) to help grind the food in the stomach, regurgitating or passing them when they became too smooth. More recent analysis, however, of the evidence for stomach stones suggests this was not the case. The strong, robust teeth of Camarasaurus were more developed than those of most sauropods and were replaced on average every 62 days (M. D'Emic et al.), indicating that Camarasaurus may have masticated food in its mouth to some degree before swallowing. Other findings indicate that Camarasaurus spp. preferred vegetation different from other sauropods, allowing them to share the same environment without competing.

Growth

Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Griebeler et al. (2013) examined long-bone histological data and concluded that the Camarasaurus sp. CM 36664 weighed 14,247 kilograms (15.7 short tons), reached sexual maturity at 20 years and died at age 26.

Metabolism

Eagle et al. performed clumped isotope thermometry on the enamel covering the teeth of various Jurassic sauropods, including Camarasaurus. Temperatures of 32.4–36.9 °C (90.3–98.4 °F) were obtained, which is comparable to that of modern mammals.

The teeth were stumpy but strong – much more robust than the peglke teeth of other sauropods – and the jaws had a powerful bite. Camarasaurus was probably capable of dealing with a wider variety of tough plants, thereby giving it an advantage in mixed forests.

Camarasaurus is the most common sauropod in North America. A number of complete skeletons have been recovered, as well as numerous partial skeletons and isolated bones. Several specimens can be seen in the rocks of the dinosaur National Monument in Utah. As a result of these fossil finds, we now know more about Camarasaurus than we know about any other of the sauropod dinosaurs.

Paleopathology

A Camarasaurus pelvis recovered from Dinosaur National Monument in Utah shows gouging attributed to Allosaurus.

In 1992, a partial C. grandis skeleton was discovered at the Bryan Small Stegosaurus Quarry of the Morrison Formation near Canon City, Colorado. This specimen preserved a partial right humerus catalogued as DMNH 2908 and associated vertebrae from the back and tail. In 2001, Lorie McWhinney, Kenneth Carpenter, and Bruce Rothschild published a description of a pathology observed on the humerus. They noted a juxtacortical lesion 25 by 18 cm wide made of bone that resembled woven fibers. Although woven bone forms in accessory dental bone, in other locations, it is a sign of injury or illness. The woven bone's "undulating fibrous bundles" were observed oriented in the direction of the m. brachialis. The lesion's fusion and lack of porosity at its near and far ends indicate the periostitis was inactive or healed. McWhinney and the other researchers argued that this injury would have been a continuous source of hardship for the animal. It would have exerted pressure on the muscles. This pressure would have compressed the muscles' blood vessels and nerves, reducing the range of motion of both the limb's flexor and extensor muscles. This effect would have hindered the mM. brachialis, m. brachoradialis, and to a lesser degree the m. biceps brachii to the lesion's position on the humerus. The researchers inferred that the inflammation of the muscles and periosteum would have caused additional complications in the lower region of the fore limb, as well. The lesion would also have caused long-term fasciitis and myosistis. The cumulative effect of these pathological processes would have moderate to severe effects on the ability of the limb to move and "made everyday activities such as foraging for food and escaping predators harder to accomplish."

Paleofauna

The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Barosaurus, Diplodocus, Apatosaurus, Brontosaurus, and Brachiosaurus. Dinosaurs living alongside Camarasaurus included the herbivorous ornithischians Camptosaurus, Gargoyleosaurus, Dryosaurus, Stegosaurus, and Othnielosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes, and Allosaurus, which accounted for up to 75% of theropod specimens, and was at the top trophic level of the Morrison food web. Camarasaurus is commonly found at the same sites as Allosaurus, Apatosaurus, Stegosaurus, and Diplodocus.

Other organisms in this region included bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans, and several species of pterosaurs such as Harpactognathus and Mesadactylus. Early mammals present were docodonts (such as Docodon), multituberculates, symmetrodonts, and triconodonts. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.

Source. www.natgeo.com

Carcharodontosaurus is a genus of carnivorous carcharodontosaurid dinosaurs that existed between 100 and 94 million years ago, during the Cenomanian stages of the mid-Cretaceous Period. It is currently known to include two species, C.saharicusand C.iguidensis, which were among the larger theropods, as large as or slightly bigger than Tyrannosaurus and possibly slightly larger than Giganotosaurus, but not quite as large as Spinosaurus.

The genus Carcharodontosaurus is named after the shark genus Carcharodon (itself named from the Greek καρχαρο (karcharo) meaning “jagged” or “sharp” and οδοντο (odonto) meaning “teeth”)), and σαυρος (sauros), meaning “lizard”.

Description

Carcharodontosaurus includes some of the longest and heaviest known carnivorous dinosaurs, with various scientists proposing length estimates for the species C. saharicus ranging between 12 and 13.3 m (39 and 44 ft) and weight estimates between 6.2 and 15.1 metric tons.

Carcharodontosaurus were carnivores, with enormous jaws and long, serrated teeth up to eight inches long. A skull length of about 1.6 meters (5.2 ft) has been restored for C. saharicus, and the skull of C. iguidensis is reported to have been about the same size. Currently, the largest known theropod skull belongs to another huge carcharodontosaurid dinosaur, the closely related Giganotosaurus (with skull length estimates up to 1.95 m) (6.4 ft). Gregory S. Paul estimates Carcharodontosaurus iguidensis at 10 m (33 ft) and 4 t (4.4 short tons).

Brain and inner ear

In 2001, Hans C. E. Larsson published a description of the inner ear and endocranium of Carcharodontosaurus saharicus. Starting from the portion of the brain closest to the tip of the animal’s snout is the forebrain, which is followed by the midbrain. The midbrain is angled downwards at a 45 degree angle and towards the rear of the animal. This is followed by the hind brain, which is roughly parallel to the forebrain and forms a roughly 40 degree angle with the midbrain. Overall, the brain of C. saharicus would have been similar to that of a related dinosaur, Allosaurus fragilis. Larsson found that the ratio of the cerebrum to the volume of the brain overall in Carcharodontosaurus was typical for a non-avian reptile. Carcharodontosaurus also had a large optic nerve.

The three semicircular canals of the inner ear of Carcharodontosaurus saharicus, when viewed from the side, had a subtriangular outline. This subtriangular inner ear configuration is present in Allosaurus, lizards, turtles, but not in birds. The semi-“circular” canals themselves were actually very linear, which explains the pointed silhouette. In life, the floccular lobe of the brain would have projected into the area surrounded by the semicircular canals, just like in other non-avian theropods, birds, and pterosaurs.

Discovery and naming

In 1924, two teeth were found in the Continental intercalaire of Algeria, showing what were at the time unique characteristics, this teeth were described by Depéret and Savornin (1925) as representing a new taxon, which they named Megalosaurus saharicus and later referred by the same authors to the subgenus Dryptosaurus. Some years later, paleontologist Ernst Stromer described the remains of a partial skull and skeleton from Cenomanian aged rocks in the Bahariya Formation of Egypt (Stromer, 1931), originally excavated in 1914, the remains consisted on a partial skull, teeth, vertebrae, claw bones and assorted hip and leg bones. The teeth in this new finding matched the characteristic of those described by Depéret and Savornin which lead Stromer to conserve the species name saharicus but found necessary to erect a new genus for this species, Carcharodontosaurus, for their strong resemblance to the teeth of Carcharodon (Great white shark).

The fossils described by Stromer were destroyed in 1944 during World War II but a new more complete skull was found in the Kem Kem Formation of Morocco during an expedition led by paleontologist Paul Sereno in 1995, not too far from the Algerian border and the locality where the teeth described by Depéret and Savornin (1925) were found, the teeth found with this new skull matched those described by Depéret and Savornin (1925) and Stromer (1931), the rest of the skull also matched that described by Stromer. This new skull was designated as the neotype by Brusatte and Sereno (2007) who also described a second species of Carcharodontosaurus, C. iguidensis from the Echkar Formation of Niger, differing from C. saharicus in aspects of the maxilla and braincase.

Classification

The following cladogram after Apesteguía et al., 2016, shows the placement of Carcharodontosaurus within Carcharodontosauridae.

Paleobiology

Hunting

A study by Donald Henderson, the curator of dinosaurs at the Royal Tyrrell Museum suggests that Carcharodontosaurus was able to physically lift animals weighing a maximum of 424 kg (935 lb) in its jaws based on a study of the strength of its jaws, neck, and its center of mass.

Pathology

SGM-Din 1, a Carcharodontosaurus saharicus skull, has a circular puncture wound in the nasal and “an abnormal projection of bone on the antorbital rim”.

Carnotaurus is a genus of large theropod dinosaur that lived in South America during the Late Cretaceous period, between about 72 and 69.9 million years ago. The only species is Carnotaurus sastrei. Known from a single well-preserved skeleton, it is one of the best-understood theropods from the Southern Hemisphere. The skeleton, found in 1984, was uncovered in the Chubut Province of Argentina from rocks of the La Colonia Formation. Derived from the Latin carno [carnis] (“flesh”) and taurus (“bull”), the name Carnotaurus means “meat-eating bull”, an allusion to the animal’s bull-like horns. Carnotaurus is a derived member of the Abelisauridae, a group of large theropods that occupied the large predatorial niche in the southern Landmasses of Gondwana during the late Cretaceous. The phylogenetic relations of Carnotaurus are uncertain; it might have been closer to either Majungasaurus or Aucasaurus.

Carnotaurus was a lightly built, bipedal predator, measuring 8 to 9 m (26.2 to 29.5 ft) in length and weighing at least 1.35 metric tons (1.33 long tons; 1.49 short tons). As a theropod, Carnotaurus was highly specialized and distinctive. It had thick horns above the eyes, a feature unseen in all other carnivorous dinosaurs, and a very deep skull sitting on a muscular neck. Carnotaurus was further characterized by small, vestigial forelimbs and long and slender hindlimbs. The skeleton is preserved with extensive skin impressions, showing a mosaic of small, non-overlapping scales approximately 5 mm in diameter. The mosaic was interrupted by large bumps that lined the sides of the animal, and there are no hints of feathers.

The distinctive horns and the muscular neck may have been used in fighting conspecifics. According to separate studies, rivaling individuals may have combated each other with quick head blows, by slow pushes with the upper sides of their skulls, or by ramming each other head-on, using their horns as shock absorbers. The feeding habits of Carnotaurus remain unclear: some studies suggest the animal was able to hunt down very large prey such as sauropods, while other studies find it preyed mainly on relatively small animals. Carnotaurus was well adapted for running and was possibly one of the fastest large theropods.

Description

Carnotaurus was a large but lightly built predator. The only known individual was about 8–9 m (26.2–29.5 ft) in length, making Carnotaurus one of the largest abelisaurids. While Ekrixinatosaurus and possibly Abelisaurus, highly incomplete, would have been similar or larger in size, a 2016 study found that only Pycnonemosaurus, at 8.9 m (29.2 ft), was longer than Carnotaurus, which was estimated at 7.8 m (25.6 ft). Its mass is estimated to have been 1,350 kg (1.33 long tons; 1.49 short tons) 1,500 kg (1.5 long tons; 1.7 short tons) and 2,100 kg (2.1 long tons; 2.3 short tons) in separate studies that used different estimation methods. Carnotaurus was a highly specialized theropod, as seen especially in characteristics of the skull, the vertebrae and the forelimbs. The pelvis and hindlimbs, on the other hand, remained relatively conservative, resembling those of the more basal Ceratosaurus. Both the pelvis and hindlimb bones were long and slender. The left thigh bone of the individual measures 103 cm in length, but shows an average diameter of only 11 cm.

Classification

Carnotaurus is one of the best-understood genera of the Abelisauridae, a family of large theropods restricted to the ancient southern supercontinent Gondwana. Abelisaurids were the dominant predators in the Late Cretaceous of Gondwana, replacing the carcharodontosaurids and occupying the ecological niche filled by the tyrannosaurids in the northern continents. Several notable traits that evolved within this family, including shortening of the skull and arms as well as peculiarities in the cervical and caudal vertebrae, were more pronounced in Carnotaurus than in any other abelisaurid.

Though relationships within the Abelisauridae are debated, Carnotaurus is consistently shown to be one of the most derived members of the family by cladistical analyses. Its nearest relative might have been either Aucasaurus or Majungasaurus; this ambiguity is largely due to the incompleteness of the Aucasaurus skull material. A recent review suggests that Carnotauruswas not closely related with either Aucasaurus or Majungasaurus, and instead proposed Ilokelesia as its sister taxon.

Carnotaurus is eponymous for two subgroups of the Abelisauridae: the Carnotaurinae and the Carnotaurini. Paleontologists do not universally accept these groups. The Carnotaurinae was defined to include all derived abelisaurids with the exclusion of Abelisaurus, which is considered a basal member in most studies. However, a 2008 review suggested that Abelisaurus was a derived abelisaurid instead. Carnotaurini was proposed to name the clade formed by Carnotaurus and Aucasaurus; only those paleontologists who consider Aucasaurus as the nearest relative of Carnotaurus use this group.

Discovery

Caudipteryx (which means “tail feather”) is a genus of peacock-sized theropod dinosaurs that lived in the Aptian age of the early Cretaceous Period (about 124.6 million years ago). They were feathered and remarkably birdlike in their overall appearance. Two species have been described; C. zoui (the type species), in 1998, and C. dongi, in 2000.

Caudipteryx fossils were first discovered in the Yixian Formation of the Sihetun area of Liaoning Province, northeastern China in 1997.

Caudipteryx, like many other maniraptorans, has an interesting mix of reptile- and bird-like anatomical features.

Caudipteryx had a short, boxy skull with a beak-like snout that retained only a few tapered teeth in the front of the upper jaw. It had a stout trunk, long legs and was probably a swift runner.

Caudipteryx has a short tail stiffened toward the tip, with few vertebrae, like in birds and other oviraptorosaurs. It has a primitive pelvis and shoulder, and primitive skull details in the quadratojugal, squamosal, quadrate, jugal, and mandibular fenestra (in the cheek, jaw, and jaw joint). It has a hand skeleton with a reduced third finger, like that of primitive birds and the oviraptorid Ingenia.

Feathers

The hands of Caudipteryx supported symmetrical, pennaceous feathers that had vanes and barbs, and that measured between 15–20 centimeters long (6–8 inches). These primary feathers were arranged in a wing-like fan along the second finger, just like primary feathers of birds and other maniraptorans. No fossil of Caudipteryx zoui preserves any secondary feathers attached to the forearms, as found in dromaeosaurids, Archaeopteryx and modern birds. Either these arm feathers are not preserved, or they were not present on Caudipteryx in life. An additional fan of feathers existed on its short tail. The shortness and symmetry of the feathers, and the shortness of the arms relative to the body size, indicate that Caudipteryxwas flightless.

The consensus view, based on several cladistic analyses, is that Caudipteryx is a basal (primitive) member of the Oviraptoridae, and the oviraptorids are nonavian theropod dinosaurs. Incisivosaurus is the only oviraptorid that is more primitive.

Centrosaurus is a genus of herbivorous ceratopsian dinosaurs from the late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago.

The massive bodies of Centrosaurus were borne by stocky limbs, although at up to 6 m (19.7 ft) they were not particularly large dinosaurs. Like other centrosaurines, Centrosaurus bore single large horns over their noses. These horns curved forwards or backwards depending on the specimen. Skull ornamentation was reduced as animals aged.

Centrosaurus is distinguished by having two large hornlets which hook forwards over the frill. A pair of small upwards directed horns is also found over the eyes. The frills of Centrosaurus were moderately long, with fairly large fenestrae and small hornlets along the outer edges.

Centrosaurus, which moved on all fours, had powerful front limbs that would have enhanced the animal’s speed and agility. A ball-and-socket joint in the neck would also have been useful in defense. it allowed Centrosaurus to turn its head swiftly and bring its sharp horn into play against large predators, such as Tyrannosaurus, that attacked from the rear.

The first Centrosaurus remains were discovered and named by paleontologist Lawrence Lambe in strata along the Red Deer River in Alberta, Canada. The name Centrosaurus means "pointed lizard" (from Greek kentron, κέντρον, "point or prickle" and sauros, σαῦρος, "lizard"), and refers to the series of small hornlets placed along the margin of their frills, not to the nasal horns (which were unknown when the dinosaur was named). The genus is not to be confused with the stegosaur Kentrosaurus, the name of which is derived from the same Greek word.

Later, vast bonebeds of Centrosaurus were found in Dinosaur Provincial Park, also in Alberta. Some of these beds extend for hundreds of meters and contain thousands of individuals of all ages and all levels of completion. Scientists have speculated that the high density and number of individuals would be explained if they had perished while trying to cross a flooded river. A discovery of thousands of Centrosaurus fossils near the town of Hilda, Alberta, is believed to be the largest bed of dinosaur bones ever discovered. The area is now known as the Hilda mega-bonebed.

Because of the variation between species and even individual specimens of centrosaurines, there has been much debate over which genera and species are valid, particularly whether Centrosaurus and/or Monoclonius are valid genera, undiagnosable, or possibly members of the opposite sex. In 1996, Peter Dodson found enough variation between Centrosaurus, Styracosaurus, and Monoclonius to warrant separate genera, and that Styracosaurus resembled Centrosaurus more closely than either resembled Monoclonius.

Classification

The genus Centrosaurus gives its name to the Centrosaurinae subfamily. Its closest relatives appear to be Styracosaurus and Monoclonius. It so closely resembles the latter of these that some paleontologists have considered them to represent the same animal. Other members of the Centrosaurinae clade include Pachyrhinosaurus, Avaceratops, Einiosaurus, Albertaceratops, and Achelousaurus,.

The cladogram presented below represents a phylogenetic analysis by Chiba et al. (2017):

Like other ceratopsids, the jaws of Centrosaurus were adapted to shear through tough plant material. The discovery of gigantic bone beds of Centrosaurus in Canada suggest that they were gregarious animals and could have traveled in large herds. A bone bed composed of Centrosaurus and Styracosaurus remains is known from the Dinosaur Park Formation in what is now Alberta. The mass deaths may have been caused by otherwise non-herding animals gathering around a waterhole during a drought. Centrosaurus is found lower in the formation than Styracosaurus, indicating that Centrosaurus was displaced by Styracosaurus as the environment changed over time.

The large frills and nasal horns of the ceratopsians are among the most distinctive facial adornments of all dinosaurs. Their function has been the subject of debate since the first horned dinosaurs were discovered. Common theories concerning the function of ceratopsian frills and horns include defense from predators, combat within the species, and visual display. A 2009 study of Triceratops and Centrosaurus skull lesions found that bone injuries on the skulls were more likely caused by intraspecific combat (horn-to-horn combat) rather than predatory attacks. The frills of Centrosaurus were too thin to be used for defense against predators, although the thicker, solid frills of Triceratops might have evolved to protect their necks. The frills of Centrosaurus were most likely used "for species recognition and/or other forms of visual display".

Source: https://en.wikipedia.org