nandi's blog

Spinosaurus

Saturday, December 3, 2016

The only known dinosaur adapted to life in water, Spinosaurus aegyptiacus swam the rivers of North Africa about 95 million years ago. Image credit: © Davide Bonadonna / National Geographic magazine.

Spinosaurus (meaning “spine lizard”) is a genus of theropod dinosaur that lived in what now is North Africa, during the lower Albian to lower Cenomanian stages of the Cretaceous period, about 112 to 97 million years ago. This genus was known first from Egyptian remains discovered in 1912 and described by German paleontologist Ernst Stromer in 1915. The original remains were destroyed in World War II, but additional material has come to light in recent years. It is unclear whether one or two species are represented in the fossils reported in the scientific literature. The best known species is S. aegyptiacus from Egypt, although a potential second species, S. maroccanus, has been recovered from Morocco.

Back to size, here is a comparison with Spinosaurus that is actually reasonable. Author: terra raptor

Spinosaurus was among the largest of all known carnivorous dinosaurs, possibly larger than Tyrannosaurus and Giganotosaurus. Estimates published in 2005, 2007, and 2008 suggested that it was between 12.6–18 metres (41–59 ft) in length and 7 to 20.9 tonnes (7.7 to 23.0 short tons) in weight. A new estimate published in 2014 and based on a more complete specimen, supported the earlier research, finding that Spinosaurus could reach lengths greater than 15 m (49 ft). The skull of Spinosaurus was long and narrow, similar to that of a modern crocodilian. Spinosaurus is known to have eaten fish, and most scientists believe that it hunted both terrestrial and aquatic prey; evidence suggests that it lived both on land and in water as a modern crocodilian does. The distinctive spines of Spinosaurus, which were long extensions of the vertebrae, grew to at least 1.65 meters (5.4 ft) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that the spines were covered in fat and formed a hump. Multiple functions have been put forward for this structure, including thermoregulation and display.

Recent fossil evidence shows Spinosaurus was the first dinosaur that was able to swim, and likely spent most of its life in the water, according to a study published September 2014 in the journal Science. “Spinosaurus had short hind limbs (like early whales and other animals that spent more and more time in the water), dense and compact bones (penguins show a similar bone profile in cross section), wide and flat claws and feet (possibly used in paddling), and a long and slender snout with conical teeth (perfect for catching fish),” said Nizar Ibrahim, a University of Chicago vertebrate paleontologist and lead author of the study.

Life reconstruction of Spinosaurus aegyptiacus based on the recent description of a new specimen. Artwork by Durbed

Function of the sail

There has been much scientific debate regarding the evolution and purpose of Spinosaurus‘ sail. Because of its size, this dinosaur did not have many predators, but the sail could have been used to ward off enemies, as the dinosaur would have appeared to be twice its size with the sail fully extended. The dinosaur’s upper spine was fairly flexible, and its vertebrae had ball-and-socket joints, meaning it was likely able to arch its back to a point. It may have been able to spread the sail when threatened or looking to attract a mate.

Size of Spinosaurus

Spinosaurus is now often regarded as the biggest known meat eating theropod dinosaur (herbivores like large sauropods were of course bigger),‭ ‬however the actual size is really just an estimate extrapolated from an educated guess.‭ ‬What is clear is that Spinosaurus was a very large animal but herein lies the problem as the larger animals get,‭ ‬the less complete their remains tend to be because it takes so much more material to bury them and protect the body from scavengers and as well as the full ravages of nature.‭ ‬The more an animal is exposed upon death means the less complete long term remains like fossils will be.

Still with a smaller estimate of just over twelve and a half meters,‭ ‬Spinosaurus would have been comparable to Tyrannosaurus,‭ ‬and only just smaller than Giganotosaurus‭ (‬it needs to be remembered that even though Giganotosaurus has a size estimate of thirteen meters,‭ ‬it would still only be marginally larger than the largest known Tyrannosaurus‭)‬.‭ ‬Comparison to other smaller spinosaurids that were consequently scaled up to the same size as the Spinosaurus material points to sizes that approach the larger length estimate as indeed being possible.‭

Tyrannosaurus, Giganotosaurus, Carcharodontosaurus, Acrocanthosaurus, Saurophaganax. Artwork by PrehistoricWildlife.com

The lifestyle of Spinosaurus

Since its discovery, Spinosaurus has been a contender for the longest and largest theropod dinosaur. Both Friedrich von Huene in 1926 and Donald F. Glut in 1982 listed it as among the most massive theropods in their surveys, at 15 meters (49 ft) in length and upwards of 6 t (5.9 long tons; 6.6 short tons) in weight. In 1988, Gregory Paul also listed it as the longest theropod at 15 meters (49 ft), but gave a lower mass estimate of 4 tonnes (3.9 long tons; 4.4 short tons).

The‭ ‬2014‭ ‬reconstruction of Spinosaurus by Ibrahim et al also supported the idea that Spinosaurus would readily enter the water and actually swim about.‭ ‬Not only did they cover isotope analysis which confirmed a great deal of exposure to aquatic environments,‭ ‬they also noted that Spinosaurus had particularly dense bones.‭ ‬This is a common feature in animals that spend a lot of time swimming in the water as the greater bone density helps the animal with buoyancy issues so that it can actually swim under the surface is necessary.‭ ‬Ibrahim et al also noted that the claws on the feet were flat-bottomed,‭ ‬which would be a further aid in pushing against the water while swimming.‭ ‬This also strongly suggests that the main swimming propulsion was provided by the rear legs.

The possibility also remains that Spinosaurus may have hunted ‬land animals,‭ ‬although no fossil evidence is known that strongly supports this.‭ ‬In South America a pterosaur bone was found with a spinosaurid tooth stuck into it,‭ ‬and recovery of the related Baryonyx revealed the presence of Iguanodon bones inside of the area that its gut would have been.‭ ‬Still these may have been cases of scavenging rather than attempted hunting.‭ ‬Baryonyx also revealed the partially digested remains of the fish Lepidotes,‭ ‬further supporting the fish specialisation hypothesis.

Because Spinosaurus disappears from the fossil record well before the end of the dinosaurs sixty-five million years ago,‭ ‬it must have succumbed to something else other than the established extinction theories that ended the dinosaurs once and for all.‭ ‬Perhaps the easiest explanation for its demise is that it simply became far too specialised,‭ ‬and when the ecosystem it was living in changed to be drier the rivers systems dried up,‭ ‬removing the prey source that Spinosaurus was best equipped to deal with.‭ ‬In the face of competition with more generalist theropods,‭ ‬Spinosaurus just could not compete with their success and was eventually driven to extinction.‭

Sail or hump,‭ ‬and more importantly why‭?

Very tall neural spines growing on the back vertebrae of Spinosaurus formed the basis of what is usually called the animal’s “sail”. The lengths of the neural spines reached over 10 times the diameters of the vertebral bodies from which they extended. The neural spines were slightly longer front to back at the base than higher up, and were unlike the thin rods seen in the pelycosaur finbacks Edaphosaurus and Dimetrodon, contrasting also with the thicker spines in the iguanodontian Ouranosaurus.

Reconstruction of the holotype fossils. Author: Ryan Somma

Spinosaurus sails were unusual, although other dinosaurs, namely the ornithopod Ouranosaurus, which lived a few million years earlier in the same general region as Spinosaurus, and the South American sauropod Amargasaurus, might have developed similar structural adaptations of their vertebrae. The sail may be an analog of the sail of the Permian synapsid Dimetrodon, which lived before the dinosaurs even appeared, produced by convergent evolution.

Spinosaurus gives its name to the Spinosauridae family of dinosaurs, which includes two subfamilies: Baryonychinae and Spinosaurinae. The Baryonychinae include Baryonyx from southern England and Suchomimus from Niger in central Africa. The Spinosaurinae include SpinosaurusIrritator from Brazil, and Angaturama (which is probably synonymous with Irritator) from Brazil. The Spinosaurinae share unserrated straight teeth that are widely spaced (e.g., 12 on one side of the maxilla), as opposed to the Baryonychinae which have serrated curved teeth that are numerous (e.g., 30 on one side of the maxilla)

2 – Baryonyx, 3 – Ichthyovenator, 4 – Oxalaia, 5 – Suchomimus, 6 – Irritator. Artwork by PrehistoricWildlife.com

Skull

The skull had a narrow snout filled with straight conical teeth that lacked serrations. There were six or seven teeth on each side of the very front of the upper jaw, in the premaxillae, and another twelve in both maxillae behind them. The second and third teeth on each side were noticeably larger than the rest of the teeth in the premaxilla, creating a space between them and the large teeth in the anterior maxilla; large teeth in the lower jaw faced this space. The very tip of the snout holding those few large anterior teeth was expanded, and a small crest was present in front of the eyes. Using the dimensions of three specimens known as MSNM V4047, UCPC-2, and BSP 1912 VIII 19, and assuming that the postorbital part of the skull of MSNM V4047 had a shape similar to the postorbital part of the skull of Irritator, Dal Sasso et al. (2005) estimated that the skull of Spinosaurus was 1.75 meters (5.7 ft) long. The Dal Sasso et al. skull length estimate was questioned because skull shapes can vary across spinosaurid species.

Skull of a privately owned reconstructed skeleton of a subadult. Skull of Spinosaurus aegyptiacus ; Morroco ; Private collection Stage : Albian-Cenomanian (112-93 Ma) Size : 1,20 m. Author: Didier Descouens

A 2013 made study performed by scientists Andrew R. Cuff and Emily Rayfield showed that Spinosaurids like Spinosaurus had relatively poor resistance in their skulls for torsion compared to other members of this group (Baryonyx) and modern alligators, thus showing Spinosaurus preyed more regularly on fish than it did on land animals, although considered predators of the former too.

Tyrannosaurus

Saturday, December 3, 2016

T. rex reconstitution. Getty Images

Tyrannosaurus (meaning “tyrant lizard”, from the Ancient Greek tyrannos (τύραννος), “tyrant”, and sauros (σαῦρος), “lizard”) is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning “king” in Latin), is one of the most well-represented of the large theropods. Tyrannosaurus lived throughout what is now western North America, on what was then an island continent known as LaramidiaTyrannosaurus had a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 68 to 66 million years ago. It was the last known member of the tyrannosaurids, and among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction.

 Size (in green) compared with selected giant theropods. Author: Matt Martyniuk. Size comparison of selected giant theropod dinosaurs and a human. Adapted from or matching illustrations and measurements published by the following authors: Spinosaurus after proportions and measurements in N. Ibrahim et al. (2014) “Semiaquatic adaptations in a giant predatory dinosaur” (silhouette adapted from image by ArthurWeasley), Carcharodontosaurus, Giganotosaurus, and Tyrannosaurus matching measurements and diagrams by G. S. Paul (2010) “The Princeton Field Guide to Dinosaurs”, pp. 97, 98, 108, 109, and Scott Hartman.

Tyrannosaurus rex has been known to science since the end of the nineteenth century,‭ ‬and to this day remains arguably the most popular dinosaur the world over.‭ ‬This is evidenced by its almost mandatory inclusion in books,‭ ‬TV shows,‭ ‬games and websites that are about dinosaurs in general.‭ ‬Tyrannosaurus also probably has more toys and merchandising relating to it than any other dinosaur.

Illustration of the tyrannosaurid Tyrannosaurus rex with minimal feathers based on phylogenetic bracketing. Author: Durbed

Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hind limbs, Tyrannosaurus fore limbs were short but unusually powerful for their size and had two clawed digits. The most complete specimen measures up to 12.3 m (40 ft) in length, up to 3.66 meters (12 ft) tall at the hips, and according to most modern estimates 8.4 metric tons (9.3 short tons) to 18.5 metric tons (20.4 short tons) in weight. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it is still among the largest known land predators and is estimated to have exerted the largest bite force among all terrestrial animals. By far the largest carnivore in its environment, Tyrannosaurus rex was most likely an apex predator, preying upon hadrosaurs, armoured herbivores like ceratopsians and ankylosaurs, and possibly sauropods. Some experts, however, have suggested the dinosaur was primarily a scavenger. The question of whether Tyrannosaurus was an apex predator or a pure scavenger was among the longest ongoing debates in paleontology. It is accepted now that Tyrannosaurus rex acted as a predator, and opportunistically scavenged as modern mammalian and avian predators do.

Tyrannosaurus specimen AMNH 5027 at the American Museum of Natural History.

T. rex‘s serrated, conical teeth were most likely used to pierce and grip flesh, which it then ripped away with its brawny neck muscles. Its two-fingered forearms could probably seize prey, but they were too short to reach its mouth.

Scientists believe this powerful predator could eat up to 500 pounds (230 kilograms) of meat in one bite. Fossils of T. rexprey, including Triceratops and Edmontosaurus, suggest T. rex crushed and broke bones as it ate, and broken bones have been found in its dung.

Predator or Scavenger?

One of the most controversial theories about Tyrannosaurus is if it was actually a predator at all,‭ ‬but instead lived the life of a scavenger.‭ ‬Some have said that its size,‭ ‬even when combined with lower weight estimates meant that it could not run,‭ ‬as in both feet off the ground at the same time.‭ ‬Biomechanical studies have also shown that it was no way near as fast as it is sometimes depicted in movies.‭ ‬It is popularly said that for a Tyrannosaurus to run at‭ ‬25‭ ‬miles per hour,‭ ‬it would need up‭ ‬to of around‭ ‬80%‭ ‬of its muscle mass in its legs,‭ ‬an unheard of scenario.‭ ‬What are considered more realistic estimates place top speed at around the‭ ‬11‭ ‬miles per hour mark.‭

A slower than expected speed does not mean that Tyrannosaurus was a scavenger however.‭ ‬You have to remember that predators need to be only fast enough to catch their prey.‭

Tyranossaurus rex menu by PrehistoricWildlife.com

Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, located at the Field Museum of Natural History under the name FMNH PR2081 and nicknamed Sue, measured 12.3 meters (40 ft) long, and was 3.66 meters (12 ft) tall at the hips, and according to the most recent studies estimated to have weighed between 8.4 metric tons (9.3 short tons) to 18.5 metric tons (20.4 short tons) when alive. However, not every adult Tyrannosaurus specimen recovered is as big. Historically average adult mass estimates have varied widely over the years, from as low as 4.5 metric tons (5.0 short tons), to more than 7.2 metric tons (7.9 short tons), with most modern estimates ranging between 5.4 metric tons (6.0 short tons) and 8.0 metric tons (8.8 short tons). Hutchinson et al. (2011) found that the maximum weight of Sue, the largest complete Tyrannosaurus specimen, was between 9.5 and 18.5 metric tons (9.3–18.2 long tons; 10.5–20.4 short tons), though the authors stated that their upper and lower estimates were based on models with wide error bars and that they “consider [them] to be too skinny, too fat, or too disproportionate” and provided a mean estimate at 13.99 metric tons (15.42 short tons) for this specimen.

Scale chart for various specimens of Tyrannosaurus rex. Relative sizes based on skeletal drawings by Scott Hartman. Silhouettes adapted from original drawings by Matt Martyniuk. Author: Matt Martyniuk

Skin and feathers

Full size model in Poland, depicting Tyrannosaurus with both feathers and scales, and with lipped jaws.

While there is no direct evidence for Tyrannosaurus rex having had feathers, many scientists now consider it likely that T. rexhad feathers on at least parts of its body, due to their presence in related species. Mark Norell of the American Museum of Natural History summarized the balance of evidence by stating that: “we have as much evidence that T. rex was feathered, at least during some stage of its life, as we do that australopithecines like Lucy had hair.”

The jaws of Tyrannosaurus were tremendously powerful with a bite force of larger individuals being measured in several tons.‭ ‬The teeth were primarily arranged into biting incisors at the front,‭ ‬with larger canines to the size and rear of the mouth.‭ ‬The incisors that are on the premaxilla form a‭ ‘‬D shaped‭’ ‬curve around the front,‭ ‬which is notable as this gave Tyrannosaurus‭ (‬and others of its group‭)‬ a‭ ‘‬U shaped‭’ ‬snout.‭ ‬Other well-known carnivorous theropods such as Allosaurus were more‭ ‘‬V shaped‭’‬.‭ ‬The‭ ‘‬U‭’ ‬shaped snout means that‭ ‬Tyrannosaurus had more‭ ‘‬pick-up‭’ ‬every time it took a bite than other dinosaurs. The teeth towards the sides of the mouth were the most suited to crushing,‭ ‬and grow anywhere up‭ ‬to‭ ‬30‭ ‬centimetres long when including the root.‭ ‬The teeth of the lower jaw‭ (‬mandible‭) ‬were smaller than those above,‭ ‬and fitted inside the upper jaw so that when closed,‭ ‬only the upper teeth would protrude out and downwards.

Close up of “Sue” T-Rex replica skull at the Field Museum of Natural History in Chicago, IL. Author: Scott Robert Anselmo

T. rex fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous period, which lasted from 67 million to 65 million years ago, toward the end of the Mesozoic Era. It was among the last of the non-avian dinosaurs to exist prior to the Cretaceous-Paleogene extinction event, which wiped out the dinosaurs.

More mobile than many other land-based dinosaurs, T. rex roamed throughout what is now western North America, at the time an island continent identified as Laramidia. More than 50 skeletons of T. rex have been unearthed, according to National Geographic. Some of these remains are nearly complete skeletons, and at least one skeleton included soft tissue and proteins.

Tyrannosaurus and other animals of the Hell Creek Formation

Tyrannosaurus lived during what is referred to as the Lancian faunal stage (Maastrichtian age) at the end of the Late Cretaceous. Tyrannosaurus ranged from Canada in the north to at least Texas and New Mexico in the south of Laramidia. During this time Triceratops was the major herbivore in the northern portion of its range, while the titanosaurian sauropod Alamosaurus “dominated” its southern range. Tyrannosaurus remains have been discovered in different ecosystems, including inland and coastal subtropical, and semi-arid plains.

Hell Creek dinosaurs and pterosaurs by durbed on Deviantart. Various dinosaurs and pterosaurs from the Hell Creek Formation. From back to front: Ankylosaurus, Tyrannosaurus, Quetzalcoatlus, Triceratops, Struthiomimus, Pachycephalosaurus, and the unnamed dromaeosaurid and caenagnathid now named Acheroraptor and Anzu respectively. Author: Durbed

Several notable Tyrannosaurus remains have been found in the Hell Creek Formation. During the Maastrichtian this area was subtropical, with a warm and humid climate. The flora consisted mostly of angiosperms, but also included trees like dawn redwood (Metasequoia) and AraucariaTyrannosaurus shared this ecosystem with Triceratops, related ceratopsians Nedoceratops, Tatankaceratops and Torosaurus, the hadrosaurid Edmontosaurus annectens and possibly a species of Parasaurolophus, the armored dinosaurs DenversaurusEdmontonia and Ankylosaurus, the dome headed dinosaurs PachycephalosaurusStygimolochSphaerotholus, and Dracorex, the hypsilophodont Thescelosaurus, and the theropods OrnithomimusStruthiomimusOrcomimusAcheroraptorDakotaraptorRichardoestesiaParonychodonPectinodon and Troodon.

Sources: www.natgeo.com, www.wiki.org, www.planetdinosaur.net

Concavenator

Saturday, December 3, 2016

Concavenator by daitengu

Concavenator is a genus of theropod dinosaur that lived approximately 130 million years ago during the early Cretaceous period (Barremian stage). The type species is C. corcovatusConcavenator corcovatus means “hump backed hunter from Cuenca”. The fossil was discovered in the Las Hoyas fossil site of Spain by paleontologists José Luis Sanz, Francisco Ortega and Fernando Escaso from the Autonomous University of Madrid and the National University of Distance Learning.

Size compared to a human.

Concavenator was a medium-sized (roughly 6 meters (20 feet) long) primitive carcharodontosaurian dinosaur possessing several unique features. Two extremely tall vertebrae in front of the hips formed a tall but narrow and pointed crest (possibly supporting a hump) on the dinosaur’s back. The function of such crests is currently unknown. Paleontologist Roger Benson from Cambridge University speculated that one possibility is that “it is analogous to head-crests used in visual displays”, but the Spanish scientists who discovered it noted it could also be a thermal regulator.

Structures for what appear to be quill knobs have been found on the ulna of the fore arms.‭ ‬If this interpretation is accurate,‭ ‬then Concavenator may have displayed sparse protofeathers from its lower arms.‭ ‬Unfortunately no feathers have been found preserved with the specimen so clarification may have to wait until further specimens can be found.

Mapusaurus

Saturday, December 3, 2016

Mapusaurus | Planet Dinosaur Wiki

Mapusaurus (“earth lizard”) was a giant carnosaurian dinosaur from the early Late Cretaceous (Cenomanian stage) of what is now Argentina.

It was similar in size to its close relative Giganotosaurus, with the largest known individuals estimated as about 12.2 metres (40 ft) in length or more and weighing 13.5 tonnes (metric tons). The longest individual for which Coria and Currie (2006) provided a concrete estimate in Table 1 (apendix lll) is the animal to which femur MCF-PVPH-208.203 belonged; this individual is estimated as 10.2 metres (33 ft) long.

Reconstructed skulls of adult and juvenile Mapusaurus

Mapusaurus was excavated between 1997 and 2001, by the Argentinian-Canadian Dinosaur Project, from an exposure of the Huincul Formation (Rio Limay Subgroup, Cenomanian) at Cañadón del Gato. It was described and named by paleontologists Rodolfo Coria and Phil Currie in 2006.

The name Mapusaurus is derived from the Mapuche word Mapu, meaning ‘of the Land’ or ‘of the Earth’ and the Greek sauros, meaning ‘lizard’. The type species, Mapusaurus roseae, is named for both the rose-colored rocks, in which the fossils were found and for Rose Letwin, who sponsored the expeditions which recovered these fossils.

Size comparison of Mapusaurus roseae and a human. Adapted from an illustration by Ville Sinkkonen. Author: Matt Martyniuk & Ville Sinkkonen

The designated holotype for the genus and type species, Mapusaurus roseae, is an isolated right nasal (MCF-PVPH-108.1, Museo Carmen Funes, Paleontología de Vertebrados, Plaza Huincul, Neuquén). Twelve paratypes have been designated, based on additional isolated skeletal elements. Taken together, the many individual elements recovered from the Mapusaurus bone bed represent most of the skeleton.

Cladistic analysis carried out by Coria and Currie definitively showed that Mapusaurus is nested within the clade Carcharodontosauridae. The authors noted that the structure of the femur suggests a closer relationship with Giganotosaurus than either taxon shares with Carcharodontosaurus. They created a new monophyletic taxon based on this relationship, the subfamily Giganotosaurinae, defined as all carcharodontosaurids closer to Giganotosaurus and Mapusaurusthan to Carcharodontosaurus. They tentatively included the genus Tyrannotitan in this new subfamily, pending publication of more detailed descriptions of the known specimens of that form.

Carcharodontosauridae

Saturday, December 3, 2016

Some of the most known Carcharodontosaurids

Carcharodontosaurids (from the Greek “shark-toothed lizards”) were a group of carnivorous theropod dinosaurs. In 1931 Ernst Stromer named Carcharodontosauridae as a family, in modern paleontology this name indicates a clade within Carnosauria. Carcharodontosaurids included some of the largest land predators ever known: GiganotosaurusMapusaurusCarcharodontosaurus, and Tyrannotitan all rivaled or slightly exceeded Tyrannosaurus in length. A 2015 paper published in PalArch by paleontologist Christophe Hendrickx and colleagues that focuses on the history of theropod dinosaur research gives a maximum length estimate of 14 meters (46 feet) for the largest carcharodontosaurids, while the smallest carcharodontosaurids were estimated at at least 6 meters (20 feet) long.

Along with the spinosaurids, carcharodontosaurids were the largest predators in the early and middle Cretaceous throughout Gondwana, with species also present in North America (Acrocanthosaurus), and Asia (Shaochilong). Their ages range from the Barremian (127-121 million years ago) to the Turonian (93-89 million years ago). Past the Turonian, they might have been replaced by the smaller abelisaurids in Gondwana and by tyrannosaurids in North America and Asia. According to Fernando Novas and colleagues, the disappearance of not only carcharodontosaurids but also spinosaurids and other fauna in both Gondwana and North America seem to indicate that this faunal replacement occurred on a global scale. However, some theropod teeth discovered in late Maastrichtian Marília Formation in Brazil, as well as a fragment of right maxilla discovered at the Campanian-Maastrichtian boundary of the Presidente Prudente Formation in Brazil, appear to belong to carcharodontosaurids, indicating the survival of this group until the latest Cretaceous, 70 to 66 mya. In December 2011, Oliver W. M. Rauhut described a new genus and species of carcharodontosaurid from the Late Jurassic (late Kimmeridgian to earliest Tithonian faunal stage, about 154-150 million years ago) of Tendaguru Formation, southeastern Tanzania. Veterupristisaurus represents the oldest known carcharodontosaurid.

Common features
Although some carcharodontosaurids genera are noted for their large size,‭ ‬not all of the carcharodontosaurids were giants.‭ ‬They do however seem to have had skulls that were proportionately large relative to their body size.‭ ‬The skulls of the larger carcharodontosaurid genera are amongst the largest dinosaur skulls known with the skull of Acrocanthosaurus being about‭ ‬1.3‭ ‬meters long,‭ ‬the skull of Carcharodontosaurus being about‭ ‬1.6‭ ‬meters long,‭ ‬and the larger estimate of the skull of Giganotosaurus being‭ ‬1.95‭ ‬meters long.‭ ‬These large sizes were possible because carcharodontosaurid had very large fenestra‭ (‬openings‭)‬,‭ ‬which meant that the skulls were not as solid,‭ ‬and therefore quite lightweight given the size.‭ ‬The antorbital fenestra‭ (‬the opening between the eye socket and nasal opening‭) ‬is often particularly large when compared to the skulls of other theropods.‭ ‬When viewed in profile the anterior‭ (‬front‭) ‬end of the lower jaws of carcharodontosaurids also tend to appear squared off.

Some very known carcharodontosaurids

Acrocanthosaurus
Carcharodontosaurus
Concavenator
Eocarcharia
Giganotosaurus
Kelmayisaurus

Mapusaurus
Sauroniops
Shaochilong
Tyrannotitan
Veterupristisaurus

Classification

The family Carcharodontosauridae was originally named by Ernst Stromer in 1931 to include the single newly discovered species Carcharodontosaurus saharicus. A close relative of C. saharicusGiganotosaurus, was added to the family when it was described in 1995. Additionally, many paleontologists have included Acrocanthosaurus in this family (Sereno et al. 1996, Harris 1998, Holtz 2000, Rauhut 2003, Eddy & Clarke, 2011, Rauhut 2011), though others place it in the related family Allosauridae (Currie & Carpenter, 2000; Coria & Currie, 2002). Carcharodontosaurids are characterized by the following morphological characters : Dorsoventral depth of anterior maxillary interdental plates more than twice anteroposterior width, squared, sub-rectangular anterior portion of the dentary, teeth with wrinkled enamel surfaces, presence of four premaxillary alveoli and a premaxillary body taller than long in lateral aspect, opisthocoelous cervical vertebrae with neural spines more than 1.9 times the height of the centrum, large, textured rugosities on the lacrimal and postorbital formed by roofing and forming broad orbital shelves, and a proximomedially inclined femoral head. With the discovery of Mapusaurusin 2006, Rodolfo Coria and Phil Currie erected a subfamily of Carcharodontosauridae, the Giganotosaurinae, to contain the most advanced South American species, which they found to be more closely related to each other than to the African and European forms. Coria and Currie did not formally refer Tyrannotitan to this subfamily, pending a more detailed description of that genus, but noted that based on characteristics of the femur, it may be a gigantosaurin as well.

In 1998 Paul Sereno defined Carcharodontosauridae as a clade, consisting of Carcharodontosaurus and all species closer to it than to either AllosaurusSinraptorMonolophosaurus, or Cryolophosaurus. Therefore, this clade is by definition outside of the clade Allosauridae.

Oviraptor

Friday, December 2, 2016

Oviraptor nesting

Oviraptor was a small, bird-like, omnivorous dinosaur. It was about 6 to 8 feet long (1.8 to 2.5 m), weighing about 55 to 76 pounds (25 to 35 kg). It was lightly built, fast-moving, long-legged, and bipedal (it walked on two legs). It had a curved, flexible, s-shaped neck, a long tail, short, strong arms, and curved claws on its three-fingered hands and three-toed feet. The claws on its large hands were about 3 inches (8 cm) long. Its fingers were long and grasping.

Size comparison between the dinosaur Oviraptor and a human. Author: Conty

Its strangely-shaped, parrot-like head had a short, toothless beak and extremely powerful jaws, built for crushing action. Oviraptors had a small, stumpy, horn-like crest on its snout, probably used for a mating display; differences in these crests may represent different oviraptor species or the difference between the male, female, and juvenile of the species.

Oviraptor lived in the late Cretaceous period, during the late Campanian stage about 75 million years ago; only one definitive specimen is known (with associated eggs), from the Djadokhta Formation of Mongolia, though a possible second specimen (also with eggs) comes from the northeast region of Inner Mongolia, China, in an area called Bayan Mandahu.

Fossilized nest (AMNH FR 6508). Photo by Steve Starer

This dinosaur was discovered during the 1920s American expeditions to Mongolia. Most of the specimens were found near nests of dinosaur eggs. Because the eggs were thought to belong to Protoceratops-a small, common ceratopsian in that region-it was assumed that Oviraptor was stealing the eggs. The eggs, however, lacked embryos. When, in the 1990s, American teams returned to Mongolia, they found more of the same kinds of eggs, including some that contained the delicate skeletons of embryos of Oviraptor, not of Protoceratops. Soon after that, more amazing fossils came to light. They were of Oviraptor skeletons sitting on nests, with their forelimbs wrapped around the eggs. These were probably skeletons of parents incubating and protecting their own eggs. Oviraptor, it would seem, was named for a crime that it did not commit.

Aside from its unjust reputation as an egg thief, Oviraptor is well known for being one of the most birdlike of all dinosaurs. This theropod possessed a sharp, toothless beak, and it may also have sported a chicken-like wattle. Although no direct evidence has been adduced from its sparse fossil remains, Oviraptor was almost certainly covered with feathers, the rule rather than the exception for the small meat-eating dinosaurs of the later Cretaceous period.

Ouranosaurus

Friday, December 2, 2016

Ouranosaurus, meaning (Brave Monitor Lizard), was an unusual Ornthopod that lived during the Late Cretaceous (Late Aptian Stage) about 110 million years ago in what is now Africa. Ouranosaurus measured about 7 metres (23 feet) in length and weighed about 4 tons. Two complete fossils were found in the Echkar (or El Rhaz) Formation, Gadoufaouna deposits, Agadez, Niger in 1966 and the animal was named by a french palaeontologist in 1976 called Phillipe Taquet.

Mounted skeleton, Museo di Storia Naturale of Venice.

This early Cretaceous ornithopod from west Africa is one of the most puzzling dinosaurs ever discovered, and paleontologists are still trying to work out what it looked like. This is surprising, because Ouranosaurus is known from an almost complete skeleton – which was discovered in 1966 – and its closest known relative, Iguanadon, is one of the best understood dinosaurs of all.

Ouranosaurus was a relatively large euornithopod. Taquet in 1976 estimated the body length at 7 metres (23 feet), the weight at 4 tonnes (4.4 short tons). Gregory S. Paul in 2010 gave a higher length estimate of 8.3 metres (27 feet) but a lower weight of 2.2 t (2.4 short tons), emphasizing that the animal was relatively light-built. The femur is 811 millimetres (2.661 ft) long.

Skull at Museo di Storia Naturale di Venezia. Author: Ghedoghedo

In January 1965 Philippe Taquet discovered dinosaurian fossils at the Camp des deux Arbres site near Gadoufaoua. The material was recovered in 1966. Taquet described the type species Ouranosaurus nigeriensis from the fossils in 1976. The generic name is derived from Tuareg ourane meaning “monitor lizard” — a totem animal to the Tuareg who consider it their ancestral maternal uncle — but itself related to Arab waran, “brave”. The specific name refers to Niger.

The holotype specimen MNHN GDF 300, was found in the Upper Elrhaz Formation dating to the Aptian, between 125 and 112 million years old. It consists of an almost complete skeleton with skull, that is today mounted in the Nigerien capital Niamey; the Museum national d’histoire naturelle displays a cast. Other finds include the paratype specimen GDF 381, a second skeleton found in 1972, and the referred specimens GDF 301, a large coracoid, and GDF 302, a femur.

Dorsal vertebrae at Museo di Storia Naturale di Venezia. Author: Ghedoghedo

Classification

Restoration of the head.

Taquet originally assigned Ouranosaurus to the Iguanodontidae, within the larger Iguanodontia. However, although it shares some similarities with Iguanodon (such as a thumb spike), Ouranosaurus is no longer placed in the iguanodontid family, a grouping that is now considered paraphyletic, a series of subsequent offshoots from the main stem-line of iguandontian evolution. It is instead placed in the clade Hadrosauroidea, which contains the Hadrosauridae (also known as “duck-billed dinosaurs”) and their closest relatives. Ouranosaurus appears to represent an early specialised branch in this group, showing in some traits independent convergence with the hadrosaurids. It is thus a basal hadrosauroid.

Some Awesome Pterosaurs

Friday, December 2, 2016

Pterosaurs (meaning “winged lizard”) were flying reptiles of the extinct clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous (228 to 66 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger. Early species had long, fully toothed jaws and long tails, while later forms had a highly reduced tail, and some lacked teeth. Many sported furry coats made up of hair-like filaments known as pycnofibers, which covered their bodies and parts of their wings. Pterosaurs spanned a wide range of adult sizes, from the very small anurognathids to the largest known flying creatures of all time, including Quetzalcoatlus and Hatzegopteryx.

Distribution of pterosaur fossil locations. Colored species or genera names correspond to their taxonomic group. Adapted from Witton (2013). Taxonomic groups based on Unwin et al. (2010). Author: Andrew Z. Colvin

Tapejara

Tapejara is but one of a larger group of distinctive pterosaurs that have large laterally compressed‭ (‬large when viewed from the side but thin from the front‭) ‬crests combined with a‭ ‬relatively short and deep set of jaws.‭ ‬The diet of Tapejara has since been the subject of a lot of debate as while most consider it to be a piscivorous fish-eater‭; ‬some consider the possibility of it and possibly other similar pterosaurs being fruit eating frugivores.

Ornithocheirus

Ornithocheirus has enjoyed a surge in popularity since the end of the twentieth century mainly in part due to possible specimens of very similar pterosaurs discovered in Brazil,‭ ‬as well as a centre stage appearance in the popular BBC series‭ ‘‬Walking with Dinosaurs‭’‬.‭ ‬However while the latter depiction was as accurate portrayal of its possible lifestyle,‭ ‬the twelve meter wingspan quoted in the show is beyond the scope of any fossil material that has been attributed to this genus.‭ ‬Instead Ornithocheirus had an upper wingspan of five meters,‭ ‬although the addition of new material may see this size increase to six meters.

No top ten pterosaur list would be complete without the member that is considered the largest of the group.‭ ‬However while Quetzalcoatlus is considered the largest,‭ ‬the exact size is a matter of scaling up missing bones by comparison to other pterosaurs,‭ ‬something that has created a‭ ‬degree of variability in size quotations.‭ ‬Also while Quetzalcoatlus is generally regarded as the largest,‭ ‬others such‭ ‬as Hatzegopteryx are in a position to take this title away from Quetzalcoatlus.‭ ‬Only a general lack of fossils results makes it hard to ascertain one or the other as an absolute.‭ ‬The large size of Quetzalcoatlus has made it hard for many to imagine such a large creature as being capable of flight as no living animal is capable of matching Quetzalcoatlus’s size with the ability to fly.‭ ‬However just because there is no living precedent to prove this,‭ ‬it does not mean that flight for‭ ‬Quetzalcoatlus was impossible.

‬Pteranodon

Probably the most instantly recognisable pterosaur due to its inclusion in so many dinosaur books and films,‭ ‬Pteranodon has not been without its share of controversy.‭ ‬This is mainly centred around the shape and function of the back crest.‭ ‬Differences between male and females individuals were for a time taken to indicate different species,‭ ‬something that was not helped by‭ ‬the fact that males had crests similar to the females until they reached maturity.‭ ‬The crest has also occasionally been depicted as supporting a skin sail,‭ ‬although most reconstructions just keep it as a bony projection from the back of the cranium.‭ ‬The name Pteranodon actually translates to English‭ ‬as‭ ‘‬toothless beak‭’‬,‭ ‬and this makes it very easy to spot inaccurate depictions as Pteranodon is often given teeth to make it look more fearsome.‭

Dsungaripterus

Another specialist feeder was Dsungaripterus which had a highly adapted beak.‭ ‬The front portion of this beak was toothless and curved upwards,‭ ‬something that is thought to have been an adaptation for digging out shellfish from soft ground.‭ ‬Like a crowbar Dsungaripterus could drive this beak into the mud and lever out shellfish that would have buried themselves‭ ‬to survive‭ ‬during‭ ‬the‭ ‬low tide.‭ ‬The teeth at the back of the mouth were also quite small and not especially sharp.‭ ‬This made them more robust and effective for crushing thin shells that would have protected shellfish from other predators.‭ ‬Further evidence for this feeding behaviour also comes from the fact that dsungaripterid pterosaurs are usually found in marine environments.

Pterodaustro

There have been many filter feeding pterosaurs discovered but Pterodaustro is easily one of the most specialised of these.‭ ‬Instead of just a few teeth arranged in a spoon shape at the end of the jaws‭ ‬ like some of the members,‭ ‬Pterodaustro had several hundred teeth that pointed up from the lower jaw that created a fine comb which allowed mouthfuls of water to flow out while small invertebrates were trapped within.‭ ‬Also many aquatic invertebrates are known to have carotenid pigment that when broken down by the liver turns to a pink/orange,‭ ‬which has led to many palaeontologists recognising the possibility that Pterodaustro may have been a bright pink to deep red in body colour.‭ ‬This may in part explain why Pterodaustro was nocturnally active as indicated by study of Pterodaustro’s scleral rings,‭ ‬something that would have made it less obvious to potential predators.

Eudimorphodon

With fossils dating back to the Norian stage of the Triassic,‭ ‬Eudimorphodon is one of the earliest pterosaurs to appear in the fossil record.‭ ‬This tells palaeontologists that while the exact common ancestor to all pterosaurs remains unknown,‭ ‬it must appear in the fossil record before the Norian stage.‭ ‬This will allow palaeontologists who are searching for this ancestor to focus their search upon deposits that date back to before this age.

Darwinopterus

Darwinopterus was a major discovery because it has features that are seen in both basal and advanced pterosaurs.‭ ‬This makes Darwinopterus what is called a transitory form‭ (‬palaeontologists generally don’t like the term‭ ‘‬missing link‭’) ‬that shows the evolution of primitive pterosaurs into their more advanced forms.‭ ‬Not only is this interesting in itself but the really exciting discovery associated with this is that the pterosaurs do not seem to have evolved their whole bodies at once but instead just evolved certain areas.‭ ‬This is termed modular evolution and is used to refer to just certain body areas such as the skull,‭ ‬hands,‭ ‬legs,‭ ‬tail,‭ ‬etc.‭ ‬changing while the rest of the body remains the same.‭

Rhamphorhynchus

Another famous pterosaur,‭ ‬Rhamphorhynchus has been used to name the Rhamphorhynchidae,‭ ‬the group of basal‭ (‬sometimes called‭ ‘‬primitive‭’) ‬pterosaurs.‭ ‬This means that Rhamphorhynchus had primitive features such as a long tail‭ (‬that in Rhamphorhynchus was straight with a vane on the end that may‭ ‬have‭ ‬been an inflight steering aid‭) ‬and short neck vertebrae that connected more to the posterior‭ (‬back‭) ‬of the skull like in lizards.‭ ‬The hands of Rhamphorhynchus are also better suited for holding onto vertical surfaces,‭ ‬an ability that would be reduced in later pterosaurs.‭ ‬The proportionately long and sharp teeth are thought to have been used to‭ ‬capture small vertebrates such as fish from near the surface of the water.

Pterodactylus

This is the pterosaur that started the science of pterosaur palaeontology as it was the first to be described as one.‭ ‬However the correct identification‭ ‬was a considerable time coming with some researchers describing it as a bat like creature,‭ ‬and some even thinking that it was an aquatic animal with the wings being used for swimming.‭ ‬In fact even after the correct identification by Georges Cuvier in‭ ‬1809‭ ‬many naturalists still held firm to the earlier ideas.‭ ‬Pterodactylus has been used to name the group of‭ ‘‬advanced‭’ ‬Pterosaurs the Pterodactyloidea.‭ ‬Although there are many key differences between genera that belong to this group they all share some common features such as short tails,‭ ‬longer neck vertebrae that attach to more underneath the base of the skull rather than the rear,‭ ‬and wings better adapted to flying.

Pterodactylus is also this pterosaur that the more common public name‭ ‘‬Pterodactyl‭’ ‬is derived from,‭ ‬a name that has resulted in the general public referring to pterosaurs as‭ ‘‬pterodactyls‭’‬.‭ ‬The problem with this is that pterodactyl is not recognised by any scientific body as being a valid description of the pterosaurs,‭ ‬or any specific genera.

Sordes

Fossils of this pterosaur have been found with the impression of an extensive covering of pycnofibres,‭ ‬loosely referred to as hairs.‭ ‬These pycnofibres are not like mammalian hair however and instead are hollow filaments,‭ ‬although they would have served an insulatory purpose like mammalian hair.‭ ‬Further discoveries such as Jeholopterus also have impressions of pycnofibres,‭ ‬and many pterosaurs are now thought to have had a covering of them,‭ ‬but due to their fragile nature impressions of pycnofibres only preserve when conditions are exactly right.

Anurognathus

‬This is a good representative of the group of basal pterosaurs that had short but wide mouths.‭ ‬These mouths had long thin teeth that show them to be specialised insectivores,‭ ‬probably taking large flying insects‭ ‬while‭ ‬on the wing.

Nyctosaurus

Very similar to Pteranodon,‭ ‬Nyctosaurus had a greatly enlarged‭ ‘‬L-shaped‭’ ‬crest that rose up from the top of its skull.‭ ‬Like with Pteranodon this has been speculated as being the support for a huge skin sail,‭ ‬but modern analysis keeps pointing to the crest just being a bony L structure.

Mounted female and male G. sternbergi skeletons at the Royal Ontario Museum

Source: www.natgeo.com

Ornitholestes

Friday, December 2, 2016

Ornitholestes (meaning “bird robber”) is a small theropod dinosaur of the late Jurassic (Brushy Basin Member of the Morrison Formation, middle Kimmeridgian age, about 154 million years ago) of Western Laurasia (the area that was to become North America).

To date, Ornitholestes is known only from a single partial skeleton with a badly crushed skull found at the Bone Cabin Quarry near Medicine Bow, Wyoming, in 1900. It was described by Henry Fairfield Osborn in 1903. An incomplete hand was later attributed to Ornitholestes, although it now appears to belong to Tanycolagreus. The type (and only known) species is O. hermanni. The specific name honors the American Museum of Natural History preparator Adam Hermann.

Ornitholestes’ reputation as a bird-eater has much in common with Oviraptor‘s reputation as an egg-stealer: these were inferences drawn on the basis of insufficient knowledge (and in the case of Ornitholestes, the myth was perpetuated by a famous painting by Charles R. Knight depicting this dinosaur preparing to eat a captured Archaeopteryx).
 
Casts of Ornitholestes hermanni. On display at the Royal Tyrrell Museum, Alberta, Canada.
The infraorder Coelurosauria, coined in 1914 by Friedrich von Huene, was traditionally a taxonomic wastebasket into which all small theropods were placed. Ornitholestes, due to its small size, was therefore generally classified as a coelurosaur. In 1986, Jacques Gauthier redefined this and several other paleontological terms in a more rigorous fashion, based on cladistic methods. Tetanurae was defined as modern birds and all theropods more closely related to modern birds than to ceratosaurs, while Coelurosauria now comprised all members of Tetanurae more closely related to modern birds than to carnosaurs. In 1988, Gregory S. Paul suggested that Ornitholestes was very similar in skull structure to Proceratosaurus, a Middle Jurassic theropod from England.

Mononykus

Friday, December 2, 2016

Mononykus

Mononykus (meaning “one claw”) was a theropod dinosaur from late Cretaceous Mongolia (Nemegt Formation, about 70 million years ago) with long, skinny legs. It moved about on two legs, was likely very nimble and could run at high speeds, something that would have been useful in the open flood plains where it lived. It had a small skull, and its teeth were small and pointed, suggesting that it ate insects and small animals, such as lizards and mammals. Its large eyes might have allowed Mononykus to hunt by night, when it was cooler and there would have been fewer predators about. Mononykus was originally named Mononychus in 1993, but later that year, it was renamed because the original name had already been used for a beetle named by Johann Schueppel, a German entomologist.
 
Size comparison of several parvicursorine dinosaurs. From left to right: Parvicursor remotus (green), Ceratonykus oculatus (red), Shuvuuia deserti (blue), and Mononykus olecranus (violet). Scaled to tibia length in their respective descriptions. Author: Matthew Martyniuk
Mononykus was a small dinosaur, only 1 metre (3.3 ft) long. Other characteristics include fused wrist bones similar to those of birds, and a keeled breastbone. It differed from close relatives Shuvuuia and Parvicursor in several details of its skeleton, including a pubic bone that is triangular in cross section, and different proportions in the toe bones.
 
Mononykus was a member of the family Alvarezsauridae and, like its relatives, had very strange, stubby forearms with one large, approximately 7.5-centimetre (3.0 in) long claw (hence its name). The other two claws had disappeared (however, a close relative of MononykusShuvuuia, had two vestigial claws, alongside one large claw). The purpose of these highly specialized arms is still a mystery, but some scientists have suggested they were used to break open termite mounds (like modern anteaters), and therefore it is possible that they fed primarily on insects.

In a 2001 study conducted by Bruce Rothschild and other paleontologists, 15 foot bones referred to Mononykus were examined for signs of stress fracture, but none were found.

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