Sauropedia

A tribute to the 1993-1998 'Dinosaurs!' collection by Orbis Publishing Ltd.

Carnotaurus January 25, 2012

Filed under: Theropoda — muzillu @ 11:34 am

This large predatory dinosaur had a thick, powerful neck, a bull-shaped head and very short forearms for its size.

Carnotaurus was previously considered to be a member of the group of dinosaurs known as the carnosaurs. However, the group has since been defined to encompass only the allosaurs and their closest kin. It is now classified as an abelisaurid. Carnotaurus had a shorter and deeper skull than Tyrannosaurus and had hornlets over its eyes.

An almost complete skeleton of Carnotaurus was extracted with difficulty from the hard mineral nodule in which it was preserved in Argentina. The deep skull suggests that it may have had an acute sense of smell, but the strength of the jaws and neck implied by the muscle attachments seem at odds with the weakness of the lower jaw and teeth.

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Name: Carnotaurus, meaning ‘meat-eating bull’

Size: 7.5m long and 3.5m high

Food: meat, mainly other dinosaurs

Lived: 100-90 million years ago in the Middle to Late Cretaceous in South America

The head is very short and squashed-looking, with a shallow, hooked lower jaw. Two horns stick out sideways from above the eyes, probably being used for sparring with rivals. The arms are extremely short with no apparent forearms, even shorter than the tiny arms of Tyrannosaurus. They form mere stumps with four miniscule fingers. The skin texture, the best-known of any theropod, has a groundmass of small, pebbly scales but with large, conical scutes forming rows along the sides.

The skull of Carnotaurus has an enormous hole in front of the eye sockets – this is known as the antorbital fossa. All theropods possess this, but only in the abelisaurids is it so large.

Its long, muscular hind legs may have made Carnotaurus much more agile than some other theropods. It would have been able to rush up on its prey and take it by surprise, probably using its sharp claws to slash and grip, while its powerful jaws took out chunks of flesh.

Although Carnotaurus had a very strong skull, it also needed to be light enough to move easily. There were spaces in the sides of the skull to help make it lighter. By jerking its head back, Carnotaurus could tear its prey apart. The teeth in the upper jaw could slice through the flesh, which was held by the lower jaw. Carnotaurus had teeth about 4cm long which curved backwards to help it keep hold of its victim.

Carnotaurus was found in a vast area of grassland and semi-desert called Patagonia in Argentina in 1985. It was an exciting find because the remains gave scientists a very good idea of what this dinosaur’s skin looked like. Along the surface of the body, from head to tail, there were rows of cone-shaped bumps. Rows of big, raised sclaes stood out from the smaller bumps on Carnotaurus’ head, making a pattern around the eyes and on the upper part of its snout.

Carnotaurus was as heavy as a car, almost as tall as an elephant and ran on two legs. Its long backbone was like a big girder supporting the weight beneath. Long rib bones from shoulder to hip gave Carnotaurus extra protection and support.

When Carnotaurus was moving at top speed it would have been unstable without its tail. Carnotaurus used its long, muscular tail to help it keep its balance. This enabled it to push its head forward to seize hold of its struggling prey.

At the top of its short deep head, Carnotaurus had a pair of small, flat horns. These jutted forward over its eyes rather like little wings. Unlike the ceratopsians, such as Triceratops, Carnotaurus’ horns were too small to have been used for defence. Experts think that they may have been coated in extra layers of horn, which would have made them longer. Like stag deer, it is also possible that the male Carnotaurus had larger horns than the females.

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Segnosaurus July 22, 2011

Filed under: Theropoda — muzillu @ 5:32 pm

Segnosaurus showed an unusual combination of features of ornithischians, theropods and prosauropods. Its pelvis looked like the pelvis of the dromaeosaurids, although it was much larger. Segnosaurus had feet with long, slender theropod-like claws and ankles, although it had four toes instead of three on each foot. The teeth, although there were many and small, resembled those of some theropods.

We know of only a few remains of Segnosaurus, but the whole animal can be restored by comparison with its close relatives. The head is based on the skull of the closely related Erlikosaurus, and the feathery covering comes from an early Cretaceous form, Beipiaosaurus, found perfectly preserved in the Liaoning sediments, in China.

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Name: Segnosaurus, meaning ‘slow reptile’

Size: 4-9m long

Food: probably plants, but some experts have suggested meat and fish

Lived: 75 million years ago in the Late Cretaceous Period in Mongolia

The fragmentary remains of this genus show the typical down-turned jaw with the leaf-shaped teeth, and the hip bones with the swept-back pubis that give the impression of an ornithischian dinosaur. These are important details in establishing the makeup of this whole line of dinosaur. It is such an important animal that the name Segnosauria has been proposed as alternative name for the group. Fossil eggs about the size of duck eggs have been attributed to these animals.

Experts are not sure what sort of food Segnosaurus ate. It had teeth at the back of its jaw to cut up food – like the bipedal carnivores. But at the front of its mouth was a toothless beak – like some of the herbivores. Indeed, the dinosaur was probably omnivorous.

Segnosaurus also had feet quite unlike those of ordinary carnivores. It had sturdy legs and short, broad feet which ended in four toes. Some experts think that the feet may have been webbed.

The scientist who named Segnosaurus in 1979 suggested that it waded, or even swam, catching fish with its claws or in its toothless beak. But scientists are still unsure; it is possible that it was a herbivore and used its beak to nip off leaves.

The restoration is largely based on the partial remains of three skeletons. It differs from other therizinosaurids by the arrangement of teeth in the jaw.

 

Herrerasaurus June 26, 2011

Filed under: Theropoda — muzillu @ 3:38 pm

Herrerasaurus was one of the first dinosaurs to roam the Earth.

A contemporary of Eoraptor on the late Triassic riverbanks of Argentina, Herrerasaurus was a much bigger and more advanced theropod. Because of the difference in size, it must have hunted different prey from its smaller relative. Its skeleton was found in 1959, although it was several decades before it was scientifically studied. The complete skull was not found until 1988.

This dinosaur held its tail high off the ground when it walked. It stood upright, moving about on its long, strong back legs and probably ran very fast to catch its prey.

 

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Name: Herrerasaurus, meaning ‘Herrera lizard’, after Victorio Herrera, its discoverer

Size: about 3-5m long and 1m high

Food: mammals, lizards and other dinosaurs

Lived: about 230-215 million years ago in the Late Triassic in the north of Argentina

Herrerasaurus represents the roots of dinosaur evolution. It cannot be classified as either a Saurischia or Ornithischia. This early and very primitive dinosaur had four toes on its back feet. This separates it from other carnivorous dinosaurs, which had three toes.

A big animal with heavy jaws and 5cm-long serrated teeth, Herrerasaurus nevertheless had the appearance and probable lifestyle of the big theropods to come. It has the hinged lower jaw of other theropods. The foot bones are quite primitive, retaining the first and fifth toes that later theropods were to lose. Herrerasaurus has complex ear bones, suggesting that it had a keen sense of hearing which would help in hunting.

Herrerasaurus lived around 230 million years ago, when dinosaurs first appeared in the Triassic Period but were not yet dominant. These earliest dinosaurs were all small predators, like Coelophysis in North America. They competed with more powerful non-dinosaur carnivores for food, including the rauisuchids, some of which were like huge crocodiles. Larger predators ate Herrerasaurus and other small dinosaurs.

Herrerasaurus killed and ate mammals, lizards and perhaps other small carnivorous dinosaurs. It attacked with its front and back feet, and tore its victim with its long claws. Herrerasaurus held its prey in its short, strong front legs.

Several skeletons of this dinosaur have been discovered in northwest Argentina in recent years. Herrerasaurus lived at a time when South America was still joined to the other continents. Members of its dinosaur family have been found as far away as China.

 

 

Deinonychus June 20, 2011

Filed under: Theropoda — muzillu @ 12:41 pm

Deinonychus was far from being one of the largest dinosaurs, but it was one of the most skillful hunters – one of the thugs of the dinosaur world. It always walked on its back legs and was armed with sharp claws and teeth that could rip into prey with alarming ease.

Known from more than nine skeletons, this is the animal over which the debate about whether dinosaurs were warm- or cold-blooded began. One remarkable deposit has several Deinonychus skeletons scattered around the remains of an ornithopod, Tenontosaurus, indicating that it was a pack hunter. It was the prototype for the ‘raptors’ in Jurassic Park, although modern representations have them covered in feathers.

 

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Name: Deinonychus, meaning ‘terrible claw’

Size: 3-4m long and 1m high

Food: meat, especially the flesh of herbivorous dinosaurs

Lived: around 115 million years ago in the Cretaceous Period in North America

Until 1964, experts thought there were two separate types of theropod – big and heavy like Tyrannosaurus or small and slim like Velociraptor. Then in southern Montana, USA, fossils of a theropod were found that made the experts think again.

The fossils they found were of an animal that had features of both types of theropod. Like all bipeds, it always walked on its back legs. It was small and fleet-footed with very special weapons – two huge, wickedly curved and pointed claws. Deinonychus carried these awesome weapons on the second toe of each foot. They were as long as carving knives and just as sharp. The other toes had much smaller claws.

When Deinonychus was running, either chasing its prey or escaping from a larger predator, it used the strong muscles in its feet to pull its special, massive, hooked claws up, away from the ground. This protected them from damage. Its other claws were smaller and blunter and were used for gripping the ground and balance.

Deinonychus was built for speed. It had a slim body supported by strong, slender legs. Its very strong ankle joints could absorb enormous amounts of pressure when it ran flat out. Deinonychus’ skull had holes in the bone and scientists think that its head was quite light. A solid bone skull would have been very heavy. They believe it could run at 40km/h when it had to – faster than a human Olympic sprinter.

Deinonychus hunted in packs, just like the wild dogs that hunt prey on the African plains do today. It probably prowled around herds of Tenontosaurus and other giant herbivores. It kept a watchful eye out for young or infirm members of the herd that strayed close to where it was waiting. Then Deinonychus attacked. It used one claw to cling on to the victim, and ripped into its soft underside with the other. Next, Deinonychus’ teeth went into action. They were sharp and curved backwards, making it impossible for the victim to wrench itself free.

The tail of Deinonychus was held stiff and straight by means of bony rods. Each vertebra had bony tendons growing from it that clasped several of the vertebrae behind, solidifying the whole structure into an inflexible pole with only limited movement at the base for balance. When the tail was held outstretched, it helped Deinonychus to balance itself as it sprinted across the land. It may also have used its tail as a sort of rudder, to help it zigzag through the rocky landscape at top speed.

When experts studied Deinonychus’ skull, they found it had large eye sockets. This made them think that the animal had eagle-sharp eyesight – perfect for spotting a likely victim some distance away.

Deinonychus’ kick was so strong that it could break its own toe. We know this because a fossil bone has been found that had been fractured and then healed. Scientists have suggested that the dinosaur may have crippled itself as it kicked out at its prey.

Its brainpower was enough to keep the animal balanced while it slashed away with the killer claw on the second toe. The long, heavily clawed hands are angled so that the palms face inwards, enabling it to clutch firmly at its prey.

 


 

Coelurus June 19, 2011

Filed under: Theropoda — muzillu @ 2:25 pm

Coelurus would eat anything it came across – even the rotting carcasses of animals killed by other dinosaurs.

It was a nippy little dinosaur, with a small head about the same size as a man’s hand. Its teeth were razor-sharp and curved. Once they had sunk into another animal, it was almost impossible for the prey to wrench itself free. Coelurus also used its powerful teeth and jaws to rip flesh from the rotting carcasses of prey killed by other carnivores.

For a long time Coelurus was thought to have been another specimen of Ornitholestes. However, studies by John Ostrom in 1976 and Jacques Gauthier in 1986 show that the hands are like those of the maniraptorans. In contrast, the neck is nothing like that of a maniraptoran and it is unclear whether this animal fits into the dinosaur family tree.

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Name: Coelurus, meaning ‘hollow tail’

Size: 2m long

Food: meat, usually dead dinosaurs it found

Lived: about 140 million years ago during the Late Jurassic Period in North America

This animal is another of the small, hunting dinosaurs. It has a strangely down-curved jaw with sharp, curved teeth. The hands are long but not particularly strong, with a wrist joint similar to that of a bird, and very flexible fingers. The ‘hollow tail’ part of the name refers to the deep excavations in the vertebrae of the back and tail, something like those found as a weight-saving measure in sauropods.

Coelurus had very light bones and a stiff tail with hollow bones in it. Its front limbs were short and slim. Its hands were small and weak, with three curved claws. Coelurus had similar, slightly blunter claws on the toes of both back limbs. It used its hands to snatch at its prey and to keep it in its grasp, while ripping it to death with the claws on its feet.

Specimens of Coelurus found in four locations in the same quarry may have come from the one individual. That individual may not even have been fully grown, and so the size estimate here may be on the small side.

 

Allosaurus June 16, 2011

Filed under: Theropoda — muzillu @ 2:51 pm

Allosaurus was as tall as a giraffe, but unlike this gentle herbivore, it was a lethal killer that may have hunted its prey in packs.

The most well-known of the late Jurassic theropods, Allosaurus was unearthed by Othniel Charles Marsh during the ‘bone wars’, and since then many specimens have been found. The Cleveland-Lloyd quarry alone has yielded more than 44 individuals. Species attributed to Allosaurus have been found as far away as Tanzania and Portugal. Sauropod bones have been found bearing marks gouged by Allosaurus teeth.

It was a theropod and it could grow up to 12m long. Although it was not as large as the largest carnivorous dinosaur Tyrannosaurus, it was just as vicious. Allosaurus was armed with enormous jaws, full of sharp, jagged teeth. It also had curved claws and a powerful tail to lash out at any animal brave enough to attack it.

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Name: Allosaurus, meaning ‘different lizard’

Size: about 12m long

Food: meat, especially other dinosaurs

Lived: about 150 million years ago in the Late Jurassic in North America, and possibly Portugal and Tanzania

Allosaurus is a familiar animal, with its massive hind legs, its strong S-shaped neck, its huge head with jaws that could bulge sideways to bolt down great chunks of meat; sharp, serrated, steak-knife teeth with 5cm-long crowns, and its short, heavy arms with three-fingered hands bearing ripping claws that were up to 15cm long. This enormous carnivore would have hunted the biggest herbivores of the time, including the massive sauropods, the remains of which were found in the Cleveland-Lloyd quarry.

If a tall man could have stood on another’s shoulders when Allosaurus was alive, he would have been at just the right height to peer into its mouth. He would have seen rows of about 70 saw-edged teeth. All its teeth curved backwards, perfect for biting the flesh of its prey and preventing it from escaping. If any of its teeth fell out or were wrenched out in a fight, each was replaced by a new one that quickly grew to fill in the gap.

Scientists think that Allosaurus moved at about 8km/h. A jogger could have just about kept up with it as it strode along on its back legs like an enormous bird. Experts can also tell from fossil footprints that each step Allosaurus took was as long as a car.

The four toes on both feet ended in sharp, bird-like claws. Three of them pointed forwards and one backwards. Each claw was strong and sharp enough to tear open the soft underside of any other dinosaur. Allosaurus also had a claw on each of the three fingers of both hands. It used them to attack and hold onto prey.

Allosaurus probably held up its long, powerful tail when walking or running, to balance the weight of its body. Its tail had about 50 bones in it and was useful for lashing out at a rival during the mating season – when male fought male for the attentions of a female. Small, carnivorous dinosaurs which attacked Allosaurus’ young were probably seen off one mighty sweep of the tail.

Allosaurus was so large that it must have needed a considerable amount of meat to fill its ever-hungry stomach. It preyed on the herbivorous dinosaurs that lived in the same area.

Allosaurus’ toothmarks have been found on the tail bones of Apatosaurus, a North American herbivore. Some of the really huge herbivores, such as Diplodocus, were far too large for Allosaurus to attack on its own, so Allosaurus may have grouped together and hunted in packs.

Several members of the Allosaurus pack charged in to attack, biting and clawing at defenceless Diplodocus until it slumped to the ground to be ripped apart by the rest of the pack. Allosaurus would have had no hesitation in attacking the young of these large dinosaurs.

Catching fresh meat was a hit and miss business, so Allosaurus probably also fed on the leftovers of animals killed by other carnivores. This is called scavenging.

Allosaurus fossils have been found at sites in Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah and Wyoming, USA.


 

Gallimimus June 15, 2011

Filed under: Theropoda — muzillu @ 2:03 pm

With a short, light body and long back legs, Gallimimus was a fast-running dinosaur. It took very long strides and could outrun most predators. It looked like a large ostrich with its long neck and toothless beak. Its stiff tail helped it to balance when running.

The ornithomimid featured in the film Jurassic Park was Gallimimus. It was a fairly good representation, except that it is now thought that these animals were covered in feathers, which would make sense if they were to be as active as they were portrayed in the film. There are skeletons of juveniles that have allowed scientists to study the growth pattern of ornithomimids in general.

Factbox

Name: Gallimimus, meaning ‘chicken mimic’

Size: 6m long and 3m high

Food: plants, eggs, insects and lizards

Lived: about 70 million years ago in the Cretaceous Period in Mongolia

Gallimimus is the largest known type of ornithomimid, but it has shorter arms in proportion to the other species. The hands, too, are quite small and the fingers are not very flexible. The head is quite long and graceful and, as in nearly all ornithomimids, the jaws have no teeth. The beak of the lower jaw is shovel-shaped, and the big eyes are situated on the sides of the head, so it did not have binocular vision.

Like the other ostrich mimics and modern birds, Gallimimus had hollow bones. This device allowed for a reduction of weight in the body, without reducing the strength, and enabled the animal to move quickly. The main difference between the two known Gallimimus species is the shape of the fingers. G. mongoliensis had shorter hands and would not have grasped as well.

Gallimimus had short arms with three claws on its hands. The claws were sharp, but Gallimimus could not grasp things very well and did not eat meat because it could not tear it up.

Gallimimus’ claws came in very useful, however, because it used them to scrape away at the soil to dig up eggs for food. It ate mostly plants, but it also fed on small insects, which it grabbed in its beak, and even chased lizards.