Sauropedia

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

Barosaurus May 18, 2011

Filed under: Sauropoda — muzillu @ 11:49 am

Huge and long-necked, Barosaurus also had a lengthy tail which it wielded as a weapon against enemies. It lived in herds, which was also useful for defence against predators. Like all members of the sauropod group, it had one large, curved claw on the inner toe of its front foot.

This species is known from five partial skeletons from the Morrison Formation, three of them in Dinosaur Natural Monument in Utah, USA. The African species, until recently known as Gigantosaurus, was part of the Tendaguru fauna, and known from four skeletons. The rearing skeleton of Barosaurus in the American Museum of Natural History, at a height of 15m, is the tallest mounted skeleton in the world, only made possible by modern techniques of producing casts of fossil bones in lightweight materials.

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Name: Barosaurus, meaning ‘slow heavy reptile’

Size: up to 27m long

Food: plants and leaves

Lived: about 150-140 million years ago in the Jurassic Period in western North America

The bones in Barosaurus’ long neck were hollow and light, which meant it could lift its head to feed quite easily. If its neck bones had been solid, it would have been too heavy to lift. Barosaurus is very much like Diplodocus – indeed the limb bones are indistinguishable between the two genera – but its tail bones are shorter and its neck bones at least one-third longer, one of which is 1m long. The two genera were in fact about the same size overall. It was longer than Apatosaurus, but its skeleton was less robust.

The way that Barosaurus and the other diplodocids were balanced at the hips suggested that they could rear up on their hind legs for feeding or for scaring off predators.

Barosaurus was once thought to have held its head like a giraffe. In order to pump blood up to the brain – a height of around 12m, 10m above the heart – the heart would have had to have weighed about 1.5 tonnes. The larger a heart, the slower it beats. A 1.5 tonne heart would beat so slowly that the blood would run back down the neck before the next beat. In fact, the length of the neck has led some palaeontologists to suggest that there were several hearts along its length, to enable the blood to reach the brain when it was feeding from high trees.

However, a recent theory was postulated that, like a giraffe, it had arterial valves in its neck. These operate in response to differentials in fluid pressure, allowing the blood to be pumped up the neck but preventing most of it from falling back down. More recent computer modelling of diplodocids like Barosaurus has shown that they probably habitually held their necks more or less horizontally, thus restricting the problem to whether the animal reared up on its hind legs or not.

 

Iguanodon May 17, 2011

Filed under: Ornithopoda — muzillu @ 10:20 pm

One of the first dinosaurs to be found, Iguanodon had strong back legs with three-toed feet and hoof-like nails.

Iguanodon usually walked on all fours but sometimes got about on just its hind legs. It weighed as much as an elephant.

Famed as being one of the first dinosaurs to be scientifically recognized, Iguanodon became something of a wastebasket taxon over the years. It was thought to have been a four-footed, rhinoceros-like animal until complete skeletons were found in a mine in Belgium in the 1880s. Thereafter, it was restored in a kangaroo-like pose. Now it is largely regarded as a four-footed animal once more.

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Name: Iguanodon, meaning ‘iguana tooth’

Size: up to 10m long and 5m high

Food: plants and leaves

Lived: about 120-110 million years ago in the Early Cretaceous Period in Europe, Mongolia, North Africa

Iguanodon is the archetypal ornithopod. Its head is narrow and beaked, with tough, grinding teeth. Its hands consist of three weight-bearing fingers with hooves. It has a massive spike on the first finger used for defence or gathering food, and a prehensile fifth finger that works like a thumb. The hind legs are heavy and the three toes are weight-bearing. The long, deep tail balanced the animal as it walked.

Although Iguanodon was found and named by Mantell in 1825, the description was based only on teeth. In 2000 the International Commission on Zoological Nomenclature ruled the type species to be I. bernissartensis described in 1881, based on complete skeletons from Belgium.

Scientists speculate that Iguanodon probably walked on its toes, like a cat or dog. When chased by a predator, it could run at speeds of 35km/h. Iguanodon’s tail was stiff and flat, and this helped it to keep its balance.

Several skeletons of Iguanodon have been found close together. This is a clue to the fact that they lived in groups or herds. Iguanodon was the second dinosaur to be named (after Megalosaurus), in 1825.

Iguanodon had very strange hands. These had four fingers and a pointed thumb that resembled a spike. Iguanodon could only move this spike from side to side and used it as a weapon to defend itself. Iguanodon was a herbivore and used its fourth finger to hook down branches for food.

Most of Iguanodon’s day was probably spent searching for food and then chewing it up. It had no teeth at the front of its jaws but used its bony beak to bite off leaves. its back teeth were like an iguana’s, but much larger. There were about a hundred of them.

In 1878, in the small town of Bernissart in Belgium, miners working 322m down a shaft struck a mass of fossil bones. They had dug right through the skeleton of an Iguanodon. Finally, the bones of 39 Iguanodon were discovered there, and were put together. The complete skeletons can still be seen in the Royal Institute of Natural Sciences in Belgium.

 

 

Megapnosaurus

Filed under: Theropoda — muzillu @ 10:00 pm

Megapnosaurus (formerly known as Syntarsus) was a small, speedy dinosaur. Some scientists think it might have been covered in feathers.

Megapnosaurus fed on lizards, small mammals and flying insects. It ran quickly on its long back legs, like a huge bird, to chase its prey. It also needed to dart about to escape from large carnivorous dinosaurs.

More than 30 Megapnosaurus skeletons were found in a bonebed in Zimbabwe, suggesting that a pack was overwhelmed by a disaster such as a flash flood. The cololites, or stomach contents, suggest that they preyed on smaller vertebrates. Another species of Megapnosaurus, found in Arizona, has a pair of crests on the head, rather like those of Dilophosaurus but smaller.

 

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Name: Megapnosaurus, meaning ‘big dead lizard’

Size: 2-3m long

Food: lizards, mammals and flying insects

Lived: about 205-195 million years ago in Zimbabwe, Africa, in the Late Triassic Period

The close similarity between Megapnosaurus and Coelophysis has led many to suggest that the two are actually the same genus, with three nimble fingers, a long neck and tail, strong hind legs and a slim body. There seem to have been two sizes of adult – the larger was probably the female and the smaller the male, judging by the size ranges in modern bird flocks. Computer reconstructions of the braincase of Syntarsus show it to be quite large compared with that of the earlier herrerasaurids, indicating an increase in intelligence. A bird-like cunning seems to have been evolving at this time.

On top of its wedge-shaped head was an odd crest. Megapnosaurus could probably turn its head quickly to snatch at its food and to watch for danger. Megapnosaurus had long arms ending in large hands with curved claws. Its tail was long and it held it up level with its body when moving at speed.

Some scientists have suggested that Megapnosaurus had feathers on its head and body. They think that it lifted them away from its body to let the air cool it down during the heat of the day. It could also lower the feathers close to its body to keep in the warmth during the cool evenings and night, using them as insulation. Other palaeontologists argue, however, that there is no proof for this and that Megapnosaurus had no feathers at all.

 

Saurolophus

Filed under: Ornithopoda — muzillu @ 9:30 pm

Despite rows of teeth and its crested head, Saurolophus was unable to defend itself against attack.

Saurolophus is one of the so-called duckbill dinosaurs, known as hadrosaurs. It used its toothless beak to nip off twigs, tough leaves and pine needles, which it ground up between its many rows of teeth.

Confusingly, Saurolophus is only very distantly related to the much more popular Parasaurolophus. The type species S. osborni is known from the remains of at least three individuals. Another species, S. angustirostris, is known from the Gobi desert. Some palaeontologists think it should be the same species as S. osborni, but others think it is a different genus altogether.

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Name: Saurolophus, meaning ‘lizard crest’

Size: 9-12m long and about 3m high

Food: tough plants and leaves, seeds, fruit

Lived: about 80-66 million years ago in western North America and eastern Asia in the Late Cretaceous Period

About as long as a bus, Saurolophus walked on its hind legs, but supported its body on its shorter front legs when feeding. It had no claws on it toes and no way of defending itself directly against carnivorous dinosaurs. However, Saurolophus, like other hadrosaurs, probably relied on keen senses of sight, hearing and smell, as well as their legs, to get out of trouble fast.

Scientists believe that Saurolophus had a pouch of skin on its face. It blew this up like a balloon to send warning signals to the herd or to attract a mate. It may also have used this pouch to increase the noises it made, just as frogs blow out their throats when croaking.

The distinguishing feature of Saurolophus is the prominent spine that rises above the eyes and projects backwards – the uniting feature between the species of Saurolophus is the presence of the backward-pointing spike above the eye. This is formed from the nasal bones that extend backwards and may have been associated with some sound-producing mechanism. The skull is quite narrow for a hadrosaurid, especially across the snout where we would expect to see the duck-like bill. The original species was the most complete to have been found in Canada at the time (1911). The Asian species is much larger.

 

Protoceratops

Filed under: Ceratopsia — muzillu @ 3:50 pm

When scientists found Protoceratops’ nests in the Mongolian desert, it was proof that dinosaurs laid eggs and that some lived in family groups or herds.

There have been dozens of skeletons of Protoceratops found, both adult and juvenile, and so the whole growth pattern is known. It was found by the expeditions to the Gobi Desert undertaken by the American Museum of Natural History in the 1920s. It seems to have lived in herds, and its remains are so abundant that it has been termed the “sheep of the Cretaceous”.

Protoceratops was a small dinosaur, only about the size of a large dog. Although it looked fierce, with its heavy head, sharp, beak-like mouth and large bony frill around its neck, Protoceratops ate only plants. It had a heavy, squat body, with a long, thick tail. Protoceratops walked on its four stumpy legs, but moved quite quickly when in danger.

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Name: Protoceratops, meaning ‘before the horned heads’

Size: 1.8-2.5m long and 1m high

Food: tough leaves and plants

Lived: about 110-66 million years ago in Mongolia in the Late Cretaceous Period

Protoceratops is a heavy animal with short legs, a deep tail and a heavy head. Although a member of the horned dinosaurs, it does not have true horns. Two forms of adult are known, a lightweight form with a low frill, and a heavier form with a big frill and a bump on the snout where a horn would have been. These probably represent the two sexes, with the males having the heavier head.

There was a bony frill or shield around its neck, which grew bigger and broader as the dinosaur grew older. The frill protected the neck of Protoceratops from attack by carnivorous dinosaurs. Males also used their frills for display, to attract females at the beginning of the mating season. Their frills made them look intimidating, which helped to ward off rival males.

Protoceratops had large, strong muscles around its jaws. These helped it bite off tough leaves and woody plants with its hooked beak. It then sliced up the plants with its scissor-like teeth.

In 1922, a scientific expedition to the Gobi Desert in Mongolia unearthed nests of Protoceratops’ eggs. These contained the first dinosaur eggs ever found. The discovery proved for the first time that dinosaurs laid eggs. Until then, no-one knew if they laid eggs or gave birth to live young. As many as thirty eggs were found in one nest. It is unlikely that one female laid so many eggs at once, so scientists speculated that two or more Protoceratops females may have shared the same nest.

Several nests have been found close together. This seems to show that Protoceratops lived in family groups or small herds. Once the eggs had hatched safely, the babies which broke out of the shells were about 30cm long. The adult females brought food to the nests until their young had grown large enough to find it for themselves.

Skeletons of Protoceratops found in Mongolia range from tiny ones still inside the eggs to small babies and fully grown adults. Some of the adults vary slightly. They have differently shaped frills, for example. Scientists have suggested that this is because the males were bigger than the females, with larger heads, frills and crests.

Protoceratops had to guard its nests against predators such as Oviraptor, whose name means ‘egg-stealer’. Dinosaur eggs would have made an ideal meal for it. A fossilised Oviraptor skeleton, with its skull smashed in, was found above a nest of Protoceratops’ eggs. Perhaps an angry parent had killed it when it tried to rob the nest.

 

 

Albertosaurus May 16, 2011

Filed under: Theropoda — muzillu @ 6:10 pm

Small dinosaurs in the forests of North America had to watch out for the frightening form of Albertosaurus.

Albertosaurus was a fierce carnivorous dinosaur related to Tyrannosaurus. Although it was smaller than the latter, Albertosaurus probably ran faster on its long, powerful hind legs. It chased after herbivorous dinosaurs, or may have pounced on them while they grazed.

The earliest dinosaur remains to be found in Alberta, Canada, were Albertosaurus bones. They were found in 1884 by J.B. Tyrrell, after whom the world-famous dinosaur museum in Drumheller was named. It was one of the most abundant predators of the North American Cretaceous plains, and despite its great weight it was probably a fast runner, running down its prey, which would have consisted of duckbills.

 

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Name: Albertosaurus, meaning ‘reptile from Alberta’

Size: 8.5-9m long

Food: meat, especially other dinosaurs

Lived: about 75 million years ago in Cretaceous Period in North America

Albertosaurus is very similar to its later cousin Tyrannosaurus, but is only about half the size. It is much better known as its remains are more numerous. Its skull is heavier, with smaller gaps in it surrounded by thicker struts of bone; the muzzle is longer and lower and also much wider; and the jaw is considerably shallower. The arms, although small, are a little larger than those of Tyrannosaurus.

When Albertosaurus attacked another dinosaur, its victim had little chance of escaping. Bitten and clawed, the victim was quickly overpowered and killed. The rear legs could deliver crushing blows, knocking the prey off balance. It could also deliver deadly wounds with its claws. The light build and long legs show that it was fast and graceful – it may have been able to run at speeds of up to 45km/h.

Albertosaurus had rows of backward-pointing, knife-like teeth in its huge mouth for tearing and chewing up meat. On each of its two feet there were three long, sharp claws and another smaller one. At the end of each of its short arms were two small claws. With these, Albertosaurus could grab and hold onto its prey – dinosaurs such as Edmontosaurus, Lambeosaurus and Chasmosaurus.

 

Lesothosaurus

Filed under: Ornithopoda — muzillu @ 5:53 pm

Lesothosaurus was one of the tiniest dinosaurs that ever lived, and a natural victim for predators.

Lesothosaurus was only about a metre long, which is no bigger than a labrador. This little dinosaur looked very much like a lizard with a long tail. It had a small head with a tough, beak-like mouth which it used to nip off leaves and plants for food. Inside its mouth, along its cheeks, were small teeth shaped like arrowheads. Lesothosaurus used these to chew up the tough and woody parts of plants before swallowing them.

The most primitive ornithischians, such as Lesothosaurus, had not evolved the complex chewing mechanism that was to characterise the later forms. Instead, they would have crushed their food by a simple up-and-down chopping action of the jaws. This is quite an unspecialised feeding method, and these animals may well have eaten carrion or insects as well as plants in order to survive.

 

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Name: Lesothosaurus, meaning ‘reptile from Lesotho’

Size: up to 1m long

Food: low-lying plants

Lived: about 190 million years ago in the Early Jurassic Period in Lesotho, southern Africa

Lesothosaurus is one of the most primitive of the ornithischians, and as such it is difficult to put into a strict classification. It is a small, two-footed herbivore, built for speed. The head, on the end of a flexible neck, is short, triangular in profile, with big eyes. The teeth are arranged in a simple row and, unlike all other ornithopods, the mouth does not seem to have cheeks. The jaw action is one of simple chopping. The snout ends with a horn-covered, vegetation-cropping beak.

Lesothosaurus is very similar to the earlier-discovered Fabrosaurus. However, the Fabrosaurus material is so poor it is impossible to make direct comparisons. If they are the same genus, then the name Fabrosaurus would have to take precedence, being applied first.

Lesothosaurus had a body that was built for speed. It was light and nimble with long, slender back legs. Always on the alert for danger, it could run very fast to escape from carnivorous dinosaurs which tried to capture and kill it.

This dinosaur had no weapons with which to defend itself. However, scientists believe it may have had a way of warning other Lesothosaurus, by a noise or signal, when a predator was on the prowl.