Sauropedia

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

Apatosaurus June 28, 2011

Filed under: Sauropoda — muzillu @ 2:16 pm

Apatosaurus, also known by the popular but scientifically redundant synonym Brontosaurus, was a sturdy beast. It had a long, whiplash tail, which had about 80 bones in it.

Apatosaurus was a huge, quadrupedal sauropod, as long as a tennis court. It fed on leaves that it snipped from plants and trees with its weak, peg-like teeth. Its very long neck, which had 15 huge bones in it, was held up by strong muscles that ran along the neck bones.

Factbox

Name: Apatosaurus, meaning ‘deceptive reptile’

Size: 21-25m long and 5.8m high

Food: leaves and shoots of trees and shrubs

Lived: about 150 million years ago in the Late Jurassic Period in North America

Apatosaurus is a heavily built diplodocid. The vertebrae have a groove along the top. This held a strong ligament that supported the weight of the neck and the tail, like the cables on a suspension bridge. The ‘deceptive lizard’ of the name refers to the fact that the chevron bones attached to the vertebrae look confusingly like those of the aquatic reptile Mosasaurus. Although the head is about the size of that of a horse, the brain is only as big as that of a cat. The whole skeleton is similar to that of Diplodocus, but is much more stocky and massive, going for weight rather than length.

Apatosaurus had an extremely long tail, almost half of which was thin and whiplike. It probably used its tail to lash out at the hungry carnivores that preyed on the weakest members of the herd, such as the young and the very old dinosaurs. Recent computer modelling suggested that sauropods such as Apatosaurus were capable of producing a whiplike cracking sound of over 200 decibels with their tails, comparable to the volume of a cannon.

To support its great weight, Apatosaurus’ pillar-like legs ended in broad feet, rather like those of an elephant. Its front feet had a claw on the inside toe, which it used to kick out at attackers.

One of the most popular dinosaurs, Apatosaurus, keeps changing its identity. For almost a century it went by the evocative name Brontosaurus, the ‘thunder lizard’. In 1877 Othniel Charles Marsh discovered A. ajax and named it. Two years later he found a more complete animal which he named Brontosaurus excelsus. It was not until the twentieth century that it was realized that these were actually two species of the same genus. When there is confusion of this kind, with one animal given two names, it is the first name given that is deemed to be the valid one, in this case Apatosaurus. The official change took place in 1903. The length of time taken for Marsh’s misclassification to be brought to public notice meant that the latter name, associated as it was with one of the largest dinosaurs, became so famous that it persisted long after the name had officially been abandoned in scientific use.

 

Stegoceras June 27, 2011

Filed under: Pachycephalosauria — muzillu @ 4:34 pm

An adult male Stegoceras would have fought fiercely with another for control of the herd. Although quite small, Stegoceras was a tough creature. A bipedal herbivore, Stegoceras was a member of an unusual group, the pachycephalosaurs (‘thick-headed reptiles’).

This is the best known of the pachycephalosaurids, with dozens of skull fragments known and also a partial skeleton. The structure of the bone in the head dome was such that the bone fibres aligned to absorb impact from the top. The vertebrae of the neck and back were very strong, lashed together with strong tendons that prevented twisting, and aligned to absorb shocks emanating from the head end. The hips were particularly wide and solid. All this is consistent with the idea that the dome was used as a weapon, like a battering ram.

 

 

Factbox

Name: Stegoceras, meaning ‘roof horn’

Size: 2.5-3m long and 1.5m high

Food: plants and ferns

Lived: 75 million years ago in the Late Cretaceous Period in North America

Pachycephalosaurs had one special feature in common – a thick, rounded skull. On Stegoceras’ head was a semicircle of small bony lumps. These bumps ran above its eyes and around the back of its neck. Experts are not certain what the lumps were for, but they could have been used in flank-butting, a widely evidenced theory. The skull was not very thick when Stegoceras was born, but it became thicker as the dinosaur got older.

Some experts believe that they have discovered examples of both male and female Stegoceras. They have found that some skulls are thicker than others and believe that these thick skulls may have belonged to the males. A male Stegoceras could have a skull up to 6cm thick – which is half as thick as a brick.

It was initially proposed that male Stegoceras (and individuals of other pachycephalosaur species) would ram each other headlong, not unlike contemporary bighorn sheep or musk oxen. It was later suggested that they engaged in flank-butting rather than ramming, a theory for which there is a great deal of evidence. Foremost, the rounded shape of the skull roof would lessen the contacted surface area during headbutting, resulting in glancing blows. Second, pachycephalosaurs would not have been able to align their head, neck and body in a perfect horizontal line (which would be needed to transmit stress) – it was more likely that they carried their neck in an S- or U-shaped curve (this to a lesser extent in Stegoceras, due to their thick neck muscles). Lastly, the relatively large width of most pachycephalosaurs would have served to protect vital organs from harm during flank-butting.

For most of the time, Stegoceras was a peaceful herbivore. It moved through the Late Cretaceous vegetation, pulling leaves and flowers from trees and low-lying plants with its beaked mouth. Its teeth were sharp and serrated like a saw. Stegoceras used them to shred leaves and plants, rather like modern goats.

The dome on the head of Stegoceras is high, but not as high as that of others in the group, and is surrounded by a frill of little horns and knobs. The teeth at the front of the jaw are very widely set and the muzzle is broad compared with other pachycephalosaurids. This may indicate a less selective feeding strategy. The very broad hips suggest that the pachycephalosaurids gave birth to live young (this is not widely accepted).

 

Huayangosaurus

Filed under: Thyreophora — muzillu @ 3:36 pm

This primitive stegosaurid is known from complete adult skeletons found in the Dashanpu quarries, China, in the early 1980s. It was re-described in 1992. The arrangement of teeth, and the fact that its front legs are long for a stegosaurid put it so far from later stegosaurids that it is placed in a family of its own.

Factbox

Name: Huayangosaurus, meaning ‘lizard from Huayang’

Size: about 4m long and 1.5m high

Food: soft, juicy plants

Lived: 162-148 million years ago in the Middle Jurassic in China

Huayangosaurus has a double row of heart-shaped plates on the neck that are replaced by long, narrow, spine-like plates on the back. They become smaller on the tail, ending about half-way down. The tip of the tail is furnished with two pairs of spines. It had extra spikes on its shoulders, which would have been very off-putting to a predator. The skull has teeth at the front of the mouth – something that was lost in later stegosaurids – and there is a pair of horns near the eyes.

This stegosaur had many primitive features. For example, its skull had a small opening in front of each eye, and there was another small opening in each half of the lower jaw. Both of these openings closed off in later stegosaurs. At the front of its snout, Huayangosaurus had 14 teeth (seven on each side). Later stegosaurs did not have these teeth. Huayangosaurus had long front limbs three-quarters longer than the back limbs. Later stegosaurs had forelimbs that were much shorter. Finally, the armour plates that ran in two rows along the back of Huayangosaurus were more narrow and much thicker than the plates on the backs of its later relatives. All these features are clues to the stegosaurs’ place in the dinosaur family tree.

Huayangosaurus lived in a land of lakes, rivers, and lush vegetation. By looking at its teeth, scientists can tell it was a herbivore. Its spiky, upstanding armour plates and shoulder spines could have protected it from predators, but they could also have been for show, perhaps to attract a mate. They may also have been used to regulate its body temperature. The plates seem too thick, however, to have been very good for this. Certainly, the animal’s tail spikes would have kept its enemies away.

 

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.

 

Factbox

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.

 

 

Maiasaura June 21, 2011

Filed under: Ornithopoda — muzillu @ 11:17 pm

Maiasaura was named ‘good mother lizard’ because scientists believe it cared for its young after they hatched.

This hadrosaurine is known from a nesting colony found in Montana in the 1970s. It lived in big herds and nested in groups, with possibly as many as 10,000 returning to the same area every year. They probably did so for protection. More than 200 skeletons, embryos, hatchlings, immature and mature adults were found.

 

Factbox

Name: Maiasaura, meaning ‘good mother lizard’

Size: about 9m long and 3m high

Food: plants, leaves, fruit and seeds

Lived: between about 90-66 million years ago in the Late Cretaceous in Montana, USA

Maiasaura was a large dinosaur, about as long as a double-decker bus. It usually walked on its long back legs and had a big, flat tail which it held out straight. When feeding on the ground it may have rested on its front legs then reared up on its back legs to reach the leaves of trees. The crest is a short, broad projection above the eyes, and is solid, distinguishing it from the hollow-crested lambeosaurines. The crest, and a pair of triangular projections on the cheekbones, form the basis for the definition of the Maiasaurini. They have batteries of self-sharpening teeth, and a jaw mechanism that allowed the surfaces to grind past each other to chew up tough vegetation.

The nests were hollows, scooped out of muddy ground, and were about the size of a big, round dining room table. The parents may have lined the nest with soft plants, before the female laid between 18 and 30 hard-shelled eggs in it.

Scientists think that Maiasaura mothers, and perhaps fathers as well, guarded the eggs in the nest, protecting them from any dinosaur that tried to steal them. The mothers may have sat on the eggs to keep them warm, going off to feed while other adults watched over them.

When the offspring hatched, the parents looked after them and brought them food. The young dinosaurs ate all sorts of plants as well as fruit and seeds. Maiasaura parents may have chewed up tough plants before giving them to the babies. Experts believe that parents fed the young until they were old enough to leave the nest and find their own food.

Before these offspring were found, scientists thought that female dinosaurs left their offspring to hatch out and take care of themselves alone.

So many nests with skeletons and pieces of eggshell have been found in one place in the USA that some palaeontologists have suggested huge herds of Maiasaura lived in North America. They roamed through the forests, but returned to the same nesting site each year. They probably used the same nests again and again. When the young had grown enough to look after themselves, they stayed with the herd. Eventually, the herd moved on in search of fresh plants to eat.

With no way of defending itself, Maiasaura probably escaped from the big carnivorous dinosaurs by running away and hiding in thick forests. It probably had good eyesight and hearing, which warned it of danger. If Maiasaura was very frightened, it may have plunged into the lakes or rivers. It swam along by waggling its tail and paddling with its front legs.

When palaeontologists discovered a single fossilised nest of Maiasaura in Montana, USA, they decided to excavate the site further. The following year, they returned to their dig and found so many nests, packed closely together, that they named the place ‘Egg Mountain’.

 

 

Tenontosaurus June 20, 2011

Filed under: Ornithopoda — muzillu @ 3:47 pm

Tenontosaurus was a bulky, powerful herbivore that weighed about the same as a large car and was about the same size as a double-decker bus. It had long, powerful limbs and a parrot-like beaked mouth.

Judging by the number of remains that have been found, including 25 skeletons and scattered bones and teeth, Tenontosaurus must have been one of the most abundant herbivores in early Cretaceous North America. It was certainly attractive to carnivores – one skeleton has been found surrounded by the bodies of several Deinonychus that had been killed while attacking it.

Factbox

Name: Tenontosaurus, meaning ‘tendon lizard’

Size: 6.5m long

Food: plants

Lived: 110 million years ago in the Middle Cretaceous Period in North America

Tenontosaurus is like a hypsilophodontid but lacks the teeth on the front part of its jaw. Otherwise it is like an iguanodontid, but the classification is still not clear. Its distinctive feature is its very long tail – longer than the rest of the body – and the network of tendons that support the spine. Its long forelimbs and strong finger bones suggest that it walked on all fours for most of the time.

A bulky dinosaur, Tenontosaurus could walk on all fours or pick its way across the landscape on its hind legs. At the end of its front limbs were stocky hands with five fingers on each. Tenontosaurus balanced on the four long toes on each back foot when it stretched into the treetops for a mouthful of leaves or twigs. When it ran, it gripped the ground with its toes, and raised its long, wide tail to balance the weight of its heavy chest and bulging stomach.

Tenontosaurus’ beak had no teeth, but it had ridged teeth running along the side of its beaked mouth. It used these to chew leaves it nipped off trees. When it was attacked, it would lash out with its tail.

 

Hylaeosaurus

Filed under: Thyreophora — muzillu @ 1:10 pm

Hylaeosaurus is the most obscure of the three animals used by Sir Richard Owen to first the new group Dinosauria, in 1842. The first Hylaeosaurus remains to be found were dug up by Gideon Mantell in 1832.

Gideon Mantell originally estimated that Hylaeosaurus was about 7.6 m long, or about half the size of the other two original dinosaurs, Iguanodon and Megalosaurus. Modern estimates range up to 6 metres in length.

Factbox

Name: Hylaeosaurus, meaning ‘woodland reptile’

Size: 4m long

Food: plants

Lived: about 130 million years ago in the Early Cretaceous Period in southern England

The fossils are entombed in a slab of limestone that can still be seen in London’s British Museum. Perhaps out of respect for the first generation of palaeontologists, no one has taken the trouble to actually prepare the fossil specimen, which seems to have been left by a dinosaur closely related to Polacanthus.

Only the front part of the dinosaur was found. Palaeontologists had to guess how the legs and body armour looked, but they are pretty certain that it looked like a long lizard with a cloak of sharply spiked armour running from its neck right down to the tip of its tail.

Hylaeosaurus was a slow-moving herbivore that nibbled ferns and other green plants for its food. If it was attacked, Hylaeosaurus was protected by its heavy armour and intimidating spikes.

It was a fairly typical nodosaur, with three long spines on its shoulder, two at the hips, and three rows of armour running down its back. It may also have had a row of plates down its tail. It had a long head, more like the head of a Nodosaurus than an Ankylosaurus and a beak, which it probably used to crop low-lying vegetation.