Dinosaur Facts

Some basic dino facts, selected for you by a professional geologist. With links to sites on other fossil groups, evolution and stratigraphy.

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Dinosaur Facts

The basics, fact and fiction?

Were dinosaurs cold-blooded, like the modern reptiles in the zoo and therefore not very energetic, moving very little? Were they clumsy and awkward? Were some are so heavy that, once fallen, they could not even get up again? Did they have tiny brains and if they did were they therefore extremely stupid. Did they need vast amounts of food to keep their gigantic bodies going? Were any fast enough to catch smaller animals for food? Was their extinction due to a lack of success in adapting?

The concept of them being large unwieldy creatures is largely a relict of the image of them portrayed in the 19th and early 20th centuries.

The real dinosaur story, however, is very different from the story this largely Victorian image which was largely perpetuated by the mass media. Thus, in these days of immense media coverage we should always be careful to distinguish between what palaeontologists believe to be correct and the exaggerations and distortions often generated to sell the stories in the media. Having said this, we have been very fortunate recently in that the BBC produced a populist series on Dinosaurs which was produced in close co-operation with palaeontologists who work with dinosaurs and which is, by general consensus, an immensely successful series both for the specialists and non-specialists alike.

We must also consider that even palaeontologists have differing opinions, but we should not confuse this scientific debate with say the difference between a palaeontologist and a journalist putting his 'spin' on a subject, nor the difference between the genuine palaeontologist and creationists who invariably preferentially select data and then dogmatically restate the information as fact. Neither the journalist nor the creationist can be described as scientists when they misreport data to benefit themselves.

Another problem with palaeontology is that what is written in one book can easily be copied into another without the review of the latest data; thus, if a book is out of date or simply wrong on certain matters, many others may be too. Palaeontologists are trained to recognise such errors. In addition, one individual professional palaeontologist will not know everything about his subject especially as we are still discovering new dinosaurs, finding out more about the old ones, and conceiving new ideas about the way these creatures lived and behaved all of the time.

As mainly the bones of dinosaurs, their eggs and traces (footprints etc) are found, with fossil dinosaur skin and other soft tissue parts being very rarely discovered, many of the most recent reconstructions of their appearance and lifestyle are no more than intelligent guesses. There is nothing wrong with this process and there are modern analogies especially among modern reptiles that can be used in the reconstruction of dinosaurs. However, when doing so it must be remembered that no one actually knows what colour the dinosaurs were, how the dinosaurs sounded, how they behaved, how they mated, or even how to tell whether a fossil is definitely a male or a female. The best reconstructions, similar to those made in the BBC series 'Walking with Dinosaurs' are a 'best guess' of what they were actually like.

Another misconception regarding dinosaurs is that all of the large creatures mentioned in the palaeoenvironmental reconstructions of the time were all dinosaurs; they were not. Dinosaurs, in such reconstructions include not only the familiar Diplodocus and Tyrannosaurus, Brontosaurus and Stegosaurus, but the marine plesiosaurs and mososaurs, the winged pterodactyls, and even the woolly mammoths which lived millions of years after the dinosaurs became extinct. Old Hollywood films even had us fighting with live dinosaurs, and this myth was recreated more recently with the use of cloning in Jurassic Park; a further example of media distorting scientific fact for their own benefit.

Dinosaurs are only one group, albeit a very special one, of prehistoric reptiles that we can call a class or a family; but within that family there are many different dinosaur genera and species. Dinosaurs were one of several groups of prehistoric reptiles that lived during the Mesozoic Era, the "Age of Reptiles."

Most importantly, all dinosaurs lived on land, although some may have ventured into swamps and lakes. None (discovered to date?) lived in the sea, and none took to the air (although the birds are considered by many as the descendants of the dinosaurs).

Dinosaurs actually managed to exhibit a very high degree diversity, adapting to many of the most diverse terrestrial habitats such as deserts, jungles and cold climates. They varied greatly in size, from the largest dinosaurs known like Argentinosaurus, Seismosaurus, and Brachiosaurus, all plant eating dinosaurs (up to 30 m long and up to 15 m tall, and as large as twenty large elephants) to the smallest which were the size of a modern chicken, weighing only a few thousand grammes. Most dinosaurs were in-between in size. Some ran around on their hind legs, but others stayed on all fours. Some could do both. Some ate only plants, others ate meat, some undoubtedly did both. Some were speedy, and some were slow and lumbering. Some were armour-plated, some had horns, crests, spikes, or frills. Some had thick, bumpy skin, and some even had primitive feathers.

The dinosaurs dominated the Earth for over 165 million years during the Mesozoic Era, but became extinct 65 million years ago. As they were the dominant life on land for over 100 million years and as they managed to exhibit such diversity, inhabiting many of the major palaeoecological niches that say modern mammals do, they can hardly be described as an unsuccessful group.

None of the different sorts, of course, lasted for the whole of their 140-million-year history. The dinosaurs, like everything else in the living world, were constantly changing; and the dinosaurs of approximately 200 million years ago, when they first evolved, were mostly very different from the last of their descendants, whose reign came to a sudden end about 65 million years before the present. Each period during the Age of Dinosaurs had its own characteristic 'collection' of these remarkable animals.

When considering dinosaur facts the discussions above must be taken into account and thus the conclusions of any study must be considered as having a different degree of accuracy, depending on the source of the data. For, example reconstructions of their skeletons based on actual recovered bones may be highly accurate, as may reconstructions of their environment based on the other fossils present in the rocks, but when it comes to their colour, or the sound they made it comes down to intelligent guesswork based mainly on modern analogies.

Reconstructions, such as the flying models of pterodactyls have been particularly useful as such models may provide feedback into the reconstruction of the skeletons, as if a certain hypothesis would mean that the pterodactyls could not fly then it would most probably be incorrect.

General facts

· Dinosaurs were reptiles and most hatched from eggs. There are about 1,300 described dinosaur types. Most dinosaurs were plant-eaters (herbivores), like Triceratops.

Dinosaurs names: Like other fossils, are generally named after a characteristic body feature, after the place where they were found, or after a person involved in the discovery. Usually the name consists of two Greek or Latin words (or combinations), for example, the Greek and Latin combination (binomen) Tyrannosaurus rex means "king of the tyrant lizards."

Dinosaur world: When the dinosaurs lived, the Earth's continents were jammed together into a supercontinent called Pangaea and the Earth was warmer than it is now.

Hot or cold blooded: Originally dinosaurs were considered likely to be cold blooded like modern lizards, but then the discovery that many dinosaurs probably walked upright and that many dinosaurs appear to have been adapted to running, not crawling, led many palaeontologists to the conclusion that they were warm-blooded. Dinosaurs were neither "warm-blooded" (endothermic) like modern mammals, nor "cold-blooded" (ectothermic) like modern lizards. Today, most specialists believe dinosaurs probably relied on a combination of both mechanisms for thermoregulation that some call "dinosaur-blooded." New unofficial terms, such as metathermic and gigantathermic have been proposed for this condition in Mesozoic dinosaurs.

Dinosaur tails: Most dinosaurs had long tails, but they held these tails straight out and off the ground for help in maintaining their balance, rather than dragging them along the ground as had been previously thought. Contrary to the traditional image of dinosaurs as sluggish, slow-moving beasts, many of them were swift-moving creatures with relatively high metabolic rates.

The first dinosaur: Mammals and dinosaurs both made their appearance in the Upper Triassic Period (about 225 million years ago). Mammals remained small and insignificant throughout the Mesozoic, while Dinosaurs ruled the Earth. But contrary to popular belief, dinosaurs were not totally dominant as they represented less than 10% of the 40 groups of reptiles from the Mesozoic Era.

· Thecodonts, Crocodile-like Archosaurs and meat-eaters from the Triassic period may have been ancestors of the dinosaurs. Thecodonts (like Chasmatosaurus) were socket-toothed reptiles that were the ancestors of dinosaurs, birds, pterosaurs, and crocodilians. These archosauriforms were low-slung, meat-eating quadrupeds had long jaws and a long tail (they looked a lot like crocodiles).

· The first dinosaurs were small and lightly built, mostly about 10-15 feet long (3 to 4.5 m). They were bipedal carnivores or omnivores, and probably very agile and fast.

· There are several contenders for first dinosaur thatl come from Argentina, in rocks that date back 225 million years, and include Eoraptor a small predator measuring about 1 metre in length, together with several larger predators and a herbivore.

· The world's oldest-known dinosaurs have been found on Madagascar, an island off the coast of SE Africa. These dinosaur fossils date from about 230 million years ago during the Triassic period.

The most recent dinosaurs: Are found in rocks that date from just before the extinction layer 66 million years ago. Again there is no single youngest dinosaur, because dinosaurs tend to be found in 'communities' of animals rather than just isolated animals. These communities include dinosaurs such as Triceratops, and Tyrannosaurus.

Dinosaur lifespan: Animal lifespans relate in part to their body size and in part to their type of metabolism. Dinosaur lifespans probably varied in length from tens of years to hundreds of years. Their possible maximum age can be estimated from the maximum lifespans of modern reptiles, such as the 66-year lifespan of the common alligator.

Dinosaur eating habits: Examples of distinctive eating habits among some dinosaurs (theropods) which lack teeth and had a bird-like beak and it is thought that these animals were rather similar to ostriches today and that they therefore may have had a similar diet, eating insects and lizards as well as fruit, seeds and leaves. Some dinosaurs ate lizards, turtles, eggs, or early mammals. Some hunted other dinosaurs or scavenged dead animals (these were omnivores, eating both meat and plants). Most, however, ate plants (but not grass, which hadn't evolved yet). Rocks that contains dinosaur bones also contain fossil pollen and spores that indicate hundreds to thousands of types of plants existed during the Mesozoic Era. Many of these plants had edible leaves, including evergreen conifers (pine trees, redwoods, and their relatives), ferns, mosses, horsetail rushes, cycads, ginkos, and in the latter part of the dinosaur age flowering (fruiting) plants. Although the exact time of origin for flowering plants is still uncertain, the last of the dinosaurs certainly had fruit available to eat .

Male & female dinosaurs: In general it is difficult to tell male and female dinosaurs apart as most of the parts of the body which indicate the sex of an animal are soft and fleshy and therefore do not preserve as fossils. In rare cases it may be possible to tell the sex of a dinosaur by anatomical markers such as the crests on the heads of duck-billed dinosaurs in North America, are large or small although of the same shape. He suggested that since these dinosaurs lived together at the same time and in the same place that they were actually male and female of the same species.

Dinosaur extinction: It is widely believed that all dinosaurs died out at the same time, apparently quite suddenly at the end of the Cretaceous Period about 65 million years ago. But of the approximately 350 known Mesozoic dinosaurs, only 10 to 20 species faced the final extinction in North America at the end of the Cretaceous. The demise of the doinsaurs may therefore have already begun in the latest Cretaceous.

· The exact cause of this extinction has puzzled scientists for decades. One theory suggested that mountain building activity so changed the environment and climate that it destroyed the lowland habitat of the dinosaurs. A related theory is that large scale volcanic activity, possibly in India caused a massive change in the climate of the world which caused the extinction. The "asteroid impact theory" of dinosaur extinction, caused by raising a huge dust cloud that lowered global temperatures, has also gained popularity. While most palaeontologists are willing to accept that an asteroid struck the Earth about this time, they do not agree that it was the only cause of the Mesozoic extinction.

· Whatever the cause, the massive extinction of many species, in addition to the dinosaurs, marks the beginning of the Cenozoic Era and the Age of Mammals. For whatever reason, mammals survived this extinction, and thereafter, filled many of the eco-niches left by the dinosaurs and other extinct species

Their early life

Dinosaur eggs: Fossil eggs have been found from only a few species of dinosaurs.but it is likely that all dinosaurs reproduced by laying eggs. Baby dinosaurs grew very quickly and, in some cases, increased in size as much as 16,000 times before reaching adulthood.

Care of their young: There is evidence that some hatchlings were cared for by their parents. The fossils of many plant-eating dinosaurs have been discovered in herds made up of both adults and young, indicating to some researchers that dinosaurs were maternal.

Dinosaur colonies: The discovery in 1978 of 14 dinosaur nests in a Montana excavation helped convince paleontologists that dinosaurs built vast colonies in order to better care for their young, much as today's penguins do. Living in groups may have also helped some dinosaurs defend against predators. It is also possible that some carnivore dinosaurs hunted in packs, and that together they could kill larger prey than a single animal could on its own.

Dinosaur embryos: For the first time, palaeontologists have recently found fossilized embryos of dinosaurs so well preserved that their delicate skin has survived in mineralized form, providing a glimpse of reptilian scales, in patterns bearing a family resemblance to the skin of modem-day lizards. The embryonic dinosaur skin was one of several important discoveries made by a fossil-hunting expedition working in the parched northern Patagonian badlands of Argentina. Everywhere the palaeontologists looked over an area more than a mile square they saw fossilised eggs, whole or in scatterings of shell, lying on the surface or buried to depths of 16 feet. They could hardly take a step without crushing eggshell fragments. The preliminary analysis by geologists indicated that the egg clusters were laid in the flood plain of ancient streams that sometimes overflowed, burying the unhatched eggs in layers of mud that protected them from scavengers and decay. The eggs were about six inches in diameter, and each one would have had the volume of a dozen chicken eggs. Some of them, were quite close to hatching. The baby dinosaurs would have started life a mere 15 inches long and grown to an adult size of up to 45 feet long.

Their size

Dinosaur size and their environment: Paleontologists don't know for certain, but perhaps a large body size protected them from most predators, helped to regulate internal body temperature, or let them reach new sources of food (some probably browsed treetops, as giraffes do today). No modern animals except whales are even close in size to the largest dinosaurs; therefore, paleontologists think that the dinosaurs' world was much different from the world today and that climate and food supplies must have been favorable for reaching great size.

Biggest and heaviest dinosaur: must also have had the largest muscles and this would have been most likely to have been the heaviest that walked on land. At present the largest known dinosaur is probably Seismosaurus from New Mexico in the United States of America. Evidence suggests it was certainly the longest of the known sauropod dinosaurs, measuring about 36 metres from head to tail. However, large and strong does not mean fit and strong in terms of winning a fight and other dinosaurs such as Tyrannosaurus may have specialised in this type of strength. Some of the biggest dinosaurs:

Argentinosaurus huinculensis - 115-130 feet long (35-40? m); 80-100 metric tons

Paralititan 35-40 m) - 70 tonnes

Seismosaurus hallorum ("Earth-shaking lizard") - 120+ feet long (37 m); 30-80 tons

Supersaurus vivianae - 100-130 feet long (30-40 m); 45-55 metric tons

Ultrasauros - 100+ feet long (30 m), +80 tons (this may be a large Brachiosaurus)

Andesaurus delgadoi 130? feet (40 m)

Bruhathkayosaurus matleyi 130? feet (40 m?)

Argyrosaurus superbus 65-130? feet (20-40 m)

Giraffatitan brancai 75-100? feet (23-30 m)

Diplodocus - grew up to 90 feet long (28 m).

Brachiosaurus - about 85 feet long (26 m), 40 feet tall, and weighed 70-80 tons.

Tallest dinosaur: was probably Sauroposeidon which was a gigantic giraffe-shaped brachiosaur, whose head may have been held 15-20 metres above the ground.

Sauroposeidon(Wedel, Cifelli & Sanders vide Franklin, 2000), a newly-found brachiosaurid from Oklahoma, +60 tons, 60 feet tall.

Ultrasaurus (Jensen vide Olshevsky, 1991) - 100+ feet long (30 m), +80 tons

Brachiosaurus (Riggs, 1903) - about 85 feet long (26 m), 40 feet tall, and weighed 70-80 tons.

Dinosaur size: The really large sauropod dinosaurs may have had extremely large bodies, but we now know that at the same time their bodies were lightened by having hollow bones. The bones of the spine are deeply pitted or honeycombed with holes in order to save weight, and rather like birds many of these holes may have had air cavities in them. In this way the really big dinosaurs may actually have been lighter than they might seem. For example Seismosaurus probably weighed little more than 50 tonnes at the very most.

Smallest dinosaur: The smallest dinosaurs, just slightly larger than a chicken;

A new, crow-sized theropod, Microraptor was recently found in China. It is about 16 inches (40 cm long) and may be an adult.

Compsognathus, a theropod (meat-eater) 2 feet (60 cm) long, from 145 million years ago. It was the size of a chicken and weighed about 6.5 pounds (3 kg).

Saltopus - a 2 feet (60 cm) long insectivore (insect-eater) from about 200 million years ago.

Lesothosaurus - a 3 feet (90 cm) long, fast running, plant-eater from Africa, 200 million years ago.

Wannanosaurus - a 39 inches (1 m) pachycephalosaur, a plant-eater from China, 83-73 million years ago.

Other characteristics

Dinosaur speed: Estimates of dinosaur speeds vary because several different methods are used to calculate them. The two basic approaches for estimating dinosaur speed are comparing to recorded speeds of modern animals of similar body size and build, and measuring distances between fossil footprints in a trackway and using these distances to calculate estimated speed. Walking-speed estimates for medium-sized bipedal (two-legged) dinosaurs vary from 4 kph to 6 kph, and peak running-speed estimates vary from 35 kph to 85 kph. The highest figure is the same as the peak speed of the currently fastest land animals.

Fastest dinosaur: Those dinosaurs combining a light body with very long legs and slender toes, features seen in the most fleet-footed of living creatures, would have enabled these dinosaurs to make long strides and move across the ground extremely quickly. One of the largest and therefore longest striding of these dinosaurs was Gallimimus from Mongolia and this may well have been one of the fastest of all dinosaurs and may well have been able to cruise for sustained periods of time at anywhere between 40 and 60 kph.

Fierce dinosaurs: The tyrannosaurs certainly look the most fierce of all dinosaurs, but in terms of overall cunning, determination and their array of vicious weapons it was the dromaeosaurs that were probably the most fierce of all. Utahraptor a recently discovered dromaeosaur measured about 8 metres from head to tail and had very long arms, with wickedly hooked talons for claws to grasp its prey; a large head and sharp, curved teeth, a long balancing tail for running swiftly to pursue its prey, and powerful legs on the end of which were huge sickle-shaped retractable talons. These dinosaurs were very powerful, highly agile and intelligent predators, nothing would have evaded them, and if they hunted in packs then they may even have been able to bring down large sauropodomorphs. Some of the biggest carnivores:

Giganotosaurus carolinii - found in Patagonia, Argentina. 47 feet long (14 m), 8 tons in weight, and 12 feet tall (4 m).

Tyrannosaurus rex - found in North America - 40-50 feet long (12-15 m), 6 tons in weight. Spinosaurus - found in Africa - 40-50 feet long (12-15 m).

Carcharodontosaurus saharicus - (meaning shark-toothed lizard) found in in Morocco, Africa, by Paul Sereno. It was probably about 45 feet long and had 5 inch long teeth. Its skull (5 feet 4 inches) is larger than T. rex's, but it had a tiny brain cavity (half the size of T. rex's).

Dinosaur skin: Is preserved in a number of species, and in general terms, the skin seems to have been rather similar to that of modem reptiles, covered in many instances in very small overlapping scales. In some cases the scales may be quite large and separated from one another, so that the skin is tough yet flexible. In the most extreme examples the armoured dinosaurs or ankylosaurs, the skin consists of large plates of bone studded with spikes, which are welded together to form a solid sheet in some instances.

Dinosaur Intelligence: It is impossible to say precisely how intelligent dinosaurs were and like many other groups the intelligence of each species may have been related to the niche it inhabited. It is now thought that the majority of dinosaurs had the brain power expected of an average reptile, neither overly bright, nor particularly stupid. This observation even applies to the supposedly very stupid dinosaurs such as Stegosaurus with its walnut sized brain. There are however some dinosaurs, particularly the smaller, highly active predators, which seem to have brains that are larger than might be expected, such as the dromaeosaurs (Velociraptor, Deinonychus). One of the few possible measures of intelligence might be a large brain in a small body. The genus that perhaps fits this description best was the Cretaceous bird-like dinosaur Troodon, which also may have had binocular vision (depth perception) and excellent eyesight and was built for speed. This implies quite high intelligence, which may well fit with the way of life of a resourceful and active predator. Even so, some palaeontologists think that this dinosaur was probably not as "intelligent" as most modern birds and mammals.

Dinosaur communication: Dinosaurs had large eyes and good hearing, so they were certainly capable of seeing and hearing one another. However we can tell a little more than this because some dinosaurs had very distinctive horns or crests on their heads. Animals today use features like this as signalling devices. Dinosaurs with horns, such as the ceratopians (Triceratops, Chasmosaurus, Styracosaurus) no doubt used their horns and frills for signalling and for fighting. Other dinosaurs, particularly the duck-billed dinosaurs, give us other clues. One duck-billed dinosaur named Parasaurolophus has an extraordinarily long, curved, tubular crest on top of its head which could possibly have acted as a resonator so that the animal could have made a trombone-like bellow in life.So dinosaurs probably communicated both vocally and visually. Defensive posturing, courtship behavior, and territory fights probably involved both vocal and visual displays. An angry Triceratops bull shaking his head at you, even silently, would have made himself very clearly understood!

Dinosaur Bone Disorders: A few examples of dinosaurs with bone disorders, similar to severe arthritis have been discovered (Iguanodon); this leaves a very distinctive pitting and knobbling on the surface of bones. Other examples of pitting on the frill of some ceratopian dinosaurs looks suspiciously similar to forms of bone cancer. Beyond these very obvious forms of illness, which leave traces on the surface of, or within, bones relatively little is known about dinosaur illness. Sick animals would have been picked off by predators and scavengers, so few traces of them would be expected to survive. There are examples of dinosaurs known which have clearly been injured (broken hip bones and spines on the backbone) and recovered but these are very much the exception.

T. rex: Debates between palaeontologists continue even with some of the most famous dinosaurs such as Tyrannosaurus. Was it a hunter or a scavenger? There is no clear distinction between hunting and scavenging. It is therefore very probably that T. rex was both a hunter and a scavenger. It had a very powerful build, and with its long legs it could easily have chased prey for short distance sprints to overpower them and eat them, it may well have been a lurking predator pouncing on its victims in a short dash, equally it would have scavenged other kills if it was hungry. However, it also had very short and relatively useless arms and even though recent discoveries of new skeletons of T. rex have revealed that the arm, although quite short, was powerful and had two large vicious claws on the end. It has been suggested that they were used as grapples so that T. rex could hold on to its prey very firmly while biting large chunks of flesh off. Most arms are used for reaching things with as well as for grasping, clearly in T. rex the arms had developed a very specific grasping function and had abandoned any reaching function at all. In any fight therefore T. rex would have had to use its jaws and tail as its main weapons. It is certainly possible that the tail could have been used to help push animals over in the midst of a fight, but this was not its main function. The tail was most important as a counterweight to the front part of its body, so that it was balanced on its back legs when running and standing.

How many are known:: Approximately 1300 types have been named. A recent scientific review suggests that many of these are based on fairly complete specimens that can be shown to be unique and separate species. These species are placed in about 300 valid dinosaur genera (Stegosaurus, Diplodocus, etc.), although about 540 have been named. Recent estimates suggest that about 700 to 900 more dinosaur genera may remain to be discovered. Most dinosaur genera presently contain only one species (for example, Deinonychus) but some have more (for example, Iguanodon). Even if all of the roughly 700 published species are valid, their number is still less than one-tenth the number of currently known living bird species, less than one-fifth the number of currently known mammal species, and less than one-third the number of currently known spider species.

Dinosaurs and Birds

Their recognition: In 1868, Thomas Henry Huxley interpreted the Archaeopteryx fossil to be a transitional bird having many reptilian features. Using the fossils of Archaeopteryx and Compsognathus, a bird-sized and bird-like dinosaur, Huxley argued that birds and reptiles were descended from common ancestors. Decades later, Huxley's ideas fell out of favor, only to be reconsidered over a century later (after much research and ado) in the 1970's. In 1986, J. A. Gauthier looked at over 100 characteristics of birds and dinosaurs and showed that birds belonged to the clade of coelurosaurian dinosaurs. [Gauthier, J.A., 1986. Saurischian monophyly and the origin of birds, in The Origin of Birds and the Evolution of Flight, California Academ of Sciences Memoir No. 8]  

Evolution of dinosaurs: Birds probably evolved from the maniraptors, a branch of bird-like dinosaurs . This idea has been hotly debated for over a hundred years. New fossil evidence is reinforcing this theory, which is now accepted by most scientists. In order to determine what animals birds evolved from, scientists use fossil evidence to trace the emergence of bird-like traits. Many Mesozoic Era bird-like creatures have been found, some which are clearly dinosaurs. There are many similarities between birds and theropod dinosaurs, including the number of openings in the skull (they're diapsids), secondary palate structure, leg and foot structure and proportions, upright stance, oviparous birth (laying eggs), bone structure (bones interlaced with vessels), and scales (modified in birds and some dinosaurs to be feathers). Recently, scientists have reorganized the groups in which many animals have been classified using a system called cladistics. Since birds are descended from dinosaurs, they are in the same group, dinosauria.

· In the last few years, many fossils of feathered dinosaurs have been found near Yianxin, in Liaoning Province, China. Two new Chinese feathered dinosaurs dating from between 145 and 125 million years ago (during the late Jurassic and early Cretaceous periods) have been found, Protarchaeopteryx robusta and Caudipteryx zoui. Their features are more dinosaur-like than bird-like, and they are considered to be theropod dinosaurs. Their feathers were symmetrical, which indicate that they could not fly (flightless birds have symmetrical feathers while those that fly have asymmetrical ones). These finds, along with the feathered dinosaur Sinosauropteryx, found a few years ago, also in the same region of China, and the bird-like Unenlagia in Argentina, reinforce the theory that birds are descended from dinosaurs.

· Archaeopteryx is one of the most famous and oldest-known fossil birds, and dates from the late Jurassic period (about 150 million years ago). It is now extinct. Although it had feathers and could fly, it had similarities to dinosaurs, including its teeth, skull, and certain bone structures. Some paleontologists think that Archaeopteryx was a dead-end in evolution and that the maniraptors led to the birds. The first Archaeopteryx fossilized feather impression was found in 1860 in a limestone quarry in Germany. A year later, a much more complete fossilized Archaeopteryx was found at the same quarry. Impressions of its feathers and bone structure were quite clear. Many more have been found since, for a total of seven.


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