About 299 million years ago, almost the entire landmass of the earth was joined into one supercontinent called Pangea apart from one small landmass called Cathaysia, the tectonic plates of North and South China. This was not the first time that all landmasses had joined into a mega continent, though it was the most recent. Pangaea was surrounded by one great ocean called Panthalassa.
A singularly massive landmass in the middle of so much water had very different climactic conditions than we can know. Pangaea’s geography was dominated by warm, Polar Regions with lush forests; the ocean was so distant from vast interiors of the supercontinent that it created extensive deserts and scrubland.
Still, many species of animals, insects and plants flourished on Pangaea, including the ancestors of mammals. But then came large-scale destruction: the Permian-Triassic boundary came to be defined by one of the worst mass extinction events in the history of the planet, which wiped out 96% of the world’s animal population. Life on Earth took some time to recover. However, the resulting environmental conditions of the period lack opened up some evolutionary opportunities for the species that had survived. The early Triassic period witnessed the rise of archosaurs, a group of reptiles whose only surviving descendents are birds and crocodiles.
Pangaea started breaking up in the late Triassic Period around 200 million years ago and the landmasses started moving towards their current continental positions. The disintegration was gradual and it created ideal ecosystems for the dinosaurs. The break-up resulted in rift valleys, which brought the ocean into the depths of the continent. The vast deserts were inundated with shallow waters, which moisturised the climate and gave rise to green vegetation.
The river valleys produced the most vegetation and attracted most of the life forms, including dinosaurs. Seasonal rainfall created new forests of fern trees with edible undergrowth at some places, while forests of primitive conifers and cypresses bloomed in other regions. By the Cretaceous, all the continents had broken away fully; they were beginning to look like what they do today and were floating towards their modern positions. Now, there were many different land areas subject to varied climactic conditions; the flora and fauna were distributed all over the earth where they further evolved separately. Hence animals, including dinosaurs and plants grew as different species on every continent.
Many of the present-day swamps and river deltas were being created along the stretches of Cretaceous coastlines. The produced the best habitats for fish-eating dinosaurs like the recently discovered Spinosaurs, who lived between 112 and 97 million years ago in North Africa. The desert wastelands had not disappeared they just became redistributed over some continents. Although deserts still had little to eat, it was enough for a variety of species to survive in the dry conditions including many dinosaurs.
Not all dinosaurs lived at the same time. The Brachiosaurus lived in the late Jurassic Period between 155.7 and 150.8 million years ago, while the Velociraptor roamed in the Cretaceous between 85 and 80 million years ago. Though Archaeopteryx and Pterodactyls, both winged reptiles, glided in European skies their lifetimes were around 80 million years apart. The former lived around 150 million years ago to the latter’s late Cretaceous origins. However, two of the most famous dinosaurs, Tyrannosaurus Rex and Triceratops did coexist in North America; while it does raise tantalising speculations about mega battles between the two there is no evidence of it yet, though T. Rex did prey on weaker and younger members of the three-horned species.
Palaeontologists have divided dinosaurs into Ornithischia (bird-hipped) and Saurischia (lizard-hipped). Surprisingly, Ornithischian dinosaurs were non-avian and birds actually evolved from the lizard-hipped variety. In any case, dinosaurs have been further classified into 500 different genera and more than 1000 species of non-avian dinosaurs. Dinosaurs were herbivores or carnivores, though some were omnivores. Though dinosaurs were ancestrally bipedal, quadruped species evolved later and some could even shift between the two walking styles.
Some of the common features of all dinosaurs are horns, crests on their necks, scales over the body. Some dinosaurs developed spines and bony armour. Many dinosaurs grew to sizes of gigantic proportions; the largest sauropod (lizard-footed) was the largest land animal; it was measured at 39.7 metres long and 18 metres tall (180 feet by 59 feet). But there were also small dinosaurs; Xixianykus was only 50 cm. long while the smallest known avian dinosaur was the bee hummingbird with a length of only 5 cm.
People have discovered dinosaur fossils for thousands of years. The fossils may have inspired the ogre and griffin myths of the Greeks and Romans and the dragon legends of China. Over 2000 years ago, a Chinese by the name of Chang Qu documented ‘dragon’ bones found in the Sichuan province. Tales of the Thunder Bird told by the Plains Indians of North America were probably inspired by discovery of the ‘winged lizard’. The first recorded find in modern history was of a huge thigh bone found in England, which was sent to Robert Plot, curator of the Ashmolean Museum, who initially thought it belonged to a giant human like that mentioned in the bible.
However, the geological and biological significance of fossils has been noted and speculated upon from the times of Aristotle and other Greek philosophers. In 1027, Persian naturalist Ibn Sana proposed an explanation for the stoniness of fossils. Around the same time, the Chinese Shen Kuo found petrified bamboos at a place not conducive to the growth; he argued for a theory of climate change. However, it was only in the seventeenth century that scholars of natural history began to see fossils as remnants of extinct animals. But this was a time when naturalists would not accept the concept of ‘extinction’ for religious and philosophical reasons.
The emerging discipline of palaeontology got a boost in 1796, when George Cuvier compared African and Indian elephants with fossils of mammoths and mastodons using comparative anatomy. He not only established that African and Indian elephants were of different species, but that mammoths and mastodons were different from both the former and from each other. Thus, the latter two species had to be extinct. Though it came later in the 19th century, Charles Darwin’s Origin of Species changed all perceptions in the life sciences.
The first dinosaur to be described in a scientific journal was the Megalosaurus, which was found in England in the 1820s and named by the clergyman William Buckland who was also a fossil collector.
Shortly after, were found fossils of Iguanodon (so-named because of its iguana-like, but larger teeth) and Hylaeosaurus or ‘woodland lizard’. By the 1840s Sir Richard Owen had examined the bones of all three fossils. He determined that they all lived on land, had similarities and were larger than any living reptile. They also had their legs directly beneath their bodies unlike modern reptiles, whose legs span out to the sides. They also had three more vertebrae in their hips than known reptiles. He came to the conclusion that these were a special group of reptiles and classified them as Dinosauria from the Greek ‘deinos’ meaning terrible and ‘sauros’, which translates to lizard. However, dinosaurs are not lizards but a different clade of reptiles.
The Bone Wars
The Natural History Museum, London, founded by Sir Richard, with the backing of Prince Albert, husband of Queen Victoria, became the first to exhibit dinosaurs. In 1858, William Parker Foulke discovered the first identifiable dinosaur, Hadrosaurus Foulkii in a marlstone quarry in New Jersey. It was one of the first almost complete dinosaur skeletons and the animal was bipedal. All the previously documented dinosaurs had been quadrupeds, like all lizards. It sparked off the first dinosaur craze in the United States.
Though many Americans scrambled to make new dinosaur discoveries, Edward Drinker Cope and Othniel Charles Marsh developed a rivalry that came to be known as the Bone Wars. Cope was funded by the U.S. Geological survey, while Marsh headed the Peabody Museum of Natural History. The feud took the forms of public attacks in scientific journals and both palaeontologists resorted to bribery, sabotage and theft.
The Bone Wars lasted for 30 years and ended with the death of Cope in 1897. Both palaeontologists were financially ruined by their attempts to disgrace one another. The Bone Wars had a negative impact on American paleontology for decades. Their often haphazard descriptions and bone-reconstructions led to misconceptions that lasted for decades. But they left behind a rich treasure trove of fossils; their work later came to represent outstanding contributions to the field of paleontology.
Before the Bone Wars, there were only 9 known species of dinosaurs in North America. Cope discovered 56 new species while Marsh introduced 86. Most of these species are the best-known dinosaurs in the world, including Triceratops, Allosaurus, Stegosaurus, Diplodocus, Coelophysis and Camarasaurus. Marsh was one of the first palaeontologists to argue that birds are descendents of dinosaurs, a view which is the common scientific consensus today. Cope’s collection is displayed at the American Museum of Natural History, while Marsh’s dinosaurs are exhibited at the Peabody Museum of Natural History.
Today, dinosaurs are exhibited in both conventional museums and theme parks, which are also outdoor museums. The Crystal Palace Dinosaurs in London, which opened in 1854, was the first of its kind in the world. It displays models representing 15 different genera of extinct dinosaurs, ichthyosaurs, plesiosaurs and other reptiles in Palaeozoic and Mesozoic settings along with some mammals from the Cenozoic Era. Some models are even inaccurate since they represent the paleontology of the time.
Dinosaur exhibits are of two types: Complete skeletal reconstructions or models. The complexity of assembling an entire skeleton is indirectly proportionate to the number of bones recovered. It takes expert knowledge of the anatomy of the animal to position the major bones. Scientists know the missing bones will resemble those of the closest relative of the animal and use them as a guide to fabricate replacements. Sometimes, the bones are too delicate or heavy to be erected, so lightweight replicas are constructed in life-like poses. Where actual bones are used the skeleton may be supported by an inconspicuous steel framework. Life-sized reconstructions of the bigger dinosaurs require two or even three lifting platforms to work in tandem.
Models need a fleshed-out skeleton, whether of real bones or fabricated. Fossilised bones often preserve scars of muscle attachments, which provide clues as to the size, location and density of the required muscle padding. A correct estimate of the animal’s weight is crucial in adding muscle. Palaeontologists can measure skeletal features and correlate them with the corresponding muscle weight in modern species.
The next steps are to add skin, colour and feathers where applicable. Sometimes sediments around the fossil retain skin impressions, which provide glimpses of the animal’s skin texture. Some dinosaurs had scaly skin and armoured exteriors. The bony part of the armour fossilises well. If a significant portion of the skeleton is recovered it can give a pretty accurate picture of the different components of the armour over various parts of the body.
Some dinosaurs also had feathers, which are rarely preserved; however some fossils include features that provide indirect evidence of feathers on the skin. A remarkably well-preserved
fossil was found at Liaoning in China, which had remains of melanosomes, the organelles that make the pigment, which gives colour to the hair, skin and feather. But not all palaeo-artists are that lucky, and have to imitate the colours of living creatures or use their imagination.
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