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Hot-blooded/Cold-blooded Debate

Hot-Blooded or Cold-Blooded?. Evidence presented on this site pertains to dinosaur physiology. After a quick review of what has transpired in the last few decades, the reader is asked to form an opinion on what dinosaurs were like. Were they sluggish and stupid as the old conventional wisdom said, or were they mammal or bird-like as in Jurassic Park? Or can we even be sure what they were like? After a few preliminary warnings and some definitions, links take the reader to evidence for and against endothermic or ectothermic dinosaurs. A third link takes the reader to a review of current hypotheses.

In the early 1970s, Robert T. Bakker drew on the work of anatomist Gerhard Heilmann and paleontologist John Ostrom and argued that dinosaurs were not slow moving, but rather warm-blooded, active, and mobile. He also argued that dinosaurs are the direct ancestors of birds, a theory that received further support with new discoveries in the 1990s.

Dinosaur - History Of Eggs

Dinosaurs are extinct (apart from their descendants the birds) and their eggs are represented today as fossils, in particular trace fossils. Trace fossils of dinosaurs are marks or indicators preserved in the rocks left by the particular vertebrate at a particular time. Other trace fossils include. They represent that product of egg laying activity and can offer clues to how dinosaurs behaved.

The eastern half of North America has produced few dinosaur fossils. In the 1980s, Paul E. Olsen studied the East Coast from Nova Scotia to New Jersey. He discovered the remains of several new Triassic dinosaurs. Olsen also found evidence of a large asteroid impact near the end of the Triassic, which may have killed other animals and allowed dinosaurs to rise to dominance.

The dinosaur eggs went through a series of major events to become known to us today as fossils. After being laid, the egg was buried by a fine covering of sediment (maybe sand). This protected it from predation and scavenging and sealed it from the air (in particular oxygen) which would break it down and destroy the egg. Ground waters flowing through the sediment go through the egg and minerals precipitate from the solution into the egg.The original shell material is actually little altered during fossilization as it is made up of the mineral calcite which is stable (resistant to change) during the fossilization process, although it may be recrystallised. This outer shell is hard and made up of a series of interlocking units, a mosaic of plates, with pores which allow the passage of air in and out of the egg. This allows the baby to breathe.

The inside is not preserved during fossilization (apart from some rare dinosaur babies).However,there are some clues to what the inside of the eggs looked like. By looking at the nearest living relatives of dinosaurs today, such as the birds and crocodiles, we can estimate to what the inside of dinosaur eggs looked like.Housed inside the egg is a thick or viscous liquid which bathes the embryo and keeps it moist, preventing it from drying out. This allows the egg to be laid on land and is a feature of animals called amniotes - all reptiles, birds and mammals. Amniotes can live on land due to this amniotic membrane, whereas amphibians do not have this ability and are restricted to the water to lay eggs.

Dinosaur eggs have been known for thousands of years, although at first they were not recognized as 'dinosaur eggs' and were used for jewellery and shaping ornaments. Many eggshells were found in late Palaeolithic or early Neolithic sites in Mongolia.The first real discovery of dinosaur eggshell was in 1859 from southern France, by Jean Jacques Pouech. The French eggs were thought to belong to giant birds at first, because of their large size. More complete eggs were found in 1869 by Matheron. He thought these eggs belonged to a giant crocodile. In 1877 Paul Gervais (1816-79) published the first detailed study of the eggs, and suggested that they could belong to a dinosaur. They are now known to have been laid by the sauropod dinosaur Hypselosaurus.In 1923 the Central Asiatic Expeditions of the American Museum of Natural History made significant new discoveries in the Gobi Desert, Mongolia. Roy Chapman Andrews found the first recognized dinosaur nests. The eggs were thought at that time to belong to Protoceratops but are now known to belong to Oviraptor.

Protoceratops andrewsi was discovered in Mongolia in 1922 by an expedition from the American Museum of Natural History led by Roy Chapman Andrews. Its genus name means "first-horned face," and its species name was in honor of the expedition's leader. Protoceratops is one of the most celebrated dinosaurs of the 20th century. Workers also discovered the skeleton of a nimble toothless predator that was later named Oviraptor philoceratops, which means "egg-stealer, lover of ceratopsians." In the Gobi Desert were parents, nests, eggs, hatchlings, and egg stealers all in one amazing deposit. This was the first discovery of dinosaur eggs, and the discovery made news everywhere.

Protoceratops may be the ancestor of all horned dinosaurs. Because of this evolutionary link, and because of all the fossils found, it has been the subject of much study. Like all ceratopsians, Protoceratops was from the Late Cretaceous, but it was older than most of its relatives.

Protoceratops was a small, compact dinosaur, only six feet long as an adult and two feet tall at the hips. It weighed less than 400 pounds. Hatchlings were only a foot long, and the eggs were eight inches long and seven inches around. Although small as adults, Protoceratops had a sturdy build. The front legs were nearly as long as the back, so it could carry its heavy head and jaws. Its toes had claws that it used to dig in low vegetation for leaves and twigs. Its heavy tail balanced the animal when it walked.

It had a parrotlike beak that was rounded and toothless. The rear of the skull was expanded into great ridges of bone where the jaw muscles attached. The bony frill was small and simple in Protoceratops but became large and elaborate in some of its giant relatives. The sides of the frill were open, which lightened the skull without losing strength. The frill extended well past the neck joint. For a small dinosaur, the head and jaws were enormous. Because of this weight, the animal needed to walk on all four limbs so it could support its head when it walked.

Protoceratops had a powerful bite; it cropped low vegetation with its beak. Behind its beak, it had dozens of teeth that chopped the tough leaves and branches into smaller pieces, perhaps in a chewing motion. Food collected in its fleshy cheeks on the sides of the jaws. Along with low-growing shrubs and trees, Protoceratops may also have eaten the newly evolving angiosperms (flowering plants) that appeared in the Late Cretaceous.

Protoceratops did not have horns on its face or a shield like those found on its relative Triceratops. Protoceratops did have a slight bump on the snout below the eyes. It may have been the beginning of a horn. The bump was larger on males, which also had larger frills. Males may have used these features to attract females. With the discovery of so many skeletons, scientists concluded that Protoceratops lived in herds.

A surprise for paleontologists was the discovery that these dinosaurs lived in the desert. The eggs were laid in shallow holes in the sand. Also, the small pores and the pattern on the shells show that the eggs were adapted for desert conditions. In the 1920s, scientists thought that all dinosaurs lived in swamps and forests.

Relatives of Protoceratops included Montanaceratops and Leptoceratops from North America, and Bagaceratops and Microceratops from Asia. All are from the Late Cretaceous and are quite similar to their more famous cousin. There may have been land connections between the northern continents in the Late Cretaceous that allowed these small ceratopsians to migrate.

Another group of primitive ceratopsians, the psittacosaurs, also had a beak and lived earlier than Protoceratops and its relatives. Psittacosaurus was also found in Mongolia by the Andrews expedition. The psittacosaurs may have been the ancestors of Protoceratops.