AboutDavid Prus Expertise I can answer any general questions about dinosaurs and on prehistoric mammals in the Cenozoic. I also know a bit about the media's various depictions of dinosaurs and their inaccuracies. I don't know much about "microfauna"-small animals, or about Paleozoic besides some knowledge about Permian animals. Plants are right out, I'm afraid.
Experience I have been interested in dinosaurs for most of my life, own a large collection of scientific papers and books on the subject, and am a member of the Field Museum in Chicago.
Education/Credentials I am in college, but studied biology and geology both in high school and as a personal effort.
Expert: David Prus Date: 12/2/2007 Subject: dinosaura
Question 1. did long neck sauropods live in deep water and use their necks as snorkles? What scientist is famous for this explanation?
2.how is the esophagus of a long necked dinosaur diffrent then humans?
3. what dinosaurs travled in heards? what advantage did this give them?
4. what is ment by scientists when they say they favor "the graudal mode of extinction theory?
5.describe the natural defences a plant must have to be able to survive the large plant eater dinosaurs?
6. what is ment by the statment "dinosaurs invented flowering plants."
7. describe 5 mass extinctions in earth history? tell when they happened and what life perished and survived. ive a possible scientific explanation for each one.
8. What is signifigant about "rayed craters"
9.describe the heart of a brachiosaurus?
10 what were mammals like at the time of dinosaurs? Explain
11. what evedience do scientists have that indicate that dinosaurs were ectothermic. 5 reasons please/
these questions come from ny report and i cant find them anywhere. Can you please answer as many as you can?
Answer 1. The Sauropod snorkel hypothesis was first postulated by Richard Owen in 1840, based on vertebra. Both Othniel C. Marsh and Edward D. Cope, while initially supporting a terrestrial hypothesis, came to the conclusion that the
massive weight of the sauropods forced them to be aquatic. In 1951, Kermak pointed out that the water pressure would have asphyxiated the sauropod's lungs. Robert Bakker later cemented this when he identified the sauropod's compact feet and narrow teeth as adaptations for life on land. (Read Dinosauria by Colbert)
2. The sheer size of sauropod throats meant that they would have to take continuous deep breaths in order to get enough oxygen. (David Gillette once found a gastrolith stuck in a sauropod's throat and surmised that the animal choked to death on the stone)
3.Footprint evidence has shown evidence for sauropod and Iguanodont herding, while masses of hadrosaur and ceratopsian skeletons suggest it for them as well. This meant their young could be protected, and it acted as a good defense against predators (watch a school of fish under attack and notice how their numbers make things hard for predators)
4.The gradual mode theory means that through climactic change (and its effects on vegetables), dinosaurs slowly became extinct over a number of millions of years. Their evidence consists of the fact that the number of dinosaur species slowly shrunk over the last half of the Cretaceous.
5. Plants adapted by many ways. Some, like Cycads, grew spines in their leaves. Others became poisonous. Flowers used simple fast breeding to survive the dinosaurs.
6. It means cooevolution. As sauropods and stegosaurs ate their way through trees, this promoted low-growing plants. The iguanodonts and nodosaurs moved into this new niche, specializing in eating low growth. The solution to this onslaught was flowers (angiosperms), which could breed quickly and spread easily. That way, no matter how many flowers were scythed by a Iguanodon, there were always more.
7. There have been seven mass extinction-
488 mya-Cambrian extinction: Lowering temperatures and glaciation deplete oxygen and wipe out 50% of life-casualties include the first order of trilobites and early reef-building inverterbrates
444 mya-Cambrian/Orodvician-Another ice age cuts brachiopods, bryozoans, trilobite, conodont and graptolite families by 50%.
360 mya-Devonian/Carboniferous-The oxygen produced by the first plants cools down the earth, creating another ice age. The aformentioned groups are all hit hard, and all placoderm fish are wiped out.
251 mya-Permian/Triassic-Scientists still argue whether it was meteorite impact, volacanism, dropping of oxygen levels, or a combination that did it, but 75% of species go extinct. Most sea-living groups get 99%, and Graptolites, blastoids, trilobites, and sea scorpions go the full 100%. On land, anapsid and synapsid reptiles take heavy losses.
200 mya-Triassic/Jurassic-The cause is still a mystery, but most crurotarians (crocodiles and such)are wiped out, along with almost all giant amphibians. 50% of all species die.
65 mya- Cretaceous/Tertiary-A probable combination of asteroid impact and climate change kill off most mollusks (including ammonites), the last pterosaurs, all nonavian dinosaurs, toothed birds, the Laurasian mammals, and most of the large sea reptiles.
NOW-Holocene-Ice ages and humans wipe out most megafauna and thousands of species from all orders around the world are dying out today.
8. Rayed craters are formed by high-speed impacts. The rays are from pulverized material shot out by the impact.
9. Sauropods had huge chests to contain their huge hearts. Their ventricles were 15 times denser than most whales. The heart itself was four-chambered, as shown by the fossil of a Thescelosaurus ("Willow").
10. Mammals were small but diverse. By the Cretaceous period they had already diversified into the egg-laying monotremes, pouched marsupials, multituberculates, and placentals. The first mammals appeared in the end of the Triassic. In Cretaceous China, the first gliding, swimming, rodentlike, termite-eating, and badger-like mammals appeared.
11. Reason #1: Growth rates-Dinosaurs grew extremely fast. A Tyrannosaur could reach a ton in ten years.
#2: Haversian canals. These tubes are found in the bones of warm-blooded animals like birds and mammals
#3: Posture:Dinosaur skeletons can only be reconstructed in an erect posture. Erect posture is associated with active lifestyles.
#4: Feathers: Dinosaurs with preserved feathers have been found, along with dinosaur-bird transitional forms.
#5. Cardiovascular systems: The preserved fossil heart of a Thescelosaur ornithopod has been found. Its size and structure indicate a muscular, active physiology. It has four chambers like a bird or mammal (crocodiles also have four chambered hearts, but are smaller and the fourth is "turned off" underwater)
