Dinosaurs

There are a couple problems with your question seeing as swimming dinosaurs didn't exist, and I'm not sure what you mean by gigantic world, but I will do my best to answer it. The largest aquatic reptile from the time of the dinosaurs was a carnivirous pliosaur 15m long. It is unamed. The largest ocean going creature at the time was Leedsichthys, a massive fish 27m long.

Brontosaurus/Apatosaurus was 40 feet or 12 meters tall,in terms of how long they were they were about 90 or 27 meters and possibly much larger in length,and in weight they were about 40 tons or more

The largest known pterosaur was quetzalcoatlus, with a 40 foot wingspan. However, while these flying reptiles live in the dinosaur time they were not dinosaurs. The true flying dinosaurs are birds. The largest flying bird known to have existed was Argentavis, which had a wingspan over 20 feet.

The dinosaurs first appeared on this earth around 230 million years ago and showed their existence for complete 160 million years.The dinosaurs existed in Triassic, Jurassic and Cretaceous period. The end of Triassic period witnessed mass extinction; about 95% species disappeared from this earth and with this went the early dinosaurs.

The Jurassic period lasted for 30 million years where reptiles were the dominant figures and so this age is known as The age Of Dinosaurs.

There are many theories as to how the dinosaurs became extinct but there is no absolute proven theory. Lets take a look at some.

Large asteroid or comet collided with Earth about 65 million years ago. Scientists think that such a large collision would throw so much dust into the air that sunlight would not be able to shine and plants and animals would die.

A huge increase in volcanic activity at around 65 millions years ago could have pumped so much ash into the air that it blocked out the sun killing the dinosaurs.

Some scientists believe that there was a severe ice age. The last one ended about 10,000 years ago. A very severe ice age could have changed temperatures and frozen a lot of Earth's water. The dinosaurs would not be able live under such conditions and that is how the dinosaurs became extinct.

It has also been suggested that desease killed off the dinosaurs. A very deadly and contagious desease may have circulated among the dinosaurs forcing them to become extinct.

Another theory is that the Earth just gradually changed in climate over a long time period and the dinosaurs were not able to adapt to the cooler, dryer climate.

There is now widespread evidence that a meteorite impact was at least the partial cause for this extinction. Impact craters are visible on most planets in our solar system.

Blue Whales are the largest known living animal species on earth. Animals that were as large as 27 meters in length (nearly 90 feet) and weighing over 170 tonnes have been recorded. Since these animals were measured and weighed after they were cut up into manageable pieces, the actual size and weight could be even more

0.02 million is the same as 20,000.

Well, it was an awful long time between the extinction of the dinosaours (about 65 million years ago) until "we" showed up - about 50 thousand years ago. So I think you'd be safe to say their extinction didn't have any effect on us, per se.. However, whatever caused their extinction did lead to the emergence of other types of animals on the planet, mammals being one of them, who may not have prospered so well had they all been eaten by dinosaurs. Despite what some people might think, 'mankind' and 'dinosaurs' never walked the earth together. Except for crocodiles, and perhaps, sharks - they've been around A Long Time, and may be the only surviving link to the age of Reptiles.

Dinosaurs were gone from the earth long, long before man came. No human being has ever seen a dinosaur. Fossil remains do not preserve skin color and for the most part do not preserve anything at all like skin. So the color of dinosaurs is only guesswork; no one knows.

Rickety -- if it's a baby dinosaur

Dinosaurs have dominated earth for 150 million years ago. This is the reason why they are so successful.

plant eaters like triceratops ate vegetation while meat eaters like T-rex ate other dinos.

Diplodocus was up to 27 metres (90 feet) long and weighed 25 tons. Its close cousin Seismosaurus was more than twice as big.

Not bigger than mine

There are several theories for why dinosaurs died out. One is that large meteors struck the earth, causing extensive damage and also causing the sky to be full of ash. While the sky was full of ash, there was no visible sun, so many plants died off, causing a chain-reaction in the food chain.

Using fossils and geographical clues, paleontologists have determined with some certainty that a meteor, not a volcano killed the dinosaurs. Although dinosaurs died out, some birds survived and today's birds are the direct descendants of the dinosaurs.

It is believed that dinosaurs came before bats.

since the very first day GOD created the heavens and earth. there were two of each animal in the garden of eden. (the first day of everything we know).

Answer2:

The above answer is the religious answer. For scientific minded people the answer would be 65 million years ago. Horses evolved from small fox sized multi-toed forest browsers. As the forests gave way to grasslands the toes slowly began to change and morph into one hoof per leg and the horse became taller to see over the long grasses and to flee from predators. The horse also developed an elongated skull with eyes placed more to the side for better vision while grazing on the long tough grasses.

Velociraptors were closely related to birds. Among other traits, both Velociraptors and birds have feathers. The proof is that the forearm bones of Velociraptor show quill knobs, which are attachment points for ligaments that hold feathers in place.

Pterodactylus was a relatively small carnivore, having a wingspan of only 5 feet. It probably ate small land animals, such as lizards, amphibians, and primitive mammals, as well as fish and insects.

Estimates of the size of the meteorite that hit near modern day Chicxulub in the Yucatan Peninsula, Mexico 65 million years ago causing the extinction of the dinosaurs range from 10 to 20 km in diameter. The Chicxulub crater left behind by the meteorite is 180 km wide.

No. If you count birds as dinosaurs, they still exist. If you don't, dinosaurs became extinct at the end of the Cretaceous, not the beginning.

a footprint.

to be honest no buddy knows that's what leads to the simple formula that species appear and disappear over time for example dinosaurs like...

velociraptor

dromaeosaurus

styracosaurus

albertosaurus

gorgorosaurus

iguanodon

pachyrhinosaurus

parasaurolophus

maiasaura

saltasaurus

pteranodon (which i count as a dinosaur)

all lived in the late cretaceous which began 78 mya the same time as they evolved though some like pteranodon and iguanodon evolved in the mid cretaceous 127 mya and since they were around 15 million years before the kt extinction they must have become extinct during that disaster but they actually become extinct not 65 but 70 mya 5 million years before extinction (At least as far as wikipedia goes) and no one knows and and another good example is the terror bird titanis which was said to become extinct 10,000 years ago when humans were taking over the world and wiped out the ice age megafauna like the mammoth, sabretooth, and titanis but it become extinct 2 mya and still no buddy knows

another example is the fact that tyrannosaurus rex became extinct 65 mya but what if it was 64 mya or 65.5 or perhaps as late as 28 or who knows maybe they're still here todays but in places in which no one has ever been to yet, so you see the cause for the extinction of allosaurus is unknown not even climate change can explain it since it's a predator that can eat just about anything so to be honest again i for one don't know