Why were dinosaurs big, was there a reason?

Answer 1

the land masses of the earth were connected at the time, forming pangea. http://geology.com/pangea.htm

anyway, the story goes that, with a large arena for life, you often end up with large animals (of course there were plenty small dinosaurs too). it is proportional. once the land masses began breaking up, the earth began seeing smaller mammals and reptiles due to the shrinking space in which they could compete (in addition to climate change and other environmental factors which the dinosaurs could not evolve to fast enough -- except those that kept their niche (sharks and crocs) or became present day birds)

*edit* weren't dinosaurs warm blooded? most of them? they weren't like lizards warming themselves on rocks, to those who point to a warmer atmosphere.

Answer 2

There may have been several reasons why some dinosaurs were so big (note that the plant-eaters got big first, and the meat-eaters got big presumably so they could kill and eat the big plant-eaters). However, the "surface area" argument that has been presented is completely backward. Larger animals in fact have _smaller_ surface area-to-volume ratios than smaller animals, so they retain heat better. This is why the animals that have a wide geographic range have larger individuals in colder areas.

Answer 3

One theory is because of a much warmer climate and different O2 content than today enabled plants to grow at a much quicker rate. Therby planteaters they have a endless amount of food so over time they become larger and so does the meat eaters that must hunt them. Another theory is because most of the small niches were taken over by small mammals were the dinosaurs could not compete.I`m not sure if they know for sure.

Answer 4

Hey there, how's it going? I like this question. I work at the Natural History Museum in London & as often as I can, I study the systematics & comparitive biology of animals, particularly the Dinosaurs. Not many Palaeontologists have mentioned why Dinosaurs were big, though. The best idea as to why, & possibly the direct answer, was proven in a U.K. University almost a decade ago. It only made a small patch in the newspapers, but a British scientist had placed a collection of plants inside a small green house. The plants, which were placed inside, were those that have been around since the Mesozoic era. Mesozoic is a term used in Palaeontology, which translates as Middle Life. Nowadays, it is known more commonly, as the Age of Reptiles, as it was a time when the dinosaurs evolved & came to dominate the planet. The oldest dinosaurs on record were small. In fact, the oldest on record was found in Madagascar & is still under scrutiny. The fossil is dated at approximately 234 million years old, yet due to the poor condition, scientists are still debating the possibility of the animal being a very ancient dinosaur. Going back to the greenhouse test, the plants were then fed unusually large amounts of Carbon Dioxide (Co2). Plants survive on Co2 & exhale the remnants as Oxygen. However, during the Mesozoic era, particularly during the Jurassic period, 206 - 144 million years ago, the giant supercontinent of Pangaea, was beginning to break up & this would've led to a continuing flux of volcanic eruptions. The heat exhaled by these eruptions, would've led to an increase in global temperatures, which progressively, would've led to the enormous growth of trees. In a nutshell, herbivores will feed on a particular type of plant. The main role of a herbivore, is to control the fluctuation of plants in a surrounding environment. In turn, carnivores of different varieties, will hunt the herbivores to control their numbers. Given that the trees were so large, including the fern prairies also, the herbivores such as Diplodocus, Brachiosaurus, & Camarasaurus for example, would've been the main quality-controllers of those trees & plants. It's a competition to survive. It has even been discovered that some trees will fight one another for space, by trying to grow in a certain area. Those that get sufficient space & sunlight, are usually the ones that survive. Yet, if these ancient trees were not controlled, they would effectively, have cancelled each other out. The largest dinosaur on official records, is Argentinosaurus huinculensis. The skeleton resides in the Great Hall of the Fernbank Museum of Natural History in Atlanta, Georgia, U.S.A. It measures 123 feet from tip to tip & is estimated to have weighed in at over 100 tons. However, many other scientists are quite conservative about the weight, reducing it to merely 50 - 55 tons. When looking at the fossil remains of a dinosaur, a good knowledge of vertebrate anatomy can help piece the skeleton back together, like a jigsaw with no picture. But estimating the weight, is another story altogether. Argentinosaurus may have weighed as much as 75 tons or more. Perhaps it did weigh only 50 tons plus. But as the techniques for determining the weight of an animal continue to modify, it will always be a major question. Also, when looking at the size, you have to try & consider the distribution of the animals' weight. The weight of the head, neck, torso, limbs & tail. The skull of an Argentinosaurus is about the size of a Smart car. The vertebrae themselves are up to 5 feet in height & width & up to 3 feet in length. The weight of Argentinosaurus may have been 100 tons or perhaps less, but in the end, the overall size of the skeleton alone, shows that these animals could grow to an almost unprecedented size. Think of Liopleurodon ferox. Liopleurodon is the largest & most powerful carnivore, ever known to exist. The best specimen is on permanent display in the Natural History Museum in Karlsruhe, Germany. The skeleton is virtually complete & is that of an individual that died prior to reaching its' full size. It measures 65 feet in length & has an array of teeth, which were so sharp, that the Mexican & German Palaeontologists who excavated it, suffered multiple cuts to their hands & fingers. The animal also, was known to have survived an attack, as they found evidence of an injury to the skull, possibly a bite mark, which healed up. Although, it was unfortunate the 2nd time round, as something larger than itself, possibly a full-grown adult, bit into the top of the beasts' head. Furthermore, the size of the Liopleurodon is considered in BBC's Walking With Dinosaurs, to be up to 25 metres (80ft) & about 150 tonnes in weight. The teeth alone were up to 10 inches long as well. However, most Palaeontologists are rather conservative about the size of the animal, particularly the weight. Being a fully adapted marine predator, which lived exclusively in the ocean, it wouldn't be a surprise if the Liopleurodon could attain a length of 80 feet & the weight matching a Blue Whale. Especially when you come to realise, the Liopleurodon in Germany, was only a youngster when it had died & had died as the result of a very large bite to the head. Who knows how big the dinosaurs & their kin could grow?

Answer 5

Actually the average size of a dinosaur was about the size of a sheep, and many were just the size of a chicken.

It's just the big ones are more exciting.

Also many reptiles seem to keep growing indefinitely unlike mammals, for example.

http://www.creationontheweb.com/content/view/4508/

Answer 6

It is a popular misconception that all dinosaurs were big, in fact there were numerous small species. There were large and small animals ,just as today, each responding to the environment they were in.

Answer 7

The earth was likely MUCH warmer and more humid during the time of the dinosaurs... and nature favored larger animals probably because it was easier for their bodies to stay cooler with more surface area. If you look in the warmer areas of the earth, that's where you find all the big animals... giraffes, elephants, hippos, etc.

Answer 8

probably the only limits to size are the sheer physics of body mass to skeletal strength. the dinosaurs (some of them) just reached the upper limit. which is not possible for today's species for a whole variety of reasons.

Answer 9

Were they big?
I always thought most of them were small.
Start digging in a mudhole or sandbank, and how many shrews or goby will you toss out to get that prized Elephant or Blue Whale skeleton.
Large things last longer and are easier to find.

Answer 10

My guess is that the world was a much hotter place back then and the larger the surface area of a cold blooded creature the more easily it can radiate heat to keep itself cool.