What was the purpose of the different sizes and shapes of dinosaurs?

Similar to todays animals, the different sizes and shapes were the result of adaptations to the dinosaurs surrounding environments. In particular, the dinosaurs were probably typical of most animals: they needed to adapt to the prevailing conditions and changing food supplies in order to survive. Many times, these adaptations took the form of certain sizes and shapes, and probably even colors.

Was there an upper limit to the size of a dinosaur?

The answer to this question probably depends on the availability and locality of the dinosaurs food supply. In general, to support a larger weight, the bone sizes also increase, or else they would literally break under the animals own weight. Plus, as the bones become thicker to support the increasing weight, the animal would become more and more cumbersome, limiting its ability to obtain food. Thus, for each dinosaur species, there was probably a definite limit to its size.

What was the average size among the dinosaurs?

The popular conception of dinosaurs is one of hugeness. But dinosaurs came in all sizes, and shapes were extremely diverse, much like todays birds. They ranged in size from the gigantic sauropods, like Brachiosaurus, to small, chicken-sized ones like Compsognathus, and every size in between. Because we have found relatively few fossils compared to how many dinosaurs scientists believed once inhabited Earth it is hard to give an average size for dinosaurs.

How do scientists determine the weight of a dinosaur?

Its not easy to determine the weight of a dinosaur. Scientists can only estimate an animals weight by looking at the bones of the animal.

One method of determining a dinosaurs weight is by studying the cross-sectional area of a limb bone. This way, scientists can estimate the weight borne by the limb. But its not only the weight times four legs that results in an estimate; its also the position of the legs, the posture of the animal, the tissue and flesh on the legs, and the limb shape. Some scientists have tried to extrapolate the weight of a dinosaur by comparing the animals to modern living species, but apparently there is really no linear relationship between the two.

Which dinosaurs were the biggest?

There are so many claims to which animals are the largest carnivorous and herbivorous dinosaurs that its difficult to keep up. The favorite contender for a carnivore is the famous Tyrannosaurus rex, the Cretaceous period carnivore found in North America and Asia. It measured over 40 feet (12 meters) in length. Several other challengers are the Giganotosaurus of South America, and the Carcharodontosaurus of North Africa, two huge meat-eaters. There is also the Spinosaurus, a dinosaur measuring up to 52 to 59 feet (16 to 18 meters) long, which is often declared the largest known carnivorous dinosaur.

Some scientists also give the lead to a certain fossil of a Tyrannosaurus whose huge pubis bone was found in Fort Peck, Montana, in 1997. This creature was so massive that scientists have given the fossil its own name: Tyrannosaurus imperator. This tyrannosaurs pubis bone measured 52.4 inches (133 centimeters) long; the pubis of Giganotosaurus was only 46.5 inches (118 centimeters) in length, which would make the Montana Tyrannosaurus about 15 to 20 percent larger than any other known meat-eating dinosaur.

The winner of the largest herbivore is even more confusing. One of the best contenders includes a massive herbivorous dinosaur called Argentinosaurus huinculensis, a South American sauropod of the Titanosauridae family that measured between 130 and 140 feet (40 and 42 meters) long. Another contender is the second-largest sauropod so far found, the Paralititan (meaning tidal Titan), a titanosaurid sauropod found in Egypt that lived about 100 million years ago. Also, Seismosaurus hallorum, which scientists believe was related to the diploducus, weighed upwards of 100 tons (90 metric tons) and was 120 feet (almost 40 meters) long. A complete skeleton of this huge beast was discovered in 1985 in New Mexico.

No doubt, the hunt for the largest carnivore and herbivore and dinosaur will continue. Paleontologists will find new dinosaur bones, and one of them may one day prove to be the largest dinosaur ever known.

Kids visiting Dinosaur Park in Münchehagen, Germany, stand beneath a replica of the Seismosaur (iStock).

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