Phil, how big were dinosaurs? >> Well, dinosaurs of course, are considered by most people to be the largest land animals that ever existed. This is a leg of a Camarasaurus, and Camarasaurus is a really big dinosaur, but it's not the largest. And there is no question that dinosaurs include some of the largest species of animals to ever walk on land. However, size is not necessarily understood by using words like the largest and the smallest. When we ask, what was the largest dinosaur, do we mean the heaviest dinosaur? The longest dinosaur? Or the tallest dinosaur? >> The sauropods or long-neck dinosaurs include the largest animal that ever walked the earth. Which of these sauropods, do you think was the heaviest? Was it A) Argentinosaurus, B) Diplodacus or C) Giraffatitan? In this case, each of these animals could be considered the biggest, depending on what you're measuring. The tallest, relatively complete Sauropod skeleton is from an animal called Giraffatitan, which is closely related to the more familiar Brachiosaurus. And stood about 12 meters tall. Giraffatitan achieved record-breaking height, thanks to its long neck and unusually long front legs which put it head and shoulders above even the more massive sauropods. The longest relatively complete sauropod skeleton is from Diplodocus and measures 25 meters in length. A more fragmentary specimen of the closely related Seismosaurus was undoubtedly even longer, perhaps spanning over 40 meters. However, both Diplodocus and Seismosaurus were actually lightly built for sauropods. Most of their length was accounted for by the relatively skinny necks and tails. Argentinosaurus is the heaviest sauropod known from a relatively complete skeleton. But how heavy was it? That's hard to say. Some estimates put Argentinosaurus at a whopping 100 metric tonnes. But any dinosaur weight estimate should be considered with a healthy amount of skepticism. In this case, the 100-tonne estimate was an extrapolation based on comparison on the limb proportions of Argentinosaurus to those of large modern mammals whose weights can be measured directly. So, A is the correct answer. >> Understanding the real sizes of different dinosaurs is a lot trickier, because we don't have the living animals to measure or weight and the fossilized skeletons really only include the bones. These skeletons are usually incomplete as well. And we can make estimates about the length and the height based on those incomplete or nearly-complete skeletons. But, understanding how heavy the dinosaur was is a lot trickier. Because, the bones have been infilled by minerals so they're too heavy. And, we do not have all of the skin, muscles, and organs of that dinosaur. Additionally, dinosaurs, like birds, often had extensive air sac systems throughout their bodies. And that means that dinosaurs, like birds, had a lot more air inside those bodies than mammals do. And that makes it difficult to equate the body weight of an elephant-sized dinosaur with an elephant, for example. >> But not all dinosaurs were big. How small were the smallest dinosaurs? Were they just smaller than a cow? Just smaller than a dog or smaller than a chicken? The answer is C, smaller than a chicken. Although dinosaurs could be incredibly large animals, one should never forget that all dinosaurs were not gigantic. The majority of dinosaurs species were no larger than the big landillian mammals we see today. Like rhinos, hippos, elephants and giraffes. As time goes on, and we make new discoveries about dinosaurs, more and more small species are being found. There were many species of small plant-eating dinosaurs and some of the smallest dinosaurs were meat eaters, smaller than modern chicken.
