Initial researches claimed that owing to their gigantic sizes and long necks, sauropods might have been aquatic reptiles. However, in the light of later findings, this claim has been completely dismissed, and it has been established that the sauropods were indeed terrestrial reptiles.

◼ Sauropoda is a group of some of the largest dinosaurs that ever existed. Apart from their overwhelming size, they are also known for their long necks and tails (often disproportionately), and their robust, pillar-like legs. ◼ These long-necked dinosaurs walked on four feet, and had very small heads in comparison to their body size. Fossilized remains of sauropods have been found virtually on every continent of the world, including Antarctica. ◼ The vast and varied geographical range that these dinosaurs covered gives us a fair idea about their adaptability and ability to survive in virtually any kind of climate. ◼ These long-necked dinosaurs are known to have first appeared during the Triassic period, some 250 to 200 million years ago. ◼ Archaeological finds tell us that they were not only geographically widespread but also much more evolved by the Late Jurassic period, around 150 million years ago. ◼ They spread and evolved even further by the Late Cretaceous period, about 100 to 67 million years ago. ◼ However, the entire group of sauropods, according to researchers, died out completely from the face of the Earth during the Cretaceous-Paleogene extinction event that happened about 66 million years ago, during which most species of non-avian dinosaurs became extinct.

◼ Until now, very few sauropod fossils have been found. However, from the limited finds that we have at our disposal, we know of certain distinct genera of these long-necked dinosaurs. ◼ The major and the most well-known amongst these are Brachiosaurus, Diplodocus, and Apatosaurus. It is worth noting that the Brachiosaurus species were amongst the heaviest dinosaurs that existed on Earth. One of the main facts about the Diplodocus species was that they were more slender in appearance than all the other sauropod species. On the other hand, amongst the Apatosaurus species were some of the longest dinosaurs that walked our planet. ◼ We also know of Titanosaurs, a diverse sauropod group that included a large number of species with armored skin. ◼ Apart from these, there are about 15 different subgroups of Sauropods, which have been identified till now, each having some or the other unique feature. However, the basic appearance of all the species remains more or less similar throughout.

◼ The most distinguishing feature of the sauropods was the length of their bodies. The longest sauropod discovered, till date, is the Amphicoelias fragillimus, that had a 190 ft long body from the top of the head to the tip of the tail. We can imagine its enormous length, especially considering that the longest terrestrial animal currently existing on Earth is the reticulated python, which is not known to measure beyond 29 ft in length. ◼ The next important characteristic of the sauropods is their height, especially considering their long necks. The tallest sauropod discovered, till date, is the Sauroposeidon proteles which probably had a maximum height of 60 ft. The tallest existing animal today is the giraffe, and it stands about 16 to 18 ft tall. ◼ We also know from the fossil remains that some of the sauropods were incredibly massive. In fact, they are amongst the heaviest creatures that ever existed on Earth. One of the sauropods, known as Bruhathkayosaurus matleyi was probably the heaviest creature that ever walked our planet with a total weight of about 175 to 220 metric tons. The heaviest terrestrial animal that exists on Earth today is the Savannah elephant, which weighs not more than 10 metric tons. ◼ All sauropods were four-legged, and their limbs were specially built for bearing their massive weights. As mentioned before, the sauropods bore robust and very thick legs, with fingers ranging from three to five (depending on the species), and external claws. ◼ A number of indentations and hollow cavities in their vertebrae, which have been seen in many fossils, quite clearly suggest that the sauropods bore a system of air sacs to facilitate ease in respiration. ◼ Some of these long-necked sauropods also bore an armor, which served as their defense mechanism. For instance, the Shunosaurus had a club-like thorny structure on its tail, while the Saltasaurus had a spiked, bony structure covering its body. ◼ The teeth of all of these herbivorous dinosaurs were large, not only owing to their size, but also due to the kind and quantity of food they consumed each day. But what is even more interesting is the rate at which tooth replacement took place. According to studies, in the Nigersaurus, tooth replacement took place every 14 days, while that in the Diplodocus took place every 35 days. ◼ The long necks of the sauropods were used to feed on vegetal matter that existed at a height, for instance on tall trees. It was initially believed that the sauropods had very flexible necks and could swivel their heads around to feed on branches of trees; however, recent researches tell us that it was not so. On the contrary, it has been suggested that the necks of the sauropods were tall, yet stiff, much like those of the ostriches. ◼ There have been several debates over the years as to why the sauropods were so huge in size. Several theories have been put forth in this respect. According to one theory, their huge size facilitated easy digestion of the quantity of food they ate each day. Other theories tell us that their size gave them immunity from predators, a longer lifespan, and enabled them to save their energy by allowing them to do more work with less efforts. ◼ While the sauropods have been unanimously defined as a group of long-necked dinosaurs, it should be noted that we also have a small number of fossil evidence of long-necked dinosaurs in other groups as well. One of these is the Plesiosaurus dolichodeirus, an aquatic dinosaur that belonged to the genus Plesiosaurus.

Here are some illustrations of long-necked dinosaurs for you to see and note the differences between species. ** Some studies claim that Plesiosaurus was not a dinosaur, but just a marine reptile of the Jurassic period.