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