Supersaurus one of the Longest Dinosaurs

Supersaurus

Supersaurus was one of the longest animals ever to live.  The current estimate is that they grew to be up to 138 feet, about 42 meters, long.  The Supersaurus display located at the Museum of Ancient Life in Lehi, Utah is 120 feet or 37 meters long.  A somewhat smaller Supersaurus is located in the Wyoming Dinosaur Center, a museum in Thermopolis, Wyoming.  Supersarus is a member of the Doplodocid group of Sauropods.

The best known member of the Diplodocid group of Sauropod dinosaurs is Diplodocus, discovered in Dinosaur Mountain near Grand Junction, Colorado.  It was about 80 feet or 24 meters long.  These animals were all very thin compared to other types of Sauropods.  They were more gracile.  Even though they were  at least 80 feet long the Diplodocus weighed only 15 tons.  On the other hand, Supersaurus is longer and heavier with an estimated weight of 35-40 tons.

The Doplodocids were also very long with a very whip-like tail.  It has been calculated that they could crack their tail like a bullwhip and this may have allowed it to break the sound barrier that would have made a sonic boom of at least 200 decimals.  This very loud sound may have been used to drive off predators or even to attract mates.  Several of these big Sauropods cracking their tail in the direction of an approaching Theropod like Allosaurus would undoubtedly have given the predators a severe headache.  At the very least the loud sound would have ruptured the Theropod's eardrum.

Diplodocids ate leaves, probably from both ground cover ferns and leaves & conifer needles high up in trees.  Grass had not yet evolved 150 million years ago, when Diplodocids lived, but there were lots of ferns probably covering the ground in some places.  With their very long necks Diplodocids could probably sweep from side to side to act kind of like a giant lawnmower... except there was no lawn, just ferns.

Some paleontologists have thought that perhaps Diplodocids could reach up even higher into trees by standing on their back legs.

Diplodocus on Hind Legs feeding on Cycad Tree

Notice that I did not draw the spikes on this one.  The spikes on the neck and back and part of the tail would have been most likely for defense.  It would be more difficult for a predatory Theropod to bite through an armored neck because they would get a mouthful of spikes.  

Apatosaurus

Apatosaurs was not a Diplodcid and you can see it had a heavier built form.  The Apatosaurs may also have been able to crack their tail like a whip.   I should also point out that if a large Sauropod managed to hit a predatory Theropod with their long tail the damage would be extensive.  In fact, Allosaurs have been found with cracked ribs.  .   .  possibly from an encounter with a long Sauropod tail.  If you think of the mass of a Sauropod tail then you realize that being hit with it would be like getting hit by a fully loaded semi truck.   

Apatosaurus Cracking the Tail like a Whip