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Diplodocids, or members of the family Diplodocidae ("double beams"), are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including Diplodocus and Supersaurus, which may have reached lengths of up to 34 m (112 ft.),[1] and the gigantic Amphicoelias, known from a single vertebra representing an individual that may have exceeded 40 meters (131 ft) or reached 60 (201 ft).
[edit] Description  While still massive, when compared to the titanosaurids and brachiosaurs, the diplodocids were relatively slender but extremely long. They had short legs, making them the "dachshund" of giant dinosaurs; and their rear legs were longer than front legs, giving their back a distinctive downward slope towards the neck. In the early 1990s, a diplodocid specimen was described with a row of keratinous (horny, not bony) spines running down the base of the tail. Further finds have shown that rather than forming a spiny ridge down the back (as in modern reptiles like the iguana), these spines were more uniformly distributed over the animal's torso. Since dermal tissue is rarely preserved in the fossil record it is not known how widespread the feature is, but spines may have been a common feature among diplodocids. Their necks were also extremely long, and according to recent computer simulations they may not have been able to lift their necks like other sauropods. Instead of reaching up into trees, they may have used their necks to graze over a broad area. They may also have used their necks to reach into dense stands of conifers, or over marshy ground. Like other sauropods, their heads were tiny with the nasal openings on the top of the head (though in life the nostrils themselves would have been close to the tip of the snout). Their teeth were only present in the front of the mouth, and looked like pencils or pegs. They probably used their teeth to crop off food, without chewing, and relied on gastroliths (gizzard stones) to break down tough plant fibers (similar to modern birds). Diplodocids also had long, whip-like tails, which were thick at the base and tapered off to be very thin at the end. Computer simulations have shown that the diplodocids could have easily snapped their tails, like a bullwhip. This could generate a sonic boom in excess of 200 decibels, and may have been used in mating displays, or to drive off predators. There is some circumstantial evidence supporting this as well: A number of diplodocids have been found with fused or damaged tail vertebrae, which may be a symptom of cracking their tails. [edit] SkinFew skin impressions of diplodocids have been found. However, at least one significant find first reported by Stephen Czerkas in 1993 preserved portions of the skin from around the tip of the tail, or "whiplash".[2] Czerkas noted that the skin preserved a sequence of conical spines, and that other, larger spines were found scattered around larger tail vertebrae. The spines appeared to be oriented in a single row along the mid-line of the tail, and Czerkas speculated that this midline row may have continued over the animals entire back and neck.[3] [edit] ClassificationThe rather dubious but spectactularly long Amphicoelias may also be a member of this family;[4] though it is sometimes classified as an incertae sedis (unknown) member of the parent clade, the Diplodocoidea. Not enough is known about the genus to classify it more precisely.
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