DIPLODOCIDS

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(Sauropodomorpha; Sauropoda; Neosauropoda; Diplodocoidea)
Diplodocids (double beams) included possibly the longest of all dinosaurs (even longer than a tennis court), yet some were lightweight giants - the longest weighed only half as much as many a sauropod half its length. A deeply hollowed backbone helped reduce weight. Diplodocids had long, low, sloping heads with weak, pencil-like teeth found only at the front of the jaws. They breathed through nostrils opening from a single hole at the top of the skull between the eyes. Their snouts were long and squarish.
The neck was long and snaky and they had a long whip-like tail used for defence. The front legs were much shorter than the back ones (and probably shorter than in any other sauropod), and the back may have been highest at the hips. Many tail bones had fore- and aft- projections (the double beam of their name), and they are characterised by high neural spine s, which in some cases may have supported a 'sail' or frill. They lived on plants, mostly cycads and tree ferns from swamps and ponds. Each rear foot had 3 claws, only 1 on each front foot.
They occurred from the late Jurassic to late Cretaceous .