Early Jurassic to late Cratecous
Sauropoda is an infraorder of Saurischia which
includes all of the large plant-eating long-necked dinosaurs.
There are five families in this infraorder which can be told
apart by the differences in the backbone, legs and head:
cetiosaurids (short head, front legs shorter than hind, solid
backbone), brachiosaurids (low snout, front legs longer than hind),
camarasaurids (short head, front legs shorter than hind, hollow
backbone), titanosaurids (long steep head, front legs shorter
than hind, slightly hollowed backbone), and diplodocoids (long
low head, front legs shorter than hind, hollow backbone).