Saurolophus angustirostris Archosauria: Ornithischia: Ornithopoda: Hadrosauridae Locality: Altan Ula, Nemegt Basin, Gobi Desert, southern Mongolia Age: Late Cretaceous (Late Campanian-Early Maastrichtian), 74 million years ago Meaning of name: "ridged or crested reptile" Size: 10 meters long    Saurolophus is one of the largest hadrosaurids, or duck-billed dinosaurs. The toothless anterior parts of the jaws in Saurolophus were flattened and widened, like a duck bill. At the same time, the numerous lateral teeth were well developed, so the animal could cut and chew very effectively aquatic vegetation which was probably its regular forage. Indeed, both the vertically-flattened tail and wide paws suggest that Saurolophus might dwell in shoals and coastal environments. The posterior part of the skull roof in Saurolophus forms a long backward directed spine with inner hollows connected to aerial ducts. Many dinosaurologists think these hollows might be acoustic resonators, that could reinforce vocalisation in Saurolophus and other species of the hadrosaurids. Relatively well-developed fore limbs in Saurolophus suggests it might be quadrupedal when moving slowly, but could take bipedal stance when travelling faster. Saurolophus is also well known in North America. There, as in Mongolia, it is common in flood plain deposits. Although not the largest hadrosaur or duck-billed dinosaur (that honour goes to Shantungosaurus giganteus from China) Saurolophus angustirostris was still one of the biggest. For some reason, skin impressions of hadrosaurs are rather common both in North America and Central Asia. They show that these animals had a scale pattern typical of reptiles. There is no suggestion of hair, feathers, or any other insulating external body covering.
Saurolophus had a horny beak that lacked any teeth with a battery of cheek teeth good
for processing resistant vegetation. The outside three fingers of the hand were joined in
a fleshy 'mitten' and the two inner fingers had sizeable, stout claws. The skull bones at
the back of the head formed a spike which continued behind the head. The back was
stiff because of the bony tendons that criss-crossed between the neural spines of
the vertebrae, and the tail was flattened from the sides. Paleontologists think that
Saurolophus spent part of the time walking as a quadraped on four legs, while at other
times, perhaps when travelling fast, walking upright on its hind legs only. The
flattened tail and the paddle-like hands suggest that this duck-billed hadrosaur
spent part of its life in water.
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