Brachiosaurus

Brachiosaurus is a huge sauropod dinosaur from the Morrison Formation of North America. Its name means "arm lizard". Brachiosaurus one of the tallest and largest dinosaurs Earth ever seen. It had features that are same for any sauropod: long neck, small head. But Brachiosaurus had features that was unusual for most sauropods. 

Like other Brachiosaurids its front legs were longer than its hind legs. These unusual feature gave Brachiosaurus a giraffe-like stance and it reached 15 meters tall. Brachiosaurus was really gigantic creature. Look at these rates: 26 meters long, 80 tons weight. Like other Brachiosaurids, it had chisel-like teeth, its nostrils were on the top of its head, and it had large nasal openings indicating that it may have had a good sense of smell.

A healthy, adult Brachiosaurus probably had no predators. The largest-known meat-eaters from that time (the late Jurassic period) and place (North America and Africa) were Allosaurus, Ceratosaurus, and Torvosaurus. These theropods were less than half the size of Brachiosaurus, and probably had much easier prey to hunt (like smaller sauropods and ornithischians like stegosaurs).

Brachiosaurus and some of the other large sauropods (the huge long-necked plant-eaters) needed to have large, powerful hearts and very high blood pressure in order to pump blood up the long neck to the head and brain. The heads (and brains) of Brachiosaurus was held high (many meters) above its heart. This presents a problem in blood-flow engineering. In order to pump enough oxygenated blood to the head to operate Brachiosaurus' brain (even its tiny sauropod brain) would require a large, powerful heart, tremendously high blood pressure, and wide, muscular blood vessels with many valves (to prevent the back-flow of blood). Brachiosaurus' blood pressure was probably over 400 mm Mercury, three or four times as high as ours.