Ichthyosaurs were not actually dinosaurs. They were more like ancient dolphins, or fish, but much bigger. Their name comes from Greek, and means 'fish lizard.'
What did they look like?
Ichthyosaurs looked like dolphins do today. They had a long nose, a fin on top, and all of the other things that would make you think of dolphins. The only two major differences were that Icthyosaurs had an extra set of tiny fins that it used in times of need and that the tail fin of an Ichthyosaur was rotated from that of a modern dolphin. Their size range was great, from 2.4 meters (eight feet) to 23 meters (75 feet). They biggest Ichthyosaurs are still the largest known sea-dwelling reptiles today!
What did they eat?
Ichthyosaurs were predatory. They lived in the sea, so they ate any food they could find, catch, and kill, including squid, fish, and shellfish. They were very good at catching food. They had streamlined bodies capable of swimming up to 40 miles an hour. They also were able to dive far into the water. Finally, their dolphin-like mouths were filled with sharp teeth, and some Ichthyosaurs may have been able to bite down hard enough to break open clams.
When did they live?
Ichthyosaurs evolved during the Mesozoic era, which was around 250 million years ago, slightly before the dinosaurs. They became extinct 90 million years ago, which was during the Cretaceous 25 million years before dinosaurs died out.