Helicoprion

No, Helicoprion was a shark-like cartilaginous fish, not a dinosaur. It lived in the Permian seas long before the first dinosaurs appeared.1

Helicoprion is estimated to have reached lengths between 5 and 12 metres, about as long as a school bus.1

Helicoprion ate soft-bodied prey like squid, belemnoids, and other cephalopods. It may also have eaten hard-shelled ammonoids and nautiloids by pulling the body out of the shell.12

Helicoprion lived from the Early to the Middle Permian, about 290 to 270 million years ago. That is before the dinosaurs.1

Helicoprion fossils have been found all over the world, including in the United States (especially Idaho), Russia, Australia, China, and Japan. It lived in many seas.12

The tooth whorl sat in the lower jaw and worked like a saw. Front teeth hooked prey, middle teeth pierced and cut, and back teeth pushed food into the throat.12

The spiral tooth whorl helped Helicoprion catch and eat soft prey like squid. It could also help shell hard-shelled animals by pulling the body out of the shell.12

No, Helicoprion went extinct about 270 million years ago, at the end of the Middle Permian. It is only known from fossils.1

Maybe up to about 30 km/h (19 mph). This is a guess: nobody knows for sure. Its body was probably shaped like a tuna or mackerel shark, so it was likely a fast swimmer.1

If Helicoprion were alive today, it would be a large, fast-swimming predator that ate squid and fish. But it lived in the Permian and is extinct, so we can only imagine.1