|This article is about a/an monster in Kamen Rider, the original series.|
- "The only place you'll be getting off this bus is in hell!"
- ―Pirasaurus before releasing his Death Mist.[src]
The first Pirasaurus Human (人間ピラザウルス Ningen Pirazaurusu, 16), also simply known as Pirasaurus (ピラザウルス Pirazaurusu) after the prehistoric creature he was modified from, was a piranha-dinosaur Shocker cyborg.
He had the human guise of a bus driver, and after using his "Death Mist" ability to kill a group of humans in a bus it was discovered his poison was so potent it killed him as well. Pirasaurus was a project from Shocker commander Maya (マヤ Maya), and she quickly looked for a stronger person to be altered.
The Pirasaurus Human's main ability, engineered from the prehistoric Pirasaurus, was releasing a poisonous breath. Appearing as a powerful mist, the Pirasaurus' poison was said to be able to kill a dinosaur in seconds. During its test run the poison of the Pirasaurus Human was able to kill a bus full of humans. However the poison was so potent it killed the Pirasaurus Human itself immediately after, thus a stronger human was needed to create a Pirasaurus Human that could survive the use of its power.