Final answer:
The term 'dinosaurs' comes from the Greek words meaning 'terrible lizard.' Dinosaurs were a diverse group of reptiles with an upright posture and included a range of species from small to enormous sizes.
Step-by-step explanation:
The group of prehistoric animals that derives its name from the Greek for "terrible lizard" is the dinosaurs. This term comes specifically from the Greek words deinos (terrible) and sauros (lizard). Dinosaurs were a diverse group of animals, which included a variety of species with different sizes and characteristics, and they were distinct from other reptiles due to their upright posture. Not all dinosaurs were gigantic; they ranged widely in size. Despite this term, it's important to remember that dinosaurs were not lizards. They belonged to the clade Dinosauria and included groups like the Saurischia ("lizard-hipped") dinos.