Ancestors

• Experts have many opinions as to which group (or groups) of reptiles were the ancestors of the dinosaurs.

• The earliest dinosaurs appeared in the Middle Triassic Period, about 230-225 mya, so their ancestors must have been around before this.

• Very early dinosaurs walked and ran on their strong back limbs, so their ancestors were probably similar.

• The thecodonts or "socket-toothed" group of reptiles may have been the ancestors of the dinosaurs.

• A thecodont's teeth grew from roots fixed into pitted sockets in the jaw bone, as in dinosaurs.

• Some thecodonts resembled sturdy lizards. Others evolved into true crocodiles (still around today).

• The ornithosuchian thecodonts became small, upright creatures with long back legs and long tails.

• The smaller thecodonts included Euparkeria, at about 25in (60cm) long, and Lagosuchus, at about 1ft (30cm) long.

• Euparkeria and Lagosuchus were fast-moving creatures that used their sharp claws and teeth to catch insects.

STAR FACT
Creatures similar to Euparkeria or Lagosuchus may have given rise to the first dinosaurs.

By: Parker, Steve, Dinosaurs