An introduction to the ‘mammal-like reptiles’ that walked the Earth millions of years before the dinosaurs – and from which all modern-day mammals would eventually evolve.
- Early reptiles split into two evolutionary branches: sauropsids, or "true reptiles", and synapsids, or "mammal-like reptiles".
- Dimetrodon and other sail-backed synapsids could maintain a steady body temperature by controlling blood flow to their sails.
- Mammals evolved from a group of synapsids called the therapsids.
- While most mammals evolved to give birth to live young, some continue to lay eggs.