When mammals roamed alongside dinosaurs
The origin of dinosaurs dates back to 230 million years BP and appears to have been located in South America. They lived alongside primitive mammals for millions of years.
Focus on eggs and flashback : the early land vertebrates used to lay soft eggs that had to be deposited in water to avoid desiccation, a strategy still in use with frogs. Around 312 million years BP, a novel group of land vertebrates started laying eggs protected by a shell : amniotic eggs. This innovation allows the embryo to develop in a protected environment., even on dry land, liberating thus vertebrates from their dependence on water for reproduction, paving the way for a broader expansion on land environments.
Two major groups then formed :
→ The Sauropsids, that comprise dinosaurs, birds and present day reptiles - turtles, lizards, snakes and crocodiles.
→ The Synapsids' lineage leading to mammals, and thereby to humans, via the mammalian reptiles .
Although mammals and dinosaurs evovled in parallel, it is the latter that would eventually rule the earth and the sky for 160 million years. Until the combined actions of a meteorite and intense volcanic activity changed the game.
