Diapsida

However, four (or three if Euryapsida is sunk into Diapsida) subclasses remained more or less universal for non-specialist work throughout the 20th century.

However, mammals hail from the synapsids (which were once described as "mammal-like reptiles") and birds are descended from the dinosaurs (a group of Diapsida ), both of which are reptiles.

Those four subclasses were: * Anapsida – no fenestrae – cotylosaurs and Chelonia ( turtles and relatives) This taxonomy does not reflect modern molecular evidence, which places turtles within Diapsida.

Towards the end of the era, large, sophisticated diapsida and synapsida were dominant and the first modern plants ( conifers ) appeared.