Definitions

1. adjective

relating to or denoting the earliest of the three geological eons, spanning from about 541 to 252 million years ago, and characterized by the formation of the first multicellular life forms and the development of complex marine ecosystems.

“The paleozoic era saw the emergence of the first trees on land.”

2. noun

a geologic era that began about 541 million years ago and ended about 252 million years ago, characterized by the formation of the first multicellular life forms and the development of complex marine ecosystems.

“The paleozoic era witnessed the rise of trilobites and other ancient marine creatures.”