The Paleozoic Era

The Phanerozoic Eon is the most recent, 541 million years ago to today, and means “visible life” because an abundance of fossils marks the Phanerozoic rock record.  Phanerozoic organisms had hard body parts like claws, scales, shells, and bones that were more easily preserved as fossils. Rocks from the older  Precambrian time are less commonly found and rarely include fossils because these organisms had soft body parts. Phanerozoic rocks are younger, more common, and contain most extant fossils. The study of rocks from this eon yields much greater detail. The  Phanerozoic is subdivided into three eras, from oldest to youngest they are  Paleozoic (“ancient life”), Mesozoic (“middle life”), and Cenozoic (“recent life”).

Marine organisms dominated life in the early Paleozoic Era, but plants and animals evolved to live and reproduce on land by the middle of the era. Fish evolved jaws, and fins evolved into jointed limbs. The development of lungs allowed animals to emerge from the sea and become the first air-breathing tetrapods (four-legged animals) such as amphibians. From amphibians evolved reptiles with the amniotic egg. From reptiles, evolved the early ancestors to birds and mammals, their scales became feathers and fur. Near the end of the Paleozoic Era, the Carboniferous Period had some of the most extensive forests in Earth’s history. Their fossilized remains became the coal that powered the industrial revolution.