GENERAL GEOLOGY

Detailed explanation-1: -During the Paleozoic Era (541 to 252 million years ago) Fish diversified and marine organisms were very abundant during the Paleozoic. Common Paleozoic fossils include trilobites and cephalopods such as squid, as well as insects and ferns. The greatest mass extinction in Earth’s history ended this era.

Detailed explanation-2: -The Devonian, part of the Paleozoic era, is otherwise known as the Age of Fishes, as it spawned a remarkable variety of fish. The most formidable of them were the armored placoderms, a group that first appeared during the Silurian with powerful jaws lined with bladelike plates that acted as teeth.

Detailed explanation-3: -Fishes, here defined as ‘non-digitate aquatic vertebrates’, first appear in the Cambrian Period at least 520 million years ago (Ma).

Detailed explanation-4: -Trilobite fossils are found worldwide, with many thousands of known species. Because they evolved rapidly, and moulted like other arthropods, trilobites serve as excellent index fossils, enabling geologists to date the age of the rocks in which they are found.

Detailed explanation-5: -Paleozoic (541-252 million years ago) means ‘ancient life. ‘ The oldest animals on Earth appeared just before the start of this era in the Ediacaran Period, but scientists had not yet discovered them when the geologic timescale was made.