GEOLOGY

Detailed explanation-1: -They first appear as fossils in rocks of earliest Cambrian age and their descendants survive, albeit relatively rarely, in today’s oceans and seas. They were particularly abundant during Palaeozoic times (248–545 million years ago) and are often the most common fossils in rocks of that age.

Detailed explanation-2: -Brachiopods have an extensive fossil record, first appearing in rocks dating back to the early part of the Cambrian Period, about 541 million years ago. They were extremely abundant during the Paleozoic Era, reaching their highest diversity roughly 400 million years ago, during the Devonian Period.

Detailed explanation-3: -The earliest unequivocal brachiopod fossils appeared in the early Cambrian Period.

Detailed explanation-4: -The oldest fossil brachiopods are found in Cambrian rocks, which are over 500 million years old. The animals first became abundant in Ordovician time and remained so throughout the Paleozoic Era.

Detailed explanation-5: -Brachiopod fossils are commonly preserved in three main ways: Unaltered remains, internal molds, or external molds (learn more about fossil preservation here). Unaltered remains preserve the original shell as if you picked it up off the ocean floor.