is not unlike one of the first life forms that appeared in the Precambrian era. Photograph by Joel Sartore, National Geographic Photo Ark The earliest multicelled animals that survived the ...

During the Proterozoic era, oxygen produced by photosynthesizing ... So what exactly were these highly diverse Precambrian creatures? Plants, animals, or of another kingdom entirely?

Despite being the largest and most diverse group of animals on the planet ... studies suggested they existed during the Precambrian period. In a recent study published in Current Biology ...

Earth formed and oxygen levels rose in the foundational years of the Precambrian. The productive Paleozoic era gave rise to hard-shelled organisms, vertebrates, amphibians, and reptiles.

It has long been suspected that the sparseness of the pre-Cambrian fossil record reflects these two problems. First, organisms may ... research suggests that the period prior to the Cambrian ...