Definition - What does Precambrian Era mean?
Precambrian Era is the period that started about 4.5 billion years ago and ended up four billion years later on. It is one of the earliest geologic ages that have discrete layers of sedimentary rocks. It covered approximately 85-90% of the entire history of the earth. The era was further categorized into the Hadean, the Proterozoic, and the Archean. It is used by paleontologists and geologists to understand the general discussions about specific eon names. Besides, the era consisted of bacterial life throughout its validity.
Petropedia explains Precambrian Era
The Precambrian Era was long originated before the Cambrian thus it consisted of different forms of earlier rocks. It is noted that the Precambrian rocks are still used for subdividing the geologic time. It was the first era when microfossils which resemble cysts of flagellates and algae were noticed. In late ages of the era, the first multicellular organisms were found. Due to the rapid expansions of the lifeforms then, the era was called the Cambrian explosion of life. The multicelled animals of this time were categorized as sponges, cnidarians, and annelids.