Prior to the Cambrian Explosion—an event defined by a burst in the diversification of Earth’s life—lifeforms were thought to be relatively simple. Trace evidence of these lifeforms isn’t the easiest to cross. Successful preservation takes a certain kind of sedimentary rock—Burgess Shale-type deposits. Such deposits from the Ediacaran Period, which preceded the Cambrian, are known only in certain localities, such as Siberia, India, Paraguay, the western United States, and south China.
In summer 2015, researchers excavated 77 specimens of ancient seaweed fossils from limestone deposits in western Mongolia. The specimens represent two new species of previously unknown multicellular marine algae, their age estimated at over 555 million years.
The research was published last week in Scientific Reports.
The two new species were named Chinggiskhaania bifurcate and Zuunartsphyton delicatum. The former species comprised the majority of the excavated specimens, while the latter is known from only three specimens.
In photos, the fossils look like wispy discolorations in stone fragments. The untrained eye may even mistake them for scratch marks. But the researchers claim they’re among the oldest examples of multicellular life ever discovered.
“This discovery helps tell us more about life in a period that is relatively undocumented,” said the study’s lead author Stephen Dornbos, of the University of Wisconsin-Milwaukee, in a statement. “It can help us correlate the changes in life forms with what we know about the Earth’s ancient environments. It is a major evolutionary step toward life as we know it today.”
According to the Univ. of Wisconsin-Milwaukee, many Ediacaran fossils, found in Burgess Shale-type deposits, are difficult to classify.
The new fossil assemblage was named the Zuun-Arts biota by the researchers. It’s “similar to all other Ediacaran (Burgess Shale-type deposits) in that it contains no unambiguous evidence for animals,” Dornbos and colleagues wrote in the study.
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