Precambrian rocks usually do not contain fossils--these rocks were deposited before multicellular organisms were abundant and diverse and before animals had shells. However, paleontologists working in a remote region of Nevada have discovered an assemblage of exquisitely preserved Precambrian fossils.
In a recently published paper in the , 51³Ô¹ÏÍøÍòÄÜ¿Æ´ó paleontologist Steve Rowland and alumna Margarita Rodriguez ('12 BS Geology), right, describe a new species of alga, the first from these newly discovered fossils to be formally described and named. The fossil is just a millimeter wide -- the thickness of a dime -- with segmented branches that are each about the diameter of a human hair.
The 560 million-year-old fossils occur in strata of the Ediacaran Period near the town of Gold Point, in Esmeralda County. The Ediacaran interval of geologic time immediately predates the Cambrian Period -- the time of the so-called Cambrian explosion of multicellular life during which most groups of multicellular organisms evolved.
"This discovery of soft-tissue preservation in Ediacaran fossils is a big deal because there are no such sites of this age anywhere else in North America, and very few anywhere in the world," Rowland said.
The Ediacaran Period is a poorly understood, yet critical time in the history of life. So paleontologists are interested in finding any fossils that predate the Cambrian explosion to better understand the early history of multicellular life on Earth, Rowland said. But such fossils are exceedingly rare and tiny.
Soft tissues open a window into the biology of the organism, Rowland said, but rarely are they preserved in fossils. In Rowland and Rodriguez's find, however, the cellular structure of the alga is visible in the fossil--though the researchers don't yet understand what set of circumstances permitted the preservation of these fossils.
Rowland added that researchers typically find only the "hard parts" of animals and plants preserved -- things like teeth and bones -- but Ediacaran organisms did not have any hard parts.
Exquisite preservation, such as with these fossils, also is called Burgess Shale-type preservation, named for a famous Cambrian-age deposit with soft-tissue preservation in the Canadian Rockies. The Esmeralda County fossils are the first known examples of Burgess Shale-type preservation in Ediacaran-age rocks in North America, and among very few examples from anywhere on Earth.
Rowland and Rodriguez named their fossil alga Elainabella deepspringensis. Elainabella honors Elaine Hatch Sawyer of Fredonia, Ariz., who is an important person in Rodriguez's life. Deepspringensis identifies the Deep Spring Formation as the rock layer in which the fossils were found.
The type specimen of the new species will be permanently housed in the research collection of the Nevada State Museum in 51³Ô¹ÏÍøÃâ·ÑApp, where it will be accessible for study by other researchers.
