March 10, 2012
Paleontologists Discover Oldest Organism With A Skeleton
Paleontologists have discovered the oldest organism with a skeleton in Australia.
The creature is called Coronacollina acula and is estimated to be between 550 and 560 million years old. Paleontologists estimate this animal is from the Ediacaran Period, before the diversification of organisms in the Cambrian Period.
The study results appeared online February 14 in Geology.
This important find could be the key to unlocking several questions about early life, evolution, and extinction. Additionally, scientists will be able to use this find as a way to better recognize earth on other planets elsewhere in the universe.
Named after the Ediacara hills in South Australia, the Ediacaran Period began 630-542 million years ago. The Cambrian Period, the period marked by rapid diversification of organisms, began 542-488 million years ago. “Up until the Cambrian, it was understood that animals were soft bodied and had no hard parts,” said Mary Droser, a professor of geology at the University of California, Riverside, whose research team made the discovery in South Australia. “But we now have an organism with individual skeletal body parts that appears before the Cambrian. It is therefore the oldest animal with hard parts, and it has a number of them - they would have been structural supports - essentially holding it up. This is a major innovation for animals.”
Paleontologists estimate Coronacollina acula to be from the Cambrian Period due to its shape. Like other sponges from this era, the reconstruction of the Coronacollina acula has three raised points on its rim with a central hollow and four spicules branching from the center cone rim. As seen in the fossils, Coronacollina acula has a depression that measures anywhere from a few millimeters to 2 centimeters deep. However, the effect of gravity and time on these rocks could have compressed the fossil. Therefore, this ancient creature could have been upwards of 3-5 centimeters tall.
Researchers believe that the sponge lived on the seafloor, and in great numbers. Since it was not capable of movement, how it reproduced is still unknown.
Finding Coronacollina acula is exciting to scientists, as it suggests that perhaps the Ediacaran Period and Cambrian Periods may not have been so different and distant as they originally thought.
“It therefore provides a link between the two time intervals,” Droser said. “We´re calling it the ℠harbinger of Cambrian constructional morphology,´ which is to say it´s a precursor of organisms seen in the Cambrian. This is tremendously exciting because it is the first appearance of one of the major novelties of animal evolution.”
The presence of a skeleton in a creature is usually a sign of a defense mechanism against predators. Not so, says Droser.
““¦Coronacollina acula used its skeleton only for support, there being no predators in the Ediacaran.”
The research for this project began as a master thesis in Droser´s lab. Erica Clites , physical science technician at Glen National Recreation Area for the National Park Service later joined the research team.
“Every aspect of the organism´s reconstruction had to be backed up by supporting statistics,” said Clites, who graduated from UCR in 2009 and is the first author of the research paper. “Through painstaking measurements and detailed descriptions, the pits and needles contained in the rock were revealed as a sponge-like animal.”
Image 1: A reconstruction of how Coronacollina would have appeared in life. Coronacollina remained in place on the sea floor, and may have used its spicules as support struts. Coronacollina resembles the Cambrian fossil sponge, Choia. The three raised points on the rim are evident, with a central hollow and four spicules extending from the cone rim. Image credit: Daniel Garson for Droser lab, UC Riverside.
Image 2: The best Coronacollina specimens showing the main body with articulated spicules. Specimens originate from different field localities. Arrows indicate main body of Coronacollina. White/black bars indicate 1 cm. A, C, D and E are photographs of fossil impressions in the rock. B and F are latex casts showing how the fossils would have looked in life, after compression. Image credit: Droser lab, UC Riverside.
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