635 mln yr old sponges were earliest animals on Earth

Washington, Feb 5 (ANI): Scientists have found evidence in the form of fossilized rocks which indicates that sponges were the earliest animals on Earth, dating back to more than 635 million years ago.

Known as Demosponges, the animals appeared 635 million years ago in era of climatic extremes and evolutionary developments.

Now, using compounds preserved in sedimentary rocks dating back to that period, researchers have found some of the earliest evidence for the existence of these organisms.

Demosponges thrived in the shallow coastal waters of what is now Oman, according to scientist Gordon Love of the University of California at Riverside and colleagues from MIT and other institutions.

"Demosponges appeared during the Neoproterozoic era, 1,000 to 542 million years ago, an era of climatic extremes and biological evolutionary developments culminating in the emergence of animals and new ecosystems," said Love.

"These sponges currently represent the oldest evidence for animals in the fossil record," he added.

The preserved compounds Love and colleagues discovered in these sponges, called steranes, exist in a wide variety of biochemical configurations, according to Stephen Macko, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

"The compounds are also known as 'biomarkers,' indicating that they can be traced directly to living organisms," said Macko.

24-isopropylcholestane, the biomarker Love and colleagues identified, is found in living demosponges, and now has been observed in 635 million-year-old rocks, but was not seen in older samples of the same rock formation.

"The fact that these biomarkers were found in samples associated with sedimentary rocks that formed in shallow waters, lends support to the hypothesis that demosponges arose in warm shallow coastal seas," said Macko.

Feeding on dissolved and particulate organic debris in the water, these animals eventually migrated to the deep sea. They now reside there, as well as in shallower coastal waters. (ANI)