The first ancestor of almost all animals including humans found by UC Riverside geologists. It is a tiny, wormlike creature, named Ikaria wariootia which is bilaterian. It means it has a front and back, two symmetrical sides, and openings at either end connected by a gut. It was found in Ediacaran Period deposits in Australia and was 2-7 millimeters long, with the largest the size of a grain of rice. It lived more than 555 million years ago.
The earliest multicellular organisms, such as sponges and algal mats, had variable shapes. These were complex, multicellular organism. But these lacked basic features of most animals, such as a mouth or gut.
A multitude of animals, from worms to insects to dinosaurs to humans, are organized around the basic bilaterian body plan. So development of bilateral symmetry was a critical step in the evolution of animal life. It was predicted that the oldest ancestor of all bilaterians would have been simple and small, with rudimentary sensory organs. But didn’t have hope to find any such fossils as it would be difficult to preserving and identify such fossils.
The paper is published in Proceedings of the National Academy of Sciences.