Study of Ancient Fossils Finds 2-to-1 Ratio of Right- to Left-Curving Spriggina

A new analysis of more than 100 fossils indicates that Spriggina floundersi, a small segmented animal that lived about 550 million years ago, preferred to bend its body to the right. Cnn reported that the study, published Thursday in the journal Scientific Reports, provides the earliest evidence of such behavioral asymmetry in any animal.

Scott Evans, lead author and assistant curator of invertebrate paleontology at the American Museum of Natural History, said most fossils curved left in the rock, meaning the living animals curved right.

The ratio of right-curving to left-curving specimens reached 2-to-1, matching patterns seen in many modern animals. Spriggina measured up to 4 inches long, though most specimens were 0.8 to 1.2 inches. Its flat body tapered to a tip at one end and carried a large curved structure at the other, making it the earliest known animal with a head.

Fossils have been found only in what is now South Australia. The research team examined rock layers covering tens of square meters that held hundreds of specimens. Specimens appeared in varied orientations and with different degrees of bending, including some preserved with sediment beneath their bodies.

These patterns indicated the animals could move independently rather than being fixed in place or aligned by currents. Paleontologists first described Spriggina fossils in 1958. Diego García-Bellido, a senior paleontology researcher at the South Australian Museum who was not involved in the study, said the statistical significance of the handedness pattern points to a nervous system capable of directing muscle movement in a preferred direction.