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90

January/February 2018^ DISCOVER^85

TOP: JIAN HAN/NORTHWEST UNIVERSITY, CHINA. BOTTOM: S CONWAY MORRIS AND JIAN HAN

Our Oldest Ancestor

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VIEWED THROUGH AN ELECTRON MICROSCOPE,

the newly discovered Saccorhytus coronarius is the oldest

and most primitive deuterostome, a major branch of

the animal kingdom that includes all vertebrates. At about

540 million years old, the millimeter-long specimen from

China (top), described in January in Nature, pushes back the

deuterostome record by tens of millions of years. Co-author and

Cambridge University paleobiologist Simon Conway Morris

believes an unusual chemical environment in its seabed home

preserved the saclike animal in “jaw-dropping” detail. Structures

around its large mouth may look like eyes and nostrils, but

the researchers believe these “body cones” (better seen in the

illustration) may have been early precursors to gills, flushing out

water that Saccorhytus swallowed.  GEMMA TARLACH