More than 500 million years ago, as myriad new lifeforms were emerging and diversifying in the world’s oceans, a small, wormlike fish called the yunnanozoan (Yunnanozoan livitidum) flourished around what is now southwestern China.
Based on the numerous fossils that have been found, this sea creature seemingly had little more to it than eyes, a rudimentary brain, and a basketlike skeleton of cartilage supporting its digestive tract. Yet as with many other organisms that emerged during this time, paleontologists have long known that yunnanozoans represent important developments in evolutionary history, especially regarding the emergence of the skeleton and, eventually, the spine. Despite this, yunnanozoans’ classification has been controversial among researchers for years, explains Nanjing University paleontologist Baoyu Jiang, as experts have interpreted various parts of its anatomy as evidence that it belonged to different ancient clades. Now, research by Jiang and his colleagues published today (July 7) in Science concludes ...
