Yunnanozoans are extinct creatures from the early Cambrian period, about 518 million years ago. They look like worms, with a length of about 3-4 centimeters. 

Scientists recently have discovered evidence that yunnanozoans are the oldest known stem vertebrates. Stem vertebrate refers to those vertebrates that are extinct, but very closely related to living vertebrates.

Researchers studied 127 fossil specimens and employed multiple methods, such as X-ray microtomography, scanning electron microscopy, transmission electron microscopy, Raman spectrometry, Fourier-transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy. 

They arrived at the conclusion that yunnanozoans had cellular cartilage in their pharynx, a feature considered specific to vertebrates. 

The research team, which included members from the Nanjing Institute of Geology and Paleontology, the Chinese Academy of Sciences and Nanjing University, published its findings in the journal Science on July 8, 2022. 

(Cover image via CFP)

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