Earliest jawed vertebrate

Gnathostomes are jawed vertebrates, and the earliest example found to date is a newly described (September 2022) fossil species named Qianodus duplicis ("double tooth from Qian/Guizhou), unearthed in Guizhou province, southern China. It is currently known only from some isolated tooth whorls, but these whorls possess non-shedding teeth arranged in a pair of rows that demonstrate a number of features found in modern gnathostome groups. They date back to the Early Silurian Period, approximately, 439 million years ago. Previously, the earliest-known gnathostome teeth dated back to the Late Silurian, around 425 million years ago. Researchers consider this new species to be a stem-chondrichthyan, i.e., an ancestor of cartilaginous fishes, such as sharks and rays. The research was published in the journal Nature on 28 September 2022.

Many additional ancient fish fossils were also found at this same site, including a number of other new, early jawed fish species. Moreover, now that the date for the existence of such species has been pushed back in time from the Late to the Early Silurian, and based also upon molecular studies, some palaeontologists are speculating that gnathostomes with jaws and teeth may well have arisen even earlier, perhaps dating back as far as 450 million years ago, thereby originating in the Ordovician Period. But only further excavations, and discoveries, can ascertain whether such speculation is warranted.

The research was a collaboration between Qujing Normal University, the Chinese Academy of Sciences, the National Synchrotron Radiation Research Center (all China) and Birmingham University (UK).