Around 20 of the teeth turned out to be from the same species. From the arrangement of the teeth and the shape of their bases, the team established that they would have come from a fish with an arched jaw margin, with offset tooth rows, similar to those found in sharks. The team used a range of techniques, including CT scanning, to establish a date for the samples, placing it in the early Silurian period.
The new species has been named Qianodus duplicis – Qian being an ancient name for Guizhou Province, odus from the Greek for tooth, and duplicis, or double, referring to the paired rows of teeth.
In a separate paper, also published today in Nature, the team also identified fossil elements that relate to ‘fin spines’, bony projections in front of the fins which can be seen today on Port Jackson sharks. These spiny structures form the basis for a new species Fanjingshania renovata – named after Mount Fanjingshan which is close to the locality from where this material was collected and renovata, renewal acknowledging remodelling of the base of the spines and scales.
“The early so-called ‘spiny sharks’ had these features on all of their fins, but the examples that we have found belong to a much earlier period,” says Dr Plamen Andreev, lead author on these papers. “These are the first creatures that we would recognise today as fish-like, evolving from creatures often referred to as ‘clams with tails’, from earlier in the Ordovician period.”
Cartilaginous fish, including sharks, separated off at some point from bony fish, from which humans eventually evolved. The point at which this occurred, however, is obscured within ghost ranges in the Ordovician period where only hints in the fossil record have been found. Precisely how and when this separation happened, therefore, is still a mystery.
