Andreolepis
Andreolepis is an extinct genus of prehistoric fish, which lived around 420 million years ago. It is placed in the monogeneric family Andreolepididae and is generally regarded as a primitive member of the class Actinopterygii based on its ganoid scale structure; however some new research regards it as a stem group of osteichthyans.
Researchers have used microremains of an Andreolepsis to determine its origins and found that it dated back to the late Silurian.
This organism is considered an ancestor where humans got their teeth from, a vertebrate. During studies, researchers found that the Andreolepsis was capable of shedding its teeth by basal resorption, and it is considered a rather primitive mode of tooth replacement.
The known species of this genus are A. hedei and A. petri. Both species inhabited Russia, and A. hedei fossils have also been uncovered in Sweden, Estonia, and Latvia.
