Phlebolepis
Phlebolepis is an extinct thelodont agnathan genus belonging to the family Phlebolepididae. Whole fossils are found in Late Silurian aged strata from Saaremaa, Estonia. Phlebolepis elegans was average-sized for a thelodont, 7 cm long.
The scales of Phlebolepis are robust and abrasion-resistant, similar to modern sharks which live among rough substrates such as rocky caves or reefs.