Thiollierepycnodus was 25 cm long, with a laterally flat body and comparatively large fins, indicating that it was a reef fish of considerable manoeuvrability.

[1] The original specimens of Thiollierepycnodus were discorvered in Cerin, France, and, in 2014, new fossils of the genus were uncovered in Wattendorf, Germany.

The name of the species, P. wagneri, was in reference to Dr Johannes Andreas Wagner, a professor of zoology who lectured at the university in Munich.

[1] Thiollierepycnodus had a total length of 25 cm, with a laterally compressed body and, without the fins, a contour resembling an almost perfect disc.

[1] Thiollierepycnodus belonged in the subfamily Proscinetinae of the Pycnodontidae family, being a sister taxon to the Proscinetini tribe.