Fossils have been found in Europe (mainly in France, Russia, Germany, Lithuania, The United Kingdom and Ukraine), East Asia (mainly in Japan),[5] Antarctica,[6] Australia,[7] India and South America.

Unlike modern members of the genus Squalus, Protosqualus had dental crowns which did not have a great degree of labiolingual compression.

Its front ledge was well-developed and slightly raised, culminating in a rounded shape firmly attached at the base of the crown.

The root was low and thick, angled slightly in relation to the crown, and exhibited minor protrusions on both its front and rear sides.

The bottom of the tooth was flat and gently curved, with the holes on the sides either separated or, less commonly, connected by a groove.

[19] Squalidae Centrophoridae Dalatiidae Etmopteridae Oxynotidae Somniosidae In 2001, Adnet & Cappetta found the following position for Protosqualus.

Echinorhinus Etmopterus Eoetmopterus Dalatias Isistius Euprotomicrus Squaliolus Euprotomicroides Microetmopterus Proetmopterus Palaeomicroides Centroscymnus Scymnodon Scymnodalatias Oxynotus Somniosus Cretascymnus Centrophorus Deania Squalus Protosqualus Protospinax Pristiophorus Squatina Protosqualus lived alongside other chondrichthyans as well as other types of fish.