It was found by the researchers José Manuel Gasca and Ainara Badiola from the Tremp Formation, in Arén of Huesca, Spain.

It was first named by Eduardo Puértolas, José I. Canudo and Penélope Cruzado-Caballero in 2011 and the type species is Arenysuchus gascabadiolorum.

The specific epithet of "gascabadiolorum" is dedicated to the researchers José Manuel Gasca and Ainara Badiola, who discovered the holotype.

One feature linking it to early crocodilians is the contact of the frontal bones with the margin of the supratemporal fenestrae, two holes in the top of the skull.

The orbit edges of more advanced crocodyloids like modern crocodiles are also raised, but those of the closest relatives of Arenysuchus are not.

Another feature of Arenysuchus that distinguishes it from other basal crocodyloids is its small palatine process, a bony plate of the maxilla that forms the front portion of the palate.

The palatine process of basal crocodyloids usually extends to the suborbital fenestrae, a pair of holes on the underside of the skull beneath the orbits.

The Tremp Formation is made up of 900 m (3,000 ft) of reddish rock in the South Pyrenean central Unit.

Lower in the formation is a mix of platform marine deposits, that are late Campanian to Maastrichtian in age.