It was first named by Marco Aurélio G. França, Jorge Ferigolo and Max C. Langer in 2011 and the type species is Decuriasuchus quartacolonia.

The specimens were found in the Alemoa Member of the Santa Maria Formation, Rosário do Sul Group.

An initial phylogenetic study of the genus placed it in the family Prestosuchidae, but found the group "Rauisuchia" to be paraphyletic.

[5] A later study involved adding Decuriasuchus to a 2011 analysis of archosaur relationships;[6] D. quartacolonia was recovered as the basalmost member of the clade Loricata[1] (the most inclusive clade containing Crocodylus niloticus but not Poposaurus gracilis, Ornithosuchus longidens or Aetosaurus ferratus[6]), with Ticinosuchus as the next most primitive taxon.

A study of the taphonomy of the site (the conditions under which the skeletons became fossilized) indicates that the assemblage represents the single burial of multiple individuals rather than the collection of unrelated remains in one spot over a longer period of time.