The geology of the formations in which Desmatosuchus is found suggests that this animal spent at least some of its time in the floodplains of rivers in ancient Texas, New Mexico, and Arizona (Small 2002; Parker 2008). The rich soils would have supported the insects that have been suggested as the mainstay of the aetosaur diet (Small 2002). Other local inhabitants would have included rauisuchians like Postosuchus and Chatterjeea, other aetosaurs like Paratypothorax and Typothorax, small metaposaurids and other temnospondyls, Arribasuchus and Leptosuchus (phytosaurs), Technosaurus (a dinosaur), and several other taxa including Shuvosaurus and Protoavis (Small 2002; Parker 2008).
The first material of what we now call Desmatosuchus was described by Cope in 1892 and named Episcoposaurus haplocerus. In 1920, Case first described Desmatosuchus spurensis, which, like E. haplocerus, was considered a phytosaur at the time. Gregory (1953) later revised the taxonomy of Cope and Case, giving us D. spurensis and D. haplocerus as the soul species of Desmatosuchus.
During the last decade or so, there has been a lot of work done on the systematic paleontology of Desmatosuchus. In 2005, Bill Parker erected a new species to the genus, D. smalli. Parker also demonstrated that “D.” chamaensis (Zeigler et al 2002) is more closely related to Paratypothorax than to Desmatosuchus, representing a different genus (2008). Heckert and Lucas (1999) have suggested that Acaenasuchus geoffreyi Long and Murry is a juvenile Desmatosuchus, but Parker cast doubt on this, citing our poor understanding of aetosaur ontogeny and insufficient morphological characters used to refer Acaenasuchus to Desmatosuchus. Finally, because D. haplocerus was found to be nondiagnostic at the species level, we are left with only two valid species: D. spuensis and D. smalli (Parker 2008).