Colossosuchus was part of an endemic radiation of phytosaurs from India, closely related to two additional forms not yet named.

Fossils of Colossosuchus were recovered from the red mudstone of the fluvial Tiki Formation, located within the Rewa Gondwana Basin of India.

The bonebed yielded 27 skull and mandible specimens and approximately 339 postcranial remains corresponding to a minimum of 21 individual animals, primarily juveniles and subadults.

These consist of the large teeth found in the terminal rosette and the distinct premaxillary and maxillary tooth sets.

According to prior publications, including Heckert et al. (2021), head to body proportions changed among phytosaurs in their evolutionary history.

The 8 m (26 ft) estimate is favored by Datta and Ray, who argue that it is most in line with the body size seen in other derived phytosaurs including Smilosuchus.

Skeletally immature members of this species are generally smaller than 5 m (16 ft) and characterized by their comparably big eyes, lacking ornamentation, unfused bones and poorly developed muscle scars.

[1] The phylogenetic analysis conducted for Colossosuchus was based on a 2021 dataset by author Debajit Data, which included 24 different taxa composed of 23 phytosaurs and Euparkeria as the outgroup.

The strict consensus tree yielded from the analysis was only poorly resolved and features multiple polytomys, yet also displays some much clearer separations.

Specifically, members of the Mystriosuchinae are clearly set apart from non-mystriosuchine phytosaurs and within the subfamily, the leptosuchomorphs likewise form a distinct cluster of species.

This grouping sits alongside Volcanosuchus, Rutiodon and the clade formed by Angistorhinus and Brachysuchus at the base of Mystriosuchinae, which further diverges into the also poorly resolved Leptosuchomorpha.

The Bayesian analysis using the dataset of Jones & Butler (2018) on the other hand differed in that it placed Colossosuchus as the most derived non-leptosuchomorph parasuchid.

This diverse phytosaur fauna highlights the endemic nature of the group, which generally appears through distinct forms inhabiting restricted ranges, rather than individual genera having a cosmopolitan distribution.

Additionally, these Indian taxa are all noted to have survived the early Norian extinction event that effectively caused the disappearance of most non-leptosuchomorph phytosaurs on a global scale.

The bonebed that yielded the remains of Colossosuchus may have been formed by the mass death of a family group, consisting of adults performing parental care.