Colossosuchus is an extinct genus or large mystriosuchine phytosaur from the Upper Triassic Tiki Formation of India. It was among the largest known phytosaurs, reaching a length of over . Among its characteristic features are the dome-shaped head and downturned tip of the upper jaw. Colossosuchus was part of an endemic radiation of phytosaurs from India, closely related to two additional forms not yet named. The genus is monotypic, only including the species Colossosuchus techniensis. History and naming Fossils of Colossosuchus were recovered from the red-mudstone of the fluvial Tiki Formation, located within the Rewa Gondwana Basin of India. The remains stem from a monotypic bonebed, meaning the collection of bones stem from only a single species. The bonebed yielded 27 skull and mandible specimen and approximately 339 postcranial remains corresponding to a minimum of 21 individual animals, primarily juveniles and subadults. All specimens are stored at the Indian Institute of Technology in Kharagpur. The type specimen is IITKGPR749, which is a cranium consisting of a partial rostrum, the skull table and the braincase. The genus name combines the Latin "colossus", a reference to the great size obtained by the animal, with the Greek "souchus" for crocodile, a common suffix used in phytosaurs due to their resemblance to modern crocodiles. The species name " techniensis" honors the Indian Institute of Technology. Description Overall, the cranium of Colossosuchus appears dome-shaped when viewed from the side. The tip of the elongated upper jaw, known as the terminal rosette, is strongly turned downward at a 70° angle. The rosette is large and bulbous, with its front flattened and the downward curvature is much steeper than in most other phytosaurs. A series of parallel crests run exclusively along the left side of the premaxilla and maxilla. The nares are located just before the eyes like in other phytosaurs and unlike in crocodiles. Just before the opening of the nares a pair of prenarial fossa are present, which Colossosuchus shares with Diandongosuchus. The naris themselves are not elevated above the eyes, but the septum is located above the rim of the narial openings. This too is similar to Diandongosuchus, as well as Ebrachosuchus and several species of Parasuchus, while setting it apart from most leptosuchomorphs. The nares overlap with the antorbital fenestra for over 50% of their length, a condition also seen in all mystriosuchines other than Volcanosuchus. The nasal bone is covered in band-like