Itasuchus is an extinct genus of itasuchid notosuchian from the Late Cretaceous of Brazil. Fossils of the type species I. jesuinoi, first described in 1955 by Llewellyn Ivor Price, have been found from the Serra da Galga Formation, though later finds also support its presence in the sediments of the Presidente Prudente Formation. It possessed a somewhat elongated and flattened snout with interlocking teeth similar to what is seen in modern crocodilians, a thick osteoderm armor potentially covered by a thick layer of leathery skin and has been estimated to have reached a total body length of 2–2.5 m (6 ft 7 in – 8 ft 2 in). Itasuchus is the namesake of the family Itasuchidae, established in 2004 to accommodate both it and Malawisuchus after Itasuchus has varyingly been regarded a goniopholidid and trematochampsid throughout the 1900s. Itasuchidae did not see widespread use at first until the clade was redefined by Pinheiro and colleagues in 2018 to include other similarly platyrostral peirosaurians like Roxochampsa and Pepesuchus, though that same year the same forms had also been used to establish the clade Pepesuchinae. It is now frequently thought that regardless of the nomenclature, Itasuchus and its relatives were close kin to the Peirosauridae within the clade Notosuchia. Itasuchus inhabitet the meandering river systems of the Presidente Prudente and Serra da Galga Formation during the late Campanian and early Maastrichtian, an environment shared with the closely related Roxochampsa, non-itasuchid notosuchians, turtles, various fish, abelisaurid theropods and titanosaur sauropods. Like other itasuchids Itasuchus too is thought to have been a semi-aquatic animal, a hypothesis supported in part due to the overall similarities to modern crocodiles. This is supported by the laterally flattened tail and keeled osteoderms, which may have been a factor in making the animal more hydrodynamic. The overall snout proportions have been described as an intermediate between longirostrine and brevirostrine forms and have been specifically likened to modern nile crocodiles.
History and naming Itasuchus was named by Brazilian paleontologist Llewellyn Ivor Price in 1955 based on fossil material recovered near Peirópolis in sediments of the Late Cretaceous (Early Maastrichtian) Bauru Group, specifically the Serra da Galga Member of the Marília Formation, which in some works has been elevated to full formation status. The original material, designated the specimen number DGM 434-R, consisted of a fairly complete lower jaw, parts of the left skull from the posterior maxilla to the quadrate, four vertebrae each of the neck, torso and tail, 20 osteoderms and other well preserved postcrania including some complete limb bones. The description of the genus, which was published in the same study as that of Peirosaurus, was chiefly based on the cranial remains, which were deemed sufficient for establishing a new genus by Price. Though mentioned, and despite having been regarded as one of the best known mesoeucrocodylian skeletons from its locality, the postcrania were neither described in detail nor figured, with Price promising that the material would be dealt with "in due course". The late 80s saw the discovery and eventual description of a complete, well-preserved semi-aquatic crocodyliform from Brazil's Araripe Basin that closely resembled Itasuchus. This form, named Caririsuchus by Brazilian paleontologist Alexander Kellner, was eventually removed from Brazil and was next mentioned as having been shipped to Europe, where it was briefly examined by Eric Buffetaut. While maintaining the status of Caririsuchus as a distinct species, Buffetaut noted several similarities to Itasuchus, ultimately regarding Caririsuchus camposi a species of Itasuchus, creating the combination Itasuchus camposi. The fossil material once again vanished after this, presumably having been sold to a private collector. Despite Buffetaut's proposal, subsequent papers generally kept Itasuchus and Caririsuchus as distinct genera. In 2004 Carvalho and colleagues established the family Itasuchidae to include both Itasuchus and Malawisuchus, but this grouping was not widely recovered in subsequent studies and generally fell out of use until 2018 when it was redefined to include several platyrostral forms similar to Itasuchus. Since the paper recovered all members of the newly revised Itasuchidae in a polytomy, Pinheiro and colleagues mentioned that it would be possible to sink all four taxa into the genus Itasuchus, but ultimately retained all four forms as distinct genera. By 2018 a second specimen, MUGEO 218-V, had also been referred to the genus Itasuchus, although only at a genus level. The specimen, represented by a mandible fragment with teeth, is notably less complete than the holotype material and comes from the Late Campanian to Early Maastrichtian Presidente Prudente Formation. A more substantial piece of a rostrum, specimen UFRJ DG 687- R, was eventually also tentatively referred to Itasuchus jesuinoi as well. This specimen, like MUGEO 218-V, came from the Presidente Prudente Formation. The name Itasuchus derives from the Tupi word "ita" for "stone" and "suchus", the Greek word for "crocodile". The species name derives from Jesuino Felicissimo Junior, who is credited for having reported the first fossils from the site that yielded the remains of Itasuchus.
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