Paranasuchus
Paranasuchus is an extinct genus of large caiman from the Late Miocene Ituzaingó Formation of Argentina. The type species was originally described as a new species of Caiman, C. gasparinae, in 2013, but a study from 2024 concluded that it differed significantly enough to represent its own genus. Paranasuchus was a large caiman with a broad skull and was only one of several generalized caimans that inhabited Paraná during the Late Miocene.
History and naming
The holotype of Paranasuchus consists of a partial snout as well as an associated skull table from Argentinas Ituzaingó Formation. Though the material had been considered to be referrable to the extant broad-snouted caiman in an unpublished doctoral thesis by Zulma Brandoni de Gasparini, a much later study from 2013 highlighted that this assumption was seemingly proposed without any actual justification or evidence. The study by Paula Bona & Ariana Paulina Carabajal instead proposed that the material represented a distinct species, which they dubbed Caiman gasparinae. In addition to the type material, they also assigned a fragment of a premaxilla to the species that had previously been known under the names Alligator? ameghinoi and Xenosuchus paranesis ameghinoi. Nearly a decade later, Caiman gasparinae was once again reanalyzed and compared to extensive caiman material as well as other fossil crocodilians from the Ituzaingó Formation. In addition to assigning even more specimens to the species, this study showed that it was not only distinct on a species level, but actually represented an entirely new genus, which was named Paranasuchus gasparinae.The name Paranasuchus translates to "Crocodile from Paraná", named so for the banks of the Paraná River where the fossils had been found. This parallels the name Paranacaiman, known from the same deposits and published in the same study. The species name meanwhile honors paleontologist Zulma Brandoni de Gasparini, chosen as she spent much of her life studying extinct crocodyliforms.
Description
In general morphology Paranasuchus bears close resemblance to modern caimans with a broad snout, though the bones that form the very tip are noticeably lower than in modern forms. Looking at the skull from above shows that it possesses sinuous margins, with well-defined curves creating a wavy outline. This is especially prominent in the region where the premaxillary bones contact the maxillae, which serves to set Paranasuchus apart from taxa like Mourasuchus, Purussaurus, Acresuchus and even the extant broad-snouted caiman, all of which have much less pronounced "festooning". The external nares face upward and are described as rounded, set apart from those of Mourasuchus by being not as wide and from those of Purussaurus due to not being as elongated. They also differ from those of modern caimans, in which the nares are shifted further forward. The nares are entirely surrounded by the premaxillary bones, preventing the nasal bones from extending into the opening as they do in modern caimans and Acresuchus.A major feature that separates Paranasuchus from Paranacaiman can be observed in the region where the prefrontals contact the frontal bone. In Paranacaiman this region bears a prominent V-shaped shelf which is absent in Paranasuchus. The part of the frontal bone known as the interorbital bridge, the section located between the two eyesockets, is wider than it is long, something otherwise only seen in species of Purussaurus amongst caimans. Unlike in Paranacaiman, the edges of the skull table converge with each other toward the front of the skull and the supraoccipital bone is not nearly as sunken in, but rather aligns well with the inclination of the neighbouring squamosals. The supratemporal fenestra, two openings in the skull roof, are not quite circular in shape rather than elongated. The ornamentation of the skull roof, which is the pattern of pits in the bone's surface, is another feature that distinguishes Paranasuchus from contemporary caimans. Specifically, in Paranasuchus the ornamentation primarily consists of interconnected ridges that create a pattern of irregular and mostly incomplete cells, whereas in Paranacaiman the ornamentation is best described as a pattern of very well-defined cells and rounded pits.