Caririsuchus is an extinct genus of itasuchid crocodylomorph from the Aptian to Albian Romualdo Formation of the Santana Group in the Araripe Basin in northeastern Brazil. The genus was described in 1987 based on multiple bones secured in a Brazilian fossil collection, but the much more complete fossil slab that these pieces were taken from was illegally shipped to Europe before being presumably sold into a private collection with its current whereabouts unknown. Some of the few remains that had stayed in Brazil were destroyed in the 2018 fire that destroyed large parts of the collection held in Rio de Janeiro.
Caririsuchus was a relatively small animal, measuring about in length. It had a triangular head similar to modern crocodiles and has been noted for the extensive osteoderm armor covering not just its back but also its tail, limbs and stomach. The genus is considered to be a member of the clade Notosuchia, usually as a close relative to other platyrostral forms like Pepesuchus and Itasuchus in the clade Itasuchidae, though some authors have placed all these forms in the peirosaurid subfamily Pepesuchinae. Caririsuchus was a semi-aquatic animal that once inhabited the coastal Romualdo Formation.
History and naming
The Araripe Basin of Brazil has long been subject to the illegal collection and selling of fossil material to foreign collectors, prompting the Brazilian Society of Paleontology to appeal researchers to focus on fossils from localities subject to exploitation and destruction. One such fossil was a nearly complete crocodylomorph only missing parts of some limbs preserved in a dark limestone slab presumably recovered from a coal mine exposing the Romualdo Formation (Santana Group). While most of the specimen was eventually shipped out of Brazil, some parts of the fossil including a portion of the rostrum and the osteoderms of multiple body regions were obtained by Rainer Alexander von Blittersdorff. These pieces were initially deposited in von Blittersdorff's Desirée Collection, though at least some osteoderms were later moved to the National Department of Mineral Production in Rio de Janeiro. Based on these remains as well as photographs of the complete fossil Brazilian paleontologist Alexander Kellner was able to determine that the animal represented a new species and genus, which he described in 1987 as Caririsuchus camposi.
Following its removal from Brazil, the specimen was next mentioned as having arrived in Europe, where it was briefly studied by Eric Buffetaut before disappearing again, presumably having been sold to a private collection. Although initially unaware of Kellner's work after being presented with the specimen, Buffetaut would later address his colleague's research in a contribution to the 1991 book "Santana Fossils : An Illustrated Atlas" by John G. Maisey. In this book Buffetaut argued that Caririsuchus was remarkably similar to Itasuchus from the Bauru Group, concluding that though distinct on a species level, Caririsuchus was a synonym of Itasuchus, creating the combination Itasuchus camposi. The book also features a photograph of a second well-preserved specimen including the skull, torso and tail including the osteoderm armor. According to Buffetaut the specimen was "reportedly also for sale" while remarking that the sale of the holotype "symbolizes the difficulty of saving scientifically valuable specimens from commercial exploitation".
The pieces that had remained in Brazil meanwhile were donated to two institutions, with two fragments ending up in the collection of the Museu Nacional in Rio de Janeiro and a third having been deposited at the Museu de Ciências da Terra, also in Rio. In 2018 the former was heavily damaged by a large fire destroying large parts of the paleontological collection. Despite salvage efforts, the Caririsuchus fossils held at the museum had not been recovered by 2024 and may have been destroyed.
Caririsuchus was named for the Kiriri people who once inhabited large parts of Brazil including the Araripe Basin. The ending "-suchus" meanwhile is a frequently used component in fossil crocodylomorph names, derived from the Greek "souchos" meaning crocodile. The species name on the other hand was chosen to honor Diogenes de Almeida Campos, a Brazilian paleontologist and geologist noted for his contribution to the study of the Araripe Basin.
Description Caririsuchus had a comparably high triangular skull with a moderately laterally-compressed, tapering platyrostral (flattened) snout that gradually widens towards the back of the skull. The forward-directed external nares are oval in shape and formed by the premaxillae and nasal bones, with the latter forming a septum that separates the nares into two distinct openings. The transition between the premaxilla and maxilla is well marked by the presence of a prominent notch that coincides with the premaxillary-maxillary suture. The maxillae are prominently sinusoidal in lateral view with pronounced festooning, resulting in a marked swelling at the location of the largest maxillary tooth. The nasals, which are paired as in other itasuchids, extend across the rostrum forming the bulging dorsal surface until reaching the bones just anterior to the eyesockets, sending posterior processes into the spaces between the frontal and prefrontal as well as the prefrontal and lacrimal.
The prefrontals are small and elongated, as are the lacrimals, which lack a ventral process and are wider towards the orbital margin and with no signs of possessing an antorbital fenestra. The frontal bone meanwhile roughly resembles an elongated triangle and consists of an anterior process that extends forward between the eyesockets to about the same level as the prefrontals and a posterior section. Overall the frontal has been described as reaching about half the length of the nasals, which it contacts along an irregular suture, inserting itself in between the two nasals. The eyesockets are large, circular and directed more laterally. Each orbit is protected by two palpebral bones, with the anterior being better developed than its posterior partner. The two bones cover most of the upper orbital margin and articulate with the surrounding bones. The anterior palpebral attaches to the prefrontal, lacrimal and frontal while the posterior rests on the frontal and postorbital bone.
The skull table is formed in part by the posterior portion of the frontal bone, which contacts the trapezoidal parietal along a straight suture and participates in forming the supratemporal fenestrae, a pair of openings notably smaller than the orbits. The parietal of Caririsuchus is relatively wide and short and forms the highest point of the animals skull. The postorbitals and squamosals form the outer edge and corners of the skull table as well as the lateral margin of the supratemporal fenestrae and the supraoccipital bone also participates in forming the skull table. As in related forms, the occipital surface of the squamosal slopes posteriorly.
In addition to their participation in the dorsal surface of the skull table, the postorbitals also possess a ventral projection that forms the dorsal half of the postorbital bar, a peg of bone that separates the orbits from the infratemporal fenestra. The postorbital bar is described as rod-like, moderately thin and positioned rather superficially instead of being inset relative to the surface of its contributing bones. The lower part of the postorbital bar is formed by the jugal, which forms the outer margin of the skull from its contact with the maxilla at the anterior end of the orbit until possibly the posterior end of the infratemporal fenestra, forming the openings lower edge. The relation between the jugal, quadratojugal and quadrate bone is poorly understood.
Mandible Like the rostrum the lower jaw of Caririsuchus is tapering, narrow in the front and more robust towards its posterior end around the oval mandibular fenestra and articulation with the upper jaw. The majority of the mandible is formed by the elongated dentary, which broadly follows the same pattern as the lower jaw as a whole, tapering towards the front and more robust in the back where it contributes to the anterior margin of the mandibular fenestra. Like the upper jaw the mandible exhibits a festooned toothrow forming two waves that the teeth are placed atop of. This feature, which sees the first wave peak around the 4th and 5th dentary tooth and the second in the region from the 8th to 14th is also seen in several other itasuchids such as Roxochampsa, Pepesuchus and Itasuchus. The remaining bones of the lower jaw's outer surface; the angular, surangular and articular; have not been described in detail by Kellner beyond contributing to the mandibular fenestra.
Dentition The upper jaw of Caririsuchus is thought to contain 21 or 22 teeth, four of which in the premaxilla and the remainder in the maxilla. The largest premaxillary teeth are the second or third while the largest maxillary teeth may be the second and third or the third and fourth depending on the total tooth count. Alexander Kellner hypothesized that the same number of teeth was present in the lower jaw, although only 12 could actually be preserved due to the preservation. The largest tooth of the lower jaw is the third or possibly the fourth dentary tooth, which shows a pseudocanine morphology. All teeth have finely serrated edges and the anterior teeth are generally more pointed whereas the teeth in the back of the jaw are smaller, blunter, more uniform and more labiolingually compressed. Pinheiro and colleagues note that the teeth of Caririsuchus were closely spaced and that the skull shows no clearly visible occlusal scars, which would suggest that like modern alligators the teeth of this taxon didn't interlock but instead were arranged in an overbite.
Limbs Alexander Kellner describes the femur as being 25% larger than the humerus.
Osteoderms Caririsuchus has been repeatedly noted for its extensive osteoderm armor, with Eric Buffetaut calling it "one of the most heavily armored of all known crocodilians". The armor stretches from just behind the head to the tip of the tail and is composed of a single parasagittal double row across the neck and torso. The individual plates are rectangular, wider than long and grow larger from the head to the middle of the body before decreasing in size towards the hip. The tail also preserves additional rows besides the midline double row, which have initially been interpreted as representing ventral armor by Kellner but were later clarified to have possibly covered the entire tail. In a 2024 abstract Pinheiro and colleagues describe a surviving section of armor likely coming from the lumbar-sacral or anterior caudal region as preserving the midline double row being accompanied by an accessory osteoderm on either side. The parasagittal osteoderms are noted as overlapping each other but lacking articulation processes at their anterolateral corner as in some other crocodylomorphs. They are further described as possessing low and wide keels down their midline and an ornamentation consisting of a pattern of pits that seems to radiate outward from the center of each scute. The accessory osteoderms differ from the midline osteoderms in being longer than wide, but share the same keels and ornamentation. The presence of ventral armor protecting the stomach is mentioned by Buffetaut, who furthermore notes that the limbs were similarly covered by bony scutes.
Size Based on the holotype specimen Caririsuchus was a relatively small animal, only measuring in length from the tip of the snout to the end of the tail.
Phylogeny