Caiman brevirostris

Caiman brevirostris was described in 1987 by Brazilian paleontologist J. D. Souzha Filho on the basis of an incomplete rostrum and associated right mandibular ramus that were collected from the Miocene age strata of the Solimões Formation in the municipality of Sena Madureira in Acre, Brazil. In the 2000s and 2010s, multiple specimens from the Urumaco Formation of Venezuela were incorrectly referred to C. brevirostris, instead actually belonging to other caimanines. In 2003 during a joint expedition between the Universidade Federal do Acre and the Universidade Federal de Rondônia, a skeleton including a complete skull and associated postcranial material of C. brevirostris was collected from the Talismã locality in Manuel Urban municipality in Amazonas, Brazil. == Classification ==

Caiman brevirostris has been included in several phylogenetic analyses, but it most frequently comes up in polytomy with other fossil Caiman species. Below is the phylogenetic analysis conducted by Salas-Gismondi et al., 2015: == Description and paleobiology ==

The most distinctive feature of Caiman brevirostris is its short and broad skull, the shortest skull known from a caimanine, that was built for crushing mollusks like its relative Globidentosuchus. This is also shown in the rostral anatomy, which has a short and wide splenial with few alveoli compared to other caimanines. The external nares are enlarged compared to other Caiman species, though this condition is similar to that of the "La Venta" Caiman from the Miocene of Colombia. The dentary has fewer alveoli compared to other Caiman species, again due to the shortening of the skull and mandible. The largest alveolus bears a blunt and low-crowned tooth, which may used for crushing feeding behavior, as in C. latirostris. Caiman brevirostris would therefore be an ecological analogue of the extant Caiman latirostris during the late Miocene in the Solimões Formation and Urumaco Formation. == Paleoenvironment ==

As the Proto-Amazonian lake system and the Pebas system began to dissipate with the onset of the transcontinental Amazon Drainage, Caiman brevirostris inhabited the wetlands of the northern Urumaco Formation and the Solimões Formation in Acre State, Brazil, into the Late Miocene before eventually dying out during the Early Pliocene like much of the large crocodilian fauna of the Miocene wetlands. These wetlands provided favorable conditions to the native reptilian fauna, with several lineages of crocodilians reaching enormous sizes during the Mid to Late Miocene and also diversifying in ecology. Some of the enormous crocodilians that coexisted with C. brevirostris included the enormous caiman Purussaurus, the bizarre Mourasuchus and large-bodied gharials of the genus Gryposuchus, some species of which reaching lengths of over 10 meters. The largest turtle known, Stupendemys, with one specimen preserving a 2.86 meter long carapace, was also present in the region as an omnivore. Other durophagous caimanines inhabited the Urumaco and the Solimões, including the unusual Globidentosuchus in Urumaco and the "shovel faced" Gnatusuchus in the Solimões. Besides the aforementioned reptiles the waterways of Late Miocene South America were also inhabited by fish, including catfish such as Phractocephalus and Callichthyidae, characids such as Acregoliath rancii and the tambaqui (Colossoma macropomum), the South American lungfish (Lepidosiren paradoxa), trahiras (e.g. Paleohoplias assisbrasiliensis) and freshwater rays and sharks. Other turtles and tortoises found in the same deposits are Chelus columbiana (a fossil relative of the mata mata) and Chelonoidis. Further aquatic vertebrates included river dolphins and the large darter "Anhinga" fraileyi. At least within the Solimões Formation Stupendemys would have inhabited a floodplain or lacustrine environment with savannahs and gallery forests. ==References==