Caiman brevirostris
| Caiman brevirostris | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Clade: | Archosauriformes |
| Order: | Crocodilia |
| Family: | Alligatoridae |
| Subfamily: | Caimaninae |
| Clade: | Jacarea |
| Genus: | Caiman |
| Species: | †C. brevirostris
|
| Binomial name | |
| †Caiman brevirostris Souza Filho, 1987
| |
Caiman brevirostris is an
Discovery and naming
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.[2] The species name "brevirostris" comes from the Greek roots brevis- meaning "short" and -rostrum meaning "snout" after the species' distinct short and robust snout.[2] Several additional specimens from the Urumaco Formation of Venezuela were incorrectly referred to the species in the 2000s and 2010s, many of these specimens actually being from other caimanines.[3][4][5][6] In 2003 during a joint expedition between the Universidade Federal do Acre and the Universidade Federal de Rondônia, a complete skull and associated postcranial material of Caiman brevirostris were collected from the Upper Miocene strata of the Solimões Formation in Talismã locality in Manuel Urban municipality in Amazonas, Brazil.[6] The specimen was deposited in the collections of the Universidade Federal do Acre and described in 2014 in a study that found only the Talismã specimen and the holotype could be referred to the species.[6] However, a single specimen, an articulated skull and mandible, from the Urumaco Formation was also referred to C. brevirostris in 2016.[7]
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.[8][6] The size of the orbits is also enlarged compared to other caimanines, but this characteristic is also present in Melanosuchus niger.[8] One of the most unique traits of C. brevirostris is the blunt & low crowned posterior teeth that were adapted for eating harder prey than other caimanines.[8] The premaxilla bears a long posterior process despite the short rostral bones.[6] This process extends posteriorly past the 3rd maxillary alveolus, a trait of brevirostry. The prefrontals are separated by the frontal only and do not meet at the midline, in contrast to Venezuelan caimanines whose prefrontals contact at the midline. The frontal anteriorly projects beyond the prefrontal's anterior tip, which is likely again caused by the skull's shortening compared to other species.[8][6]
Majority of the diagnostic traits of C. brevirostris lie in the mandible. C. brevirostris' mandible is short and wide, though the dentary symphysis is broken in all known specimens, leaving gaps in the knowledge of its anatomy. The splenial is completely different from those of other caimanines in that it is extremely robust and approaches the symphysis. The splenial contributes to half of the breadth of the mandibular ramus, forming a wide floor posteriorly, similar to that of Caiman latirostris, but is more pronounced and differs greatly from that of narrow-snouted caimanines.[6] The wide posterior part of the splenial in C. brevirostris and the wide mandibles as a whole may be due to frequent usage of the posterior blunt and crushing teeth, as possibly being used for greater muscle attachment, but the muscles present in the area play only a minor role in jaw mechanics.[9] The dentary has fewer alveoli compared to other Caiman species, again due to the shortening of the skull and mandible. The largest alveolus bares a blunt and low-crowned tooth, which may used for crushing feeding behavior, as in C. latirostris.[10][11][6] Caiman brevirostris would therefore be an ecological analogue of the extant Caiman latirostris during the late Miocene in the Solimões Formation and Urumaco Formation.[6]
Classification
Caiman brevirostris has been included in several phylogenetic analyses, but it most frequently comes up in polytomy with other fossil Caiman species.[6][8]
Below is the phylogenetic analysis conducted by Salas-Gismondi et al., 2015:[8]
| Globidonta |
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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
References
- PMID 34567843.
- ^ a b Souza-Filho, J. D. (1987, July). Caiman brevirostris sp. nov., um novo Alligatoridae da Formação Solimões (Pleistoceno) do Estado do Acre, Brasil. In Anais X Congresso Brasileiro de Paleontologia, Rio de Janeiro (Vol. 1, pp. 173-180).
- ^ Aguilera, O. A. (2004). Tesoros paleontológicos de Venezuela: Urumaco, patrimonio natural de la humanidad. Caracas: Editorial Arte.
- S2CID 85950121.
- ^ Riff, D., Romano, P. S. R., Oliveira, G. R., Aguilera, O. A., & Hoorn, C. (2010). Neogene crocodile and turtle fauna in northern South America.[dead link] Amazonia. Landscapes and Species Evolution: A Look Into the Past, 259-280.
- ^ S2CID 86506092.
- ^ Scheyer, T. M., & Delfino, M. (2016). The late Miocene caimanine fauna (Crocodylia: alligatoroidea) of the Urumaco Formation, Venezuela. Palaeontologia Electronica, 19(3), 1-57.
- ^ PMID 25716785.
- ^ Bona, P., & Desojo, J. B. (2011). Osteology and cranial musculature of Caiman latirostris (Crocodylia: Alligatoridae). Journal of Morphology, 272(7), 780-795.
- ^ Ősi, A., & Barrett, P. M. (2011). Dental wear and oral food processing in Caiman latirostris: analogue for fossil crocodylians with crushing teeth. Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen, 201-207.
- ^ Medem, F. (1983). Los Crocodylia de Sur America, Volume 2. Universidad Nacional de Colombia, Bogota, 270 pp.
- ^ Head, J. J. (2001). "Systematics and body size of the gigantic, enigmatic crocodyloid Rhamphosuchus crassidens, and the faunal history of Siwalik Group (Miocene) crocodylians". Journal of Vertebrate Paleontology. 21 (Supplement to No. 3): 59A.
- PMID 32095528.
- ISSN 1519-7530.