Caiman brevirostris

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Caiman brevirostris
Temporal range: Late Miocene, 11.6–5.3  Ma [1]
Scientific classification OOjs UI icon edit-ltr.svg
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 extinct species of caiman that lived during the Late Miocene, around 11.6 million years ago, to the end of the Miocene 5.3 million years ago in Acre and Amazonas, Brazil as well as Urumaco, Venezuela. Several specimens have been referred to the species, but only 3 of them are confidently placed in the species. C. brevirostris was originally named in 1987 on the basis of a single, incomplete rostrum with an associated mandibular ramus that had been found in Acre, Brazil. C. brevirostris is very distinct among Caiman species and caimaninae overall in that it preserves a characteristically short and robust skull that bears blunt posterior teeth that were built to break down harder foods. This was an adaption for durophagy (the diet of hard-shelled organisms), likely to crush shells of mollusks and clams which were common in the wetlands that C. brevirostris resided in.

Contents

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

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. [12] The largest turtle known, Stupendemys, with one specimen preserving a 2.86 meter long carapace, was also present in the region as an omnivore. [13] 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. [14]

Related Research Articles

<span class="mw-page-title-main">Alligatoridae</span> Family of crocodilians including alligators, caimans and kin

The family Alligatoridae of crocodylians includes alligators, caimans and their extinct relatives.

<i>Caiman</i> (genus) Genus of reptiles

Caiman is a genus of caimans within the alligatorid subfamily Caimaninae. They inhabit Central and South America. They are relatively small sized crocodilians, with all species reaching lengths of only a couple of meters and weighing 6 to 40 kg on average.

<i>Melanosuchus</i> Genus of caiman

Melanosuchus is a genus of caiman. The black caiman of South America is the sole extant (living) species, and is the largest living member of the subfamily Caimaninae, as well as the entire alligator family Alligatoridae.

<i>Purussaurus</i> Extinct genus of reptiles

Purussaurus is an extinct genus of giant caiman that lived in South America during the Miocene epoch, from the Friasian to the Huayquerian in the SALMA classification. It is known from skull material found in the Brazilian and Peruvian Amazon, Colombian Villavieja Formation, Panamanian Culebra Formation, Urumaco and Socorro Formations of northern Venezuela.

<i>Stupendemys</i> Extinct genus of turtles

Stupendemys is an extinct genus of freshwater side-necked turtle, belonging to the family Podocnemididae. It is the largest freshwater turtle known to have existed, with a carapace over 2 meters long. Its fossils have been found in northern South America, in rocks dating from the Middle Miocene to the very start of the Pliocene, about 13 to 5 million years ago. Male specimens are known to have possessed bony horns growing from the front edges of the shell and the discovery of the fossil of a young adult shows that the carapace of these turtles flattens with age. A fossil skull described in 2021 indicates that Stupendemys was a generalist feeder.

<i>Mourasuchus</i> Extinct genus of reptiles

Mourasuchus is an extinct genus of giant, aberrant caiman from the Miocene of South America. Its skull has been described as duck-like, being broad, flat, and very elongate, superficially resembling Stomatosuchus from the Late Cretaceous.

<span class="mw-page-title-main">Caiman</span> Subfamily of reptiles

A caiman is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans inhabit Mexico and Central and South America from marshes and swamps to mangrove rivers and lakes. They have scaly skin and live a fairly nocturnal existence. They are relatively small-sized crocodilians with an average maximum weight of 6 to 40 kg depending on species, with the exception of the black caiman, which can grow more than 4 m (13 ft) in length and weigh in excess of 1,000 kg. The black caiman is the largest caiman species in the world and is found in the slow-moving rivers and lakes that surround the Amazon basin. The smallest species is the Cuvier's dwarf caiman, which grows to 1.2 to 1.5 m long. There are six different species of caiman found throughout the watery jungle habitats of Central and Southern America. The average length for most of the other caiman species is about 2 to 2.5 m long.

<i>Gryposuchus</i> Extinct genus of gavialoid crocodilian

Gryposuchus is an extinct genus of gavialid crocodilian. Fossils have been found from Argentina, Colombia, Venezuela, Brazil and the Peruvian Amazon. The genus existed during the Miocene epoch. One recently described species, G. croizati, grew to an estimated length of 10 metres (33 ft). Gryposuchus is the type genus of the subfamily Gryposuchinae, although a 2018 study indicates that Gryposuchinae and Gryposuchus might be paraphyletic and rather an evolutionary grade towards the gharial.

Hesperogavialis is an extinct genus of gryposuchine gavialid. Fossils have been found from Venezuela and Brazil that date back to the Middle to Late Miocene. Although Hesperogavialis is one of the best known gavialoids from South America, the posterior portion of the skull is still unknown, making any attempts at classification within the family somewhat more difficult than other gavialoids in which much of the skull is present. The genus possibly comprises three species. The type species, H. cruxenti, has been found in the Urumaco Formation in Venezuela. A second possible species, named H. bocquentini, has been described from the Solimões Formation in Acre, Brazil, and can be distinguished from H. cruxenti by the asymmetry seen in the anterior portion of the nasals and the small distance between alveoli. A third species can be recognized from the same locality in Acre, although a formal name has yet to be given to it.

Ikanogavialis is an extinct genus of gavialid crocodilian. Fossils have been found in the Urumaco Formation in Urumaco, Venezuela and the Solimões Formation of Brazil. The strata from which remains are found are late Miocene in age, rather than Pliocene as was once thought. A possible member of this genus survived into the Late Holocene on Muyua or Woodlark Island in Papua New Guinea.

Culebrasuchus is an extinct, monotypic genus of caiman alligatorid known from the Early to Middle Miocene (Hemingfordian) of the Panama Canal Zone of Panama. It contains a single species, Culebrasuchus mesoamericanus.

Centenariosuchus is an extinct genus of caimanine crocodylian known from the Miocene of the Panama Canal Zone of Panama. It contains a single species, Centenariosuchus gilmorei, that was named in 2013 in honor of the upcoming centennial anniversary of the digging of the Panama Canal. Two fossil specimens consisting of skull fragments were found in the Early to Middle Miocene Cucaracha Formation in 2009 and 2011, and may belong to a single individual. The species is diagnosed by a combination of skull features that it shares with basal caimans like Tsoabichi, Eocaiman, Culebrasuchus, and the living genus Paleosuchus, as well as more derived caimans such as those in the genus Caiman. One feature that distinguishes Centenariosuchus from all other caimans is the straight outer margin of a hole on the underside of the skull called the suborbital fenestra. According to one phylogenetic analysis of caimanine relationships, Centenariosuchus falls within a clade or evolutionary grouping of caimans that includes the very large and highly specialized forms Purussaurus and Mourasuchus, known from the Miocene of South America.

Globidentosuchus is an extinct genus of basal caimanine crocodylian known from the late Middle to Late Miocene of the Middle and the Upper Members of the Urumaco Formation at Urumaco, Venezuela. Its skull was very short and robust, with large units of spherical teeth used to break the shells of molluscs as part of its durophagus diet. It is thought to be one of the most basal Caimanines, even sharing some traits with alligatorids.

<i>Caiman wannlangstoni</i> Extinct species of reptile

Caiman wannlangstoni is an extinct species of caiman that lived in what is now the Amazon Basin and surrounding areas during the Middle and Late Miocene. Fossils of C. wannlangstoni have been found in the Pebas Formation near Iquitos in Peru and include partial skulls and isolated skull bones. Other fossils were uncovered from the Urumaco Formation in Venezuela and the Laventan Honda Group of Colombia. The species was first described in 2015. Features that in combination distinguish C. wannlangstoni from other caimans include a deep snout, a wavy upper jaw margin, a large and upward-directed narial opening, and blunt teeth at the back of the jaws. Based on the sizes of the skulls, its estimated body length is about 211 to 227 centimetres.

<i>Kuttanacaiman</i> Extinct genus of reptiles

Kuttanacaiman is a monotypic genus of extinct caiman represented by the type species Kuttanacaiman iquitosensis. Kuttanacaiman lived in what is now the Amazon basin during the Middle Miocene, approximately 13 million years ago (Ma). The species was named in 2015 on the basis of one nearly complete skull and a second partial skull from the Pebas Formation near Iquitos, Peru. K. iquitosensis is characterized by a short, rounded snout and blunt teeth at the back of its jaws that were likely adapted to crushing freshwater bivalves. Its estimated total body length is 171.2 to 189.1 centimetres.

<i>Gnatusuchus</i> Extinct genus of reptiles

Gnatusuchus is an extinct genus of caiman represented by the type species Gnatusuchus pebasensis from the Middle Miocene Pebas Formation of Peru. Gnatusuchus lived about 13 million years ago (Ma) in a large wetland system called the Pebas mega-wetlands that covered over one million square kilometers of what is now the Amazon Basin.

<i>Astorgosuchus</i> Extinct genus of reptiles

Astorgosuchus is an extinct monospecific genus of crocodilian, closely related to true crocodiles, that lived in Pakistan during the late Oligocene period. This crocodile may have reached lengths of up to 8 m (26 ft) and is known to have preyed on many of the large mammals found in its environment. Bite marks of a large crocodile have been found on the bones of juvenile Paraceratherium, however if these were left by Astorgosuchus cannot be said with certainty. The genus contains a single species, Astorgosuchus bugtiensis, which was originally named as a species of Crocodylus in 1908 and was moved to its own genus in 2019.

The Urumaco Formation is a formation in Venezuela that includes deposits from the Late Miocene. It is the site of several "giant forms": the turtles, crocodiles, sloths and rodents of Urumaco are among the largest of their groups.

Bairdemys is an extinct genus of side-necked turtles in the family Podocnemididae. The genus existed from the Late Oligocene to Late Miocene and its fossils have been found in South Carolina, Puerto Rico, Panama and Venezuela. The genus was described in 2002 by Gaffney & Wood and the type species is B. hartsteini.

Acresuchus is an extinct monospecific genus of medium-sized caiman from the Late Miocene of western Brazil and Venezuela. The genus contains a single species, Acresuchus pachytemporalis. Acresuchus is a close relative of the giant caiman Purussaurus.

References

  1. ↑ Rio, Jonathan P.; Mannion, Philip D. (6 September 2021). "Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem". PeerJ . 9: e12094. doi: 10.7717/peerj.12094 . PMC   8428266 . PMID   34567843.
  2. 1 2 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).
  3. ↑ Aguilera, O. A. (2004). Tesoros paleontológicos de Venezuela: Urumaco, patrimonio natural de la humanidad. Caracas: Editorial Arte.
  4. ↑ Aguilera, Orangel A.; Riff, Douglas; Bocquentin‐Villanueva, Jean (2006-01-01). "A new giant Purussaurus (Crocodyliformes, Alligatoridae) from the Upper Miocene Urumaco Formation, Venezuela". Journal of Systematic Palaeontology. 4 (3): 221–232. doi:10.1017/S147720190600188X. ISSN   1477-2019. S2CID   85950121.
  5. ↑ 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.
  6. 1 2 3 4 5 6 7 8 9 10 Fortier, Daniel C.; De Souza-Filho, Jonas P.; Guilherme, Edson; Maciente, Andréa A. R.; Schultz, Cesar L. (2014-06-07). "A new specimen of Caiman brevirostris (Crocodylia, Alligatoridae) from the late Miocene of Brazil". Journal of Vertebrate Paleontology. 34 (4): 820–834. Bibcode:2014JVPal..34..820F. doi:10.1080/02724634.2014.838173. ISSN   0272-4634. S2CID   86506092.
  7. ↑ Scheyer, T. M., & Delfino, M. (2016). The late Miocene caimanine fauna (Crocodylia: alligatoroidea) of the Urumaco Formation, Venezuela. Palaeontologia Electronica, 19(3), 1-57.
  8. 1 2 3 4 5 6 Salas-Gismondi, Rodolfo; Flynn, John J.; Baby, Patrice; Tejada-Lara, Julia V.; Wesselingh, Frank P.; Antoine, Pierre-Olivier (2015-04-07). "A Miocene hyperdiverse crocodylian community reveals peculiar trophic dynamics in proto-Amazonian mega-wetlands". Proceedings of the Royal Society B: Biological Sciences. 282 (1804): 20142490. doi:10.1098/rspb.2014.2490. PMC   4375856 . PMID   25716785.
  9. ↑ Bona, P., & Desojo, J. B. (2011). Osteology and cranial musculature of Caiman latirostris (Crocodylia: Alligatoridae). Journal of Morphology, 272(7), 780-795.
  10. ↑ 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.
  11. ↑ Medem, F. (1983). Los Crocodylia de Sur America, Volume 2. Universidad Nacional de Colombia, Bogota, 270 pp.
  12. ↑ 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.
  13. ↑ Cadena, E.-A.; Scheyer, T. M.; Carrillo-Briceño, J. D.; Sánchez, R.; Aguilera-Socorro, O. A; Vanegas, A.; Pardo, M.; Hansen, D. M.; Sánchez-Villagra, M. R. (2020-02-14). "The anatomy, paleobiology, and evolutionary relationships of the largest extinct side-necked turtle". Science Advances. 6 (7): eaay4593. Bibcode:2020SciA....6.4593C. doi:10.1126/sciadv.aay4593. ISSN   2375-2548. PMC   7015691 . PMID   32095528.
  14. ↑ Bocquentin, Jean (2006-08-30). "Stupendemys souzai sp. nov. (Pleurodira, Podocnemididae) from the Miocene-Pliocene of the Solimões Formation, Brazil". Revista Brasileira de Paleontologia. 9 (2): 187–192. doi: 10.4072/rbp.2006.2.02 . ISSN   1519-7530.
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