''Hesperogavialis'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of gryposuchine gavialid.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s have been found from

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

and

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

that date back to the Middle to Late Miocene. Although ''Hesperogavialis'' is one of the best known

gavialoid Gavialoidea is one of three superfamilies of crocodylians, the other two being Alligatoroidea and Crocodyloidea. Although many extinct species are known, only the gharial ''Gavialis gangeticus'' and the false gharial ''Tomistoma schlegelii'' are ...

s 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 In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

, ''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 The Pebas Formation is a lithostratigraphic unit of Miocene age, found in western Amazonia. The formation extends over , including parts of Brazil, Peru, Ecuador and Colombia.Wesselingh et al., 2006 It is interpreted as representing the deposits ...

Acre The acre is a unit of land area used in the imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imp ...

, 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 Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...

. A third species can be recognized from the same locality in Acre, although a formal name has yet to be given to it.

Phylogenetics

Although considered a South American gryposuchine, ''Hesperogavialis'' may actually have had closer relations to the extant ''

Gavialis ''Gavialis'' is a genus of crocodylians that includes the living gharial ''Gavialis gangeticus'' and one known extinct species, '' Gavialis bengawanicus.'' ''G. gangeticus'' comes from the Indian Subcontinent, while ''G. bengawanicus'' is known ...

'' known from Asia. This has been concluded on the basis of a lack of a

nasal Nasal is an adjective referring to the nose, part of human or animal anatomy. It may also be shorthand for the following uses in combination: * With reference to the human nose: ** Nasal administration, a method of pharmaceutical drug delivery ** ...

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

ry contact on the rostrum that can be seen in the extinct South American gavialoids. The position of these bones bears a closer resemblance to ''Gavialis'' by being rather slender and extending from the orbits to the middle of the rostrum while being considerably separated from the premaxilla. This close relationship suggests that there may have been multiple gavialid dispersal events from the

Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by the ...

to South America. It has also been proposed that this is just an independently derived characteristic unique to ''Hesperogavialis'' among the gryposuchines, and that it does not suggest any relationship to Asian gavialoids.Langston, W. and Gasparini, Z. (1997). Crocodilians, ''Gryposuchus'', and the South American gavials. ''In:'' Kay, R. F., Madden, R. H, Cifelli, R. L., and Flynn, J. J., eds., ''Vertebrate paleontology in the neotropics''. Smithsonian Institution Press; Washington, DC. pp. 113-154.

References

{{Taxonbar, from=Q13413889 Gavialidae Miocene crocodylomorphs Miocene reptiles of South America Prehistoric pseudosuchian genera Huayquerian Chasicoan Mayoan Neogene Brazil Fossils of Brazil Neogene Venezuela Fossils of Venezuela Fossil taxa described in 1981