Hesperogavialis
Encyclopedia
Hesperogavialis is an extinct genus
of gryposuchine
gavialid
. Fossil
s have been found from Venezuela
and Brazil
that date back to the late Miocene
and Pliocene
. 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 from the Urumaco Formation in Venezuela. A second possible species, named H. bocquentini, has been described from 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.
-premaxilla
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 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.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of gryposuchine
Gryposuchinae
Gryposuchinae is an extinct subfamily of gavialid crocodylians. Gryposuchines lived mainly in South America during the Oligocene and Miocene epochs. Most were long-snouted coastal forms. The group was named in 2007 and includes genera such as Gryposuchus and Aktiogavialis.-Description:Gryposuchines...
gavialid
Gavialidae
Gavialidae is a family of reptiles within the order Crocodilia. Gavialidae consists of only one surviving species, the gharial , which is native to India. Many extinct species are also known...
. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s have been found from Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
and Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
that date back to the late Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
and Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
. 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
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, H. cruxenti, has been found from the Urumaco Formation in Venezuela. A second possible species, named H. bocquentini, has been described from Acre
Acre (state)
Acre is one of the 27 states of Brazil. It is situated in the southwest of the Northern Region, bordering Amazonas to the north, Rondônia to the east, Bolivia to the southeast and the Ucayali Region of Peru to the south and west. It occupies an area of 152,581.4 km2, being slightly smaller...
, 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.
Phylogenetics
Although a South American gryposuchine, Hesperogavialis may actually have had closer relations to the extant Gavialis known from Asia. This has been concluded on the basis of a lack of a nasalNasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
-premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
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 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.
External links
- Hesperogavialis in the Paleobiology DatabasePaleobiology Database' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...