Ilchunaia is an extinct genus

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 sebecid

Sebecidae

Sebecidae is an extinct family of prehistoric crocodylomorphs. They lived mostly in Argentina.This group included many medium and large - sized genera, from Sebecus to a giant indeterminate unnamed species from the Miocene.-Phylogeny:...

 mesoeucrocodylia

Mesoeucrocodylia

Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....

n. Fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s have been found from the Divisadero Largo Formation of Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 dating back to the Late Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

, and a locality in Mendoza, Argentina

Mendoza, Argentina

Mendoza is the capital city of Mendoza Province, in Argentina. It is located in the northern-central part of the province, in a region of foothills and high plains, on the eastern side of the Andes. As of the , Mendoza's population was 110,993...

 dating back to the Oligocene

Oligocene

The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

. Little material is known from the genus, with only the anterior portion of the skull being present to study (the holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 has since been lost).

The placement of Ilchunaia within Sebecosuchidae has been questioned in the past, and many recent phylogenetic analyses have shown the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 to be entirely paraphyletic, with members most likely being basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 sebecosuchia

Sebecosuchia

Sebecosuchia is an extinct group of mesoeucrocodylian crocodyliforms that includes the families Sebecidae and Baurusuchidae. The group first appeared in the Late Cretaceous with the baurusuchids and went extinct in the Miocene with the last sebecids. Fossils have been found primarily from South...

ns ancestral to the baurusuchids

Baurusuchidae

Baurusuchidae is a Gondwanan family of mesoeucrocodylians that lived during the Late Cretaceous. It is a group of terrestrial hypercarnivorous crocodilians from South America and possibly Pakistan. Baurusuchidae has been defined as a clade containing the most recent common ancestor of Baurusuchus...

.

External links

• Ilchunaia in the Paleobiology Database
  Paleobiology 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...