''Siquisiquesuchus'' (meaning " Siquisique crocodile" after the town in

Lara Lara may refer to: Places * Lara (state), a state in Venezuela *Electoral district of Lara, an electoral district in Victoria, Australia * Lara, Antalya, an urban district in Turkey * Lara, Victoria, a township in Australia * Lara de los Infa ...

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 ...

, near where the first described specimens were found) 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 ...

gavialid Gavialidae is a family of large semiaquatic crocodilians with elongated, narrow snouts. Gavialidae consists of two living species, the gharial (''Gavialis gangeticus'') and the false gharial (''Tomistoma schlegelii''), both occurring in Asia. Man ...

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

n. It is known from cranial remains and a few

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...

l bones found in

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

-age rocks of the Castillo Formation in northwestern Venezuela.

Description

''Siquisiquesuchus'' is based on the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

MBLUZ–P–5050, a nearly complete skull and lower jaws. It was found near Lara in rocks of the Early Miocene-age Castillo Formation. Two other partial skulls, partial

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

e, a

thigh bone The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

, partial

upper arm In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...

, and partial

shin bone The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

were recovered from another locality. These bones were described by Christopher Brochu and Ascanio Rincón in

2004 2004 was designated as an International Year of Rice by the United Nations, and the International Year to Commemorate the Struggle Against Slavery and its Abolition (by UNESCO). Events January * January 3 – Flash Airlines Flight 6 ...

. 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 ...

is ''S. venezuelensis''. Like other gavialoids, ''Siquisiquesuchus'' had a long, narrow

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

on its skull, accounting for approximately 60% of the skull's length. The number of teeth in the

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 bones at the tip of the snout is not known, but the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

e making up most of the rostrum had at least 20 teeth each, and the

dentaries In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

of the lower jaws had at least 23. Some details of the described skulls cannot be determined because the sutures are not visible. ''Siquisiquesuchus'' was found by Brochu and Rincón to be the oldest known gavialoid from South America, sharing various anatomical details with '' Gryposuchus colombianus'' (to which it is particularly similar) and other South American gavialoids. Later studies have concurred with a gavialoid identity, finding the genus to be related to such genera as ''

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 ...

'', ''Gryposuchus'', ''

Ikanogavialis ''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 t ...

'', and ''

Piscogavialis ''Piscogavialis'' is an extinct monospecific genus of gryposuchine gavialid crocodylian. The only species yet known is ''P. jugaliperforatus''. Fossils of ''Piscogavialis'' have been found from the Mio-Pliocene Pisco Formation of the Sacaco Bas ...

''. Vélez–Juarbe and colleagues (2007) found it to be a

gryposuchinae Gryposuchinae is an extinct subfamily (biology), subfamily of Gavialidae, gavialid crocodylians. Gryposuchines lived mainly in the Miocene of South America. However, ''Ikanogavialis, "Ikanogavialis" papuensis'' may have survived more recently, in ...

, while Jouve and colleagues (2008) did not assign families or subfamilies. Brochu and Rincón noted that ''Siquisiquesuchus'' was found in marginal marine deposits. This, along with similarities to

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 ...

gavialoids, was interpreted as evidence that gavialoids "dispersed across a marine barrier to the

Neotropics The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropics, tropical Ecoregion#Terrestrial, terrestrial ecoregions of the Americas and the entire South American temperat ...

during the

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

References

{{Taxonbar, from=Q7525885 Gavialidae Prehistoric pseudosuchian genera Neogene crocodylomorphs Miocene reptiles of South America Friasian Santacrucian Colhuehuapian Neogene Venezuela Fossils of Venezuela Fossil taxa described in 2004