Allognathosuchus 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 alligatorine

Alligatorinae

Alligatorinae are one of two subfamilies of the family Alligatoridae.-Taxonomy:* Subfamily Alligatorinae** Genus Chrysochampsa ** Genus Hassiacosuchus ** Genus Navajosuchus ** Genus Ceratosuchus...

 crocodylian with a complicated taxonomic

Taxonomy

Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 history. This small alligatorine is known for its stout jaws and bulbous teeth, found near the rear of the tooth row in upper and lower jaws. These adaptations have historically been interpreted as having been for crushing mollusks

Mollusca

The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...

. Isolated bulbous teeth are often assigned to this genus, although such teeth are known from other crocodyliform

Crocodyliformes

Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians."In 1988, Michael J. Benton and James M. Clark argued that all traditional names for well-known groups of animals should be restricted to their crown clades, that is, used only for...

 lineages. 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...

, A. polyodon, is from the 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...

-age Bridger Formation of Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

; it is based on

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...

 fossils that are difficult to distinguish from other Paleogene

Paleogene

The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...

 alligatorids. A. heterodon is from the Eocene-age Wasatch Formation of Wyoming, A. wartheni is from the Eocene-age Wildwood Formation (also known as the "Wildwood alligatorid," and possibly two species), and A. woutersi, which may belong to Diplocynodon

Diplocynodon

Diplocynodon is an extinct genus of alligatoroid that lived during the Paleocene to middle Miocene 49 million years ago in Europe. It looked very similar to the modern caiman in that it was small and had bony armour scutes covering its neck, back, belly, and tail...

instead, is from the Early Eocene of Belgium

Belgium

Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

. A. polyodon, A. heterodon, and A. wartheni span the Clarkforkian

Clarkforkian

The Clarkforkian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 56,800,000 to 55,400,000 years BP lasting . It is usually considered to be within the Paleocene, more specifically the...

, Wasatchian

Wasatchian

The Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 55,400,000 to 50,300,000 years BP lasting . It is usually considered to be within the Eocene, more specifically the...

, and Bridgerian North American Land Mammal Ages

North American Land Mammal Ages

The North American Mammal Ages establishes a geologic timescale for prehistoric North American fauna beginning 66.5 Ma during the Paleocene and continuing through to the Late Pleistocene...

.

Several other genera and species have been assigned to Allognathosuchus over the years, giving it a potential Upper Cretaceous-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...

 stratigraphic

Stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....

 range, and a geographic range covering North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, and Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

. Christopher Brochu reviewed the genus in 2004 and, in light of the fragmentary remains of several of the species involved, recommended conservative usage of the genus. He excluded Albertochampsa langstoni

Albertochampsa

Albertochampsa is an extinct genus of globidontan alligatoroid from the Late Cretaceous of Alberta. It was named in 1972 by Bruce Erickson, and the type species is A. langstoni. It is known from a skull from the Campanian-age Dinosaur Park Formation, where it was rare; Leidyosuchus is the most...

, Arambourgia gaudryi

Arambourgia

Arambourgia is an extinct genus of alligatorine crocodylian from Europe. It was named in 1905 and synonymized with Allognathosuchus haupti in 1990, but later reassigned as its own genus once again in 2004. It is thought to have been closely related to Hispanochampsa and Procaimanoidea...

, and Wannaganosuchus brachymanus

Wannaganosuchus

Wannaganosuchus is an extinct genus of small alligatorid...

from Allognathosuchus, and, finding the species Allognathosuchus haupti and A. mooki to not group with A. polyodon to the exclusion of other alligatorines, recommended using previously established generic names for those species instead: Hassiacosuchus haupti

Hassiacosuchus

Hassiacosuchus is an extinct genus of small alligatorid from the early Eocene of Germany, found at the Messel pit. It was named in 1935 by K. Weitzel, and the type species is H. haupti. A second species, H. kayi, was named in 1941 by C.C. Mook for material from the Bridgerian of Wyoming, but was...

and Navajosuchus mooki

Navajosuchus

Navajosuchus is an extinct genus of alligatorine crocodylian. Its fossils have been found in the Paleocene-age Nacimiento Formation of the San Juan Basin, New Mexico . It was named in 1942 by Charles C. Mook, and the original type species was N. novomexicanus. N. novomexicanus was based on...

.