''Allognathosuchus'' (meaning "other jaw crocodile") 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 ...

alligatorine Alligatorinae is a subfamily within the family Alligatoridae that contains the alligators and their closest extinct relatives, and is the sister taxon to Caimaninae (the caimans). Many genera in Alligatorinae are described, but only the genus ''A ...

crocodylia 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 with a complicated

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

history. It was named in 1921. Allognathosuchus gracilis

Description

''Allognathosuchus'' was a medium-sized predator up to 1.5 m in length. This 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 is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

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

crocodyliform Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the only pseudo ...

lineages.

Taxonomy

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 ...

, ''A. polyodon'', is from the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

-age

Bridger Formation The Bridger Formation is a geologic formation in southwestern Wyoming. It preserves fossils dating back to the Ypresian Epoch of the Paleogene Period. The formation was named by American geologist Ferdinand Vandeveer Hayden for Fort Bridger, whi ...

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

; it is based on fossils that are difficult to distinguish from other

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

alligatorids. ''A. heterodon'' is from the Eocene-age

Wasatch Formation The Wasatch Formation (Tw)Shroba & Scott, 2001, p.3 is an extensive highly fossiliferous geologic formation stretching across several basins in Idaho, Montana Wyoming, Utah and western Colorado.Wildwood Formation (also known as the "Wildwood alligatorid" and possibly two species), and ''A. woutersi'', which may belong to ''

Diplocynodon ''Diplocynodon'' is an extinct genus of alligatoroid that lived during the Paleocene to Middle Miocene 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, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...

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

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 (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting . Considered t ...

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 (NALMA), typically set from 55,400,000 to 50,300,000 years BP lasting . It is usually co ...

, and

Bridgerian The Bridgerian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 50,300,000 to 46,200,000 years BP lasting . It is usually c ...

North American Land Mammal Ages The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when ref ...

. Several other genera and species were previously assigned to ''Allognathosuchus'', giving it a potential

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostrati ...

range, and a geographic range covering

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, and

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. Christopher Brochu reviewed the genus in 2004, and in light of the fragmentary remains of several of the species involved, recommended conservative use of the genus. He excluded '' Albertochampsa langstoni'', '' Arambourgia gaudryi'', and '' Wannaganosuchus brachymanus'' from ''Allognathosuchus'', and resurrected ''

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 ...

'' and ''

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 (United States). It was named in 1942 by Charles C. Mook, and the original ...

'' from synonymy with ''Allognathosuchus'' after finding them not to group with ''A. polyodon'' to the exclusion of other alligatorines. Recent studies have consistently resolved ''Allognathosuchus polyodon'' and ''Allognathosuchus wartheni'' as members of

Alligatorinae Alligatorinae is a subfamily within the family Alligatoridae that contains the alligators and their closest extinct relatives, and is the sister taxon to Caimaninae (the caimans). Many genera in Alligatorinae are described, but only the genus ' ...

, although their relative placement is disputed, as shown by the

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

s below. Cladogram from 2018 Bona ''et al.'' study: Cladogram from 2019 Massonne ''et al.'' study: Cladogram from 2020 Cossette & Brochu study:

References

{{Taxonbar, from=Q4733055 Alligatoridae Eocene crocodylomorphs Eocene reptiles of Europe Eocene reptiles of North America Prehistoric pseudosuchian genera Fossil taxa described in 1921