''Listrognathosuchus'' is an extinct

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 ...

alligatoroid Alligatoroidea is one of three superfamilies of crocodylians, the other two being Crocodyloidea and Gavialoidea. Alligatoroidea evolved in the Late Cretaceous period, and consists of the alligators and caimans, as well as extinct members mor ...

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 ...

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s date back to the middle

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

epoch. In 1997, the generic name replaced that of ''

Leidyosuchus ''Leidyosuchus'' (meaning " Leidy's crocodile") is an extinct genus of alligatoroid from the Late Cretaceous of Alberta. It was named in 1907 by Lawrence Lambe, and the type species is ''L. canadensis''. It is known from a number of specimens fro ...

'' for the species ''L. multidentatus'' (now 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 ...

of ''Listrognathosuchus''). ''"L." multidentalis'' was first described by Charles Mook in 1930 on the basis of the holotype

AMNH The American Museum of Natural History (abbreviated as AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. In Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 26 inter ...

5179, consisting of a partial vertebral column,

mandible 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 tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

, partial left ilium, and left

tibia 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 ...

, found from a locality in Torrejon Arroyo,

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

(then referred to as the Torrejon beds, and now thought to be part of the

Nacimiento Formation The Nacimiento Formation is a sedimentary rock formation found in the San Juan Basin of western New Mexico (United States). It has an age of 61 to 65.7 million years, corresponding to the early and middle Paleocene. The formation has yielded an ...

Phylogenetics

The fragmentary nature of the material referable to ''Listrognathosuchus'' have made it hard to classify within Crocodylia, but it is now thought to be a relatively basal alligatoroid. ''Listrognathosuchus'' is closely related to ''

Borealosuchus ''Borealosuchus'' (meaning "boreal crocodile") is an extinct genus of crocodyliforms that lived from the Late Cretaceous to the Eocene in North America. It was named by Chris Brochu in 1997 for several species that had been assigned to ''Leidyos ...

'', a more basal eusuchian that is not an alligatoroid, but rather a close relative of a monophyletic group of which the superfamilies Alligatoroidea and Crocodyloidea comprise. In fact, ''Borealosuchus'' was first used as a replacement name for four species of ''Leidyosuchus'', the same genus that ''Listrognathosuchus multidentatus'' once belonged to. Prior to the reassessment of ''Leidyosuchus'' in 1997, many relationships for the genus within Crocodilia have been considered. It was suggested to be a possible member of

Diplocynodontinae ''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 ...

or a relative of later crocodylids, and even as a member of its own subfamily of broad snouted early eusuchians, Leidysuchinae.Simpson, G. G. (1937). An ancient eusuchian crocodile from Patagonia. ''American Museum Novitates'' 965:1-20. However, with the naming of ''Listrognathosuchus'' and ''Borealosuchus'', most species previously assigned to ''Leidyosuchus'' are now believed to have had little relation to any of the mentioned crocodilians.

References

{{Taxonbar, from=Q16984742 Crocodilians Paleocene crocodylomorphs Paleocene reptiles of North America