Listrognathosuchus
Encyclopedia
Listrognathosuchus is an extinct genus
of alligatoroid
crocodilia
n. Fossil
s date back to the middle Paleocene
epoch. In 1997, the generic name replaced that of Leidyosuchus
for the species L. multidentatus (now the type species
of Listrognathosuchus). "L." multidentalis was first described by Charles Mook in 1930 on the basis of the holotype AMNH
5179, consisting of a partial vertebral column, mandible
, partial left ilium
, and left tibia
, found from a locality in Torrejon Arroyo, New Mexico
(then referred to as the Torrejon beds, and now thought to be part of the Nacimiento Formation
).
alligatoroid. Listrognathosuchus is closely related to Borealosuchus
, 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 or a relative of later crocodylids, and even as a member of its own subfamily of broad snouted early eusuchians, Leidysuchinae. 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.
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 alligatoroid
Alligatoroidea
Alligatoroidea is a superfamily of crocodilians that evolved in the Late Cretaceous period. Cladistically, it is defined as Alligator mississippiensis and all crocodylians more closely related to A. mississippiensis than to either Crocodylus niloticus or Gavialis gangeticus ....
crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
n. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s date back to the middle Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
epoch. In 1997, the generic name replaced that of Leidyosuchus
Leidyosuchus
Leidyosuchus 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 from the middle Campanian age Dinosaur Park Formation...
for the species L. multidentatus (now 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...
of Listrognathosuchus). "L." multidentalis was first described by Charles Mook in 1930 on the basis of the holotype AMNH
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...
5179, consisting of a partial vertebral column, mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
, partial left ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...
, and left tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
, found from a locality in Torrejon Arroyo, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
(then referred to as the Torrejon beds, and now thought to be part of the Nacimiento Formation
Nacimiento Formation
The Nacimiento Formation is a sedimentary rock formation found in the San Juan Basin of western New Mexico and named for the Nacimiento Mountains...
).
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 basalBasal (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:...
alligatoroid. Listrognathosuchus is closely related to Borealosuchus
Borealosuchus
Borealosuchus is an extinct genus of crocodilian 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 Leidyosuchus. The species assigned to it are:B...
, a more basal eusuchian that is not an alligatoroid, but rather a close relative of a monophyletic group of which the superfamilies
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
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 or a relative of later crocodylids, and even as a member of its own subfamily of broad snouted early eusuchians, Leidysuchinae. 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.