''Shansisuchus'' (meaning "

Shanxi Shanxi; Chinese postal romanization, formerly romanised as Shansi is a Provinces of China, province in North China. Its capital and largest city of the province is Taiyuan, while its next most populated prefecture-level cities are Changzhi a ...

Province crocodile") is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of archosauriform reptile belonging to the family Erythrosuchidae that lived during the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

in what is now China. The first fossils of ''Shansisuchus'' were discovered from the Ermaying Formation of

(Shansi) province in 1964 by Chinese paleontologist Yang Zhongjian. Like other erythrosuchids, ''Shansisuchus'' was a large-bodied carnivore with a large, deep skull. ''Shansisuchus'' is unique among early archosauriforms in having a hole in its skull called a subnarial fenestra.

Description

''Shansisuchus'' is a large erythrosuchid distinguished from other members of the group by two characters: a tongue-and-groove articulation between 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 mammals h ...

and

nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...

s of the skull and the presence of a subnarial fenestra. In ''Shansisuchus'' the premaxilla, a bone that makes up the front of the snout, projects backward and fits into a groove in the nasal, a bone that makes up the top of the snout. The subnarial fenestra is present between the external nares (nasal opening) and the

antorbital fenestra An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with Archosauriformes, archosauriforms, first appearing during the Triassic Period. Among Extant ...

, a hole in front of the eye socket. It is separated from the antorbital fenestra by a vertical projection of the

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

bone. A subnarial fenestra is present in a few other more derived archosauriforms such as some

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s and pseudosuchians, but its morphology in ''Shansisuchus'' is unique.

History of research

''Shansisuchus'' is known from many fossil skeletons representing more than a dozen individuals, making it one of the best known erythrosuchids. However, all but one specimen discovered in 2010 (a complete skull and 14 vertebrae from Jixian County) are disarticulated, meaning that many aspects of its anatomy had been poorly understood before that specimen was described. Most specimens have been found in a fossil locality in Wuxiang County, and others have been found in localities in Ningwu, Yushe,

Jingle A jingle is a short song or tune used in advertising and for other commercial uses. Jingles are a form of sound branding. A jingle contains one or more hooks and meanings that explicitly promote the product or service being advertised, usually ...

, and

Xing Xing may refer to: * an abbreviation for crossing such as Pedestrian crossing, Pedestrian Xing or Wildlife crossing, Wildlife Xing, primarily used in North America * Chinese surname (姓, ''xing'') * Xing (surname) (邢), a Chinese surname * Xing ...

counties. Three species of ''Shansisuchus'' have been named: the

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

''Shansisuchus shansisuchus'', which is known from over ten individuals; ''S. heiyuekouensis'', which is known from five individuals; and ''S. kuyeheensis'', which is known from one individual.

Relationships

''Shansisuchus'' belongs to a group of reptiles called Archosauriformes, which is today represented by

crocodilian Crocodilia () is an Order (biology), order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorp ...

s and

birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

but also includes a diversity of extinct forms extending back to the

Late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...

. It is a basal archosauriform that lies outside Archosauria, the

crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor ...

originating with the

last common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...

of birds and crocodilians. When ''Shansisuchus'' was first described, Yang placed it in its own family, Shansisuchidae. In 1992 ''Shansisuchus'' was reassigned to the family Erythrosuchidae and proposed to be the closest relative of the genus '' Vjushkovia'' (now considered a synonym of''Garjainia''). A

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analysis published in 2013 found that ''Vjushkovia'' was more closely related to ''Erythrosuchus'', and that ''Shansisuchus'' lied outside the ''Vjushkovia''+''Erythrosuchus''

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

as a more basal erythrosuchid. Below is a

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

from the 2013 analysis:

References

{{Taxonbar, from=Q1008362 Erythrosuchidae Prehistoric reptile genera Middle Triassic reptiles of Asia Triassic China Fossils of China Fossil taxa described in 1964 Taxa named by Yang Zhongjian