''Gorgetosuchus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 ...

aetosaur Aetosaurs () are heavily armored reptiles belonging to the extinct order (biology), order Aetosauria (; from Ancient Greek, Greek, (aetos, "eagle") and (, "lizard")). They were medium- to large-sized Omnivore, omnivorous or Herbivore, herbivor ...

from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

of the

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

, represented by 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 ...

''Gorgetosuchus pekinensis''. It is mainly known from

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of Extant taxon, extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, Temnospondyli, ...

, including the front half of an articulated

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

. ''Gorgotesuchus'' is typically considered a basal desmatosuchin, though alternative interpretations exist.

Discovery

''G. pekinensis'' was named and described by Heckert ''et al.'' (2015) on the basis of ten rows of bony plates called

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amph ...

s, representing the front part of an armored

that would have covered the back of the animal. These plates were found embedded in

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

and conglomerate boulders near a brick quarry in

Chatham County, North Carolina Chatham County ( )
, from the North Carolina Collection's website at the University of North Car ...

, which likely originated from the Late Triassic

Pekin Formation The Pekin Formation is a Late Triassic (Carnian) geological Formation (geology), formation in North Carolina. The Pekin Formation is specific to the Sanford Sub-Basin of the Deep River Basin of North Carolina, although it may be equivalent to the ...

. (The Pekin Formation consists of interbedded red

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

s, sandstones and conglomerates; it was the fine-grained mudstones and siltstones that the mining operation was targeting for

brick-making A brickworks, also known as a brick factory, is a factory for the manufacturing of bricks, from clay or shale. Usually a brickworks is located on a clay bedrock (the most common material from which bricks are made), often with a quarry for cl ...

, so coarser-grained blocks were removed from the pit). ''Gorgetosuchus'' was part of a diverse faunal community in a continental

rift valley A rift valley is a linear shaped lowland between several highlands or mountain ranges produced by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear ...

system during the Late Triassic, which also included

traversodontid Traversodontidae is an extinct family of herbivorous cynodonts. Traversodonts were primarily Gondwanan, with many species known from Africa and South America. Recently, traversodonts have also been found from Europe and North America. Traversodon ...

phytosaur Phytosaurs (Φυτόσαυροι in Greek, meaning 'plant lizard') are an extinct group of large, mostly semiaquatic Late Triassic archosauriform or basal archosaurian reptiles. Phytosaurs belong to the order Phytosauria and are sometimes ref ...

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

s, and

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...

s. ''Gorgetosuchus'' coexisted with two other aetosaurs, '' Lucasuchus'' and ''

Coahomasuchus ''Coahomasuchus'' is an extinct genus of aetosaurine aetosaur. Remains of the genus have been found from deposits in Texas and North Carolina that date to the Otischalkian faunachron (lower late Carnian) of the Late Triassic. It was small for a ...

''.

Description

''Gorgetosuchus'' is unique among aetosaurs in having cervical (neck) osteoderms that nearly wrap around the entire neck and are strongly angled to give the neck a hexagonal shape in cross-section. The lateral (side) and paramedian (upper) osteoderms each bear prominent spines. Other aetosaurs such as '' Longosuchus'' also have neck spines, but only on the lateral osteoderms. The cervical osteoderms are wider than they are long, a feature that unites ''Gorgetosuchus'' with basal "

aetosaurine Aetosaurinae is one of the two main clades of aetosaurs, the other being Desmatosuchia. It is a stem-based taxon defined as all aetosaurs more closely related to ''Aetosaurus'' than ''Desmatosuchus''. Aetosaurinae currently comprises ''Aetosauru ...

" aetosaurs. However, several features of the osteoderms (such as a flange on the lateral cervical osteoderms that overlaps the paramedian osteoderms) link it with the

desmatosuchine Desmatosuchinae is a major subfamily of aetosaurs within the clade Desmatosuchia. It is a stem-based taxon defined as all aetosaurs more closely related to ''Desmatosuchus'' than to ''Stagonolepis,'' ''Aetosaurus'', or ''Paratypothorax''. The c ...

s, a more derived group of aetosaurs.

Classification

Among aetosaurs, ''Gorgetosuchus'' closely resembles ''Lucasuchus'' and ''Longosuchus'', both of which are desmatosuchines. A

phylogenetic analysis 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 data ...

conducted by Heckert ''et al.'' (2015) placed ''Gorgetosuchus'' close to these taxa as the most basal desmatosuchine, but the results were not statistically well supported. Below is a strict consensus tree from their analysis showing the placement of ''Gorgetosuchus'': ''Gorgetosuchus'' was also placed as the basal-most member of Desmatosuchini (traditional desmatosuchines) in an analysis by Parker (2016). However, an analysis by Hoffman ''et al.'' (2018), based on an earlier analysis by Schoch & Desojo (2016), placed it within

Typothoracinae Aetosaurinae is one of the two main clades of aetosaurs, the other being Desmatosuchia. It is a stem-based taxon defined as all aetosaurs more closely related to ''Aetosaurus'' than ''Desmatosuchus''. Aetosaurinae currently comprises ''Aetosaurus ...

, closely related to ''

Typothorax ''Typothorax'' is an extinct genus of typothoracine aetosaur that lived in the Late Triassic. Its remains have been found in North America. Two species are known: ''T. coccinarum'', the type species, and ''T. antiquum''. Description ''Typothor ...

'' and ''

Redondasuchus ''Redondasuchus'' is an extinct genus of aetosaur. It may be a junior synonym of '' Typothorax coccinarum'', another aetosaur. ''Redondasuchus'' is a member of the clade Typothoracisinae within the subfamily Aetosaurinae, and lived during the mi ...

''. Typothoracines and desmatosuchins are known to have a large degree of

homoplasy Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize ...

(convergent evolution) in certain osteoderm traits observed in ''Gorgetosuchus''. On the other hand, other skeletal traits strongly diverge between the two groups, so the position of ''Gorgetosuchus'' would likely stabilize if more non-osteoderm bones were discovered.

References

{{Taxonbar, from=Q20647355 Aetosaurs of North America Fossil taxa described in 2015 Late Triassic pseudosuchians Fossils of North Carolina Prehistoric pseudosuchian genera