''Euscolosuchus'' 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 ...

suchia Suchia (from Ancient Greek σούχος (''soúkhos''), meaning "crocodile") is a clade of archosaurs containing the majority of pseudosuchians (crocodilians and their extinct relatives). It was defined as the least inclusive clade containing ''A ...

n archosaurs 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 ...

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

. It is probably an aetosauriform, as the sister taxon to '' Acaenasuchus'' and a relative of

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 ...

Discovery

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 preserve ...

s have been found from the Tomahawk Creek Member of the

Turkey Branch Formation The Doswell Formation (also known as the Doswell Group) is a geologic unit of Upper Triassic age, part of the Newark Supergroup. The Doswell Formation was originally named to refer to a geological sequence which forms the lower part of the sediment ...

(part of the

Newark Supergroup The Newark Supergroup, also known as the Newark Group, is an assemblage of Upper Triassic and Lower Jurassic sedimentary and volcanic rocks which outcrop intermittently along the east coast of North America. They were deposited in a series of Tr ...

), outcropping in the Richmond Basin of east-central

. The locality from which the material was found dates back to the early

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227.3 ...

stage of the

, based on

palynological Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the mic ...

studies. These strata are known for the abundance of fossil material belonging to

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

s in relation to other sites of the Newark Supergroup in the Richmond Basin that generally lack such material. The site is unique among others in the supergroup and closely resembles localities in the southern hemisphere, as is suggested by the presence of numerous fossils of

traversodont 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 ...

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s found from the area. Other tetrapods present include

procolophonia Procolophonia is an extinct suborder (clade) of herbivorous reptiles that lived from the Middle Permian till the end of the Triassic period. They were originally included as a suborder of the Cotylosauria (later renamed Captorhinida Carroll ...

ns, chiniquodontids, and sphenodonts.

Description

The name ''Euscolosuchus'', meaning "well pointed crocodile" in

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

, refers to the prominent lateral spikes projecting from the posterior cervical and dorsal

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 that are characteristic of the genus. These osteoderms imbricate (overlap) paramedially down the back and form a narrow dorsal

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 ...

similar to 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 ...

stagonolepidids. A spinal table formed by broadened

neural arch Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

es help support these osteoderms on the back. The

scutes A scute () or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterio ...

interlock with one another through a series of grooves and projections, with each plate overlapping the one posterior to it and having an anterolateral articulatory process project anteriorly from it and lie over the plate in front of it. These osteoderms, as well as the fragmentary vertebrae, are all that are known from the genus and thus the only material from which the genus can be classified.

Classification

''Euscolosuchus'' is widely considered to be a

pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

n, the side of archosaur reptiles which are more closely related to crocodiles than to birds and other dinosaurs. It was originally described as a close relative of

crocodylomorphs Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably more ...

, a long-lasting pseudosuchian

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 ...

that includes living crocodilians. Other pseudosuchians initially thought to be closely related to crocodylomorphs include the lightly-built ''

Gracilisuchus ''Gracilisuchus'' (meaning "slender crocodile") is an extinct genus of tiny pseudosuchian (a group which includes the ancestors of crocodilians) from the Late Triassic of Argentina. It contains a single species, ''G. stipanicicorum'', which is pl ...

'' and possibly ''

Erpetosuchus ''Erpetosuchus'' is an extinct genus of pseudosuchian from the Late Triassic. The type species of ''Erpetosuchus'' is ''E. granti''. It was first described by E. T. Newton in 1894 for remains found in northeastern Scotland, including four specim ...

''. More recently, the large carnivorous

rauisuchids Rauisuchidae is a group of large (up to ) predatory Triassic archosaurs. Some disagreement exists over which genera should be included in the Rauisuchidae and which should be in the related Prestosuchidae and Poposauridae, and indeed whether thes ...

such as ''

Postosuchus ''Postosuchus'', meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, ''P. kirkpatricki'' and ''P. alisonae'', that lived in what is now North America during the Late Triassic. ''Postosuchus'' is a ...

'' have been singled out as the closest relatives of crocodylomorphs, and some early crocodylomorphs (such as ''

Carnufex ''Carnufex'' is an extinct genus of crocodylomorph suchian from the Late Triassic of North America. The genus was first described in 2015 by Zanno ''et al.'', who named the Binomial nomenclature, binomial ''Carnufex carolinensis'', meaning "Carol ...

'' and '' Redondavenator'') were similarly large carnivores. In the midst of these interpretations of archosaur evolution, ''Euscolosuchus'' was left without clear affinities. Some compared it with '' Acaenasuchus'', an equally ambiguous armored archosaur from the

Chinle Formation The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In ...

. ''Acaenasuchus'' was generally considered a valid small aetosaur or juvenile fossils from an already established aetosaur genus. A 2020 redescription recovered ''Acaenasuchus'' and ''Euscolosuchus'' as sister taxa (each other's closest relative), and as members of the

Aetosauriformes Aetosauriformes is an extinct clade of early-diverging pseudosuchians (the group of archosaurs that contains modern crocodylians and their stem group relatives). It includes the aetosaurs, a group of heavily armoured and at least partially herbiv ...

. This means that they were not true aetosaurs, but were still related to them. The herbivorous archosaur ''

Revueltosaurus ''Revueltosaurus'' ("Revuelto lizard") is an extinct genus of suchian pseudosuchian from Late Triassic (late Carnian to middle Norian stage) deposits of New Mexico, Arizona and North Carolina, United States. Many specimens, mostly teeth, have bee ...

'' was also placed as an aetosauriform, a result recovered by many previous analyses.

References

External links

''Euscolosuchus''
in the

Paleobiology Database The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Pale ...

{{Taxonbar, from=Q5414219 Late Triassic archosaurs of North America Prehistoric pseudosuchian genera