''Stagonolepis'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

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 ...

stagonolepidid Aetosaurs () are heavily armored reptiles belonging to the extinct order Aetosauria (; from Greek, (aetos, "eagle") and (, "lizard")). They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs ...

aetosaur Aetosaurs () are heavily armored reptiles belonging to the extinct order Aetosauria (; from Greek, (aetos, "eagle") and (, "lizard")). They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs ...

known 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 ...

(

Carnian The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by t ...

stage)

Hassberge Formation The Hassberge Formation is a geologic formation in Bavaria, Germany. It preserves fossils dating back to the Carnian stage of the Triassic period. Hassberge Formationat Fossilworks.org Fossil content Insects ;Coleoptera * '' Carabilarva tr ...

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

, the Drawno Beds of

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populous ...

, and the

Lossiemouth Sandstone The Lossiemouth Sandstone is a Middle to Late Triassic (Ladinian to Norian) age geological formation. It is exposed on the south side of the Moray Firth near Lossiemouth and near Golspie in Sutherland. Dinosaur remains are among the fossils tha ...

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

. Supposed fossils from

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

have been placed into their own genera, ''

Calyptosuchus ''Calyptosuchus'' (meaning "covered crocodile") is an extinct genus of aetosaur from the Late Triassic of North America. Like other aetosaurs, it was heavily armored and had a pig-like snout used to uproot plants. Description ''Calyptosuchus'' ...

'' and ''

Aetosauroides ''Aetosauroides'' (meaning "''Aetosaurus''-like") is an extinct genus of aetosaur from the Late Triassic of South America. It is one of four aetosaurs known from South America, the others being ''Neoaetosauroides'', '' Chilenosuchus'' and ''Aetob ...

'', respectively.

Description

''Stagonolepis robertsoni'' was about long. It was a quadrupedal animal covered in thick armoured scales that ran down the length of its body. A slow-moving browser, it would have used this heavy body armour to repel attacks from contemporary

thecodont Thecodontia (meaning 'socket-teeth'), now considered an obsolete taxonomic grouping, was formerly used to describe a diverse "order" of early archosaurian reptiles that first appeared in the latest Permian period and flourished until the end of th ...

carnivores. ''Stagonolepis'' had a very small head for its size; it was only , accounting for less than 10% of the total body length. It had no

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

in the front of its

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

s, but instead had a beak-like tip that arched upwards. This would have allowed it to uproot plants in a similar manner to a modern

pig The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus s ...

. The peg-like teeth at the back of its mouth would have been suitable for chewing tough vegetation, including

horsetail ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Eq ...

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s, and the newly evolved

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...

s. A 2018 paper suggested that ''Stagonolepis olenkae'''s forelimb morphology is an adaptation for scratch-digging. According to paleontologist Dawid Dróżdż, "''S. olenkae'' might have used its robust forelimbs to break through the compacted soil with its claws and proceed to dig in search of food in softened substrate with the shovel-like expansion at the tip of its snout."

Species

Fossil remains of ''S. robertsoni'' have been found in

, while ''S. olenkae'' is known from deposits near

Krasiejów Krasiejów (german: Krascheow) is a village in the administrative district of Gmina Ozimek, within Opole County, Opole Voivodeship, in south-western Poland. It lies approximately east of Ozimek and east of the regional capital Opole. The villa ...

. ''S. olenkae'' is

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostrati ...

ally younger the type species of ''Stagonolepis'', ''S. robertsoni'', although it is questioned by some researchers and described as an example of intraspecific variety (e. g. sexual dimorphism) The genus ''

'' from

has been considered a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

of ''Stagonolepis'' by some paleontologists. Two species of ''Aetosauroides'' were named, ''A. scagliai'' and ''A. subsulcatus''. In 2002, Andrew B. Heckert and Spencer G. Lucas proposed that smaller specimens of both species belong to ''Stagonolepis robertsoni'', and larger specimens to ''S. wellesi''. ''S. wellesi'' itself was originally named ''

'', a stagonolepidid from the

Dockum Group The Dockum is a Late Triassic (approximately late Carnian through Rhaetian, or 223–200 Ma) geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern Color ...

of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, which was considered to be a species of ''Stagonolepis'' by Murray & Long in 1989. However, most of the sequential studies conclude that both ''Aetosauroides'' and ''Calyptosuchus'' are valid and

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genera, the former occurs only in South America and the latter only in the United States. ''Stagonolepis'' is restricted to the

stage of Scotland and Poland.

References

{{Taxonbar, from=Q133950 Aetosaurs Carnian genera Late Triassic reptiles of Europe Triassic England Fossils of England Triassic Germany Fossils of Germany Fossils of Poland Late Triassic reptiles of North America Triassic United States Fossils of the United States Chinle fauna Paleontology in New Mexico Fossil taxa described in 1844 Taxa named by Louis Agassiz Prehistoric pseudosuchian genera