''Stagonolepis'' 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 ...

of stagonolepidid

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 ...

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 a ...

(

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) Hassberge Formation of

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, the Drawno Beds of

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

, and the Lossiemouth Sandstone of

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

. 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 considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

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 '' Ae ...

'', 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

archosauriform Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles encompassing archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemming from the last common anc ...

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 jaws are a pair of opposable articulated structures 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 ...

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''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus '' Sus''. Some authorities cons ...

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

horsetail ''Equisetum'' (; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Equisetidae, which ...

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

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 Lossiemouth Sandstone of

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

. ''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: lithost ...

ally younger than the type species ''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 In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

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 of the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, 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 "unisp ...

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 Aetosauria 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