''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 ...

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 (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 The Hassberge Formation is a Formation (geology), geologic formation in Bavaria, Germany. It preserves fossils dating back to the Carnian stage of the Triassic Period (geology), period.

at Fossilworks.org Fossil content ...

of Germany, the Drawno Beds of Poland, and the Lossiemouth Sandstone of Scotland. Supposed fossils from North America, North and South America have been placed into their own genera, ''Calyptosuchus'' and ''Aetosauroides'', respectively.

Description

''Stagonolepis robertsoni'' was about long. It was a quadrupedal animal covered in thick scute, 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 Archosauriformes, archosauriform 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 in the front of its jaws, 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 peg-like teeth at the back of its mouth would have been suitable for chewing tough vegetation, including horsetails, ferns, and the newly evolved cycads. A 2018 paper suggested that ''Stagonolepis olenkae'''s forelimb morphology is an adaptation for Fossorial, 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 Scotland, while ''S. olenkae'' is known from deposits near Krasiejów, Poland. ''S. olenkae'' is stratigraphically 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 ''Aetosauroides'' from South America has been considered a junior synonym 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 ''Calyptosuchus'', a stagonolepidid from the

Dockum Group of the United States, 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 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