Stagonolepis

Stagonolepis is an extinct genus of stagonolepidid aetosaur known from the Late Triassic (Carnian stage) Hassberge Formation of Germany, the Drawno Beds of Poland, the Lossiemouth Sandstone of Scotland, the Chinle Formation of Arizona and Utah and the Bluewater Creek Formation of New Mexico.
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 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 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 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 "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 Late Triassic 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 Carnian stage of Scotland and Poland.