Diagnoza

The anterior part of the maxilla is proportionally deeper and shorter in S. robertsoni than in S.

olenkae. In S. robertsoni the antorbital fossa on the dorsal process of maxilla is proportionally deeper and the angle between the ventral and dorsal margins of the antorbital fossa is greater than in S. olenkae. The area between the anterior edge of the antorbital fossa and the suture between the maxilla and the nasal is wide in S. olenkae, whereas only a ridge is present in S. robertsoni. The ventral edge of the dorsal process of the maxilla is proportionally longer in S. robertsoni than in S. olenkae. The flattened area on the ventral surface of the maxilla between the teeth and the contact with the palatine is relatively larger and wider in S. robertsoni than in S. olenkae. The ventral margin of the maxilla is more strongly convex (in lateral view) in S. robertsoni than in S. olenkae. Stagonolepis robertsoni has a relatively wider supraorbital fenestra (based on the difference between palatines) than S. olenkae. Stagonolepis olenkae has a massive ridge on the ventral surface of the palatine at its anterior end. In S. olenkae, large tubercules are present on the parietals and the medial edge of the dorsal row is straight, whereas in S. robertsoni a small ridge is present in an equivalent position to the tubercules and a distinct curvature occurs on the medial edge of the dorsal row. Stagonolepis robertsoni has nine to ten dentary teeth, compared to seven to nine in S. olenkae. The narrow and unflattened shaft of the tibia distinguishes S. wellesi from S. olenkae.

Porównanie

In S. robertsoni the ventral margin of the antorbital fenestra and the ventral edge of the maxilla are almost parallel, whereas in S. olenkae they are at an oblique angle to one another (9° in smaller individuals of S. olenkae and 25° in larger individuals). In S. olenkae the squamosal is relatively deeper and the postorbital is relatively more massive than in S. robertsoni. It is likely that all of these differences may be connected to allometry. In S. robertsoni there is a horizontal ridge on the medial side of the dorsal process of the maxilla that does not occur in S. olenkae. The absence of a massive ridge on the ventral surface of the palatine in S. robertsoni is visible on the specimens BMNH R8581, GSM 37049, and GSM 37051. According to Long & Murry (1995) and Heckert & Lucas (1999), the presacral vertebrae of S. wellesi have higher neural spines than in S. robertsoni, but this difference is so small that it may represent intraspecific variation. Long & Murry (1995) observed that S. wellesi possesses presacral vertebrae with very long transverse processes, but Parker (2007: 5) stated that ‘these assignments are extremely tentative and should be viewed with great caution’. The morphology of the tibia differentiates S. wellesi from both European stagonolepids. The proposed differences between S. wellesi and S. robertsoni in terms of bosses on the plates are doubtful. Stagonolepis olenkae bears a flat area on the dorsal surface of the narrow anterior process of the nasal.

Autekologia

Omnivorous

Występowanie geograficzne

Poland

Zasięg czasowy

Late Carnian

Materiały muzealne

Hundreds of isolated bones and fragments of skeletons in articulation (e.g. manus and tail)

Literatura

Desojo, J. B., Heckert, A. B., Martz, J. W., Parker, W. G., Schoch, R. R., Small, B. J., Sulej, T. 2013. Aetosauria: a clade of armoured pseudosuchians from the Late Triassic continental beds. In S. J. Nesbitt, J. B. Desojo and R. B. Irmis (eds.) Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications, 379.

Dzik, J. & Sulej, T. 2004. Pierwszy polski dinozaur. 80 pp, Śląskie Wydawnictwo ADAN, Opole.

Dzik, J. & Sulej, T. 2007. A review of the early Late Triassic Krasiejów biota from Silesia, Poland. Palaeontologia Polonica 64, 1-27.

Scheyer, T.M., Desojo, J.B., Cerda, I.A. 2014 Bone histology of phytosaur, aetosaur, and other archosauriform osteoderms (Eureptilia, Archosauromorpha). The Anatomical Record. 297,  240–260

Sulej, T. 2010. The skull of an early Late Triassic aetosaur and the evolution of the stagonolepidid archosaurian reptiles. Zoological Journal of the Linnean Society 158, 860–881.