Gorgetosuchus

''Gorgetosuchus'' is an extinct genus of aetosaur from the Late Triassic of the North Carolina, represented by the type species ''Gorgetosuchus pekinensis''. It is mainly known from osteoderms, including the front half of an articulated carapace. ''Gorgotesuchus'' is typically considered a basal desmatosuchin, though alternative interpretations exist.

Discovery

''G. pekinensis'' was named and described by Heckert ''et al.'' (2015) on the basis of ten rows of bony plates called osteoderms, representing the front part of an armored carapace that would have covered the back of the animal. These plates were found embedded in sandstone and conglomerate boulders near a brick quarry in Chatham County, North Carolina, which likely originated from the Late Triassic Pekin Formation. (The Pekin Formation consists of interbedded red mudstones, siltstones, sandstones and conglomerates; it was the fine-grained mudstones and siltstones that the mining operation was targeting for brick-making, so coarser-grained blocks were removed from the pit). ''Gorgetosuchus'' was part of a diverse faunal community in a continental rift valley system during the Late Triassic, which also included traversodontids, phytosaurs, dicynodonts, and temnospondyls. ''Gorgetosuchus'' coexisted with two other aetosaurs, '' Lucasuchus'' and ''Coahomasuchus''.

Description

''Gorgetosuchus'' is unique among aetosaurs in having cervical (neck) osteoderms that nearly wrap around the entire neck and are strongly angled to give the neck a hexagonal shape in cross-section. The lateral (side) and paramedian (upper) osteoderms each bear prominent spines. Other aetosaurs such as '' Longosuchus'' also have neck spines, but only on the lateral osteoderms. The cervical osteoderms are wider than they are long, a feature that unites ''Gorgetosuchus'' with basal "aetosaurine" aetosaurs. However, several features of the osteoderms (such as a flange on the lateral cervical osteoderms that overlaps the paramedian osteoderms) link it with the desmatosuchines, a more derived group of aetosaurs.

Classification

Among aetosaurs, ''Gorgetosuchus'' closely resembles ''Lucasuchus'' and ''Longosuchus'', both of which are desmatosuchines. A phylogenetic analysis conducted by Heckert ''et al.'' (2015) placed ''Gorgetosuchus'' close to these taxa as the most basal desmatosuchine, but the results were not statistically well supported. Below is a strict consensus tree from their analysis showing the placement of ''Gorgetosuchus'':

''Gorgetosuchus'' was also placed as the basal-most member of Desmatosuchini (traditional desmatosuchines) in an analysis by Parker (2016). However, an analysis by Hoffman ''et al.'' (2018), based on an earlier analysis by Schoch & Desojo (2016), placed it within Typothoracinae, closely related to ''Typothorax'' and ''Redondasuchus''. Typothoracines and desmatosuchins are known to have a large degree of homoplasy (convergent evolution) in certain osteoderm traits observed in ''Gorgetosuchus''. On the other hand, other skeletal traits strongly diverge between the two groups, so the position of ''Gorgetosuchus'' would likely stabilize if more non-osteoderm bones were discovered.

References

{{Taxonbar, from=Q20647355

Aetosaurs of North America
Fossil taxa described in 2015
Late Triassic pseudosuchians
Fossils of North Carolina
Prehistoric pseudosuchian genera