The anatomy and phylogenetic position of the erythrosuchid archosauriform Guchengosuchus shiguaiensis from the earliest Middle Triassic of China

BUTLER, RICHARD J.; EZCURRA, MARTÍN D.; LIU, JUN; SOOKIAS, ROLAND B.; SULLIVAN, CORWIN

PeerJ

PeerJ

Año: 2019 vol. 7

Erythrosuchidae is a clade of early archosauriform reptiles, which were apex predatorsin many late Early andMiddle Triassic ecosystems, following the Permo-Triassic massextinction. Erythrosuchids had a worldwide distribution, with well-preservedfossil material known from South Africa, European Russia, and China. We hereredescribe the anatomy and revise the taxonomy of Guchengosuchus shiguaiensis,which is one of the stratigraphically oldest erythrosuchids and is known from a singlepartial skeleton from the lowermost Middle Triassic (lower Anisian) lower ErmayingFormation of Shaanxi Province, China. We provide a new differential diagnosisfor Guchengosuchus shiguaiensis, and identify a series of autapomorphies relating tothe morphologies of the skull roof and vertebrae. Incorporating updated anatomicalinformation for Guchengosuchus into the most comprehensive morphologicalphylogenetic analysis available for early archosauromorphs recovers it as an earlybranching member of Erythrosuchidae, outside of the clade formed by Garjainia,Erythrosuchus, Chalishevia, and Shansisuchus. Fugusuchus hejiapanensis, fromthe uppermost Lower Triassic to lower Middle Triassic Heshanggou Formation ofChina, is recovered as the earliest branching member of Erythrosuchidae.