Mass extinctions change the trajectory of evolution and restructure ecosystems. The largest mass extinction, the end-Permian, is a particularly interesting case due to the hypothesized delay in the recovery of global ecosystems, where total trophic level recovery is not thought to have occurred until 5-9 million years after the extinction event. Diapsids, especially archosauromorphs, play an important role in this recovery, filling niches left vacant by therapsids and anapsids.
View Article and Find Full Text PDFThe Cretaceous-Paleogene (KPg) boundary, one of Earth's five major extinction events, occurred just before the appearance of Placentalia in the fossil record. The Gobi Desert, Mongolia and the Western Interior of North America have important fossil mammals occurring just before and after the KPg boundary (e.g.
View Article and Find Full Text PDFThe Placerias/Downs' Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic vertebrate locality known. We report a new short-faced archosauriform, Syntomiprosopus sucherorum gen. et sp.
View Article and Find Full Text PDFFollowing the Permo-Triassic mass extinction, Archosauriformes-the clade that includes crocodylians, birds, and their extinct relatives outside crown Archosauria-rapidly diversified into many distinct lineages, became distributed globally, and, by the Late Triassic, filled a wide array of resource zones. Current scenarios of archosauriform evolution are ambiguous with respect to whether their taxonomic diversification in the Early-Middle Triassic coincided with the initial evolution of dietary specializations that were present by the Late Triassic or if their ecological disparity arose sometime after lineage diversification. Late Triassic archosauriform dietary specialization is recorded by morphological divergence from the plesiomorphic archosauriform tooth condition (laterally-compressed crowns with serrated carinae and a generally triangular lateral profile).
View Article and Find Full Text PDFAetosaurs comprise a clade of quadrupedal, armored, omnivores to herbivores that lived across much of the supercontinent of Pangea during the Late Triassic. Their relative abundance in many units, and the rarity of other Triassic herbivores, points to them as key components of Late Triassic ecosystems. Debate persists about whether they were growing more or less slowly when compared to extant crocodylians, and bone histology is sparsely sampled within the group.
View Article and Find Full Text PDFAetosauria is a clade of heavily armored, quadrupedal omnivorous to herbivorous archosaurs known from the Late Triassic across what was the supercontinent of Pangea. Their abundance in many deposits relative to the paucity of other Triassic herbivores indicates that they were key components of Late Triassic ecosystems. However, their evolutionary relationships remain contentious due, in large part, to their extensive dermal armor, which often obstructs observation of internal skeletal anatomy and limits access to potentially informative characters.
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