Rethinking dinosaur origins: oldest known equatorial dinosaur-bearing assemblage (mid-late Carnian Popo Agie FM, Wyoming, USA).

This article focuses on the discovery and analysis of *Ahvaytum bahndooiveche* gen. et sp. nov., the oldest known Laurasian (northern hemisphere) dinosaur from the mid–late Carnian (approximately 230 million years ago) Popo Agie Formation in Wyoming, USA. High-precision radioisotopic dating and phylogenetic analyses place *Ahvaytum bahndooiveche* as an early-diverging saurischian, likely a sauropodomorph, contemporaneous with the oldest Gondwanan dinosaurs, challenging previous hypotheses that dinosaur dispersal from Gondwana to Laurasia was delayed by environmental barriers. Additionally, the presence of a silesaurid (a close dinosaur relative) in the same deposits and new tridactyl dinosaur trace fossils from the region support a more cosmopolitan distribution of early dinosauromorphs across Pangaea during the Carnian, rather than a geographically restricted origin. These findings underscore the importance of integrating body-fossil and ichnological records and highlight how sampling biases and stratigraphic gaps have influenced interpretations of early dinosaur evolution and biogeography.