Basal dinosauriform and theropod dinosaurs from the mid–late N orian ( L ate T riassic) of P oland: implications for T riassic dinosaur evolution and distribution

The rise of dinosaurs during the T riassic is a widely studied evolutionary radiation, but there are still many unanswered questions about early dinosaur evolution and biogeography that are hampered by an unevenly sampled Late Triassic fossil record. Although very common in western N orth A merica and parts of S outh A merica, dinosaur (and more basal dinosauriform) remains are relatively rare in the Upper Triassic deposits of E urope, making any new discoveries critically important. One of the most diverse dinosauriform assemblages from E urope comes from the P oręba site in P oland, a recently described locality with exposures of the Z bąszynek B eds, which have a palynomorph assemblage characteristic for the mid–late Norian in the biostratigraphic schemes of the G ermanic B asin. Using a synapomorphy‐based approach, we evaluate several isolated dinosauriform specimens from P oręba. This assemblage includes a silesaurid, a herrerasaurid and remains of another type of theropod (potentially a neotheropod). The P oręba herrerasaurid is the first record of this rare group of primitive dinosaurs from E urope and one of the youngest records worldwide, whereas the silesaurid is the youngest record of a silesaurid from E urope. These findings indicate that silesaurids persisted alongside true dinosaurs into the mid–late N orian of E urope and that silesaurid–herrerasaurid–neotheropod assemblages (which are also known from the N orian of N orth A merica, at low latitudes) were more widespread geographically and latitudinally than previously thought. Silesaurid–herrerasaurid–neotheropod assemblages may have been a common ecological structuring of dinosaurs during their early evolution, and their widespread distribution may indicate weak palaeolatitudinal controls on early dinosaur biogeography during the latest T riassic.