Not even here is safe from Leafs jokes...

This work not have been possible without the generous support of NSF-EAR, @acs.org PRF, Bureau of Land Management, and @baylor.bsky.social

This has been truly collaborative study. I am grateful to @stevebrusatte.bsky.social, @danpeppe.bsky.social, Matt Heizler for co-leading this study, to all my co-authors for their hard work, and @nataliajagielska.bsky.social for her awesome artwork.

Lastly, this N-S bioprovincialism persists after the mass extinction and is seen in early Paleocene mammalian communities suggesting that the biogeographic structure was not destroyed by the mass extinction event.

We then used ecological modeling to show dinosaur communities were partitioned into two different bioprovinces during the terminal Cretaceous across western North America, driven by differences in climate. This suggests dinosaurs in North America diverse & thriving leading up to the K/Pg boundary.

This Naashoibito dinosaur community was dominated by the giant sauropod Alamosaurus and crested Lambeosaurine hadrosaurs, which is a marked difference than the coeval Hell Creek Formation.

Using magnetostratigraphy and Ar/Ar geochronology, we were able to constrain the age of Naashoibito Member deposition, and the major vertebrate fossil localities, to no older than 66.38 Mya.

We provide new age constraints on the Naashoibito Member in the San Juan Basin of NW New Mexico showing these rocks, and their unique dinosaurs, are among the last non-avian dinosaurs from the last 340 Kyr of the Cretaceous, contemporaneous with the famous Hell Creek fauna. doi.org/10.1126/scie...