Pterosaur material from the uppermost Jurassic of the uppermost Morrison Formation, Breakfast Bench Facies, Como Bluff, Wyoming, including a pterosaur with pneumatized femora

Abstract

Pterosaur fossils are rare in the Morrison Formation, and most are poorly preserved. The Breakfast Bench Facies (BBF) at Como Bluff produces incomplete but uncrushed limbs. One proximal and two distal femora match a complete femur (BYU 17214) referred to Mesadactylus. Unexpectedly, both of the BBF distal femora possess a large intercondylar pneumatopore. BYU 17214 also possesses an intercondylar pneumatopore, but it is smaller than in the BBF femora. Distal femoral pnuematicity is previously recognized only in Cretaceous azhdarchoids and pteranodontids. A peculiar BBF jaw fragment shows strongly labiolingually compressed, incurved crowns with their upper half bent backwards; associated are anterior fangs. We suspect this specimen is a previously undiagnosed pterosaur. Additional BBF material documents a diverse pterosaur fauna including a humerus with a greatly expanded ectepicondyle possibly from a non-pterodactyloid monofenestratan.