An avian quadrate from the Late Cretaceous Lance Formation of Wyoming

Abstract

ABSTRACT Based on an extensive survey of quadrate morphology in extant and fossil birds, a complete quadrate from the Maastrichtian Lance Formation has been assigned to a new genus of most probably odontognathous birds. The quadrate shares with that of the Odontognathae a rare configuration of the mandibular condyles and primitive avian traits, and with the Hesperornithidae a unique pterygoid articulation and a poorly defined (if any) division of the head. However, the quadrate differs from that of the Hesperornithidae by a hinge-like temporal articulation, a small size of the orbital process, a well-marked attachment for the medial (deep) layers of the protractor pterygoidei et quadrati muscle, and several other details. These differences, as well as the relatively small size of about 1.5–2.0 kg, suggest a feeding specialization different from that of Hesperornithidae.