A non-archaeopterygid avialan theropod from the Late Jurassic of southern Germany.

Abstract

The Late Jurassic 'Solnhofen Limestones' are famous for their exceptionally preserved fossils, including the urvogel <i>Archaeopteryx</i>, which has played a pivotal role in the discussion of bird origins. Here we describe a new, non-archaeopterygid avialan from the Lower Tithonian Mörnsheim Formation of the Solnhofen Archipelago, <i>Alcmonavis poeschli</i> gen. et sp. nov. Represented by a right wing, <i>Alcmonavis</i> shows several derived characters, including a pronounced attachment for the pectoralis muscle, a pronounced tuberculum bicipitale radii, and a robust second manual digit, indicating that it is a more derived avialan than <i>Archaeopteryx</i>. Several modifications, especially in muscle attachments of muscles that in modern birds are related to the downstroke of the wing, indicate an increased adaptation of the forelimb for active flapping flight in the early evolution of birds. This discovery indicates higher avialan diversity in the Late Jurassic than previously recognized.