Soft-tissue and dermal arrangement in the wing of an Early Cretaceous bird: Implications for the evolution of avian flight.

Guillermo Navalón,Jesús Marugán-Lobón,Ángela D Buscalioni,José Luis Sanz,Luis M Chiappe

doi:10.1038/srep14864

Abstract

Despite a wealth of fossils of Mesozoic birds revealing evidence of plumage and other soft-tissue structures, the epidermal and dermal anatomy of their wing’s patagia remain largely unknown. We describe a distal forelimb of an enantiornithine bird from the Lower Cretaceous limestones of Las Hoyas, Spain, which reveals the overall morphology of the integument of the wing and other connective structures associated with the insertion of flight feathers. The integumentary anatomy, and myological and arthrological organization of the new fossil is remarkably similar to that of modern birds, in which a system of small muscles, tendons and ligaments attaches to the follicles of the remigial feathers and maintains the functional integrity of the wing during flight. The new fossil documents the oldest known occurrence of connective tissues in association with the flight feathers of birds. Furthermore, the presence of an essentially modern connective arrangement in the wing of enantiornithines supports the interpretation of these primitive birds as competent fliers.

Highlights

Despite a wealth of fossils of Mesozoic birds revealing evidence of plumage and other soft-tissue structures, the epidermal and dermal anatomy of their wing’s patagia remain largely unknown
The connective tissue associated with the plumage shows the same post-mortem folding of the skeletal elements, indicating that these soft tissues are preserved in anatomical position
The parallel pattern of plait-like fibers alternating with an unorganized matrix in MCCMLH31444 is characteristic of modern tendons and ligaments that are subject to multidirectional mechanical stresses[19,21]

Summary

Introduction

Despite a wealth of fossils of Mesozoic birds revealing evidence of plumage and other soft-tissue structures, the epidermal and dermal anatomy of their wing’s patagia remain largely unknown. The fossil preserves the anatomy of the wing’s patagia[10] and different connective structures associated with the attachment of the remigial feathers[9] in exceptional detail.

Results

Conclusion