Mummified precocial bird wings in mid-Cretaceous Burmese amber.

Lida Xing,Ryan C Mckellar,Kuowei Tseng,Jingmai K O’Connor,Yan Wang,Weiwei Zhang,Gang Li,Michael J Benton,Xing Xu,Martin G Lockley,Jianping Zhang,Ming Bai,Min Wang

doi:10.1038/ncomms12089

Abstract

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans.

Highlights

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals
The combined fossil record of amber and compression fossils has provided many insights into how the feather types associated with modern birds developed[11,12], but these glimpses are restricted by preservation in each fossil type
As in most basal avialans[21,22], alular phalanx-1 fails to reach the distal end of the major metacarpal (Fig. 1b,e), but the opposite is true in most non-avialan theropods, such as dromaeosaurids and scansoriopterygids[17,23]

Summary

Introduction

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. The discovery of two partial bird wings in Burmese amber unites taxonomic and ontogenetic information from osteology with microscopic preservation down to the level of individual feather barbules and their pigment distributions This new source of information includes integumentary features incompletely known in the compression fossil record[13]. Barbs within the alula have much broader and more asymmetrical barbules than in the primaries and coverts, distal barbules have a well-developed a b mi ma ul mim mam

Methods

Results

Conclusion