A flattened enantiornithine in mid-Cretaceous Burmese amber: morphology and preservation

Lida Xing; Jingmai K O'Connor; Ryan C McKellar; Luis M Chiappe; Ming Bai; Kuowei Tseng; Jie Zhang; Haidong Yang; Jun Fang; Gang Li

doi:10.1016/j.scib.2018.01.019

A flattened enantiornithine in mid-Cretaceous Burmese amber: morphology and preservation

Sci Bull (Beijing). 2018 Feb 28;63(4):235-243. doi: 10.1016/j.scib.2018.01.019. Epub 2018 Jan 31.

Authors

Lida Xing¹, Jingmai K O'Connor², Ryan C McKellar³, Luis M Chiappe⁴, Ming Bai⁵, Kuowei Tseng⁶, Jie Zhang⁷, Haidong Yang⁵, Jun Fang⁸, Gang Li⁹

Affiliations

¹ State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China; School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China.
² Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing 100044, China.
³ Royal Saskatchewan Museum, Regina, Saskatchewan S4P 4W7, Canada; Biology Department, University of Regina, Regina, Saskatchewan S4S 0A2, Canada; Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence 66045, USA. Electronic address: ryan.mckellar@gov.sk.ca.
⁴ Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles 90007, USA.
⁵ Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
⁶ Department of Exercise and Health Science, University of Taipei, Taipei 11153, China.
⁷ Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
⁸ School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China.
⁹ Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China. Electronic address: lig@ihep.ac.cn.

PMID: 36659012
DOI: 10.1016/j.scib.2018.01.019

Abstract

Cretaceous amber from Myanmar (∼99 Ma Burmese amber) has become a valuable supplement to the traditional skeletal record of small theropod dinosaurs preserved in sedimentary rocks, particularly for coelurosaurs and enantiornithines. The specimens recovered from this deposit preserve skeletal material and soft tissues in unmatched detail. This provides opportunities to study three-dimensional preservation of soft tissues, microstructure, and pigmentation patterns that are seldom available elsewhere in the fossil record. Ultimately, this line of research provides insights into life stages that are difficult to preserve, the ecology and appearance of the groups involved, and the evolutionary-development of structures such as feathers. Here we describe the most recent discovery from Burmese amber, an articulated skeleton of an enantiornithine bird. This individual has been sectioned along the coronal plane, providing a unique view inside multiple body regions. Osteological observations and plumage patterns support placement within the Enantiornithes, and suggest that the animal may have been a juvenile at the time of death. The specimen has a complex taphonomic history that includes exposure at the surface of a resin flow prior to encapsulation, and may include scavenging by some of the insects trapped within the same amber piece. The chemical composition observed along surface exposures and shallowly buried regions of the body indicate that the specimen has not undergone significant exchange with its surroundings. High iron concentrations are present in regions that preserve soft tissues as carbon films, and calcium distribution corresponds to regions where bones breach the surface of the amber.

Keywords: Enantiornithes; Juvenile; Osteology; Soft tissue preservation.