A new ichnotaxon of fossil bird track from the Early Cretaceous Tianjialou Formation (Barremian-Albian), Shandong Province, China

Abstract

A single set of 5 bird tracks was discovered in the Tianjialou Formation (Barremian-Albian) of Junan County, Shandong Province, China. After careful study we infer that it is a new type of bird tracks, and a new ichnogenus was erected and the name Shandongornipes was given. The characteristics of the new bird track are as follows: Moderately large tetradactyl footprints with well-developed hallux impression. Track width (about 5.8 cm) almost equal to track length (excluding hallux); total length of track (including hallux) 8.7 cm. The digit impressions are slender, with distal ends showing long sharp claw marks. Hallux posteriorly-directed, and hallux impressions well-developed. Digits II, III and IV point anteriorly, exhibiting mesaxonic asymmetry: divarication angle between II and III much larger than that of III and IV, the former ranging from 91° to 118°, and the latter less than 30°. Divarication between digits II and IV ranging from 128° to 142°. Without web structures. Digital pads recognizable, usually at least three in digits III and IV, but sometimes only two due to preservation. The trackway shows slight positive (inward) rotation of feet. The bird tracks occur in association with abundant dinosaur tracks, and are believed to have formed in flood plain environments.