Cellular preservation of musculoskeletal specializations in the Cretaceous bird Confuciusornis

Abstract

The hindlimb of theropod dinosaurs changed appreciably in the lineage leading to extant birds, becoming more ‘crouched' in association with changes to body shape and gait dynamics. This postural evolution included anatomical changes of the foot and ankle, altering the moment arms and control of the muscles that manipulated the tarsometatarsus and digits, but the timing of these changes is unknown. Here, we report cellular-level preservation of tendon- and cartilage-like tissues from the lower hindlimb of Early Cretaceous Confuciusornis. The digital flexor tendons passed through cartilages, cartilaginous cristae and ridges on the plantar side of the distal tibiotarsus and proximal tarsometatarsus, as in extant birds. In particular, fibrocartilaginous and cartilaginous structures on the plantar surface of the ankle joint of Confuciusornis may indicate a more crouched hindlimb posture. Recognition of these specialized soft tissues in Confuciusornis is enabled by our combination of imaging and chemical analyses applied to an exceptionally preserved fossil.

Paleoproteomics of Mesozoic Dinosaurs and Other Mesozoic Fossils

“…These methods can detect extremely low abundance compounds with great sensitivity and spatial resolution. Thus, synchrotron studies have been used to identify remnant outlines of original soft tissues in sediments, distinct from environmental signal, and can be applied to larger specimens . However, synchrotron analyses are dependent upon surface chemistry, and its great sensitivity makes it prone to detecting contaminants, if present, over endogenous materials .…”

“…ToF‐SIMS is being applied to some fossil materials with increasing frequency (e.g., refs. []), and is particularly appropriate for detecting and mapping metal‐associated functional moieties (e.g., heme; melanin), but is less optimal for proteins.…”

“…Although controversial, the recovery of molecular data from very old fossils, including those from the Mesozoic (≈250–65 million years before present [Ma]), is becoming more common, and has encompassed a variety of approaches that differ in their sensitivity, specificity, and methodological limitations. Here, we provide an overview of the history and promise of ancient biomolecular recovery.…”

Micro-XRF study of the troodontid dinosaurJianianhualong tengireveals new biological and taphonomical signals

“…Chemistry of exquisitely preserved fossil animals including several iconic flying/gliding capable theropods have been investigated to reveal information of their paleobiology and the fossilization process [1,6,9,10,[12][13][14]. Various chemical imaging techniques, e.g., Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray spectroscopy, and secondary-ion mass spectroscopy (SIMS)), have been employed to track the molecular, elemental and isotopic information [1,5,6,[8][9][10][11][12][13][15][16][17][18].…”

Peer Review #1 of "The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae (v0.2)"

“…ornithuromorphs. The plantar surface of the labum may represent the origin of the m. extensor hallucis longus, or may have supported a cartilaginous hypotarsus(Jiang, Zhao et al 2017). The proximocranial margin of the medial cotyla slopes mediodistally.…”