SEM Analyses of Fossilized Chondrocytes in the Extinct Birds Yanornis and Confuciusornis: Insights on Taphonomy and Modes of Preservation in the Jehol Biota

Calcified cartilage is a vertebrate tissue that has unique characteristics, such as high percentage of calcification, avascularity and cells with apparently delayed autolytic processes after death. All these factors suggest fossilized may be favorable to exceptional cellular preservation, but little known about chondrocyte fossilization overall in paleontology. To further understand the spectrum preservation this tissue, we analyze morphology chemistry some intralacunar content seen previously published avian from Early Cretaceous Jehol biota (in Yanornis Confuciusornis ). For this, combine standard paleohistology Scanning Electron Microscopy (SEM) Energy Dispersive Spectroscopy (EDS). better identify structures , compare them experimentally decayed biofilm-invaded cartilage. Histological images show resemble cell nuclei within lacunae. An SEM analysis on shows lacunae are filled type vivo mineralization (similar micropetrotic lacunae) others small spherical silicified surrounded by an amorphous carbonaceous material. These underwent postmortem shrinkage do not constitute nuclei. filamentous, non-spherical mostly made silicon carbon. This does typical healthy chondrocytes, based comparison decaying, biofilm-infiltrated extant material, most plausible conclusion were partially autolyzed prior their mineralization. In respectively, silicification alumino-silicification responsible for preservation; while ironization occurred soft tissues. quite common mechanism soft-tissue biota. Moreover, two different morphologies (spherical filamentous) reflect taphonomical histories, including timings permineralization (one rapid one much more delayed). paired actuotaphonomy experiments will needed future potential chondrocytes other types fossil record.