Iron-mediated deep-time preservation of osteocytes in a Middle Triassic reptile bone

ABSTRACT

Fossil bone cells (osteocytes) are known mainly from the shape-casting vacuities they leave behind after cell decay; however, they may occasionally be preserved as three-dimensionally fossilized soft parts. Here we present brownish to rust-coloured microbodies, extracted from a Middle Triassic (ca. 245 Ma) bone of the reptile Nothosaurus, which are morphologically consistent with bone cells of present-day vertebrates. In situ imaging shows that these structures, which are reminiscent of bone cells, are harboured in lacunae framed by the bone matrix. Chemical characterization using energy-dispersive X-ray, Raman, and X-ray photoelectron spectroscopy revealed the presence of various phases of iron oxide mineralization. The predominant mineral phases are hematite and goethite; magnetite and maghemite appear to occur sporadically. It is not clear how these nanograined mineral phases were formed. Most likely mineralization proceeded very early and was triggered by local microenvironmental conditions favouring the precipitation of iron phases. The absence of a distinct signal indicating organic molecules suggests that the original bone cells underwent autolysis or other degradative processes before or during mineralization.

KEYWORDS:

• Microtaphonomy
• osteocytes
• Triassic
• ferruginous minerals
• Poland

Acknowledgments

We are grateful to the late Dr Henryk Wistuba for his important tips regarding the application of the vacuum filtration kit. Jasmina Wiemann (Yale University, New Haven, CT) kindly offered important opinions and comments which contributed greatly to improving our manuscript. We also thank the Editor and two anonymous reviewers for their work on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental material

Supplementary data for this article can be accessed here.

Additional information

Funding

This work was supported by the National Science Centre, Poland under grant no. [2011/01/N/ST10/06989].