Preservation of soft tissue in fossil bone is incredibly rare. So rare in fact, that reports of fossil soft tissues tend to attract a lot of flak, with the most common argument being that the ‘tissues’ are simply organic residues of fairly modern bacteria. This is why the very recent article from Johan Lindgren and colleagues is so fantastic: not only is protein shown to be preserved in mosasaur bone, but the authors also describe the titanic effort that went into ruling microbial contamination. And, of course, they used spectroscopy.
Infrared spectroscopy results are presented from analyses of a partly demineralised Prognathodon bone. The IR absorbance spectra show bands from the bone mineral – phosphate and carbonate stretches – as well as very clear bands due to organic material. These bands are also shown in a modern lizard bone, and in the spectrum of type 1 collagen. The spectra are also compared to analyses from microbes, which actually have very similar overall spectra. This is unsurprising, as the spectral bands are just informing about organic material, not collagen per se. ‘Fingerprinting’ for certain proteins (i.e. collagen) works by looking at the presence of certain bands, their positions, and their relative intensities – none of the microbes can truly mimic the Prognathodon protein spectrum. Head over to PLoS ONE for the exquisite details…
Lindgren, J., Uvdal, P., Engdahl, A., Lee, A.H., Alwmark, C., Bergquist, K.-E., Nilsson, E., Ekstro, P., Rasmussen, M.,Douglas, D.A., Polcyn, M.J., Jacobs, L.L. 2011. Microspectroscopic evidence of Cretaceous bone proteins. PLoS One 6(4): e19445. doi:10.1371/journal.pone.0019445
Image from Wikimedia Commons