Endogenous proteins found in a 70-million-year-old giant marine lizard

Fossil – just stone? No, a research team in Lund, Sweden, has discovered primary biological matter in a fossil of an extinct varanoid lizard (a mosasaur) that inhabited marine environments during Late Cretaceous times. 

One of the most well preserved mosasaur sculls in the world. Fossil at Museum of Paleonthology, University of California Berkeley, California [Credit: Johan Lindgren]

Using state-of-the-art technology, the scientists have been able to link proteinaceous molecules to bone matrix fibres isolated from a 70-million-year-old fossil; i.e., they have found genuine remains of an extinct animal entombed in stone. 

Bone matrix fibers in mosasaur bone: (a) Histologic preparation that shows how the fibres surrounds a vascular duct. (b) SEM-picture that shows etched fibres. (c) Detail of histologic preparation showing fibres encapsulated in bioapatite. (d) Histo-chemical stain (blue) showing that the fibres contain biological matter [Credit: Johan Lindgren]

With their discovery, the scientists Johan Lindgren, Per Uvdal, Anders Engdahl, and colleagues have demonstrated that remains of type I collagen, a structural protein, are retained in a mosasaur fossil. 

The scientists have employed e.g., synchrotron radiation-based infrared microspectroscopy at MAX-lab in Lund (Sweden) to show that amino acid containing matter remains in fibrous tissues obtained from a mosasaur bone. 

Osteocytes: Confocal microscopic pictures of an osteocyte-similar structure. Osteocytes are cells that are producing typ I collagen [Credit: Johan Lindgren]

Previously, other research teams have identified collagen-derived peptides in dinosaur fossils based on e.g., mass spectrometric analyses of whole bone extracts. The present study provides compelling evidence to suggest that the biomolecules recovered are primary and not contaminants from recent bacterial biofilms or collagen-like proteins. 

Infrared microspectroscopy of fibres isolated from a mosasaur bone: (a) SEM-picture of the fibres. The white square marks the area measured by synchrotron light. (b) Absorbans spectra from the fibre bundle reproduced in a (red=synchrotron light; blue=conventional light). (c) Comparison between absorbans spectra from recent typ I collagen, osteoid from a recent monitor lizard (varan), and fibres from a mosasaur (Prognathodon) [Credit: Johan Lindgren]

Moreover, the discovery demonstrates that the preservation of primary soft tissues and endogenous biomolecules is not limited to large-sized bones buried in fluvial sandstone environments, but also occurs in relatively small-sized skeletal elements deposited in marine sediments.  

Facts: 

• Mosasaurs are a group of extinct varanoid lizards that inhabited marine environments during the Late Cretaceous (approx. 100-65 million year ago).
•  Collagen is the dominating protein in bone.
•  The scientists have applied a broad spectrum of sophisticated techniques to achieve their results. In addition to synchrotron radiation-based infrared microspectroscopy, mass spectrometry and amino acid analysis have been performed. Virtually all experiments have been made in Lund. At MAX-lab, the experiments have been conducted at the MAX I ring, beamline 73.   

A paper reporting the discovery is now available in the scientific journal PLoS ONE. 

Source: MAX-lab [May 02, 2011]