A scientific discovery of soft tissues in the dissolved remains of Tyrannosaur bone revealed three years ago marked a turning point among paleontologists, giving them hope that they will be able to extend their knowledge on extinct animals based on the preserved biomolecules. However, a new study signed by Thomas G. Kaye from the Burke Museum of Natural History and colleagues reveals a new side of the story.

Unlike the previous research, which required the fossil bone to be dissolved in acid in order to expose what they believed to be tissues, the team of researchers used scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to examine the interior of the fossil dinosaur bone prior to dissolution in acid. Instead of the mysterious tissues, they positively identified a bacterial biofilm which they explained it mimics the soft structure that created confusion three years ago.

These finding suggest that what scientists previously thought to be “tissues” were in fact the result of either modern contamination or natural processes. The specimens analyzed belonged to the same group of fossils, dating back 68 million years ago.

In order to see whether the fossil bones are capable of acting as a containment vessel for biomolecules, scientists used a perfectly preserved turtle phalange for an SEM examination. What they uncovered were iron-oxygen spheres in an ammonite suture, with no relationship with iron derived from blood. The spheres were identified as framboids, which can be found in black smokers, algal mats and sediments, the team of scientists explained.

Another structure revealed by the examination consisted of soft, pliable, branching tubules, which resembled blood vessels. However, after the dissolution of the bone, the structures did not remain present in the bone.

A closer investigation of the cracked surface of a vascular canal in the trabecular bone revealed traces of an inorganic process, which led scientists to the idea that the cracks were in fact formed by free-swimming microbes or bacteria in a viscous medium, which supports the biofilm theory.

In order to establish whether the biofilms were of a modern or ancient origin, scientists used the 14C dating, which revealed “greater than modern” origin of the material.

The previous study excluded the framboids theory due to the lack of sulfur in their structures, which would have indicated a standard pyrite framboid. However, the sulfur in pyrite framboids can be oxidized and replaced by iron oxides in time.

The new study explains how the iron-oxygen spheres are far too common in multiple formations to be the result of extraordinary preservation. Framboid morphology can be deceiving, and make them look like biological structures, when in fact they are inorganically produced.

“Biofilms are complex systems produced by virtually all bacteria on almost any water/surface boundary and are ubiquitous in nature,” the scientists explained. “Recent biofilms would be naturally pliable and elastic while duplicating the shape of the surfaces they form on.”

The biofilm is capable of maintaining the original morphology of a substrate, even when that substrate is removed, which explains the quantity and similarity of structures if the fossil bone. This indicates that the most probable explanation for the dinosaurian “tissues” is bacterial activity. The study was published this week in the Public Library Of Science One .