Abstract
A scanning electron microscope survey was initiated to determine if the previously reported findings of “dinosaurian soft tissues” could be identified in situ within the bones. The results obtained allowed a reinterpretation of the formation and preservation of several types of these “tissues” and their content. Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time. They represent bacterial biofilms common throughout nature. Biofilms form endocasts and once dissolved out of the bone, mimic real blood vessels and osteocytes. Bridged trails observed in biofilms indicate that a previously viscous film was populated with swimming bacteria. Carbon dating of the film points to its relatively modern origin. A comparison of infrared spectra of modern biofilms with modern collagen and fossil bone coatings suggests that modern biofilms share a closer molecular make-up than modern collagen to the coatings from fossil bones. Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids. Our observations appeal to a more conservative explanation for the structures found preserved in fossil bone.
Highlights
The previous discovery of soft, pliable tissues recovered from the dissolved remains of Tyrannosaur bone in 2005 [1], potentially marked a major turning point in the science of paleontology given that it extended the known range of preserved biomolecules by many orders of magnitude
Examination of demineralized specimens under the light microscope displayed small red spheres clustered in the tubular structures (Fig. 4A)
The iron-oxygen spheres identified here as framboids, ranged in size from 5–29 microns and fall in the range previously described by Schweitzer and Horner [6] with an average size of 25 microns
Summary
The previous discovery of soft, pliable tissues recovered from the dissolved remains of Tyrannosaur bone in 2005 [1], potentially marked a major turning point in the science of paleontology given that it extended the known range of preserved biomolecules by many orders of magnitude. The implication that these were preserved dinosaurian soft tissues held the promise of biologic investigations of extinct animals. The original discovery centered on several tyrannosaur specimens From this single report, it could not be determined if this was a wholly unique one-of-a-kind preservation, or these structures remained undiscovered in other fossil material. The previous work required that the fossil bone be dissolved in acid to expose the preserved microstructures
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