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Hard times for soft tissues: Dinosaur soft parts reinterpreted as bacterial biofilms.

The mineralized remains of bones and teeth provide vertebrate paleontologists with most of the data they use for interpreting the biology of extinct creatures.  By contrast, soft tissues (like skin or muscle) are extremely rare in the fossil record.  Only a few cases of soft tissue preservation have been reported for large terrestrial vertebrates, such as frozen mammoths, 'mummified' dinosaurs, and in some cases dinosaur skin (or at least the impressions of skin). As a result, it's no wonder why the recent discovery of blood cells, vessels, and other soft tissues in the bones of Cretaceous dinosaurs like Tyrannosaurus was met with some skepticism.

Burke Museum research associate, Tom Kaye, was one such skeptic. To test the 'soft tissue' hypothesis, Kaye fractured the bones of a number of Burke Museum specimens, which included vertebrate bones ranging from the Pleistocene as far back as the Cretaceous, and looked inside to see if he could find structures similar to those reported by earlier workers. In 2008, Kaye and his colleagues presented the results of their electron microscope research, arguing that microscopic structures previously attributed to 'fossilized' soft tissues were more easily explained as filamentous and spherical bacteria and their associated biofilms. A 'biofilm' is a sticky substance (which may be composed of many different types of proteins) that is secreted by colonial bacteria to adhere to the surfaces on which they live, and can be found in abundance in almost any environment. Kaye and his colleagues suggested that the biofilms formed natural casts of the original biological structures, such as body vessel networks and hollowed recesses (lacunae) for bone cells—they therefore mimicked the shapes of blood vessels and bone cells. Bacterial trails observed, carbon dating on the films, and comparisons of infrared spectra in the biofilms with modern collagen further supported Kaye's claims.

Publication

Kaye, T. G., Gaugler, G., Sawlowicz, Z. 2008. Dinosaurian soft tissues interpreted as bacterial biofilms. PLoS ONE 3(7): e2808. doi:10.1371/journal.pone.0002808 [Read Full Article]

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Tom Kaye's lab
Tom Kaye's lab in front of the electron microscope which he has used extensively in the micro-analysis of fossils.
Tom Kaye investigating micro-fossils
Tom Kaye investigating micro-fossils in front of one of his more powerful microscopes. Tom's lab holds an array of instruments capable of analyzing elements, molecules, and compounds. Looking at the smallest parts of fossils has lead to some of the b
dinosaur toe bone
A small dinosaur toe bone (UWBM 89327) from the Upper Cretaceous Lance Formation of eastern Wyoming. This element was fractured and examined with Tom’s scanning electronic microscope
tube-like structures
These are examples of transparent, tube-like structures that Tom found after demineralizing fossil bones. Similar structures were previously identified as blood vessels. The small red grains inside the tubes were found by Tom to be iron oxide framboi