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Dinosaur blood vessel with adjacent bone matrix still containing bone cells. These structures have perfect morphological conservation over hundreds of millions of years, but are chemically transformed by oxidation crosslinking. The extract comes from a sauropod dinosaur. Credit: Jasmina Wiemann / Yale University
According to a new study by Yale, burnt toasts and dinosaur bones share a common trait. Both contain chemicals that, under good conditions, transform the original proteins into something new. This is a process that can help researchers understand how soft tissue cells of dinosaur bones can survive for hundreds of millions of years.
A team of researchers from Yale, the American Museum of Natural History, the University of Brussels and the University of Bonn announced the discovery on November 9 in the newspaper Nature Communications.
Fossil soft tissue in dinosaur bones has been a controversial topic among researchers for some time. Hard tissues, such as bones, eggs, teeth and enamel scales, are able to survive extremely well with fossilization. Soft tissues, such as blood vessels, cells and nerves, which are stored inside hard tissues, are more delicate and are thought to decompose soon after death. These soft tissues are composed mainly of proteins, which would degrade completely after about four million years.
Yet dinosaur bones are much older, about 100 million years old, and they sometimes retain organic structures similar to cells and blood vessels. Various attempts to resolve this paradox have failed.
"We have taken up the challenge of understanding protein fossilization," said Yale paleontologist Jasmina Wiemann, the lead author of the study. "We tested 35 fossil bone samples, eggshells and teeth to determine whether they were preserving proteinaceous soft tissues, determining their chemical composition and determining under what conditions they could survive during millions of years. "
Experimental processing initiates glycoxidation / lipoxidation in a fresh eggshell matrix sample. Local browning of the otherwise translucent sample represents the formation of N-heterocyclic polymers. Credit: Jasmina Wiemann / Yale University
The researchers found that soft tissues are preserved in samples from oxidizing environments such as shallow sandstones and shallow marine limestones. Soft tissues were transformed into finished products of advanced glycoxidation and lipoxidation (AGE and ALE) resistant to decomposition and degradation. They are also structurally comparable to chemical compounds that stain dark crust on toast.
EFAs and FTAs are characterized by a brownish color that stains the fossil bones and teeth that contain them. The compounds are hydrophobic, which means that they resist the normal effects of water and that their properties prevent the bacteria from consuming them.
Wiemann and his colleagues made their discovery by decalcifying the fossils and visualizing the soft tissue structures released. They applied Raman microspectroscopy – a non-destructive method to badyze both the inorganic and organic content of a sample – to extracted soft-tissue fossils. During this process, the laser energy directed at the tissue causes molecular vibrations that carry the spectral imprints of the chemicals present.
Co-author Derek Briggs, professor of geology and geophysics at the G. Evelyn Hutchinson Chair at Yale and curator at the Yale Peabody Museum of Natural History, said the study indicated places where tissues soft could be found in fossil bones, including sandstones deposited in rivers, dune sands and shallow marine limestones.
"Our results show how chemical alteration explains the fossilization of these soft tissues and identifies the types of environment in which this process occurs," Briggs said. "The result is a way to target the parameters on the ground where this preservation is likely to occur, which is an important source of evidence of the biology and ecology of ancient vertebrates."
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