(Inside Science) -- Ancient proteins may have been detected within a 195-million-year-old dinosaur bone, a new study finds. This discovery could beat the record for the oldest proteins seen in fossils by more than 100 million years.
Although fossil skeletons have undoubtedly shed light on the vast diversity of life that previously existed on Earth, these petrified bones and teeth only hint at what the rest of animals' bodies were once like. However, in the past decade or so, researchers have successfully unearthed organic remains from exceptionally preserved dinosaur bones dating as far back as 75 million years. These tiny scraps of flesh and blood "can lead to a better understanding of these animals -- their overall biology, evolution, reproduction, feeding," said study senior author Robert Reisz, a paleontologist at the University of Toronto Mississauga.
Unfortunately, the methods used to analyze these ancient organic compounds often require their extraction from fossils. This has led critics to argue that any organic molecules that scientists have detected could merely be the result of external contamination.
In the new work, scientists employed a state-of-the-art method for scanning the contents of fossils without extracting any of their contents and thus risking contamination. This new technique relied on synchrotrons, which use magnetic fields to spin particles, typically electrons, at nearly the speed of light inside a ring. As these electrons accelerated around each bend of the ring, they gave off extraordinarily bright beams of infrared light that the researchers focused on tiny spaces in the fossils. The scientists analyzed which wavelengths of infrared light the samples absorbed, which in turn revealed the materials' composition.
Reisz and his colleagues focused on 195-million-year-old bones from Lufengosaurus, a plant-eating dinosaur that reached up to roughly 26 feet (8 meters) in length. It gets its name from where it was first discovered, Lufeng county in China's southwestern Yunnan Province. Lufengosaurus was a sauropodomorph -- a group of long-necked, long-tailed dinosaurs that included the largest creatures to ever walk the Earth, such as Brontosaurus.
Previously, the scientists found traces of organic remains preserved in dinosaur embryos of about the same age, also from Lufeng. Encouraged by those findings, they wanted to look for more such evidence in bigger adult specimens from the same area.
When hunting for traces of ancient organic compounds in fossils, scientists normally look in larger bones such as thighbones, Reisz said. Surprisingly, the researchers got their best results in a relatively thin Lufengosaurus rib.
The scientists examined canals within thin slices of the rib. Their scans uncovered flat transparent fragments roughly 20 to 50 microns large whose infrared signatures were typical of the protein collagen. The researchers suggest these fragments are the remains of blood vessels in the bone's canals. "It's by far the oldest evidence of protein preservation in the fossil record," Reisz said.
Laser scans of the fossils also revealed spherical particles of hematite, an iron-containing mineral, about 6 to 8 microns wide in the bones' canals. The researchers suggest these are likely remnants of hemoglobin and other iron-rich compounds within blood cells. The researchers suggest that the hematite may have helped protect the collagen both by acting as a chemical preservative and by sealing the bones' canals from the outside environment.
"The great antiquity of this find shows us that the future potential for the study of soft tissue preservation is real," Reisz said.
However, Mary Schweitzer, an evolutionary biologist and vertebrate paleontologist at North Carolina State University who did not take part in this research, cautioned that this new work does not conclusively prove the presence of collagen in these fossils. This is, she claimed, because all proteins respond similarly to the methods the scientists used, so they "cannot identify any type of protein with certainty," she said.
Schweitzer said that other techniques could be used to confirm or deny the presence of collagen in these fossils. These include electron microscopy, which can spot the banded fiber structure typical of collagen, or antibodies, which each respond very specifically to just one kind of molecule, she said.
Reisz disputed Schweitzer's comment, saying that collagen has a unique infrared signature that their approach clearly identified.
Still, Schweitzer said this new work does suggest that scientists can identify organic compounds in fossils older than any previously examined. Future research can investigate what such preserved molecules "actually tell us about the biology, physiology, ecology and evolution of these ancient animals," she said. "These studies can help us understand where we are going by better understanding where we came from."
The scientists detailed their findings online Jan. 31 in the journal Nature Communications.