Trumpeting a dinosaur horn
Science | A partially fossilized triceratops horn offers evidence the animal lived less than 65 million years ago, say scientists who discovered it
by Daniel James Devine
Posted 7/25/14, 10:35 am
A few miles outside Glendive, Montana, on May 12, 2012, the sun beat down on three researchers as they hammered away at sandstone. They were hunting fossils scattered in the Hell Creek Formation, a geological trove for dinosaur bones. They had no power tools—just chisels, muscle, and the excitement of watching a large triceratops horn emerge inch-by-inch from sediment that swallowed it long ago.
The team spent three hours chipping away the rock. “That wears you out, especially for a bunch of old scientists,” recalled Kevin Anderson, a member of the team and a microbiology professor at Arkansas State University in Beebe, Ark. The Triceratops horridus horn they excavated was about 3 1/2 feet long: “We always joked, this would have been the grandpa triceratops.”
After paying the landowner $3,000 for the fossil, the scientists hauled it to their lab to see if it contained any unfossilized soft tissue the ravages of time might have left untouched. After giving the fossil an acid bath that dissolved the hard material, they found—sure enough—soft tissue and structures that appeared to be original dinosaur cells.
In February 2013, Anderson and another member of the dig team, Mark Armitage, a part-time employee at California State University, Northridge, (CSUN) published their discovery in the journal Acta Histochemica. A few days afterward, CSUN dismissed Armitage from his job in the microscope lab, claiming it had inadequate funding to continue his position.
This week, the Pacific Justice Institute filed a religious discrimination lawsuit against the school on Armitage’s behalf. The organization claims the school fired Armitage because of his view that the Earth was created a few thousand years ago. Both Armitage and Anderson are affiliated with the Creation Research Society, a creation science organization based in Chino Valley, Ariz.
Pacific Justice Institute declined to make Armitage available for an interview because of the pending lawsuit, but Anderson, the co-author of the triceratops horn paper, spoke to me about the fossil discovery and its implications. While the Acta Histochemica paper doesn’t make any claim on the age of the fossil, Anderson said the preservation of soft tissue—absent a convincing explanation—suggests the horn is far less than 65 million years old, the approximate date that would be assigned to the triceratops based on a standard interpretation of the Hell Creek Formation.
This isn’t the first time scientists have found soft tissue inside a dinosaur fossil. In 2005, North Carolina State University researcher Mary Schweitzer famously reported her discovery of “transparent, flexible, hollow blood vessels” inside a Tyrannosaurus rex leg bone. Others have found soft tissue inside fossils from a mosasaur (an extinct marine reptile), a Brachylophosaurus (a duck-billed dinosaur), and a Tarbosaurus (a theropod).
Soft tissue has also emerged from triceratops bones, but Anderson and Armitage were the first to report the discovery of soft tissue within a triceratops horn—a structure presumably less likely than bone to preserve original tissue over a long period.
Once the two scientists had decalcified the fossil by submerging it in a mild acid for four weeks, they discovered, in the words of their report, “clear to milky-white or reddish brown pieces of soft material, which swayed gently upon bone surfaces when solutions were disturbed.” When Armitage examined the horn under a powerful scanning electron microscope, he saw structures appearing to be vessels that would have supplied blood to the horn, and even what may have been crystalized blood proteins. In addition, he found what appear to be osteocytes, cells involved in building and maintaining bone.
“These are real dinosaur tissues, loaded with real dinosaur cells,” Anderson said. “How is it they were preserved?” He believes the preservation of soft tissue challenges the assumption that the fossil is at least 65 million years old. According to the evolutionary timescale, triceratops lived at the end of the Cretaceous Period, which would have spanned 65 to 145 million years ago. “We have biological evidence that it’s not 65 million years,” Anderson said of his discovery.
Other scientists have recognized the quandary created by soft dinosaur tissue. In 2008, some researchers attempted to solve the problem by suggesting the soft tissue was not part of the original dinosaur, but a later “biofilm” formed by bacteria.
Anderson and Armitage explained in their paper why they thought the biofilm theory broke down on consideration. It is unclear, they wrote, “how such biofilm structures could themselves survive the ravages of time, as once produced other microorganisms could begin to digest even these.”
Other researchers have also been unconvinced by the biofilm explanation. Instead, they’ve proposed another solution: Last year, Schweitzer, who discovered the T. rex tissue, co-authored a paper in Proceedings of the Royal Society B suggesting the iron in hemoglobin molecules played a role in preserving the tissue for millions of years by producing a chemical effect similar to formaldehyde. Other than that, the paper admitted, “the persistence of original soft tissues in Mesozoic fossil bone is not explained by current chemical degradation models.”
As a test of the theory, Schweitzer submerged ostrich blood vessels in hemoglobin, and found it preserved them for more than two years.
Anderson says extrapolating a two-year laboratory study to 60 or 80 million years of deep time leaves “a lot of questions” unanswered. He remains unconvinced soft tissues could survive so much longer than the dinosaurs that produced them.