Traces of dino blood, soft tissue found even in junk bones
Discovery gives scientists new places to search for clues to when warm-bloodedness evolved
DRIED BLOOD A scanning electron micrograph of a sliver of a theropod’s toe claw reveals oval-like structures that resemble the red blood cells seen in living birds. The colors correlate to density: less dense, carbon-based material appears red and denser mineralized material appears green.
S. Bertazzo et al/Nature Communications 2015
When it comes to finding dinosaur blood, any dino bone could do.
Researchers from London have found hints of blood and collagen in a hodgepodge of 75-million-year-old dinosaur bones. The fossils were poorly preserved, suggesting that dinosaur bones containing traces of soft tissue may be more common than previously thought, the scientists argue June 9 in Nature Communications. If soft tissue is still preserved in most bones, it might be easier to determine when dinosaurs switched from cold-blooded to warm-blooded creatures, the scientists say.
Until now, researchers thought traces of soft tissue existed only in exceptionally well-preserved fossils (SN: 3/26/2005, p. 195). “It’s exciting to think that we may have more soft tissue in dinosaur bones kicking around,” says Matthew Collins, an expert in the study of ancient proteins at the University of York in England who was not involved in the study.
Susannah Maidment, a paleontologist at Imperial College London, and colleagues identified the soft tissue in slivers of eight dinosaur bones, including a toe claw from a theropod and a rib from a duck-billed dinosaur. Scanning electron microscope images revealed structures that resemble red blood cells, and transmission electron microscope images revealed nanometer-scale banding structures similar to patterns formed by collagen proteins in human bone. Chemical analyses showed that the bone slices contained amino acids and other molecules similar to those found in emu blood and in collagen from rabbit bone.
“Those results tell us that there are actual original components of blood and collagen preserved in the fossil bones,” Maidment says. The preserved blood — specifically, the size of the cells — could help scientists determine which dinosaurs had faster, more warm-blooded, birdlike metabolisms and which ones had slower, reptilian-like metabolisms, she says. Smaller red blood cells indicate faster metabolisms.
“The ancestors of dinosaurs are thought to have been cold-blooded animals, while the birds, the descendants of the dinosaurs, are warm-blooded. This means that somewhere on the line to birds, within the dinosaur group, warm-bloodedness evolved,” Maidment says. “At the moment, we have no direct evidence for this transition from bones alone.” Having access to preserved blood cells in a greater number of dinosaur bones could change that, she says.
Collins argues, however, that scientists need to go beyond pointing out that amino acids and proteins exist in fossil dinosaur bones — something that’s been known since the 1970s. He says the next big advance will be extracting the preserved proteins to determine the order of the amino acids in each one. That information could help scientists fill in the gaps in dinosaur evolution.
Preliminary studies have delivered this kind of dinosaur sequence data, but the results have not been reproducible, Collins says. “That’s what we’re waiting for now.”
