For all we know about what dinosaurs looked like, there's an awful lot we don't know about what dinosaurs looked like.
Research has found that some dinosaurs had feathers -- and that some of those feathers might have been red. And now a new study uncovers the first evidence that even the eggs dinosaurs hatched from were brighter than we might have thought.
"Until today it was common sense that colored eggs are limited to our modern birds," said Jasmina Wiemann, the lead author of a new study presented for publication in the journal PeerJ. "Our study shows that eggshell coloration evolved much earlier."
Wiemann, now a graduate student at the University of Bonn, along with Tzu-Ruei Yang and Dr. Martin Sander, looked at a clutch of 67-million-year-old eggs from bird-like oviraptor dinosaurs that were unearthed in China. The eggs still had blue pigments preserved in the shells.
"The blue-greenish coloration we reconstructed can only be produced by the organic color pigments biliverdin (blue) and protoporphyrin (red)," Wiemann told CBS News. Those pigments give robin eggs their blue hues and make some chicken eggs reddish brown.
"These molecules are relatively stable against degradation, but of course, after 67 million years a part of the originally contained pigments got washed out and faded away. So we can safely assume that the original color of Heyannia huangi eggs was much more intensive. Originally the eggs may have been comparable to those of emus or cassowaries."
The authors argue that the color of the eggs suggests the dinosaurs laid them in at least partially open nests and that the green-blue pigmentation helped to camouflage them from predators. Among modern birds that lay eggs of this color, males often provide more care, so the study also posits that the same could have been true in dinosaurs.
"Since most hypotheses on dinosaur reproduction are controversially discussed, our study acts like the missing piece of puzzle to understand dinosaur reproduction and bird evolution," said Wimann. "Now we know that oviraptor built open nests, and that the males played an important role in parental care."