Protein identified in dinosaur fossils.

A team of molecular biologists and paleontologists has identified a protein preserved in dinosaur bones, opening up the possibility of using ancient molecules to help sort out the controversial relationships among dinosaurs and other vertebrates.

Scientists have long considered it highly unlikely that they would find proteins in material more than a few million years old, because such organic molecules usually decay far sooner. Yet several research teams in the past few years have reported detecting proteins in very old fossils, including dinosaur bones (SN: 5/4/91, p.277). In the dinosaur case, however, the researchers did not know which proteins they had detected, and many scientists wondered whether the proteins had come from bacteria or other sources of contamination.

Now, Gerard Muyzer of Leiden University in the Netherlands and his colleagues report using immunological tests to identify a specific bone protein called osteocalcin in several dinosaur fossils that date back 75 million and 150 million years. They discuss their work in the October GEOLOGY.

"If it is indigenous, then it is the oldest protein," says Lisa Robbins, a micro-paleontologist at the University of South Florida in Tampa.

Muyzer's group identified the dinosaur protein through an antibody that binds to osteocalcin, a small molecule present in the bones of vertebrate animals. The antibody test found osteocalcin in the bones of hadrosaurs, a ceratopsian, and a sauropod dinosaur. It also detected the protein in several mammal fossils and an ancient turtle bone.

The researchers believe the osteocalcin is indigenous to these fossils because invertebrates and bacteria do not produce this protein. Their tests did not show any osteocalcin present in fossilized seashells. Another procedure showed that the dinosaur fossils contained relatively high concentrations of gamma-carboxy glutamic acid (Gla), an amino acid absent in invertebrates and microbes, say the researchers.

Other researchers, however, remain skeptical about the possibility of finding proteins from so far back. Jeffrey L. Bada from the Scripps Institution of Oceanography in La Jolla, Calif., says a study he did on Gla shows that it doesn't last more than 100,000 years. "I worry greatly about the stability of Gla. Why would it remain unaltered over tens of millions of years?" he wonders.

Muyzer and his colleagues had hoped to isolate the osteocalcin and then determine its amino acid sequence. By comparing that with osteocalcin sequences from birds and crocodiles, the researchers could address the long-standing question of how closely birds and dinosaurs are related. At present, paleontologists can only use dinosaur bones to make comparisons.

Muyzer's group did not succeed in isolating the protein. But advances in laboratory procedures may soon make the job easier. "The techniques are improving daily. It's just a matter of the techniques catching up with what we want to do," Robbins says.