Fossils Yield 10-Million-Year-Old Bone Marrow -- A First

Richard A. Lovett
for National Geographic News
July 25, 2006
Fossilized bone marrow has been discovered in ten-million-year-old frogs and salamanders from an ancient lake bed in Spain, scientists announced Friday.

The specimens are the first examples of fossilized bone marrow ever to be discovered. They are so well preserved that the original color of the tissue is still visible.

An international team of paleontologists, spearheaded by Maria McNamara of Ireland's University College Dublin, made the find while studying the remains of more than a hundred ancient frogs and salamanders.

The discovery suggests that many other fossil bones may contain well-preserved remnants of bone marrow, the scientists say.

Although fossil remains of muscles, skin, and internal organs have been found, they are rare because soft tissues usually decay before they can be fossilized.

And when traces of such tissues are found, the original organic matter has usually been replaced by minerals during fossilization.

Not so with the Spanish amphibians.

"The marrow is organically preserved," McNamara said. "The original color of the marrow is preserved."

Like modern frogs, she says, the bones show an inner zone of yellow, fatty marrow, encircled by an outer zone of red marrow.

The find will allow "incredible insights" into the makeup of ancient animals, McNamara predicts.

The simple discovery that the marrow was red likely means that the animals made red blood cells in their bones, rather than solely in their spleens, as is the case with some modern salamanders, she says.

The team announces its discovery in the August issue of the journal Geology.

Tyrannosaurus Rex

The finding is surprising because bone marrow is thought to decay quickly in all but the most extraordinary conditions.

But such unusual conditions may not in fact be necessary to preserve marrow, McNamara says, because the surrounding bone contains many tiny pores.

These pores are too small to allow decay-causing bacteria into the tissue. The pores also let water out while allowing in chemicals that help block decay.

The finding is "very interesting," said John Horner, curator of paleontology at Montana State University's Museum of the Rockies in Bozeman.

Horner was part of a team that in 2005 found remnants of blood vessels in the bones of a Tyrannosaurus rex.

(Read "T. Rex Soft Tissue Found Preserved" [March 24, 2005].)

In many ways, he says, the new find is similar.

"We don't know what they're composed of," he said of the T. rex fossils.

"They look like blood vessels. They're stretchy and all sorts of things, but whether they're the original substance or not, we just don't know."

(See a National Geographic magazine feature on re-creating a virtual Tyrannosaurus rex.)

"I think what they've got here is going to be a lot of fun to work on," Horner said of McNamara's finding.

Jurassic Park?

The next step, McNamara says, is to determine what the fossilized marrow is made of.

"We have started the analysis, but we're not finished," she said.

The fact that part of the marrow is red, however, makes it likely that it carries some of the original biological materials, such as remnants of hemoglobin, the oxygen-carrying substance that gives blood cells their color.

But Jurassic Park notwithstanding, she finds it unlikely that DNA might have survived that long.

"The whole subject of DNA preservation in fossils is controversial," she said.

"If we get traces of protein or something, we'd be quite happy."

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