In the series "A Modest Proposal," my colleagues and I will propose inventions and projects that I think are eminently doable and would love made real.

I had suggested last year that one could create 3-D scans of fossils while they are still trapped within the rock using, say, X-rays. Imagine 3-D models of all these vast libraries of fossils placed online where students in schools all around the world might take a look at them either on their computers or by using 3-D printers to manufacture replicas and maybe even dinosaur robots.

Now German scientists have used CT scans with 3-D printers to make accurate copies of a dinosaur vertebra still embedded in rock and plaster, research appearing in the journal Radiology. The fossil was originally buried under rubble in the basement of a museum in Berlin after a World War II bombing raid.

However, these researchers are far from the first to CT scan fossils and 3-D print replicas of the bones. Vertebrate paleontologist Michael Polcyn at Southern Methodist University in Dallas tells me this has been done for years.

For instance, below are fossil bird bones that paleontologist Brett Nachman of the University of Texas at Austin printed for a colleague, all scanned while still within the matrix that held them.

And here are 3-D replicas of juvenile fossil primate jaws with teeth, printed by Eric Delson at the City University of New York's Lehman College, alongside the original fossil.

And here is a reconstruction of an ancient mollusk known as a multiplacophoran that lived about 390 million years ago, a multicolored, textured model in clay, resin and silicone based off a micro-CT scan:

To derive a good 3-D model, Polcyn notes there needs to be reasonable contrast between the rock and the fossil, "and this is not always the case." The cost of CT scanning and the data-processing needed to derive a 3-D model good enough for printing may also exceed the cost of traditional fossil preparation.

In addition, the resolution of scans typically decreases as the size of specimens increases "both due to the size of the machine that can accommodate the fossil and the practical computing and memory limitations encountered when processing the huge data sets," Polcyn said. "In the case of very large fossils, there are only a few CT scanners that can be used, and these are generally designed for use by the aerospace industry for scanning aircraft components."

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