CT scan unscrambles rare, ancient egg

From Bozeman, Mont., at the 61st annual meeting of the Society for Vertebrate Paleontology

A tangled heap of bones and bone fragments found inside an ancient bird egg may

soon be reassembled thanks to high technology–and scientists won’t even have to

crack open the egg to do it.

Huge flightless birds called elephant birds strolled their Madagascar homeland

until they went extinct about 400 years ago. Believed to be the heaviest birds

that ever lived, they weighed half a ton and were about 3 meters tall. Their eggs

were the largest single cells in the animal kingdom and could hold about 7.5

liters of material.

When researchers at the University of Texas at Austin recently performed a

computerized tomography (CT) scan of an unbroken elephant bird egg, they

discovered a tiny, dismembered skeleton. Amy M. Balanoff, a vertebrate

paleontologist at the school, constructed digital models of individual bones.

Using the rapid-prototyping techniques common in the automotive and aerospace

industries, she then made three-dimensional plastic copies of the bones.

So far, Balanoff has made three-times-life-size copies of about 100 bone

fragments. After making similar copies of the few remaining fragments, she’ll

assemble a replica of the embryo. Balanoff estimates that the embryo was about 70

percent of the way to hatching when it died inside the eggshell. By comparing its

stage of development with that of embryos of ostrichlike emus, Balanoff estimates

that elephant bird eggs took 47 days to hatch.

Future CT scans of other intact elephant bird eggs may reveal embryos at other

stages of development, Balanoff notes. Analyzing a series of embryos should give

scientists a better understanding of how the elephant bird grew so large.