CT-Scanning the Past

CT scans have been done on mummies (showing that King Tut wasn’t murdered), dinosaurs (determining, for instance, what parasaurolophus sounded like) and other pieces of the past, and now scientists have put computed tomography (CT) technology to another nifty use: taking skull fragments of a rare extinct lemur which were found at sites thousands of miles apart and virtually assembling them to produce a nearly-complete skull.

The first fossil of the extinct lemur called Hadropithecus stenognathus, which last lived 2,000 years ago, was found in 1899 in Andrahomana Cave in Madagascar. Since then the jaw and partial skull have resided in Vienna, remaining annoyingly incomplete. But in 2003 scientists excavated new cranial fragments and limb bones of Hadropithecus. Alan Walker of Penn State, who happened to have CT scans of the Vienna skull in his lab for another project, realized that the new pieces might fit into the incomplete skull.

As Walker and colleagues describe in a paper in the early online edition of the Proceedings of the National Academy of Sciences Monday evening, they CT-scanned the new fragments and found that they fit into the Vienna skull perfectly.

That let them measure the lemur’s cranial capacity (115 ml.) and, using limb and trunk bones of the same guy, infer that it was as large as a large male baboon. Hadropithecus, it seems, had a relative brain size (as a fraction of body size) as large as some large monkeys, and one of the largest of any known prosimians (a group that includes lorises, lemurs and bushbabies). Hadropithecus, similar to today's sifaka, was one more piece of the stunning mosaic of biological diversity that Madagascar once supported, at least before the island was gripped by an extinction crisis.