( cially crucial for acrobatic animals th...)Reconstructing the biology of extinct species: A new approach

To make the discovery, the scientists scanned skull samples of each species, measuring the size of each semicircular canal and calculating the radius of curvature. Most of the specimens were scanned at the Center for Quantitative Imaging at Penn State on the OMNI-X high-resolution x-ray CT scanner, which can resolve features approximately 1/100 the size of those detected by medical CT scanners. In addition, experienced field workers used personal knowledge or film of animals in the wild to classify species into one of six locomotor categories ranging from very slow and deliberate to fast and agile. The scientists then compared the canal size of each species to its category of movement.

The results revealed a highly significant statistical relationship between the radius of curvature of the semicircular canals and the species' habitual way of moving. More acrobatic species consistently have semicircular canals with a larger radius of curvature than do slower-moving ones. For example, a small, fast-moving leaper like a bushbaby has semicircular canals that are relatively and absolutely much bigger than those of the similar-sized, slow-moving loris. However, because larger animals have absolutely larger canals, the analysis had to take body size into account. The research revealed that this functional tie between the semicircular canals and locomotor pattern is evident both within the primates alone and within the entire mammalian sample.

"How an animal moves is a basic adaptation," says Walker, an expert in primate locomotion. "Now we have a way to reconstruct how extinct species moved that is completely independent of analysis of the limb structure. For the first time, we can test our previous conclusions using a new source of information."

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Source:Penn State