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 (sĕm′ē-lo͞o′nāt′, sĕm′ī-)
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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individual tracks are elongate and straight, or comma-shaped to semilunate in plan view, with their long axes oriented oblique to trackway midlines.
For instance, the late Yale professor John Ostrom famously pointed out in the 1970's that the wrists of both birds and bird-like dinosaurs possess a very similar, half-moon shaped bone called the semilunate, and that this bone resulted from the merging of two bones present in dinosaurs.
When dinosaurs such as the veloci-raptor evolved a new bone called the semilunate carpal," Johnson writes, "it enabled them to swivel their wrists with far more flexibility.