In paleontology, a small tooth-like or pointed structure found in certain brachiopod fossils, used for classification of ancient shell creatures.
From Greek 'cheilos' meaning 'lip' and '-idium' (a diminutive suffix), referring to small lip-like structures. The term was coined by paleontologists studying fossilized marine organisms from hundreds of millions of years ago.
Paleontologists use these tiny fossil structures like fingerprints to identify which ancient brachiopod species they're looking at—it's amazing that creatures from 400 million years ago left behind such distinctive markers!
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