Lacking a carina or keel-like ridge; in biology, describing a structure without a sharp ridge or prominent longitudinal edge.
From Latin e- (without) + carina (keel, from the naval ship terminology). Renaissance naturalists adopted 'carina' to describe ridges on insects and shells. The prefix e- marks anatomical absence.
A 'carina' was originally a ship's keel—ancient naturalists looked at beetle shells and thought 'hey, that ridge looks like a ship's bottom!' and the name stuck forever!
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