Plural or alternate form of exostrum; a rostrum or beak-like projection on the outside of a structure, especially in zoology.
From Latin 'exo-' (outside) + 'rostrum' (beak/projection). Specialized zoological term rarely used in modern English, surviving primarily in historical taxonomic descriptions.
This is one of those ultra-specialized Latin scientific terms that modern biologists rarely use—it was more common when all scientific names and descriptions were written in Latin, back when scientists thought like Romans.
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