Of or pertaining to organisms with firm breastbone structures; an extended technical adjective form used in anatomical studies.
Formed from firmisterna with the suffix '-ial' (variant of '-al'), creating a more elaborate adjectival form common in 19th-century scientific literature.
The more suffixes you add to a Latin root, the more specialized and narrow the meaning becomes—'firmisternial' is so specific it barely appears in modern science anymore.
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