A small bone in fish that connects the gill arches to the hyoid bone, part of the skeletal support system for the gills.
From Greek 'branchia' (gill) + 'hyoid' (relating to a U-shaped bone in the neck). The term combines Latin anatomical terminology to describe this specific gill-support structure discovered during detailed fish anatomy studies in the 19th century.
Fish have entire skeletal sub-systems just for gills that mammals completely lost when we evolved lungs—the branchihyal is like finding evidence of evolutionary trade-offs written in bone.
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