epibranchial

Epibranchial refers to any of the dorsal elements of a pharyngeal (branchial) arch in vertebrate anatomy. In most gnathostomes, the pharyngeal skeleton is organized into a series of paired elements that support the gill apparatus; the epibranchials lie dorsal to the ceratobranchials and contribute to the upper part of each gill arch, together with adjacent pharyngobranchial elements.

Epibranchials can be cartilage or bone, depending on lineage and developmental stage. Their number and organization vary among taxa and arch position, and they are typically associated with other visceral skeleton elements such as basibranchials (ventral), ceratobranchials (lateral), hypobranchials, and pharyngobranchials.

In development, epibranchials arise from neural crest cells and undergo chondrification or ossification as the pharyngeal arches form. In many tetrapods, discrete epibranchial bones are greatly reduced or incorporated into hyoid or other cranial elements, and only remnants may persist in the adult skeleton. In fishes, especially most teleosts and cartilaginous fishes, epibranchials are commonly preserved as part of the gill-arch skeleton.

Functionally, epibranchials provide structural support for gill slits and serve as attachment points for muscles and ligaments involved in the movement of the gill arches and feeding apparatus.

See also: pharyngeal arch, visceral skeleton, basibranchial, ceratobranchial.