extrabranchial

from The Century Dictionary.

• Lying outside of or external to the branchial arches; forming the external support of the branchial septa.
• noun A term applied by W. K. Parker to certain cartilages which take part in the formation of supports for the divisions between the gill-chambers in tadpoles, lampreys, and sharks.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Anat.) Outside of the branchial arches; -- said of the cartilages thus placed in some fishes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective anatomy Outside of the branchial arches.