in taxon Strigiformes sesamoid bone facial bone scleral ossicle scleral sesamoid bone scleral sesamoid A sesamoid bone that lies adjacent to the tendon of one of the muscles responsible for adducting the nictitating membrane (the pyramidal nictitating muscle). UBERON:0010311 During contraction, the scleral sesamoid bone acts to anchor the pyramidal nictitating muscle to the sclera and divert the tendon from pro- jecting over the cornea. It remains to be determined whether this is indeed a true sesamoid (sensu; Vickaryous and Olson, 2006), as the scleral sesa- moid is actually invested within the synovial tendon sheath and not the tendon per se sesamoideum esclerae scleral sesamoid element