The funnel–mantle locking apparatus is a structure found in many cephalopods that connects the mantle and hyponome (funnel) and restricts their movement relative to each other.[1] It consists of two interlocking components: one located on the mantle (often fibrous) and the other on the funnel (often cartilaginous).[1] The apparatus may permit some anterior–posterior displacement or prevent movement altogether.[1]
Six major forms of the funnel locking apparatus are recognised among teuthids (lazy-T shape, inverted-T shape, straight shape, triangular shape, oval with tragus and/or antitragus, and oval shape) and several more are found in the sepioids (including the boomerang shape and keyhole shape).[2]