Gladius (cephalopod)

Gladii are known from a number of extinct cephalopod groups, including teudopseids (e.g. Actinosepia, Glyphiteuthis, Muensterella, Palaeololigo, Teudopsinia, Teudopsis, and Trachyteuthis), loligosepiids (e.g. Geopeltis, Jeletzkyteuthis, and Loligosepia), and prototeuthids (e.g. Dorateuthis, Paraplesioteuthis, and Plesioteuthis).

Morphology

Gladii are shaped in many distinctive ways and vary considerably between species, though are often like a feather or leaf. The equivalent part in cuttlefish is the cuttlebone. Below are examples of gladii from various families of squid;