#2764, 2765, & 2766 - Dentalium, Laevidentalium, & Fissidentalium - Tusk Shells
Fossil scaphopods from three genera and two families.
Tusk Shells live in deeper water, buried entirely in the sediment, inhaling and exhaling water through a small aperture at the narrow end of the shell, and collecting foraminifera and other organic matter from the sediment with tiny tentacles at the other end. The largest known species is 18 cm long - Fissidentalium metivieri.
Genetic evidence suggests they're the sister group of the cephalopods, but their fossil remains only go back to the early Carboniferous. The route they took to evolve into these things remains a topic of debate.
Despite being a comparative rarity on beachs (being fairly fragile and not found in intertidal waters, usually) Māori traditionally used the shells for rings and necklaces. The shells were collected as shell money by the indigenous peoples of the Pacific Northwest, and for belts and headdresses by the Natufian culture of the Levant 15000 to 11500 years ago. Excavations at Mehrgarh in what is now Pakistan, over 500km from the coast and six millennia BCE, uncovered elaborate headbands made from Dentalium shells.
University of Otago Geology Museum, Dunedin, Aotearoa New Zealand.