this state resembling a pucker rather than a disk). According to the World Register of Marine Species: Dentaliida da Costa, 1776 family Anulidentaliidae Chistikov, 1975 – 3 genera family Calliodentaliidae – 1 genus family Dentaliidae Children, 1834 – 14 genera family Fustiariidae Steiner, 1991 – 1 genus family Gadilinidae Chistikov, 1975 – 3 genera family Laevidentaliidae Palmer, 1974 – 1 genus family Omniglyptidae Chistikov, 1975 – 1 genus family Rhabdidae Chistikov, 1975 – 1 genus Gadilida Starobogatov, 1974 sub-order Entalimorpha Steiner, 1992 family Entalinidae Chistikov, 1979 – 9 genera sub-order Gadilimorpha Steiner, 1992 family Gadilidae Stoliczka, 1868 – 8 genera family Pulsellidae Scarabino in Boss, 1982 – 3 genera family Wemersoniellidae Scarabino, 1986 – 2 genera Evolution Fossil record There is a good fossil record of scaphopods from the Mississippian onwards, making them the youngest molluscan class. The Ordovician Rhytiodentalium kentuckyensis has been interpreted as an early antecedent of the scaphopods, implying an evolutionary succession from ribeirioid rostroconch molluscs such as Pinnocaris. However, a competing hypothesis suggests a Devonian/Carboniferous origin from a non-mineralized ancestor, or from a more derived, Devonian, conocardioid rostroconch. Phylogeny The scaphopods are largely agreed to be members of the Conchifera, however their phylogenetic relationship with the other members of this subphylum remains contentious. The Diasoma concept proposes a clade of scaphopods and bivalves based on their shared infaunal lifestyle, burrowing foot, and possession of a mantle and shell. Pojeta and Runnegar proposed the extinct Rostroconchia as the stem group of the Diasoma. An alternative hypothesis proposes the cephalopods and gastropods as sister to the scaphopods with helcionellids as the stem group. A review of deep molluscan phylogeny in 2014 found more support for the scaphopods, gastropods, or cephalopods than for scaphopods and bivalves, thus the shared body features of scaphopods and bivalves may be convergent adaptations due to similar lifestyles. Analysis of the scaphopod nervous system demonstrated that both scaphopods and cephalopods share a similar nervous system structure, with ventrally shifted pedal nerves and lateral nerves that extend dorsally. These similarities led to the conclusion that scaphopods are sister to the cephalopods with gastropods as sister to them both. Human use The shells of Dentalium hexagonum and Dentalium pretiosum were strung on thread and used by the natives of the Pacific Northwest as shell money. Dentalium shells were also used to make belts and headdresses by the Natufian culture of the Middle East, and are a