Palaeos		Scaphopoda
Mollusca		Scaphopoda

Scaphopoda

MOLLUSCA
|--ACULIFERA
`--CONCHIFERA
   |==Tryblidiida (Monoplacophora)
   |   `--Cephalopoda
   `==Helcionelloida
       |==Rostroconchia
       |   `--Scaphopoda
       |--Bivalvia
       `--Gastropoda

Antalis entalis (Scaphopoda: Dentaliida: Dentaliidae); empty shells washed up after storms; Swanage Beach, England. Photo © BioImages Creative Commons Non-Commercial Attribution Share Alike via Encylopedia of Life.

The Scaphopods are called tooth or tusk shells because some types resemble miniature elephant tusks. These little-known molluscs are actually relict survivors of a more diverse Paleozoic group known as Rostroconchs. Where they belong on the molluscan evolutionary tree is uncertain; they have been variously grouped with bivalves and cephalopods (it is hard to imagine two more diverse clades of molluscs), such is the lack of consensus in molluscan phylogeny. MAK120614