Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as being basal lophotrochozoans, or even molluscs.
Hyolitha
Hyoliths from the Middle Ordovician of northern Estonia; these are internal molds.
Haplophrentis carinatus from the Stephen Formation, Burgess Shale (Middle Cambrian), Burgess Pass, British Columbia, Canada.
Lophotrochozoa is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. The clade includes animals like annelids, molluscs, bryozoans, and brachiopods.
Lophotrochozoa