#2767 - Petaloconchus sp.
Snails with worm-like shells, usually found growing cemented onto a hard surface, or cemented together in colonies. The inner surface is smooth, unlike the tubes of the better-known Tube Worms. Since the shape of the tubes is highly variable, Vermetid taxonomy is a nightmare, even with the living species.
According to one source I've looked up, there are 135 recognized living species of Vermetidae and 16 genera. The Paleobiology Database recognizes 11 fossil genera and 114 fossil species of Vermetidae. They've been around since the Triassic (250-201Mya) - the fossil up the top is from the Late Oligocene, in the Waitakian Stage (25.2-21.7Mya).
Since Vermetids can't move from where they grow attached to the seafloor, they feed by capturing plankton - either filtered from the water passing over the gills, or by spinning a mucus net in which plankton is trapped.
Unusually for a sessile animal, vermetids are of separate sexes, with sperm packets captured in the feeding web of females and eventually fertilizing her eggs. Fertilized eggs are brooded in her mantle cavity, and released as crawling or free-swimming larvae.
University of Otago Geology Museum, Dunedin, Aotearoa New Zealand
