A new gastropod, Kaneconcha knorri gen et sp. nov., was found in marlstone dredged
from the surface of Adam Dome at Kane Megamullion on the flank of the Mid-Atlantic
Ridge in an area of former hydrothermal activity. The snail is interpreted as a large
provannid similar to the chemosymbiotic genera Ifremeria and Alviniconcha. This is the
first record of presumably chemosymbiotic provannids from the Atlantic Ocean and also
the first fossil record of such large provannids associated with hydrothermal venting.
Extant Alviniconcha and Ifremeria are endemic to hydrothermal vents in the Pacific and
Indian oceans. Kaneconcha differs from Ifremeria in having no umbilicus and a posterior
notch, and it differs from Alviniconcha in having the profile of the whorl slightly
flattened and having no callus on the inner lip. A dark layer covering the Kaneconcha
shell is interpreted here as a fossilized periostracum. The shell/periostracum interface
shows fungal traces attributed to the ichnospecies Saccomorpha clava. We hypothesize
that large chemosymbiotic provannids (i.e., Kaneconcha, Ifremeria, and Alviniconcha)
form a clade that possibly diverged from remaining provannids in the Late Jurassic, with
the Late Jurassic/Early Cretaceous Paskentana being an early member.