Bathysoma

Bathysoma is an extinct genus of marine lampriform ray-finned fish from the early-mid Paleocene. It contains a single species, B. lutkeni from Sweden. Its fossils are common in exposures of the Danian København Limestone Formation at Limhamns kalkbrott, one of the largest quarries in northern Europe. A single specimen is also known from an erratic boulder from the Selandian Lellinge Greensand Formation of southern Sweden.
It is the second oldest lampriform known, after Nardovelifer of Campanian/Maastrichtian Italy. B. lutkeni has a disk-shaped body and an elongated head. It was originally described as a menid bony fish. Later, it was described as being a basal snake mackerel. Eventually, anatomical similarities with the turkmenids were noted, and B. lutkeni is now regarded as an extremely basal lamprid.