OCTOPODS AS PREDATORS IN THE FOSSIL RECORD

The body fossil record of Octopodoidea is very limited with only a single species (Styletoctopus annae) known from the early Late Cretaceous (Cenomanian). Despite this limited body fossil record due to their soft body, their presence can be tracked in a different way. Members of multiple families of modern Octopodoidea attack molluscan and crustacean prey and often leave behind a characteristic ~0.2–2 mm drill hole. These holes are oval to rounded in outline and are ascribed to the ichnospecies Oichnus ovalis and O. simplex. Holes attributed to octopodoids are known from Plio-Pleistocene barnacles, decapod crustaceans, bivalves, and gastropods from a variety of assemblages. From the earlier part of the Cenozoic, Miocene and Eocene bivalves with such holes have been reported. Most studies show a limited number of octopodoid-attributed drill holes from a restricted geographic region and stratigraphic range. We present case studies from three geographic regions. First, based on large collections of mollusks from the Miocene – Holocene of Japan, we find an increase in the frequency of such holes from < 1% to > 3%. Pectinid bivalves are drilled preferably. Another case study on Plio-Pleistocene cypraeid gastropods from southern Florida shows a relatively high drilling intensity (13%) and strong site selectivity. Most of these drill holes are found in the left ventral posterior region of the shell, which is where the columellar muscle anchoring the soft tissue to the shell interior is attached. Finally, three lucinid bivalve specimens from the Late Cretaceous (Campanian) of South Dakota exhibit holes that resemble those produced by modern octopodoids. These case studies demonstrate that the drilling traces produced by octopodoids are not necessarily rare and that their fossil record can be leveraged further to study the evolution of octopod occurrence and behavior.