Boreholes in the Middle Devonian blastoid Heteroschisma and their implications for gastropod drilling

Boreholes in over 100 specimens of the Devonian blastoid Heteroschisma and the presence of the gastropod Platyceras (Orthonychia) sp. attached to a specimen of Heteroschisma subtruncatus (Hall 1858) suggest that platyceratid gastropods were capable of drilling their hosts at least as early as the Middle Devonian and thus represent the first known gastropods to have evolved this ability. The presence of similar holes in numerous other Devonian and Mississippian blastoids and the occurrence of several additional examples of platyceratids attached to blastoids indicate that the interaction between gastropods and blastoids was not infrequent; as in the case of the gastropod/crinoid interaction, this relationship is interpreted as having been parasitic rather than predatory. The parasitic, drilling platyceratids may have been a factor in the Paleozoic precursor of the Mesozoic marine revolution: some of the anti-predatory defenses of crinoids described from the Late Paleozoic may have been strategies of avoiding platyceratid infestation.