Bulletin of the Mizunami Fossil Museum

Bulletin of the Mizunami Fossil Museum Vol. 51, No. 1

A recent article described an orthoceratid cephalopod from the Silurian of eastern midcontinental USA that is encrusted by two blastozoan echinoderms, with one attachment structure preferentially encrust-ing the attachment structure of the other. Discussion of the palaeoecological significance of this spec-imen centered around interactions between encrusting echinoderms, but as a note of secondary signif-icance, it was reported that this occurrence supposedly represented the first published example of dip-loporitan encrustation of a cephalopod substratum that was not completely overgrown by the aboral region of the echinoderm. This claim is inaccurate, however, as two previously published examples have been documented. Nevertheless, the specimen represents the first published Silurian example of such a phenomenon, as both previously published examples were from other Palaeozoic systems. An additional Silurian cephalopod specimen (Dawsonoceras annulatum) displaying encrustation by a diploporitan echinoderm—the second example documented from Silurian strata—seemingly indicates that this relationship is less rare than the paucity of currently published descriptions suggests.