SANCTUM ERICKSON AND BOUCHARD: MISCONCEPTIONS CORRECTED

In 2005 and 2007, Wyse-Jackson and Key discussed the ichnology of Mid Ordovician bryozoan substrates from Estonia. Without mention of the trepostome identities, the authors categorized various properties of the assorted borings and tunnels that were present in numerous specimens, both ramose fragments and domal colonies. Some aspects of the traces were recognized as characteristic of Sanctum laurentiensis Erickson and Bouchard, 2001, whereas some were attributed to Trypanites sp. Wyse-Jackson and Key (2007) corrected misconceptions about the systematics of S. laurentiensis that they had expressed earlier in Wyse-Jackson, Key and Burns (2005), but they have included a reinterpretation of the monotypic Sanctum that is not in accord with the generic description. Further explication of the matter is required.

We do not accept the revision of Sanctum as proposed by Wyse-Jackson and Key (2007) as the characters are not reflected in the type species, S. laurentiensis. Tunnels have a single entrance. Tunnels made by two separate organisms (or groups) sometimes intersected inadvertently resulting in a tunnel complex that therefore may have multiple openings. Tunnel shapes are not defined by the exozone but rather by the choices of the excavators of what endozone to remove and what to leave.

S. laurentiensis is a tunnel rather than a boring. It has rough, uneven walls and often a varying width produced by excavating endozonal portions of zooecia in live ramose bryozoan colonies. The mined tunnels were empty of micrite, mud or other sediment when in use by the original constructors. We do not accept the revision of as proposed by Wyse-Jackson and Key (2007) as the characters are not reflected in the type species. Tunnels have a single entrance. Tunnel shapes are not defined by exozone as Wyse-Jackson and Key suggested but rather by choices of the excavators of what endozone to remove and what to leave.

Wyse-Jackson and Key have shared with us a specimen of the domal colony-type from their study. At least some tunnels in these reached the colony base and made a smooth-walled boring into the exozonal portion of zooecia. This unique arrangement may reflect a Baltic trace which could stand as a second species of Sanctum. Possibilities will be illustrated and discussed further.