Teichichnus zigzag Frey and Bromley, 1985: a probable echiuran or holothurian burrow from the Jurassic offshore Norway

Arcuate to V-shaped spreiten burrows are common in marginal-marine Jurassic deposits from offshore Norway and are described in detail from well-core material. Well-preserved specimens show a tripartite architecture with convex-down stacked laminae (retrusive) in the lower part, convex-up stacked laminae (protrusive) in the upper part of the burrow, and a passively filled terminal causative burrow in between. A large funnel-shaped structure and/or a homogeneous area can also occur in the upper part of the burrow. Based on their morphology and features, these burrows can be assigned to the ichnogenus Teichichnus Seilacher, 1955, although they appear to be more developed and complete than hitherto described Teichichnus ichnospecies. Similar burrows were described as Teichichnus zigzag Frey and Bromley, 1985. The overall morphology and details of the burrows, in comparison with modern analogues and neoichnological experiments, suggest echiurans (spoon worms) or holothurians (sea cucumbers) with a combined suspension- and deposit-feeding behaviour as potential producers.