Gyrochorte Heer, 1865

Diagnosis. Wall-like burrow with a top part (positive epirelief) consisting of two convex lobes with a median furrow and a bottom part (negative hyporelief ) consisting of two grooves and a median ridge. The lobes on the top (and more rarely the grooves at the base) commonly exhibit transverse meniscus-like discontinuities and often obliquely aligned plaits. Internal structure (when recognizable) consists of repetitive biconvex-up modular units (spreiten). Burrows exhibit an irregular meandering or arcuate course, but more rarely they may be straight or gently curved (emended by Gibert and Benner, 2002).

Remarks. The producers are endobenthic organisms, possibly gastropods, crustaceans or worms. See Gibert and Benner (2002) for a discussion of their ethology. According to Heinberg (1973), Gyrochorte is produced by the oblique movement of an elongated organism within the substrate. Gibert and Benner (2002) considered that the most likely producer is an annelid. The ichnogenus has been associated with a wide range of salinities, supporting an opportunistic behaviour for the producers in a context of environmental
stress related to high and/or fluctuating salinities. It is common in sandy facies from shallow marine deposits of high to moderate energy, including bars, beaches and embayments (Gibert and Benner, 2002).