A 'Phoebichnus look-alike': a fossilised root system from Quaternary coastal dune sediments, New Zealand

摘要

Phoebichnus trochoides Bromley and Asgaard, is a large and unusual compound, deep-tier trace fossil described from the Jurassic of Jameson Land, Greenland and is of restricted occurrence in a few other Mesozoic sequences. The trace maker is an unknown marine organism. A remarkably similar structure, here called a 'Phoebichnus look-alike' is preserved in a Quaternary coastal dune setting from northern New Zealand. This structure reflects the root architecture of the endemic nikau palm, Rhopalostylis sapida (Wendl et Drude). Apart from age, the only discernable difference between P. trochoides and the 'Phoebichnus look-alike' is the absence of bi-directional, back-fill menisci in radiating rays of the latter. It is suggested that care should be taken when identifying the ichnotaxon P. trochoides (s.s.) in the absence of these menisci. Structures of a "phoebichnus look-alike' kind may be of local palaeoenvironmental significance and aid in the identification of damp, swaley environments in coastal sand dune settings.