Giant Paleodictyon in eocene flysch

A giant Paleodictyon gomezi with a maximum mesh diameter of 13 cm and cover ing more than 0.5 m(2) occurs in the lower Eocene flysch near Zumaya. The g iant Paleodictyon occurs with flute casts and, therefore, must have been pr oduced deeply in the sediment. The lengthening of mesh cells parallel and p erpendicular to the flute casts implies changing current directions during trace production. Rows of elongate and offset mesh cells reflect the row-by -row production of the trace; however: the base line followed by the trace fossil producer (meandering or spiral) cannot be reconstructed because of i ncomplete preservation. The extraordinary size of this giant Paleodictyon c ontradicts the evolutionary trend of deep-sea trace fossils toward optimiza tion and miniaturization, since similar large Paleodictyon specimens occur in Silurian flysch. (C) 2000 Elsevier Science B.V. All rights reserved.