The Piedra Chamana Fossil Forest in northern Peru, which is associated with Calipuy volcanics dated at 39 Ma, includes a large amount of fossil wood occurring across an 8-km-long area. In one part of the site, woods are weathering out of a volcanic mudflow (lahar) deposit and in growth position in an underlying ashfall that also contains fossil leaves. The general geologic context and inferred taphonomy of the fossils has been described in Woodcock et al, 2009. Recent fieldwork, and ongoing studies of the fossil material, has added to our understanding of the assemblage and also shown that fossil sites are more extensive than had been thought. Analysis of the fossils and their spatial occurrence indicates that three plant associations are represented at the sites we have studied most intensively (Fig. 1): • 1) Lowland tropical forest with a diversity of monocots and dicots. Preliminary...