Diversity in Cenomanian forests: an example from the Envigne valley (Vienne, France)
Résumé
In the last years, thousands of silicified wood fragments were collected from the middle Cenomanian of two localities in the Envigne valley, western France. These two plant fossil assemblages are exceptional for both the high species diversity and the exquisite tissue preservation as well as their association with animal remains. For instance, wood commonly found in contemporaneous deposits is there often preserved with medulla, bark or both. Teredinid bivalves with soft parts emerging out of some wood specimens were also observed.
As far as taxonomy is concerned, conifers are the most abundant and diversified with at least five taxa belonging to Araucariaceae, Cheirolepidiaceae, Podocarpaceae, and Pinaceae. They represent around 89% of the megafossils. They consist of large trunks transported into an estuarine or a nearshore environment. Besides less abundant, being around 11%, and of smaller diameter, Angiosperms have a higher diversity with at least seven taxa. In particular, a vessel-less angiosperm closely resemble the living Winteraceae. A few specimens, around 0.1%, correspond to the emblematic Cretaceous tree fern Tempskya Corda.
Although angiosperm pollen grains and leaves have been frequently reported from the Cenomanian of western France, contemporaneous wood described so far mostly consists of lignite and conifer genera. These two new plant fossil assemblages are thus of great interest in our knowledge of the record and rise to dominance of Cretaceous angiosperms in Europe and worldwide.