Big survivors with small flowers : Fossil history and evolution of Laurales and Chloranthaceae

Sammanfattning: This thesis provides palaeobotanical evidence on Cretaceous Laurales and Chloranthaceae, and discusses and evaluates the material in a phylogenetic framework. Chloranthaceae extend back to the Barremian or Aptian and Laurales to the Albian (both Early Cretaceous). The global occurrence of Chlorantbaceae in the Cretaceous demonstrates that the current distribution of the family is relictual.The flower Virginianthus calycanthoides, which is the oldest known fossil with probable affinity to Calycanthaceae, is described from the Albian of North America. Several new species of Lauraceae (e.g., Mauldinia bohemica, Neusenia tetrusporangiata) are described from the Czech Republic (Cenomanian) and NorthAmerica (Santonian/Campanian). Based on the observed diversity in inflorescence and anther features, possible evolutionary scenarios for these features are discussed. Two species of Chloranthistemon (Chloranthaceae) from the Santonian/Campanian of Sweden are documented based on inflorescence fragments and complete flowers. These and other well-documented chloranthaceous fossils are investigated together with extant Chloranthaceae using parsimony analysis. The results support monophyly of the family and indicate the presence of two distinct clades: one Chloranthus/Sarcandra-clade and one Ascarina/Hedyosmum-clade. The results indicate that the common ancestor of Chloranthaceae included half-shrubs with naked unisexual flowers in spicate inflorescences. Female flowers consisted of a single carpel and male flowers of a single stamen.