The importance of paleobotanical whole plant reconstructions: Morphology and anatomy of Lythraceae and Lauraceae from the Princeton Chert

This dissertation presents new data on two fossil angiosperm species from the Middle Eocene Princeton Chert, British Columbia, Canada: Decodon allenbyensis Cevallo-Ferriz et Stockey (Lythraceae, loosestrife family), and Similkameena borealis gen. et sp. nov., (Lauraceae, laurel family). Several criteria are used to reconstruct plants: (1) close association of organs in same chert blocks, (2) consistent co-occurrence of organs in a chert layer, (3) anatomical comparisons to extant and fossil taxa, (4) anatomical characters shared by isolated organs, (5) developmental sequences that connect isolated organs at different stages of maturity, and (6) attachments of plant organs.; Decodon allenbyensis, originally described based only on fruits and seeds, is reinvestigated on the basis of vegetative remains. Anatomy of both stems and roots of the extant, monotypic Decodon verticillatus (L.) Ell. is also described and compared to the fossil axes. A further developmental study on roots of D. allenbyensis indicates a pattern of anatomical changes that is distinct from that seen in members of the sister family Onagraceae (evening primrose family). In addition, this developmental study also reveals an attachment of roots to large axes bearing a novel type of aquatic bark. This level of developmental information is unknown in other extant or fossil Lythraceae. Finally, a comparative study on leaves of extant Lythraceae sensu lato reveals a combination of anatomical characters diagnostic for Duabanga grandiflora Roxburgh ex DC Walpers (Subfamily Duabangoideae) that match those in fossil leaves associated with the axes of Decodon. The mutual abundance and association of Decodon axes and Duabanga-like leaves in the chert produces the hypothesis that these leaves are those of Decodon allenbyensis.; Similkameena borealis is represented by inflorescence axes that reveal a unique combination of inflorescence architecture and floral organization. My investigations show a developmental sequence from young flowers to mature fruits. This sequence allows for the amplification of the concept of Similkameena and is the first study of fruit development in fossil Lauraceae. Moreover, the fruit characters contribute to the distinctiveness of the taxon, and show that different developmental stages of the same species, preserved in the fossil record, may be dubiously assigned to separate taxa.