The largest amber-preserved flower revisited.

Amber exquisitely preserves the delicate organs of fossil flowers for millions of years. However, flower inclusions can be rare and usually do not exceed 10 mm in size. Here we report an exceptionally large flower from late Eocene Baltic amber, measuring 28 mm across, which is about three times as large as most floral inclusions. This fossil was described over 150 years ago as Stewartia kowalewskii (Theaceae) and has never been revised. The analysis of pollen extracted from the anthers of the flower inclusion, however, revealed strong affinities to Asian species of Symplocos (Symplocaceae), prompting the new combination Symplocos kowalewskii comb. nov. et emend. This fossil represents the first record of Symplocaceae from Baltic amber and supports affinities of its flora to evergreen broadleaved and mixed mesophytic forests of present-day East and Southeast Asia. The rarity of such large-sized flower inclusions is likely due to the size of the resin outpouring and its properties, which might affect the embedding of plant organs.

Unravelling the palaeobiogeographical history of the living fossil genus Rehderodendron (Styracaceae) with fossil and extant pollen and fruit data.

BACKGROUND: The relict genus Rehderodendron (Styracaceae), the species of which are restricted to mostly warm temperate to tropical climate in East Asia today, is known from fossil fruits and pollen in Europe during warmer periods from the lower Eocene to Pliocene. To infer which extant species are most closely related to the fossils, new data of pollen and fruit morphologiesy of six extant species, and additional new data of fossil pollen and previously described fossil fruits of Rehderodendron, are compared. RESULTS: Both fossil pollen and fruits resemble a morphological mixture of the extant species R. indochinense, R. kwantungense, R. macrocarpum, and R. microcarpum, thus implying that these extant taxa and the fossil European taxa represent an old Eurasian lineage, whereas the pollen and fruit morphology of the extant R. kweichowense and R. truongsonense differ considerably from the fossils and other extant species investigated, and are considered to have evolved independently. CONCLUSIONS: The palaeobiogeographical history of Rehderodendron reveals that its fossil members of the European lineage were most prominent during climatic optima such as the Palaeocene-Eocene Thermal Maximum (PETM), Early Eocene Climate Optimum (EECO) and Middle Miocene Thermal Maximum (MMTM). However, when during the Pliocene the climate changed to colder and less humid conditions, the genus went extinct in Europe but migrated eastwards, most likely in two dispersal events along the Tethys Sea prior to extinction. One of the former most westerly stepping stones is suggested by the refugial occurrence of R. microcarpum in the southeastern Himalaya, whereas R. macrocarpum and R. kwangtungense, the taxa distributed more to the east, might have migrated eastwards already before the Miocene.

Eocene Loranthaceae pollen pushes back divergence ages for major splits in the family.

BACKGROUND: We revisit the palaeopalynological record of Loranthaceae, using pollen ornamentation to discriminate lineages and to test molecular dating estimates for the diversification of major lineages. METHODS: Fossil Loranthaceae pollen from the Eocene and Oligocene are analysed and documented using scanning-electron microscopy. These fossils were associated with molecular-defined clades and used as minimum age constraints for Bayesian node dating using different topological scenarios. RESULTS: The fossil Loranthaceae pollen document the presence of at least one extant root-parasitic lineage (Nuytsieae) and two currently aerial parasitic lineages (Psittacanthinae and Loranthinae) by the end of the Eocene in the Northern Hemisphere. Phases of increased lineage diversification (late Eocene, middle Miocene) coincide with global warm phases. DISCUSSION: With the generation of molecular data becoming easier and less expensive every day, neontological research should re-focus on conserved morphologies that can be traced through the fossil record. The pollen, representing the male gametophytic generation of plants and often a taxonomic indicator, can be such a tracer. Analogously, palaeontological research should put more effort into diagnosing Cenozoic fossils with the aim of including them into modern systematic frameworks.

Lythrum and Peplis from the Late Cretaceous and Cenozoic of North America and Eurasia: new evidence suggesting early diversification within the Lythraceae.

PREMISE OF THE STUDY: To fully understand the evolution of today's angiosperms, the fossil record of plant families and genera must be used to determine their time of origin and phytogeographic history. As within many angiosperm families, the interrelationships of extant Lythraceae are hard to resolve without sufficient data from the geological past. Here we establish the earliest fossil occurrences of Lythraceae and start resolving the interrelationships and evolution of two of its genera, Lythrum and Peplis. METHODS: We studied several Cretaceous and Cenozoic palynofloras from the northern and southern hemispheres. Using the single-grain technique, we screened the treated samples for Lythrum- and Peplis-type pollen. The same individual pollen grains were observed under both the light- and scanning electron microscope, allowing a high taxonomic resolution to be achieved. KEY RESULTS: Fossil Lythraceae pollen grains are rare in palynological samples. Nevertheless, we were able to identify Lythrum and Peplis pollen from Late Cretaceous sediments and thereby extend the fossil record of the two genera by ca 70 million years. CONCLUSIONS: The appearance of Lythrum and Peplis in North America and Peplis in Asia at approximately the same interval in the mid Late Cretaceous points to an already wide geographical distribution by then. These findings add vital information for the time of origin of the Lythraceae and suggest a higher diversity within the family. They also indicate that the distribution of particular genera during the Cretaceous was wider than previously thought.