The recent discovery of diverse fossil flowers and floral organs in Cretaceous strata has revealed astonishing details about the structural and systematic diversity of early angiosperms. Exploring the rich fossil record that has accumulated over the last three decades, this is a unique study of the evolutionary history of flowering plants from their earliest phases in obscurity to their dominance in modern vegetation. The discussion provides comprehensive biological and geological background information, before moving on to summarise the fossil record in detail. Including previously unpublished results based on research into Early and Late Cretaceous fossil floras from Europe and North America, the authors draw on direct palaeontological evidence of the pattern of angiosperm evolution through time. Synthesising palaeobotanical data with information from living plants, this unique book explores the latest research in the field, highlighting connections with phylogenetic systematics, structure and the biology of extant angiosperms.

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We present a phylogenetic dating of asterids, based on a 111-taxon tree representing all major groups and orders and 83 of the 102 families of asterids, with an underlying data set comprising six chloroplast DNA markers totaling 9914 positions. Phylogenetic dating was done with semiparametric rate smoothing by penalized likelihood. Confidence intervals were calculated by bootstrapping. Six reference fossils were used for calibration. To explore the effects of various sources of error, we repeated the analyses with alternative dating methods (nonparametric rate smoothing and the Langley-Fitch clock-based method), alternative tree topologies, reduced taxon sampling (22 of the 111 taxa deleted), partitioning the data into three genes and three noncoding regions, and calibrating with single reference fossils. The analyses with alternative topologies, reduced taxon sampling, and coding versus noncoding sequences all yielded small or in some cases no deviations. The choice of method influenced the age estimates of a few nodes considerably. Calibration with reference fossils is a critical issue, and use of single reference fossils yielded different results depending on the fossil. The bootstrap confidence intervals were generally small. Our results show that asterids and their major subgroups euasterids, campanulids, and lamiids diversified during the Early Cretaceous. Cornales, Ericales, and Aquifoliales also have crown node ages from the Early Cretaceous. Dipsacales and Solanales are from the Mid-Cretaceous, the other orders of core campanulids and core lamiids from the Late Cretaceous. The considerable diversity exhibited by asterids almost from their first appearance in the fossil record also supports an origin and first phase of diversification in the Early Cretaceous.

Over the past 25 years the discovery and study of Cretaceous plant mesofossils has yielded diverse and exquisitely preserved fossil flowers that have revolutionized our knowledge of early angiosperms, but remains of other seed plants in the same mesofossil assemblages have so far received little attention. These fossils, typically only a few millimetres long, have often been charred in natural fires and preserve both three-dimensional morphology and cellular detail. Here we use phase-contrast-enhanced synchrotron-radiation X-ray tomographic microscopy to clarify the structure of small charcoalified gymnosperm seeds from the Early Cretaceous of Portugal and North America. The new information links these seeds to Gnetales (including Erdtmanithecales, a putatively closely related fossil group), and to Bennettitales--important extinct Mesozoic seed plants with cycad-like leaves and flower-like reproductive structures. The results suggest that the distinctive seed architecture of Gnetales, Erdtmanithecales and Bennettitales defines a clade containing these taxa. This has significant consequences for hypotheses of seed plant phylogeny by providing support for key elements of the controversial anthophyte hypothesis, which links angiosperms, Bennettitales and Gnetales.