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 Including previously unpublished results based on research into Early and Late Cretaceous fossil floras from Europe and North America, the authors draw on direct palaeontological evidence of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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AlSSTKACT have been discovered within the past 15 to 20 years. These floras are particularly abundant in I p per Cretaceous sediments and have been reported from widely sepaiate geographic regions in the Northern Hemisphere. The first comprehensive studies were based on European material, and rich Lite Cretaceous floras are known from Cenomanian to Maastrichtian strata of the Czech Republic. Germanv. \ustria, the Netherlands, Portugal, and S\eden (

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.

M ore than half a century ago, two pivotal reviews 1,2 showed that while the fossil history of angiosperms "is extra ordinarily and increasingly well documented in postEarly Cretaceous sediments…no bona fide angiosperm remains, either megafossil or microfossil, have yet been described from rocks older than Early Cretaceous" 1 . Here, we revisit this conclusion and assess the extent to which the situation has changed, given a substantial increase in the quantity and quality of palaeobotanical data and an increasing number of reports of angiosperms from older rocks.Since the key reviews of the 1960s, great progress has been made in understanding the major patterns in the angiosperm fossil record [3][4][5] . There have also been significant advances in understand ing evolutionary relationships within the angiosperm clade-espe cially in using DNA sequences from living plants to reconstruct phylogenetic patterns 6 . Widely accepted hypotheses indicate that more than 99% of angiosperm species occur in three major clades (eudicots, monocots, (eu)magnoliids), which are embed ded in a paraphyletic assemblage of other early diverging lineages that includes Amborellales, Austrobaileyales, Ceratophyllales, Chloranthales and Nymphaeales [6][7][8] . More controversial are esti mates of the age of the most recent common ancestor of extant angiosperms based on molecular clock techniques, and hypotheses of the phylogenetic position of angiosperms in relation to other seed plant lineages. As molecular clock estimates are most often calibrated using palaeontological data, and because the closest rela tives to angiosperms are almost certainly extinct groups, fossils are integral to progress in both of these areas.Building on important advances made during the 1970s preserved as compressions or impressions from Early Cretaceous strata [11][12][13] . Taken together, these discoveries and their sequence of appearance in the fossil record are broadly consistent with the patterns of relation ships established among extant angiosperms using molecular data, and the associated patterns of character evo lution. All of the reproductive structures recognized so far from Early Cretaceous sediments are either extinct forms, apparently with no close relatives among living angiosperms, or are related to Austrobaileyales, Chloranthales, Nymphaeales, various groups of eumagnoliids, or early branches of eudicots or monocots (Fig. 1, for references see refs 10 and 14). Preservation of fine structural details in some of these Early Cretaceous fossils further confirms their inferred relation ship with extant lineages that are hypothesized to have diverged at an early stage in angiosperm diversification based on molecular phylogenetics 15 . The improved angiosperm fossil record from the Cretaceous has facilitated the calibration of molecular clock age estimates for various angiosperm clades and for the age of angiosperms as a whole [16][17][18][19][20][21] . While current techniques remain susceptible to prob lems resulting from significantly different ...

Gnetales comprise three unusual genera of seed plants, Ephedra, Gnetum, and Welwitschia. Their extraordinary morphological diversity suggests that they are survivors of an ancient, more diverse group. Gnetalean antiquity is also supported by fossil data. Dispersed ''ephedroid'' (polyplicate) pollen first appeared in the Permian >250 million years ago (Myr), and a few megafossils document the presence of gnetalean features in the early Cretaceous. The Cretaceous welwitschioid seedling Cratonia cotyledon dates the split between Gnetum and Welwitschia to before 110 Myr. Ages and character evolution of modern diversity are, however, controversial, and, based on molecular data, it has recently been suggested that Ephedra is very young, only 8 -32 Myr. Here, we present data on the evolutionary history of Ephedra. Fossil seeds from Buarcos, Portugal, unequivocally link one type of Cretaceous polyplicate pollen to Ephedra and document that plants with unique characters, including the peculiar naked male gametophyte, were established already in the Early Cretaceous. Clades in our molecular phylogeny of extant species correspond to geographical regions, with African species in a basal grade͞clade. The study demonstrates extremely low divergence in both molecular and morphological characters in Ephedra. Features observed in the fossils are present in all major extant clades, showing that modern species have retained unique reproductive characters for >110 million years. A recent origin of modern species of Ephedra would imply that the Cretaceous Ephedra fossils discussed here were members of widespread, now extinct sister lineage(s), and that no morphological innovations characterized the second diversification. molecular phylogeny ͉ fossil record ͉ Gnetales ͉ molecular dating

Phylogenetic analyses have identified the water lilies (Nymphaeales: Cabombaceae and Nymphaeaceae), together with four other small groups of flowering plants (the 'ANITA clades': Amborellaceae, Illiciales, Trimeniaceae, Austrobaileyaceae), as the first diverging lineages from the main branch of the angiosperm phylogenetic tree, but evidence of these groups in the earliest phases of the angiosperm fossil record has remained elusive. Here we report the earliest unequivocal evidence, based on fossil floral structures and associated pollen, of fossil plants related to members of the ANITA clades. This extends the history of the water lilies (Nymphaeales) back to the Early Cretaceous (125-115 million years) and into the oldest fossil assemblages that contain unequivocal angiosperm stamens and carpels. This discovery adds to the growing congruence between results from molecular-based analyses of relationships among angiosperms and the palaeobotanical record. It is also consistent with previous observations that the flowers of early angiosperms were generally very small compared with those of their living relatives.