Almost every living and fossil group of gymnosperms has been proposed as a possible ancestor of angiosperms. A common problem with many of these proposals is their reliance on hypothetical intermediate forms. Another common problem is finding correctly-oriented organs homologous to all the important reproductive structures of angiosperms. These problems are least troublesome for a glossopterid origin of angiosperms. Recently discovered ovule-bearing organs of these plants may represent evolutionary intermediates, or analogous plants, between glossopterids and angiosperms. According to recent reinterpretations of glossopterid ovule-bearing organs, they have structures in an orientation which may be homologous with both the outer ovular integument and the carpel of angiosperms. Considering the reproductive and vegetative features of glossopterids, the hypothesis that they may be part of a stock ancestral to angiosperms should be seriously considered.
The head and mouthpart structures of 11 species of Eurasian scorpionflies represent three extinct and closely related families during a 62-million-year interval from the late Middle Jurassic to the late Early Cretaceous. These taxa had elongate, siphonate (tubular) proboscides and fed on ovular secretions of extinct gymnosperms. Five potential ovulate host-plant taxa co-occur with these insects: a seed fern, conifer, ginkgoopsid, pentoxylalean, and gnetalean. The presence of scorpionfly taxa suggests that siphonate proboscides fed on gymnosperm pollination drops and likely engaged in pollination mutualisms with gymnosperms during the mid-Mesozoic, long before the similar and independent coevolution of nectar-feeding flies, moths, and beetles on angiosperms. All three scorpionfly families became extinct during the later Early Cretaceous, coincident with global gymnosperm-to-angiosperm turnover.
Angiosperms are the dominant and most diverse plant group living today. They are also found in the greatest number of terrestrial ecosystems on Earth of any group of plants (Judd et al. 2002; Soltis and Soltis 2004). They provide human beings and other terrestrial animals, directly or indirectly, with the majority of their nutrition (e.g. Theissen and Melzer 2007). Much of these foods, such as fruits, nuts, seeds, and grains, are the direct products of flowers, and pollination is an essential step in their formation. Pollination biology has long been an interest of biologists and agricultural scientists (e.g. Faegri and van der Pijl 1979; Proctor et al. 1996; Aizen et al. 2009; Lonsdorf et al. 2009; Mitchell et al. 2009). However, our understanding of the early phases of the evolution of angiosperm pollination is still limited and attempts to reconstruct the history of the interactions between angiosperms and pollinators are challenging (Hu et al. 2008; Taylor and Hu 2010). Evolutionary biologists have attempted to deduce the possible histories of pollination syndromes (summarized in Taylor and Hu, 2010) based upon usually incomplete and limited early angiosperm flower fossil records (e.g. Dilcher 1979; Retallack and Dilcher 1981; Crane et al. 1986; Herendeen et al. 1995; Crepet and Nixon 1996; Friis et al. 1999, 2000, 2006; Crepet 2008), limited insect fossil records(e.g. Grimaldi 1999; Labandeira 2000, 2002; Grimaldi and Engel 2005; Ren et al. 2009), parsimony analysis (e.g. Hu et al. 2008; Friedman and Barrett 2008; Taylor and Hu 2010), investigation on pollination biology of the most basal angiosperms (e.g.Thien et al. 2009), and angiosperm pollen fossil records (e.g. Hu et al. 2008; Taylor and Hu 2010).
Iara iguass, um novo taxon de angiosperma aquatica da paleoflora do Crato (Eocretaceo, Formacao Santana, Bacia do Araripe, nordeste do Brasil). Iara iguassu gen et sp. nov., uma angiosperma aquatica pertencente a paleoflora do Crato e descrita. A inedita planta fossil lanca nova luz ao estudo da morfologia, diversidade e evolucao das primeiras angiospermas do Cretaceo, ja que o Gondwana ocidental pode ter sido o cenario dispersor destas. O Membro Crato consiste em calcarios laminados de origem lacustre rasa com influencia marinha, de idade neoaptiana/eoalbiana. Os especimes, preservados como impressoes, consistem num caule cilindrico, articulado e sulcado, do qual emergem apicalmente folhas sesseis, arranjadas num verticilo. As longas folhas cilindricas, sulcadas e flexiveis portam apice arredondado ou filamentoso, alem de denteacoes papilosas marginais. Longos, delgados e estriados pedunculos emergem do no e terminam numa estrutura fusiforme, tambem estriada, representando estruturas ferteis flutuadoras. Caracteristicas similares parecem ser compartilhadas com as atuais familias de ervas aquaticas: Potamogetonaceae, Ruppiaceae e Cymodoceaceae (Monocots) e Podostemaceae (Eudicots). O habito aquatico e sugerido a partir da morfologia cilindrica, filamentosa e flexivel bem como da organizacao verticilada. A planta viveria parcialmente submersa em corpos lacustres, talvez em aguas salinas, paleoambientes ja descritos para o Membro Crato. Iara iguassu pode representar uma convergencia de habito e, assim, uma linhagem extinta de angiosperma aquatica, nao relacionada a monocots ou dicots.
The majority of environments are dominated by flowering plants today, but it is uncertain how this dominance originated. This increase in angiosperm diversity happened during the Cretaceous period ( ca. 145–65 Ma) and led to replacement and often extinction of gymnosperms and ferns. We propose a scenario for the rise to dominance of the angiosperms from the Barremian ( ca. 130 Ma) to the Campanian ( ca. 84 Ma) based on the European megafossil plant record. These megafossil data demonstrate that angiosperms migrated into new environments in three phases: ( i ) Barremian ( ca. 130–125 Ma) freshwater lake-related wetlands; ( ii ) Aptian–Albian ( ca. 125–100 Ma) understory floodplains (excluding levees and back swamps); and ( iii ) Cenomanian–Campanian ( ca. 100–84 Ma) natural levees, back swamps, and coastal swamps. This scenario allows for the measured evolution of angiosperms in time and space synthesizing changes in the physical environment with concomitant changes in the biological environment. This view of angiosperm radiation in three phases reconciles previous scenarios based on the North American record. The Cretaceous plant record that can be observed in Europe is exceptional in many ways. ( i ) Angiosperms are well preserved from the Barremian to the Maastrichtian ( ca. 65 Ma). ( ii ) Deposits are well constrained and dated stratigraphically. ( iii ) They encompass a full range of environments. ( iv ) European paleobotany provides many detailed studies of Cretaceous floras for analysis. These factors make a robust dataset for the study of angiosperm evolution from the Barremian to the Campanian that can be traced through various ecosystems and related to other plant groups occupying the same niches.
Dilcheb, David L. (Yale U., New Haven, Conn.) Cuticular analysis of Eocene leaves of Ocotea obtusifolia. Amer. Jour. Bot. 50(1): 1–8. IIlus. 1963.—Several specimens of Ocotea obtusifolia collected from the Eocene clays at Puryear, Tennessee, were examined in detail. The megascopic and cuticular features of the leaves are described and their variations discussed. The lower epidermis was found to be less variable and a better tool to use in the cuticular analysis of this species than the upper epidermis. The cuticle of several genera and species of modern Lauraceae were also examined. Since none could be identified with the fossil cuticle, the designation Ocotea obtusifolia as based on megascopic characters is satisfactory.
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