[ Origin of Angiosperms ]
Solving the riddle of the origin of flowering plants might be viewed by some naturalists as the "Holy Grail" of botany. Angiosperms might be a loose amalgam of parallel evolutionary lines traceable to surviving geographically disparate early Triassic remnants of already divergent Permian seed plant lineages.
Assuming coevolution of phytophagous Coleopterans with angiosperms, various proposals on rapid diversification of flowering plants during the Albian Age of the Gallic Epoch of the early Cretaceous Period are inconsistent with molecular-based phylogenies of Coleoptera that suggest a Triassic origin of certain non-chrysomelid beetle lineages.
Selection pressures in populations of Permo-Triassic seed plant populations were probably much greater than believed. An herbaceous origin of flowering plants cannot be explained by mutualism and coevolution of insects and seed-bearing shrub hosts alone.
A late Jurassic aquatic origin for flowering plants is incongruent with likely deleterious effects of sulfuric acid poisoning of lakes, shorelines, and wetlands, caused by basalt outpouring from the Central Atlantic Magmatic Province (CAMP) associated with the Triassic-Jurassic boundary carbon cycle event (TrCCE).
[ Reading List ]
This reading list of papers, review articles, and books is intended for persons with advanced college level biology training who have an interest in current research on the origin of flowering plants ... KEY TO THE LITERATURE
[ Permian Gigantopterids ]
Gigantopterids have been described from fossil compressions, impressions, and permineralizations representing the remains of Paleozoic foliage. They were a diverse group of probably unrelated seed plants constituting one of several terrestrial vegetation types of the Hercynian Mountains and coastal regions of Pangaea of the Permian Period, more than 251 million years ago.
Gigantopterids were almost certainly not angiosperms. "Form genera" described from fossils in Permian rocks of Cathaysia are regarded by some workers as morphological analogs of flowering plants and not direct antecedents (Glasspool et al. 2004).
Some gigantopterids had seed-bearing simple leaves with four orders of veins. Permian fossils of China unearthed and studied by Li Xingxue and Yao Zhaoqi in 1983, yielded a rare glimpse of fertile material: ovules and pollen-bearing organs were attached to leaves and leaf-midribs. Some of these plants had vessels, a bifacial cambium, and petioles with abscission layers of tissue.
Scientific evidence from the stratigraphic distribution of oleonone triterpanes and fossilized plants suggests a close, possibly evolutionarily based connection between the Bennettitales, Gigantopteridales, and dicotyledonous flowering plants (D. W. Taylor et al. 2006). Were oleananes products of diagenesis of certain plant growth hormones and volatiles?
Cathaysian gigantopterids are distinct from glossopterids, extinct Permo-Triassic seed plants, whose stratigraphic distribution supports Wegener's Theory of Continental Drift.
The leaves of some gigantopterids were of varying sizes having erect vernation and clasping leaf-bases. While the appearance of whole gymnospermous gigantopteroid seed plants is unknown they could have been lianas and shrubs possibly resembling cycads, cycadeoids, ginkgophytes, gnetophytes, peltasperms, nilssonialeans, and flowering plants (including palms) ... LINK TO THE GIGANTOPTERIDS OF PANGAEA
[ Jurassic Floras ]
Professor Vakhrameev's treatise on Jurassic floras is summarized in this chapter.
This discourse explores the fate of surviving anthophytic populations following the Triassic-Jurassic carbon cycle event (TrCCE) ... DISCUSSION OF JURASSIC FLORAS
[ Cretaceous Flowering Plants ]
The "gigantopteroid" web site boils-down the great body of literature on Cretaceous floras, angiosperm megafossils, palynomorphs, and permineralized wood, with a goal to trace the origins of modern flowering plant orders from Permo-Triassic ancestral stock.
The essay shows the depth of the chasm between what is known about the number of extant plant genera and the (scanty) fossil record to date of preserved reproductive organs ... LINK TO THE CRETACEOUS PERIOD
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Over millions of years of Permian time as global oxygen levels and temperature gradually declined certain chewing, crawling, ovipositing, piercing, and sucking insects became obligate residents of host seed plant shrubs and trees. Air pockets at the base of sheathing leathery leaves and around developing stems and organs, and reproductive modules of Permo-Triassic seed plants provided phytophagous insects with oxygen gas, food, and shelter from predators, cold, and ultraviolet radiation.
Resident phytophagous insect associates of certain developmentally plastic Permian seed plant shrubs and trees (possibly including glossopterids and undescribed gigantopterids, among other seed plant groups) survived the end-Permian extinction (EPE). Acidification of substrates, fragmentation of biomes, hypoxia, and increases in ambient temperature adversely affected both insects and tetrapods in a hot-house world ... PALEOECOLOGY OF GLOBAL CATASTROPHE
When answered by scientific studies the following questions may help us to better understand the origin of angiosperms:
Could the biomechanical and thigmostimulatory forces applied by feeding paleoherbivores to seed plant cell surfaces of shoot apical meristems and developing fertile axes (SAMs) activate regionalizing and polarizing morphogens and upregulate homeotic genes that orchestrate reproductive growth and development? ... SAMs AND DEVELOPMENTAL SWITCHES
What was the effect of gene duplications, genome doubling, developmental recombination, and genetic accommodation on phenotypes and adaptations in long extinct Permo-Triassic seed plant populations and species? ... GENE DUPLICATIONS
Were calcium ion-rich, peptide-laden, volicitin- and jasmonate-containing secretions of insect eggs, larvae, and adults, when applied to shoot apical meristems (SAMs) with mechanical force, a source of signals that affected plant growth and development at the genetic level in nuclei of host cells of certain monopodial Permo-Triassic seed plants? ... SIGNALS
Did compartments (shrub lifeboats) of interacting Permo-Triassic insect colonies and seed plant hosts meet the definition of a coevolutionary relationship being reciprocal, simultaneous, and specialized? ... COEVOLUTIONARY ECOLOGY
[ Triassic Seed Plants ]
This essay explores the Triassic fossilized descendants of seed plant and insect lineages that survived the global, ecologic catastrophe at the close of the Permian Period.
The purpose of this research is to lay the groundwork for a preliminary understanding of the Pangaean origins, radiation, and dispersal of the forerunners of Mesozoic bennettitaleans, caytonialians, corystosperms, flowering plants, ginkgophytes, gnetophytes, and cycads ... TRIASSIC PORTAL
[ Paleobiogeography and Paleofloras ]
This section is written to facilitate discussion of paleobiogeography, paleofloras, and vicariance of living and fossil descendants of the putatively several, possibly independent lines of flowering plant evolution from "fossil island arcs" formed by the break-up of Pangaea.
Geophysical mechanisms behind plate tectonics, sea floor spreading, island arc orogenesis and "fossilization," and movements of continental cratons are re-evaluated.
Possibly vicariant Podocarpaceae belonging to the genus Acmopyle are known only from Viti Levu Island and Nouvelle Caledonie, two high islands of the tectonically complex southwest Pacific Basin ... PALEOBIOGEOGRAPHY OF PACIFIC ISLAND ARCS
[ Living "Fossil" Magnoliids: Degeneriaceae of Fiji ]
The family Degeneriaceae has been cited in classic work on the origin of flowering plants as "living fossil angiosperms." According to A. C. Smith (1991, Flora Vitiensis Nova 5:587) two species exist in tropical forests of the Fiji archipelago.
Cucujiform nitidulid coleopterans feed on male reproductive modules of Degeneria vitiensis as evidenced by pollen found lodged in beetle mandibles and palps ... FEATURE ARTICLE
[ Statement on Evolution ]
The gigantopteroid web site owner and writer, colleagues, peer reviewers, and contributors adopt the Botanical Society of America's policy and statement on evolution ... BOTANICAL SOCIETY OF AMERICA
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