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Anatomically preserved lycophytes of the Lycopodiales and Selaginellales have been discovered among a diverse assemblage of plants and fungi in carbonate marine concretions at the Apple Bay locality along the shore of Holbert Inlet near the northern end of Vancouver Island, British Columbia, Canada. Lycopodialean stems are plectostelic and actinostelic, branch dichotomously, and are similar to both Lycopodicaulis oellgaardii and Lycoxylon spp. The Selaginella specimens represent the first anatomically preserved Selaginellales with excellent internal cellular preservation in the fossil record, and are described as Selaginella quatsinoense Rothwell et Stockey sp. nov. Stems have three and five exarch, monarch stelar segments, each of which is surrounded by an aerenchymatous endodermis with trabeculae. The leaf base is indented on the adaxial surface, suggesting the position of a ligule. These fossils document that species with diagnostic internal anatomy of modern Lycopodiales and Selaginellales evolved no later than the Valanginian of the early Cretaceous. [ABSTRACT FROM AUTHOR]

Premise of research. Ten anatomically preserved conifer seed cone specimens are preserved on the surfaces of, and within, three interlocking rock fragments of terrestrial limestone discovered as float along the Colville River on the North Slope of Alaska, providing additional evidence for the diversification of taiwanioid Cupressaceae during the Upper Cretaceous–Cenozoic interval. Methodology. Specimens on rock surfaces were measured and photographed, and then serial anatomical thin sections were prepared by the cellulose acetate peel technique. Three-dimensional images of selected specimens were also captured using micro–computed tomography (micro-CT). Pivotal results. The structure of these seed cones is similar to that of living Taiwania cryptomerioides in cone shape, the presence of subtending scalelike leaves, helically arranged and imbricating foliate ovuliferous complexes (OCs), the absence of a separate ovuliferous scale tip, variation in numbers of OCs, and by having two adaxially positioned winged seeds per complex. However, abruptly upturned OC, details of OC vasculature, and distinctive histological features reveal that these seed cones represent a new species of the extinct genus Mukawastrobus. Conclusions. When added to the existing record of fossil seed cones, the new species Mukawastrobus arnoldii highlights the recent discovery that among early-diverging lineages of Cupressaceae, there has been considerable Cretaceous, Paleogene, and Neogene evolution that is reflected by variations among subtle characters that are not recognizable in any but the most completely preserved specimens. [ABSTRACT FROM AUTHOR]

Premise: An anatomically preserved fossil fern sporeling has been discovered in a Lower Cretaceous marine concretion from Vancouver Island, British Columbia, Canada, providing an opportunity to characterize rhizome growth from an extinct species. Methods: The specimen was studied from serial transverse sections prepared by the cellulose acetate peel technique. Results: The rhizome ranges from ~0.7 to 1.1 mm in diameter, has a sclerenchymatous pith, a stele that attains a dictyoxylic architecture, and sclerenchymatous outer cortex, features that are characteristic of osmundaceous rhizomes. Cauline xylem forms a medullated protostele or solenostele at some levels, but is dissected into discrete xylem bundles at others. Fronds diverge in a helical phyllotaxis, range up to 1.1 mm in greatest dimension, and have a C‐shaped trace and outer cortex of sclerotic cells. Inside the sclerenchyma of the petioles are two lateral sclerotic strands and a sclerotic bundle adaxial to the trace. Together, these characters reveal the occurrence of a new species, Todea minutacaulis and provide evidence for developmental changes that occur in the rhizome as the sporeling increased in size. Conclusions: Small size of the specimen, medullated protostelic‐dictyoxylic solenostelar vascular architecture, and incompletely sclerified cells apically reveal that osmundaceous sporeling development has remained constant since at least the Early Cretaceous. Together with Todea tidwellii and Osmunda vancouverensis that also are present in the Apple Bay flora, this sporeling documents the occurrence of a multispecies assemblage of osmundaceous ferns and demonstrates that the genus Todea was diversifying rapidly by the Early Cretaceous. [ABSTRACT FROM AUTHOR]

Premise of research. Two permineralized inflorescences have been found in calcium carbonate concretions from the Eocene Appian Way locality on Vancouver Island, British Columbia, increasing sampling density and helping clarify the pattern of phylogeny for Alismatalean monocots. Methodology. Serial sections of specimens were prepared by the cellulose acetate peel technique and studied with light microscopy. Phylogenetic analyses using a morphological matrix of living and fossil Araceae and Acoraceae were performed using TNT version 1.5 to help establish relationships of the fossil inflorescences. Pivotal results. Inflorescences are cylindrical spikes, >37 mm long and 8.1 mm wide, with a peduncle at least 14.5 mm long, bearing numerous helically arranged, bisexual sessile flowers with hooded tepals. Fruits are trilocular, with basal axile placentation and one seed per locule. Remnants of probable stamens are present in most flowers. Conclusions. Flower structure was compared to those of other petalloid, spicate, bisexual flowers in the monocot families Acoraceae and Araceae (Alismatales). The number of carpels is similar to that in Acorus (Acoraceae) and Spathiphyllum (Araceae, Monsteroideae) and some Pothoideae. Single-seeded ovaries are common in Araceae, while the locules in Acorus contain several apically attached seeds. Phylogenetic analyses place Appianospadix in Proto-Araceae near the base of the aroid tree. This inflorescence with a unique combination of characters is described as Appianospadix bogneri , a new genus and species of Alismatales (family: Araceae). [ABSTRACT FROM AUTHOR]

Premise of research. Numerous large permineralized fossil seeds from the Jurassic of Haida Gwaii, western Canada, provide evidence for the mode and tempo of cycad evolution. Methodology. Fossil seed specimens are studied from external morphology and serially sectioned by the classic cellulose acetate peel technique to reveal anatomical features of the integument, vascular system, nucellus, and gametophyte. Fossils are compared to living cycad seeds that are also examined from external views, dissections, and anatomical preparations. Pivotal results. The fossil seeds are described as Traskia maahlae gen. et sp. nov. Features of the integument and vascular system reveal that T. maahlae is a stem group cycad that shares seed architecture and mode of germination with living Cycas spp. Conclusions. Traskia maahlae adds to a growing body of paleontological data on stem and crown group cycads. Results suggest that modern pollination and postpollination biology and the two contrasting modes of cycad seed germination evolved during the Mesozoic but that crown group cycad species may not have appeared until the Cenozoic. [ABSTRACT FROM AUTHOR]

Premise: Anatomically preserved evidence for a novel clade of gymnosperms emphasizes diversity of seed plants immediately prior to the appearance of angiosperm fossils in the paleontological record. Methods: Cupulate seeds from the Early Cretaceous Apple Bay locality (Vancouver Island) are described from serial cellulose acetate peels and three‐dimensional reconstruction. Phylogenetic context is assessed through the comparative analysis of gymnosperm seed producing fructifications and maximum parsimony analysis of a revised morphological data set for seed plant phylogeny. Results: Xadzigacalix quatsinoensis gen. et sp. nov. is characterized by an orthotropous ovule with an elongated micropyle and complex integument, enclosed within a radial cupule. The micropylar canal is elongated; and the nucellus extends into the micropyle to seal the post pollination ovule. Except at the apex of the micropyle, the seed is completely enclosed by a parenchymatous cupule with ca. 20 axially elongated secretory ducts. The cupulate seed is produced upon a triangular woody stele, consisting of a parenchymatous pith surrounded by radially aligned tracheids. The stele produces three short terete traces that terminate within the base of the cupule as transfusion tissue at the seed chalaza. Conclusions: Organography, vascularization, nature of the integument and nucellus, and configuration of the micropylar canal distinguish Xadzigacalix quatsinoensis from all other gymnosperm clades. Cladistic analyses suggest the new plant may have affinities with gnetophytes or angiosperms. These results are complemented with a critical re‐evaluation of ovulate structures for Mesozoic gymnosperms, providing new insight into plant diversity immediately antecedent to the explosive diversification of flowering plants. [ABSTRACT FROM AUTHOR]

Anatomically preserved fossil gleicheniaceous fern remains in carbonate marine concretions from Vancouver Island, British Columbia, Canada support the development of a whole plant concept for an Eocene species of Gleichenia , and provide data to develop the first organismal concept for an extinct species of Gleichenia from the Cenozoic fossil record. New information for completing the plant reconstruction includes anatomically preserved pinnule fragments with attached radial exindusinate sori of six to seven annulate sporangia containing trilete spores. While the overall pattern of evolution within Gleicheniaceae remains incompletely understood because well-documented fossils from pre-Cretaceous deposits are inconsistently preserved, this organismal plant concept strengthens evidence that all diagnostic features of the family Gleicheniaceae were present, and that essentially modern species were well-established and diversifying during the Cretaceous and Paleogene. • First whole plant reconstruction of a Cenozoic species of Gleichenia. • Characterized by both external morphology and internal anatomy. • Evidence of stems, frond fragments, and sori of sporangia containing spores. • Essentially modern species of Gleicheniaceae evolved no later than the Paleogene. • Family Gleicheniaceae is inconclusively present in pre-Cretaceous deposits. [ABSTRACT FROM AUTHOR]

PREMISE: Mosses are a major component of Arctic vegetation today, with >500 species known to date. However, the origins of the Arctic moss flora are poorly documented in the fossil record, especially prior to the Pliocene. Here, we present the first anatomically preserved pre‐Cenozoic Arctic moss and discuss how the unique biology of bryophytes has facilitated their success in polar environments over geologic time. METHODS: A permineralized fossil moss gametophyte within a block of Late Cretaceous terrestrial limestone, collected along the Colville River on the North Slope of Alaska, was studied in serial sections prepared using the cellulose acetate peel technique. RESULTS: The moss gametophyte is branched and has leaves with a broad base, narrow blade, and excurrent costa. We describe this fossil as Cynodontium luthii sp. nov., an extinct species of a genus that is known from the High Arctic today. Cynodontium luthii is the oldest evidence of the family Rhabdoweisiaceae (by ≥18 Ma) and reveals that genera of haplolepideous mosses known in the extant Arctic flora also lived in high‐latitude temperate deciduous forests during the Late Cretaceous. CONCLUSIONS: The occurrence of C. luthii in Cretaceous sediments, together with a rich Pliocene‐to‐Holocene fossil record of extant moss genera in the High Arctic, suggests that some moss lineages have exploited their poikilohydric, cold‐ and desiccation‐tolerant physiology to live in the region when it experienced both temperate and freezing climates. [ABSTRACT FROM AUTHOR]

Premise: Exceptional anatomical preservation of a fossil araucarian seed cone from a marine carbonate concretion from Vancouver Island, British Columbia, Canada provides unusually complete evidence for cone structure including seeds, megagametophytes, microgametophytes, and embryos of an Upper Cretaceous (Campanian) species of Araucaria, providing important new insights into the structure and relationships of Cretaceous Northern Hemisphere Araucariaceae. Methods: The cone was studied from serial thin sections prepared by the coal ball peel technique. Phylogenetic analysis using a modified morphological matrix with both discrete and continuous characters was performed using TNT version 1.5. Results: The nearly spherical cone, 6 × 6 cm in diameter, has helically arranged cone‐scale complexes, consisting of a large bract with an upturned tip and a small, fleshy ovuliferous scale. Vascularization of the cone‐scale complex is single at its origin. Widely winged bracts, with a bulging base, contain numerous vascular bundles, interspersed with transfusion tissue, and a large number of resin canals. Seeds are ovoid, 1.2 cm long, 1.2 cm in diameter. Nucellus is free from the integument, except at its base, with a convoluted apex, containing possible pollen tubes. Megagametophytes and mature cellular embryos occur in several seeds. Conclusions: This small cone with attached, imbricate leaves, wide bracts, and unusually large seeds, most closely resembles those of Araucaria Section Eutacta. Width and continuity of secondary xylem in the cone axis, and intact cone‐scale complexes indicate that this cone probably did not disarticulate readily at maturity. When added to a modified, previously published phylogenetic analysis, Araucaria famii sp. nov. enhances our understanding of the Cretaceous radiation of Northern Hemisphere Araucaria Section Eutacta. [ABSTRACT FROM AUTHOR]

Premise of research. A single cylindrical conifer seed cone has been discovered in a calcium carbonate marine concretion from the Upper Cretaceous Eden Main Quarry, dated as early Coniacian (∼89 Ma), 35 km northwest of Courtenay on Vancouver Island, British Columbia, Canada. Methodology. The specimen was sectioned with a rock saw, and serial sections were prepared using the classical cellulose acetate peel technique. Peel sections were mounted on microscope slides. Reconstructions of the cone and seeds were rendered with Avizo. Pivotal results. The cone is somewhat abraded, at least 2.3 cm long and 1 cm wide, with the apex missing and most of the base coalified. The well-preserved midsection shows bract/scale complexes inserted at a steep angle. The bract/scale complex has a central rhomboidal shaft and two lateral winglike extensions. Xylem of the cone axis is robust, with secondary xylem tracheids that have circular-bordered pits. A single circular vascular trace enters the bract/scale complex. Three resin canals enter the base of the scale and divide to form up to eight or nine canals distally. Six overlapping, inverted winged seeds, ∼8 mm long and 1 mm thick, with two large, fleshy wings are borne on the adaxial surface of each scale. The nucellus is free from the endotesta to its base. Megagametophytes and embryos occur in some seeds. Cells of the megagametophyte have granular contents. This cone shows similarities in overall structure and vasculature to those of living Taiwania (Cupressaceae); however, the fossil cone size is generally larger, with six seeds per scale versus two, and seeds are extremely large and fleshy with a unique submicropylar structure. Conclusions. This cone is compared with living and fossil taxa of Cupressaceae and described as Comoxostrobus rossii gen. et sp. nov. (Cupressaceae subfamily Taiwanioideae), revealing that taiwanioid Cupressaceae were much more diverse and widespread during the Cretaceous. [ABSTRACT FROM AUTHOR]

Premise of research. Two permineralized stems of Medullosa leuckartii Göppert & Stenzel provide evidence for the stelar architecture and mode of leaf trace production and for the growth form of a complex Early Permian species of medullosan seed ferns. Methodology. Anatomical features were characterized from the surfaces of stem cross sections and from ground thin sections mounted on microscope slides. Vascular architecture and the mode of leaf trace production were reconstructed from the analysis of protoxylem strands. Pivotal results. Protoxylem consists of a ring of independent cauline bundles that divide repeatedly to produce numerous leaf traces to each frond. Some leaf traces diverge as small collateral bundles. Others separate from the stele as a large body of primary xylem surrounded by secondary vascular tissues and divide distally into small collateral bundles. As is common for gymnosperms with helical phyllotaxis, the number of cauline bundles appears to conform to numbers of the Fibonacci series. Some tracheids near the periphery of the stelar region extend horizontally around the circumference of the stem, as do the girdling leaf traces that characterize stems of the Cycadales. Conclusions. Despite complex anastomosing vascular segments that each consist of primary xylem surrounded by secondary vascular tissues, protoxylem architecture reveals that M. leuckartii has an incompletely dissected eustele that is basically similar to the steles in more typical gymnosperms. Secondary growth specializations are characteristic of lianas, and the absence of cauline adventitious roots suggests that the plant grew as a canopy-supported vine. While variations over the length of stems and the nature of horizontally oriented tracheids that are reminiscent of girdling leaf traces remain to be clarified, this study demonstrates that stems of M. leuckartii differ from more typical eustelic seed plants primarily by having specializations for vine architecture. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented which includes articles on topics including analysis of polytrichacean moss phylogeny, overall patterns of phylogeny for marattialean ferns and dipteridacean ferns and flowering plant evolution and phylogeny from fagalean inflorescences.

Premise of the Study: Recent clarification of the distribution of Marattiales through time provides the impetus for “total evidence” phylogenetic analyses of a major fern clade with a rich fossil record. These analyses serve as empirical tests for results from systematic analyses of living species and also of the belief that relationships among living species accurately reflect the overall pattern of phylogeny for clades with an extensive fossil record and a large percentage of extinction. Methods: Species of living and fossil Marattiaceae are analyzed employing a “total evidence approach” via maximum parsimony. Analyses were conducted using TNT implemented through WinClada. Key Results: Systematic analyses of living species and of living + extinct species provide roughly concordant topologies for living taxa. However, living species of Marattiales are only one component of a much larger clade with two major subclades. One consists of Psaroniaceae and extends through time to at least the Early Cretaceous. The other consists of Marattiaceae and includes all living species. Various analyses support the generic‐level clades of living species from earlier analyses, but the arrangement of such clades varies from analysis to analysis. Conclusions: Marattiales is a monophyletic group that is extremely common in late Paleozoic and early Mesozoic deposits, with a stem group Psaroniaceae and a crown group Marattiaceae. Because Marattiaceae represents only a small component of overall marattialean diversity, living species alone neither account for evolutionary changes within the clade over time, nor accurately reflect the overall pattern of marattialean fern phylogeny. [ABSTRACT FROM AUTHOR]

Premise of research. A large number of floating aquatic aroid fossils have been recovered from pond sediments in the Hell Creek Formation (Upper Cretaceous) of South Dakota, providing valuable new data about aquatic vegetation of the uppermost Cretaceous, that are used to describe a newspecies of the genus Cobbania, and to evaluate associated reproductive structures and phylogenetic relationships among floating aquatic monocots. Methodology. Fossils were uncovered as needed with fine needles to reveal surface features of the specimens. Images were captured with a digital scanning camera, and phylogenetic analyses were conducted with TNT implemented through WinClada. Pivotal results. The new species, Cobbania hickeyi Stockey, Rothwell & Johnson, extends the range of the genus to the uppermost Cretaceous, supports the taxonomic integrity of the genus Cobbania, and increases our understanding of structural variation and species richness within the genus. Associated reproductive structures include an aroid spadix, strengthening the assignment of Cobbania to the Araceae. Phylogenetic analyses using "total-evidence" data help resolve conflicting results from either morphological or nucleotide sequence analyses of relationships among floating aquatic aroids, and the fossil taxon Aquaephyllum does not nest among the other floating aquatic species in any of our results. Conclusions. Species of the genus Cobbania were an important component of aquatic vegetation across the Northern Hemisphere during the Late Cretaceous. In tests of competing hypotheses for relationships among Pistia stratiotes, Cobbania spp., and species of Araceae subfamily Lemnoideae, the results from a "total-evidence" analysis suggest that specializations for the floating aquatic life form may be overwhelming other characters in the results of morphological analyses alone. [ABSTRACT FROM AUTHOR]

An anatomically preserved seed cone from Late Cretaceous (Santonian-Coniacian) sediments of the Yezo Group on the Japanese Island of Hokkaido documents additional diversity among sequoioid conifers, and reveals previously unknown mechanisms for pollination and post-pollination seed enclosure in the conifer family Cupressaceae. The cylindrical seed cone of Stockeystrobus interdigitata gen. et sp. nov., consists of a central axis bearing helically arranged bract-scale complexes. Individual complexes are tightly packed and peltate in form, with completely fused bracts and scales. Peltate heads of adjacent complexes are attached to each other by elongated interdigitating epidermal trichomes. Each complex bears 6-8 inverted seeds on the adaxial surface of the inside of the peltate bract-scale complex head. Seeds occur in a single row, are roughly disk shaped, with broad wings in the major plane of symmetry. The nucellus is attached to the seed integument at the chalaza and free distally, with a convoluted apex. This cone reveals greater diversity of sequoioid reproductive biology than is represented among living species, and demonstrates that completely enclosed cones with well protected seeds were produced by Late Cretaceous fossil conifers of the Cupressaceae. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Discovery of cupulate ovules of Doylea tetrahedrasperma within a compact, compound seed cone highlights the rich diversity of fructification morphologies, pollination biologies, postpollination enclosure of seeds, and systematic diversity of Early Cretaceous gymnosperms. METHODS: Specimens were studied using the cellulose acetate peel technique, three-dimensional reconstructions (in AVIZO), and morphological phylogenetic analyses (in TNT). KEY RESULTS: Doylea tetrahedrasperma has bract/fertile short shoot complexes helically arranged within a compact, compound seed cone. Complexes diverge from the axis as a single unit and separate distally into a free bract tip and two sporophylls. Each sporophyll bears a single, abaxial seed, recurved toward the cone axis, that is enveloped after pollinaton by sporophyll tissue, forming a closed cupule. Ovules are pollinated by bisaccate grains captured by micropylar pollination horns. CONCLUSIONS: The unique combination of characters shown by D. tetrahedrasperma includes the presence of cupulate seeds borne in conifer-like compound seed cones, an ovuliferous scale analogue structurally equivalent to the ovulate stalk of Ginkgo biloba, gymnospermous pollination, and nearly complete enclosure of mature seeds. These features characterize the Doyleales ord. nov., clearly distinguish it from the seed fern order Corystospermales, and allow for recognition of another recently described Early Cretaceous seed plant as a second species in genus Doylea. A morphological phylogenetic analysis highlights systematic relationships of the Doyleales ord. nov. and emphasizes the explosive phylogenetic diversification of gymnosperms that was underway at the time when flowering plants may have originated and/or first began to radiate. [ABSTRACT FROM AUTHOR]

Premise of research. A distinctive new species of osmundaceous fern, based on a permineralized trunk from Lower Cretaceous deposits of Haida Gwaii (formerly the Queen Charlotte Islands) off the west coast of mainland Canada, provides additional data for addressing the Mesozoic diversity and the overall pattern of phy-logeny for osmundaceous filicalean ferns. Methodology. The specimen was cut into segments and studied from both external morphology and anatomical sections prepared by the cellulose acetate peel technique. Microscope slides of sections were examined, and images were captured under transmitted light. Pivotal results. The fossil represents a new species of Osmundacaulis, which is only the third Northern Hemisphere representative of this predominantly Southern Hemisphere genus. Conclusions. Osmundacaulis whittlesii sp. nov. increases the Northern Hemisphere diversity of Cretaceous Osmundaceae, thus providing new data about Mesozoic diversity of the clade, potential sister-group relationships of crown-group Osmundaceae, and the overall pattern of phylogeny for Osmundaceae. [ABSTRACT FROM AUTHOR]

Premise of the study: Two ovulate conifer cones, one of which is attached terminally to a short leafy shoot, reveal the presence of a new species of Hughmillerites in the Early Cretaceous Apple Bay flora of Vancouver Island, British Columbia, Canada. This ancient conifer expands the diversity of Cupressaceae in the Mesozoic and reveals details about the evolution of Subfamily: Cunninghamioideae. • Methods: Specimens were studied from anatomical sections prepared using the cellulose acetate peel technique. • Key results: Vegetative shoots have helically arranged leaves that are CunninghamiaAike. Seed cones have many helically arranged bract/scale complexes in which the bract is larger than the ovuliferous scale. Each ovuliferous scale has three free tips that separate from the bract immediately distal to an inverted seed. Several ovuliferous scales show interseminal ridges between seeds. • Conclusions: This study documents a new extinct species of cunninghamioid conifers, Hughmillerites vancouverensis, expanding the record of the genus from the Late Jurassic to the Early Cretaceous. This new extinct species emphasizes the important role that conifers from subfamily Cunninghamioideae played in the initial evolutionary radiation of Cupressaceae. In light of recent findings in conifer regulatory genetics, we use H. vancouverensis to hypothesize that variations of expression in certain gene homologues played an important role in the evolution of the cupressaceous ovuliferous scale. [ABSTRACT FROM AUTHOR]

Early Cretaceous fossilized leaves assignable to the extinct seed plant order Bennettitales occur within an exceptionally diverse Early Cretaceous (Valanginian) flora of anatomically preserved plant fossils at Apple Bay on Vancouver Island, British Columbia, Canada. One of the bennettitalean leaf types has an entire margin, with laminae that are attached near the adaxial surface of the midvein. Leaves are 10-15 mm wide with an adaxial surface that shows distinct corrugations, and a midrib that is exposed adaxially. The vascular system of the midrib consists of a crescent-shaped ring of collateral bundles. Lateral veins diverge from midrib at ∼90°, are typically simple but occasionally branch at base of the lamina. Vein density is 12-15 per cm. Leaves are hypostomatic with syndetocheilic stomata that are randomly oriented between veins. Internal anatomy consists of an adaxial hypodermis of closely-spaced isodiametric cells, mesophyll that is differentiated into adaxial palisade and abaxial spongy zones, and collateral bundles that show a distinct bundle sheath with bundle sheath extensions. This novel combination of characters represents the diverse bennettitalean genus Nilssoniopteris. Nilssoniopteris corrugata new species is only the second species of the genus for which internal anatomy is preserved. This species increases the known variation of bennettitalean leaf anatomy, and reinforces our appreciation for the global distribution of bennettitalean seed plants during the Mesozoic. [ABSTRACT FROM AUTHOR]

An organismal concept for the Late Devonian/Mississippian hydrasperman seed fern Tetrastichia bupatides is developed from specimens collected at Oxroad Bay, East Lothian Scotland and Ballyheigue, County Kerry, Ireland. Specimens include interconnected fragments of stems, frond rachides, pinnae, pinnules, roots, pollen organs with enclosed pre-pollen, and cupules, as well as dispersed ovules. Both morphological and anatomical features are documented. The plant produces an unbranched, upright stem with a branched taproot, and small adventitious roots at the base of the stem. Stems have a mesarch actinostele with sympodial protoxylem architecture. Phyllotaxis ranges from helical to opposite/decussate, with planar fronds that typically fork twice at the base, and then produce pinnules of the Rhodea -type. Compact aggregate pollen organs are attached distally on secondary rachides and are constructed of cruciately forking axes that terminate in inverted, round, simple synangia of six elongated microsporangia attached to a basal pad of tissue. Ovulate cupules of the Calathospermum fimbriatum type are attached at the base of the frond. Ovules possibly could be Salpingostoma dasu or Eospermum oxroadense. Tetrastichia bupatides is now one of the most completely reconstructed of all Devonian-Mississippian hydrasperman seed ferns, and the most ancient gymnosperm for which the pattern of rooting has been established. The occurrence of a taproot at the base of the stem suggests that the plant may exhibit bipolar growth derived from a cotyledonary embryo. • An organismal concept for the seed fern Tetrastichia bupatides is developed. • Structure of fronds, pollen organs, and the rooting system are described. • Interconnections of organs are documented. • Relationships among the most ancient hydrasperman seed ferns are evaluated. [ABSTRACT FROM AUTHOR]

Paleontology yields essential evidence for inferring not only the pattern of evolution, but also the genetic basis of evolution within an ontogenetic framework. Plant fossils provide evidence for the pattern of plant evolution in the form of transformational series of structure through time. Developmentally diagnostic structural features that serve as "fingerprints" of regulatory genetic pathways also are preserved by plant fossils, and here we provide examples of how those fingerprints can be used to infer the mechanisms by which plant form and development have evolved. When coupled with an understanding of variations and systematic distributions of specific regulatory genetic pathways, this approach provides an avenue for testing evolutionary hypotheses at the organismal level that is analogous to employing bioinformatics to explore genetics at the genomic level. The positions where specific genes, gene families, and developmental regulatory mechanisms first appear in phylogenies are correlated with the positions where fossils with the corresponding structures occur on the tree, thereby yielding testable hypotheses that extend our understanding of the role of developmental changes in the evolution of the body plans of vascular plant sporophytes. As a result, we now have new and powerful methodologies for characterizing major evolutionary changes in morphology, anatomy, and physiology that have resulted from combinations of genetic regulatory changes and that have produced the synapomorphies by which we recognize major clades of plants. [ABSTRACT FROM AUTHOR]

Premise of research. The occurrence of six ovulate cones and six leafy branching systems, two of which show attachment of the ovulate cone, reveals a new cunninghamioid fossil conifer from the Cretaceous Apple Bay locality of Vancouver Island, Canada. This anatomically preserved plant expands our understanding of basal Cupressaceae in the fossil record. Methodology. Specimens were studied from anatomical sections prepared by the classic cellulose acetate peel technique. Pivotal results. Vegetative shoots have helically arranged Cunninghamia-like leaves with a single vascular bundle and one to three resin canals. Ovulate cones consist of numerous helically arranged bract/scale complexes with a large bract and a small ovuliferous scale with three separate tips. There are three inverted seeds/ ovules attached adaxially, immediately proximal to the free scale tips. Conclusions. This discovery reveals the presence of a new genus and species of basal Cupressaceae, Hubbardiastrobus cunninghamioides, in the Early Cretaceous (Valanginian; ~136 Ma) of the Northern Hemisphere. These data expand the species richness of fossil Cupressaceae and further document the Cretaceous evolutionary radiation of subfamily Cunninghamioideae. [ABSTRACT FROM AUTHOR]

Premise of research. A third genus of anatomically preserved conifer seed cones has been recognized from a Late Jurassic deposit in northeastern Scotland. This cone is described as Bancroftiastrobus digitata Rothwell, Mapes, Stockey et Hilton. Methodology. The cone was sectioned with the classic coal ball peel technique and studied and photographed with transmission light. Pivotal results. Bancroftiastrobus digitata is a cylindrical cone with large, helically arranged ovuliferous scales subtended by short bracts, each bract/scale complex bearing two unwinged inverted seeds on the adaxial surface of the ovuliferous scale. Ovuliferous scales have abaxial plications in the midregion and divide distally, forming up to nine free distal lobes that are vascularized and covered by a dense ramentum of trichomes. The cone axis forms a continuous woody cylinder that surrounds a parenchymatous pith. There are numerous resin canals in the cortex of the cone axis that extend into each bract/scale complex, both abaxial and adaxial to the vascular traces. Vascular tissue to the bract diverges as a prominent terete bundle that separates from the stele immediately below a large inverted-U-shaped scale trace. More distally, the scale trace flattens and divides into a single row of C-shaped woody bundles. Conclusions. This new genus provides additional evidence for the diversity of stem group conifers that lived during the interval when most crown group conifer families originated. The new species is reminiscent of both Sciadopityaceae and Pinaceae. However, like the three anatomically preserved species of Pararaucaria Wieland (Cheirolepidiaceae), this cone does not clearly conform to any family with living species. Rather, these taxa have novel combinations of characters that make fossils vital for resolving deep internal nodes of the seed plant tree and that help to resolve the overall pattern of phylogeny. [ABSTRACT FROM AUTHOR]

A fossil seed cone with characters that have been hypothesized as transitional to the origin of crown group gnetophytes has been discovered in Lower Cretaceous deposits on Vancouver Island, British Columbia, Canada. This cone, described as Protoephedrites eamesii gen. et sp. nov., provides the first anatomically preserved fossil evidence for the evolution of gnetophyte cones with seeds. The cone is a compound shoot system consisting of a primary axis with nodes that bear bracts and axillary fertile shoots in an opposite/decussate arrangement. The secondary fertile shoot axis produces one or two pairs of diminutive bracteoles and a pair of erect ovules in an opposite/decussate pattern. In contrast to crown group gnetophytes, bracteoles subtend rather than surround and enclose the ovules. Ovules have a single multiseriate integument that is adnate to the nucellus in the basal region and free distally. The micropylar tube is short with a thick integument, but it displays distinctive cells of the inner integumentary epidermis that are characteristic of gnetophyte seeds. Each seed produces a large pollen chamber with a uniseriate wall. Paired erect ovules conform to the pleisomorphic morphology previously hypothesized for Ephedra seed cones, thus supporting the proposal that ancestral gnetophyte seeds are borne terminally on oppositely arranged sporophylls. The combination of gnetophyte synapomorphies and putative pleisomorphic characters displayed by Protoephedrites broadens the known range of morphologies for the most ancient gnetophytes. Detailed comparisons to several species of Bennettitales confirm that there are fundamental structural differences separating the seeds of Gnetales from those of Bennettitales, support the hypothesis that the outer seed envelope evolved within the gnetophyte clade, and suggest that Bennettitales are not as closely related to Gnetales as hypothesized by some authors. [ABSTRACT FROM AUTHOR]

A cylindrical permineralized conifer seed cone has been identified from the Officer Member of the Trowbridge Formation, near Izee, in east-central Oregon. The cone is preserved in a Middle Jurassic (Callovian) marine calcium carbonate concretion, associated with araucarian seed cones, conifer twigs and wood, cycad seeds, fern rachides, and lycopodialean remains and was prepared by the cellulose acetate peel technique. The specimen is abraded, 2.8 cm long and 1.3 cm wide, and consists of a cone axis with helically arranged bract/scale complexes, with a large ovuliferous scale and a broad, flattened bract. The bract/scale trace arises as a cylindrical unit from the cone axis, in which the bract and scale traces are separated by ground tissue. The traces separate immediately in the cortex to form a crescent-shaped bract trace and a horseshoe-shaped scale trace with associated sclerenchyma bands that form two triangular bundles toward the distal end of the scale. Ovuliferous scale tissue covers one inverted seed per scale, forming a pocket that contains the seed. Seeds are attached at the chalaza to the inside of the pocket. Seed integuments have an outer epidermis of isodiametric cells with dark contents; one or two layers of palisade cells, occasionally appearing in I-beam configuration; and several inner layers of randomly arranged cells. The nucellus is adnate to the integument, to near the apex, where it forms a cellular mound of tissue. Cylindrical cones with helically arranged bract/scale complexes, bract and scale free to the base, one seed per scale enclosed in a pocket, and triangular sclerenchyma bands are characteristic of the genus Vararaucaria, which recently has been placed in the extinct conifer family Cheirolepidiaceae. This third species extends the known range of Pararaucaria from the Southern Hemisphere to the Northern Hemisphere and emphasizes that the association of araucarian and pararaucarian conifers extended over a wide geographic area during the Jurassic. [ABSTRACT FROM AUTHOR]

This study describes a specimen that extends the oldest fossil evidence of Pinus L. to the Early Cretaceous Wealden Formation of Yorkshire, UK (131--129 million years ago), and prompts a critical reevaluation of criteria that are employed to identify crown group genera of Pinaceae from anatomically preserved seed cones. The specimen, described as Pinus yorkshirensis sp. nov., is conical, 5 cm long, and 3.1 cm in maximum diameter. Bract/scale complexes are helically arranged and spreading. Vasculature of the axis forms a complete cylinder with few resin canals in the wood, and the inner cortex is dominated by large resin canals. Bracts are short, with two resin canals, and separate from the scale base laterally. Distally, the ovuliferous scales broaden and thicken to form a rhomboidal apophysis with a dorsal umbo, characters found only in the genus Pinus among living conifers. Resin canals enter the ovuliferous scale abaxial to the vascular tissue, which divides distally to form a row of adaxially convex bundles. A short interseminal ridge separates two inverted and winged seeds on the adaxial surface of the ovuliferous scale. Seeds contain megagametophyte tissue and polycotyledonary embryos. Numerical cladistic analysis of anatomically preserved seed cones yields a wellresolved phylogeny of crown and stem group Pinaceae that is roughly concordant with the results of analyses that include living species only. All of the included species of Pinus form a clade with three very Pinus-like species that currently are assigned to the stem genus Pityostrobus. These results call to question the utility of traditional methods for assigning fossil seed cones to Pinus, resolve relationships among stem and crown group genera, and highlight the unnatural circumscription of Pityostrobus. This suggests that some species of Pityostrobus may actually represent the genus Pinus, and it demonstrates that the evolutionary diversification of Pinaceae began earlier than previously recognized from fossil evidence. [ABSTRACT FROM AUTHOR]

This study describes a specimen that extends the oldest fossil evidence of Pinus L. to the Early Cretaceous Wealden Formation of Yorkshire, UK (131-129 million years ago), and prompts a critical reevaluation of criteria that are employed to identify crown group genera of Pinaceae from anatomically preserved seed cones. The specimen, described as Pinus yorkshirensis sp. nov., is conical, 5 cm long, and 3.1 cm in maximum diameter. Bract/scale complexes are helically arranged and spreading. Vasculature of the axis forms a complete cylinder with few resin canals in the wood, and the inner cortex is dominated by large resin canals. Bracts are short, with two resin canals, and separate from the scale base laterally. Distally, the ovuliferous scales broaden and thicken to form a rhomboidal apophysis with a dorsal umbo, characters found only in the genus Pinus among living conifers. Resin canals enter the ovuliferous scale abaxial to the vascular tissue, which divides distally to form a row of adaxially convex bundles. A short interseminal ridge separates two inverted and winged seeds on the adaxial surface of the ovuliferous scale. Seeds contain megagametophyte tissue and polycotyledonary embryos. Numerical cladistic analysis of anatomically preserved seed cones yields a wellresolved phylogeny of crown and stem group Pinaceae that is roughly concordant with the results of analyses that include living species only. All of the included species of Pinus form a clade with three very Pinus-like species that currently are assigned to the stem genus Pityostrobus. These results call to question the utility of traditional methods for assigning fossil seed cones to Pinus, resolve relationships among stem and crown group genera, and highlight the unnatural circumscription of Pityostrobus. This suggests that some species of Pityostrobus may actually represent the genus Pinus, and it demonstrates that the evolutionary diversification of Pinaceae began earlier than previously recognized from fossil evidence. [ABSTRACT FROM AUTHOR]

Fifty-nine stems of Tetrastichia bupatides, numerous frond segments, and roots from Oxroad Bay, Scotland, have recently been analyzed. They reveal that many characters originally used to describe this species exhibit a wider range of variation than previously suspected. These data suggest that ribs of the protostele are most commonly four in number but range from three to five. Phyllotaxy ranges from opposite decussate to two-fifths, and rachis forking can be equal or unequal. Secondary xylem could be produced by all stems regardless of size, and rachis trace morphology ranges from "butterfly" shaped, to U-, to broadly U-, to T-shaped. Pinnules are vascularized by a single trace that diverges from the outermost protoxylem strand of a pinna trace. These ranges of variation for many characters complicate identification of isolated specimens, but stems can be identified by a consistent mode of rachis trace production, and frond parts can be correlated by common histological characters and a continuous range of variation in trace configuration. These wide ranges of variation in numerous characters demonstrate that phenotypic plasticity could be far greater in some hydrasperman seed ferns than previously realized and the taxonomic diversity at Oxroad Bay may be lower than previously thought. [ABSTRACT FROM AUTHOR]

Reexamination of fossilized plant material from the westernmost Pennsylvanian-age wetland flora in North America reveals that material of Pecopteris oregonensis Arnold represents a filicalean fern frond with annulate sporangia and anatomically preserved vascular tissues of the rachis. The frond, which is redescribed as Senftenbergia oregonensis (Arnold) Hillier et Rothwell comb. nov., is pinnately compound, with five orders of catadromous dissection, and it appears to have reached a length of 80 cm or more. The rachis displays an anchor-shaped xylem bundle, and dichotomizing aphlebiae are produced at the base of primary pinnae. The rachis, primary pinnae, and secondary pinnae have a dense covering of coarse trichomes. Secondary and tertiary pinnae display a length :width ratio of 2.5 : 1. The pecopterid pinnules measure 1.5--6 mm in length and 1.0--2.0 mm in width, with dichotomous venation, smooth-to-undulating margins, and a rounded tip. Sporangia are marginal and recurved under the abaxial pinnule surface to form two rows that are parallel to the midvein. Each sporangium has a narrow stalk, longitudinal dehiscence, and a terminal multiseriate annulus. The fern is assigned to the Tedeleaceae, and a combination of characters for distinguishing genera within the family is proposed. [ABSTRACT FROM AUTHOR]

• Premise of the study: Seed cone morphology and anatomy reflect some of the most important changes in the phylogeny and evolutionary biology of conifers. Reexamination of the enigmatic Jurassic seed cone Pararaucaria patagonica reveals previously unknown systematically informative characters that demonstrate affinities with the Cheirolepidiaceae. This paper documents, for the first time, internal anatomy for seed cones of this important extinct Mesozoic conifer family, which may represent the ghost lineage leading to modern Pinaceae. • Methods: Morphology and anatomy of cones from the Jurassic La Matilde Formation in Patagonia are described from a combination of polished wafers and thin section preparations. New photographic techniques are employed to reveal histological details of thin sections in which organic cell wall remains are not preserved. Specific terminology for conifer seed cones is proposed to help clarify hypotheses of homology for the various structures of the cones. • Key results: Specimens are demonstrated to have trilobed ovuliferous scale tips along with a seed enclosing pocket of ovuliferous scale tissue. Originally thought to represent a seed wing in P. patagonica, this pocket-forming tissue is comparable to the flap of tissue covering seeds of compressed cheirolepidiaceous cones and is probably the most diagnostic character for seed cones of the family. • Conclusions: Pararaucaria patagonica is assigned to Cheirolepidiaceae, documenting anatomical features for seed cones of the family and providing evidence for the antiquity of pinoid conifers leading to the origin of Pinaceae. A list of key morphological and anatomical characters for seed cones of Cheirolepidiaceae is developed to facilitate assignment of a much broader range of fossil remains to the family. This confirms the presence of Cheirolepidiaceae in the Jurassic of the Southern Hemisphere, which was previously suspected from palynological records. [ABSTRACT FROM AUTHOR]

* Premise of the study: Pinaceae and nonpinoid species are sister groups within the conifer clade as inferred from molecular systematic comparisons of living species and therefore should have comparable geological ages. However, the fossil record for the nonpinoid lineage of extant conifer families is Triassic, nearly 100 million years older than the oldest widely accepted Lower Cretaceous record for Pinaceae. An anatomically preserved fossil conifer seed cone described here extends the stratigraphic range of Pinaceae nearly 30 million years, thus reducing the apparent discrepancy between evidence from the fossil record and inferences from systematic studies of living species. * Methods: Material was prepared as serial thin sections by the cellulose acetate peel technique, mounted on microscope slides, and viewed and photographed using transmitted light. * Key results: A large cylindrical cone consisting of bract-scale complexes that diverge from the cone axis in a helical phyllotaxis has bracts and scales that separate from each other in the midregion and are of equal length and of nearly equal width. The cone has two inverted and winged seeds that are attached to the adaxial surface of each cone scale and, thus, represents an early member of the Pinaceae. * Conclusions: Eathiestrobus mackenziei gen. et sp. nov. extends the fossil record for well-documented members of the family Pinaceae from the Lower Cretaceous to the Kimmeridgian Stage of the Upper Jurassic. This species also clarifies the set of characters that are diagnostic for seed cones of Pinaceae and reveals possible plesiomorphic characters for seed cones of the family. [ABSTRACT FROM AUTHOR]

Abstract: Anatomically preserved Jurassic conifer seed cones originally described as Conites juddi Seward and Bancroft are reinvestigated and assigned to Hughmillerites juddii gen. et comb. nov. using the original specimens and new material from the type locality. This allows for a more thorough characterization of seed cone structure, for systematic placement of the species, and for establishing homologies of cupressaceous bract/scale complexes. Incomplete cones range 2.2–3.6cm in diameter and 3.0–4.3cm long, and have distinctly woody axes bearing helically arranged bract/scale complexes with a thickened bract tip. Mature complexes display three inverted seeds attached to the adaxial surface immediately proximal to three free ovuliferous scale tips. In each bract/scale complex there is a single large resin canal abaxial to the vascular bundle and three or more smaller adaxial resin canals at the level of seed attachment. Seeds are inverted at maturity, display 180° rotational symmetry, and show differentiation of sclerotesta and sarcotesta. The results of a phylogenetic analysis support placement of H. juddii among the basal grade of taxodioid Cupressaceae (). A transformational series of ovuliferous bract/scale complexes from voltziacean Voltziales to crown group Cupressaceae is presented to reveal the pattern and antiquity of evolution for modern cupressaceous conifer seed cone morphologies. Developmental studies of living cupressaceous seed cones indicate that the range of mature morphologies is strongly correlated with differences in the timing and rate of development for the bract, scale, and ovules, thus supporting the hypothesis that heterochrony plays a major role in the evolution of bract/scale form. This hypothesis is further supported by our growing understanding of developmental regulatory genetics. There are no currently recognized synapomorphies for living+fossil conifers. Nevertheless, these combined results do not support the hypotheses that some conifers have ancestrally simple seed cones nor that there have been parallel origins of Northern and Southern Hemisphere conifers. The overall body of evidence from both extinct and living conifers strongly supports the hypotheses of deep homology for seed cones and of monophyly for conifers s.s. [Copyright &y& Elsevier]

Evolution of plant form proceeds through sequential alterations in the development of plant organs. Leaves (or fronds) are organs that have diagnostic characteristics, including definite arrangement on a stem, bilateral symmetry (abaxial/adaxial identity), and determinate growth. Evolution of those diagnostic characteristics represents a series of critical steps in plant evolution that resulted from specific developmental alterations. The fossil record reveals a transformational series in leaf evolution that highlights steps that have occurred in parallel but independently in both leptosporangiate ferns and seed plants, resulting in superficially similar frond morphologies. In this study, the fronds of the most ancient fossil fern, Psalixochlaena antiqua, and the most ancient reconstructed seed plant, Elkinsia polymorpha, are characterized and compared with leaves of modern plants in order to identify the sequence in which features of leaves in two distinct clades of euphyllophytes arose. While both fronds show a combination of characters attributable to ancestral vegetative axes and characters attributable to leaves, each plant displays different combinations of those characters. These data document dissimilar sequences of character originations and, therefore, the independent evolution of developmental mechanisms in seed plants and ferns. [ABSTRACT FROM AUTHOR]

Fossils reported previously from the Early Silurian (Llandovery) lower Massanutten Sandstone (Virginia, USA) are formally described here as Prattella massanuttense gen. & sp. nov. Organization into cellular filaments embedded in extracellular matrix, the sizes of cells and filaments and the fluvial origin of deposits that host the fossils are all consistent with cyanobacterial affinity. Prattella massanuttense combines preservation as carbonaceous compression at a macroscopic scale with cellular preservation by mineral replacement of cell contents at a microscopic scale. These fossils provide the earliest direct evidence for the occurrence of cyanobacteria in fluvial habitats and add to the knowledge of terrestrial ecosystems that hosted early stages of land plant evolution. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160, 284–289. [ABSTRACT FROM AUTHOR]

Three types of anatomically preserved vegetative shoots with features that characterize crown group Equisetwn have been discovered in Lower Cretaceous deposits (≈136 Ma) of British Columbia. Canada, suggesting the genus is much older than currently believed. Specimens include two types of aerial shoots described as E. haukeanum sp. nov. and E. vancouverense sp. nov. and one type of subterranean rhizome. Shoots are 1-2 mm in diameter, jointed, and in cross section have fluted stems with a hollow pith. Distinctive patterns of cortical sclerenchyma and different ridge morphologies characterize each shoot morphotype. Nodes display irregular branching, highly fused leaf sheaths, and a nodal diaphragm. The aerial stem morphospecies have vallecular canals on alternating radii with carinal canals of an equisetostele surrounded by only a few tracheids. No secondary tissues are produced. Bands of surficial stomata flank the furrows of one morphospecies. Rhizomes and aerial shoots are of a similar size, suggesting that the plants were equivalent in stature to the smallest living Equisetuin species. These fossils augment our understanding of evolutionary transformations that led from Paleozoic Archaeocalamitaceae and Calamitaceae to crown group Equisetaceae, suggesting that the initial diversification of Equisetum began far earlier than suggested by molecular-clock-based estimates. [ABSTRACT FROM AUTHOR]

A remarkably diverse Lower Cretaceous (Valanginian-Hauterivian) flora at Apple Bay, Vancouver Island, preserves seed plants at an important time of floristic evolutionary transition, about the same time as the earliest flowering plant megafossils. The fossils are permineralized in carbonate concretions and include tetrahedral seeds within cupule- or carpel-like structures. These enclosing structures, composed of elongate sclerenchyma cells with spiral thickenings that grade externally to a few layers of parenchyma, are vascularized by one collateral vascular bundle and lack trichornes. They apparently broke open to release the tightly enclosed seeds by valves. Seeds are similar to those of the Triassic seed fern Petriellaea, but arc about 100 million years younger and differ in size, vascularization, integumentary anatomy, seed attachment, and number of seeds/cupule. These new seeds ale described as Doylea zetrahedraspernia gen. et sp. nov., tentatively assigned to Corystospermales. Inverted cupules are reminiscent of an outer angiosperm integument rather than a carpel. Like fruits, cupules opened to release seeds at maturity, thereby foretelling several aspects of angiospermy. They show that nearly total ovule enclosure, a level of organization approaching angiospermy, was achieved by advanced seed ferns during the Mesozoic. [ABSTRACT FROM AUTHOR]

Bennettitales is an extinct group of seed plants with reproductive structures that are similar in some respects to both Gnetales and angiosperms, but systematic relationships among the three clades remain controversial. This study summarizes characters of bennettitalean plants and presents new evidence for the structure of cones and seeds that help clarify relationships of Bennettitales to flowering plants, Gnetales, and other potential angiosperm sister groups. Bennettitales have simple mono- or bisporangiate cones. Seeds are borne terminally on sporophylls. They have a unique structure that includes a nucellus with a solid apex, no pollen chamber, and a single integument, and they are clearly not enclosed by a cupule or other specialized structures. Such features differ substantially from Gnetales, flowering plants, and the seed fern Caytonia, providing no compelling evidence for the origin of the angiospermous camel. Cladistic tests were performed to assess the strength of the "anthophyte hypothesis" and possible relation- ships of Bennettitales, Gnetales, and Caytonia to flowering plants. Our results do not support the anthophyte hypothesis for the origin of angiosperms by a transformation of fertile organs that were already aggregated into a cone or flower-like structure. However, the anthophyte topology of the seed plant tree continues to be supported by morphological analyses of living and extinct taxa. [ABSTRACT FROM AUTHOR]

Developmental morphology and anatomy of Botrychium s.l. were studied to clarify rhizome ontogeny and patterns of tissue maturation that can be used to test the hypothesis that ferns of the Ophioglossales may represent living progymnosperms. Serial anatomical sections of the rhizomes of B. virginianum and B. dissectum reveal that apical meristematic activity and vascular tissue maturation occur over an extended period of several years and then stop. Most of the xylem consists of radial rows of tracheids and interspersed ray-like xylem parenchyma cells that are similar in these respects to secondary xylem, but pits occur on all tracheid walls as is characteristic of primary xylem. No vascular cambium is initiated in mature primary tissues, nor is there secondary phloem. Radial rows of xylem cells are produced by the direct continuation of divisions that begin at the shoot apical meristem, forming a cylinder of radially aligned procambial cells before the differentiation of protoxylem. Continuing divisions over a period of several years increase the number of thin-walled cells and tracheids in each radial row back to about one internode behind where the current year's frond trace diverges from the rhizome stele. At more proximal levels of the rhizome, procambial cell divisions cease and there is no additional tracheid differentiation. These data reveal that the rhizome matures over an exceedingly long period of several years, but that growth is ultimately determinate, thus supporting hypotheses that the Ophioglossales is more closely related to other groups of living ferns than to progymnosperms and seed plants. [ABSTRACT FROM AUTHOR]

The first fossil evidence for the fern genus Todea has been recovered from the Lower Cretaceous of British Columbia, Canada, providing paleontological data to strengthen hypotheses regarding patterns of evolution and phylogeny within Osmundaceae. The fossil consists of a branching rhizome, adventitious roots, and leaf bases. The dictyoxylic stem has up to eight xylem bundles around a sclerenchymatous pith. Leaf traces diverge from cauline bundles in a typical osmundaceous pattern and leaf bases display a sheath of sclerenchyma around a C-shaped xylem trace with 2-8 protoxylem strands. Within the adaxial concavity of each leaf trace, a single sclerenchyma bundle becomes C-shaped as it enters the cortex. The sclerotic cortex is heterogeneous with an indistinct outer margin. The discovery of Todea tidwellii sp. nov. reveals that the genus Todea evolved by the Lower Cretaceous. A phylogenetic analysis combining morphological characters of living and extinct species with a previously published nucleotide sequence matrix confirms the taxonomic placement of T. tidwellii. Results also support the hypothesis that Osmunda s.l. represents a paraphyletic assemblage and that living species be segregated into two genera, Osmunda and Osmundastrum. Fossil evidence confirms that Osmundaceae originated in the Southern Hemisphere during the Permian, underwent rapid diversification, and species extended around the world during the Triassic. Crown group Osmundaceae originated by the Late Triassic, with living species appearing by the Late Cretaceous. [ABSTRACT FROM AUTHOR]

The emerging field of evolutionary developmental biology (evo-devo) seeks to identify the specific genetic basis for plant evolution. Whereas molecular biological studies are rapidly exposing the developmental mechanisms of evolution, paleontological studies reveal the sequence in which evolutionary changes have occurred. Aspects of both fields are reviewed in this article. Plant structure develops along genetically patterned pathways, some of which produce distinctive morphological features. Such features serve as ‘fingerprints’ for regulatory mechanisms, thus providing a record of growth regulation for both living species and plant fossils. Transformational series of structure through geological time form the contextual framework for inferring evolution from the fossil record, but the most widely practiced application of transformational series for plants, Telome Theory, has no developmental basis. By contrast, the fossil record of leaf evolution in seed plants documents morphological changes to which a growing understanding of genetic pathways can be correlated. Leaves are defined by a number of features, including determinacy and adaxial/abaxial identity. Fossils of early seed plants show stepwise acquisition of these characters, from which we can infer developmental modifications leading to the evolution of the characters. Previous work has revealed that an interregulated network of genes is involved in the specification of these features. The genes identified as being involved in various aspects of leaf development provide clues to the evolution of each character. In particular, expression of the AS1 and AS2 genes appears to facilitate both determinacy and bilateral patterning. The novel expression pattern of these genes may have been the key innovation that resulted in the evolution of leaves in seed plants. Combining molecular biological studies with knowledge of evolutionary patterns gleaned from the fossil record brings a new depth of understanding to the evolution of fundamental plant form. [ABSTRACT FROM AUTHOR]

The fossil record of aquatic flowering plants broadens our understanding of their former diversity and origins from terrestrial ancestors. This paper describes a floating aquatic monocot from 71 whole plants and several isolated leaf fragments from Upper Cretaceous oxbow lake sediments in the Dinosaur Park Formation, Alberta, Canada. The new material is represented by rosettes of leaves and roots attached to short stems that are interconnected by stolons and corresponds to the fossil aroid originally described as Pistia corrugata Lesquereux. Up to six plants have been found interconnected on a single slab suggesting that these plants grew in extensive floating mats covering lakes and calm stretches of rivers. Stems have up to six leaves and large numbers of branched aquatic roots. The leaf is trumpet-shaped with an elongate clasping petiole, large aerenchymatous base, and a nearly circular blade rim. Leaf bases are often filled with sediment giving the leaf the appearance of having a basal pouch. Petioles have 6-9 veins that divide into an upper and lower set, and veins converge at an apical notch. A submarginal collective vein and at least two marginal veins with branching veins form the leaf rim. A series of dichotomizing and anastomosing veins characterize the adaxial leaf surface. Tertiary and quatemary veins form polygonal areolae. Leaf surfaces are covered in trichomes that, like those in Pistia stratiotes, probably aided in buoyancy. A reconstruction of the plant is presented. Based on unique leaf morphology, these fossil plants are clearly not assignable to the genus Pistia and are described as Cobbania corrugata (Lesquereux) Stockey, Rothwell et Johnson gen. et comb. nov. Recent systematic analyses using molecular characters resolve two separate origins of floating aquatic aroids included in the duckweeds and the genus Pistia. This new fossil genus increases our understanding of colonization of aquatic habitats by revealing a third possible origin of the floating aquatic habit within Araceae. [ABSTRACT FROM AUTHOR]

Abstract: Discovery of a permineralized fossil cone in Mesozoic deposits of southern England provides an opportunity to document the first detailed evidence of internal pollen cone anatomy for the extinct conifer family Cheirolepidiaceae. The specimen, described here as Classostrobus crossii sp. nov., occurs in a calcareous nodule recovered from Middle Jurassic marine sediments of the Lower Callovian Sigaloceras calloviense biozone, Kellaways, near Cirencester, England. The cone is 2.0 cm long and 1.8 cm wide. Sporophylls diverge helically from the axis. Each sporophyll displays a narrow stalk and a distal lamina approx. 11 mm long that tapers to a pointed tip. There is also a basal keel that bends inward at the bottom and sides to form a shallow pocket. A single vascular bundle diverges from the cone axis, extends distally into the sporophyll stalk at the contact of two distinctly different histological zones, and further expands into the distal lamina as transfusion tracheids. Several pollen sacs are attached abaxially at the juncture of the sporophyll stalk and keel. Pollen is roughly spheroidal, 26–35 μm in diameter, with unequal polar caps separated by a striated belt with a subequatorial furrow. This specimen helps clarify the range of variation in the morphology of Mesozoic conifer pollen cones. [Copyright &y& Elsevier]

A compression macrofossil with structure consisting of mineral-replaced filaments embedded in an amorphous carbonaceous matrix is described as a macrophytic cyanobacterial colony from continental assemblages of the Early Silurian (Llandovery) Passage Creek biota, in the lower Massanutten Sandstone (Virginia, USA). Filaments are predominantly multiseriate and consist of spheroidal crystalline aggregates representing early pyrite (subsequently replaced by iron hydroxides) precipitated preferentially inside cells. Interpretation of the fossils as cyanobacteria is based on close similarities to modern organisms in terms of overall morphology and production of copious extracellular investments, filament and cell sizes, and continental epigeal (freshwater or terrestrial) habitat. This interpretation incorporates data on cyanobacterial taphonomy and mechanisms of diagenetic mineral precipitation. These fossils are part of the oldest macrofossil assemblages documenting well-developed and diverse communities on continents. They provide the earliest direct evidence for cyanobacteria in strictly continental habitats, corroborating the commonly held but poorly documented view that cyanobacteria were among the initial colonizers of continents. [ABSTRACT FROM AUTHOR]

Recent phylogenetic analyses have yielded conflicting results regarding relationships among ferns and other major groups of vascular plants and have prompted some authors to propose novel patterns of tracheophyte phylogeny based on analyses that include only living taxa. The results of one such study resolve seed plants as the sister group to all nonlycophyte pteridophytes and place equisetophytes and psilotophytes within a clade that also includes all of the living ferns. That hypothesis of phylogeny differs markedly from the results of a recent analysis that utilizes morphological data from both living and extinct taxa, which resolves ferns as a polyphyletic assemblage. To evaluate these competing hypotheses and to increase our understanding of the differing results, several tests were performed. Tests identify a high level of character conflict among the various gene sequence data matrices used in the analysis of living taxa. Contrary to the expectations of some, inclusion of extinct taxa in analyses of morphological characters produces striking changes in the topology of the resulting vascular plant tree when compared with the analysis of living taxa only. Together, these tests reveal that relationships among major groups of vascular plants are far less completely understood than claimed by some and that ferns s.l. are probably a polyphyletic assemblage. They also suggest that the impressive successes of gene sequence data in resolving relationships within smaller clades may not be easily duplicated when addressing deep internal nodes of the polysporangiophyte tree. Additional refinement of morphological characters for a combination of living and well-reconstructed extinct taxa, improved character/taxon ratios, fuller sampling of extinct clades, and tests that utilize rare genetic markers and developmental pathways may hold the greatest promise for ultimately resolving the overall pattern of vascular plant phylogeny. [ABSTRACT FROM AUTHOR]

Permineralized rhizomes and stipe bases of filicalean ferns occur in the Upper Cretaceous (Campanian) Horseshoe Canyon Formation near the town of Drumheller in southern Alberta, Canada, and these provide an opportunity to describe the first anatomically preserved Mesozoic species of Blechnaceae/Dryopteridaceae. The two new fossil species also provide evidence that modern stelar architecture and stipe anatomy evolved in these families before the end of the Mesozoic. Midlandia nishidae gen. et sp. nov. has an apparently ascending radial rhizome from which stipes diverge in a helical pattern that approaches a 5/8 arrangement. The dictyostele is made up of amphicribral meristeles, and stipe traces consist of two hippocampiform bundles that flank three to four smaller circular bundles. The rhizome of Wessiea oroszii is somewhat smaller, with a dictyostele of five to seven cauline meristeles, from which stipe traces diverge as a pair of hippocampiform bundles. In both species, gaps in the stele are initiated by the divergence of a root trace, whereas stipe traces separate from the sides of the meristeles that flank the gap. The new species show numerous anatomical similarities to living blechnoid and dryopteroid ferns and strongly support hypotheses that these highly derived ferns originated before the Upper Cretaceous. [ABSTRACT FROM AUTHOR]

Anatomically preserved foliage of a dipteridaceous fern has been identified in both calcareous nodules and fine-grained, carbonate-cemented sandstone from the early Cretaceous (Hauterivian-Barremian) Apple Bay locality from Vancouver Island, British Columbia, Canada. Fronds with attached sporangia containing spores are preserved as both compression/impressions and as permineralizations. Fan-shaped laminar segments display paired teeth along the margin. Major veins dichotomize to the lamina edge, and finer veins reticulate, forming square to polygonal areoles, with freely ending veinlets. Veins are enclosed by sclerenchymatous sheaths, and the abaxial epidermis is recessed, producing concave areas between veins. Adaxial cuticle is thick, and the epidermis contains rectangular cells with undulating walls. Anomocytic scattered stomata occur on the abaxial surface. Sporangia and trichomes are scattered across the abaxial epidermis in the areolar concavities. Sporangial stalks are short, two to three cells long and four to six cells wide throughout their length. Sporangia have a vertical annulus that is interrupted by the stalk, and they contain trilete spores that correspond to Cibotiumspora jurienensis. Leaf morphology is similar to that of extant Dipteris novoguineensis and fossil Hausmannia spp. A unique combination of characters demonstrates that Hausmannia is a distinct genus of fossil dipterids. An examination of leaves from extant Dipteris rhizomes of various ages suggests that the genus Protorhipis may represent juvenile Hausmannia at some localities. The association of Hausmannia with small pieces of delicate moss gametophytes, fern sporelings, and vegetative remains of Lycopodium and Selaginella at Apple Bay reinforces the interpretation that these fossil dipterids were deposited under storm conditions and that Hausmannia may have grown in disturbed habitats. [ABSTRACT FROM AUTHOR]

A new genus and species of anatomically preserved fossil filicalean ferns Dickwhitea allenbyensis gen. et sp. nov. is described from the Middle Eocene Princeton Chert of southern British Columbia, Canada. Rhizomes have a parenchymatous pith surrounded by a ring of five amphiphloic cauline bundles and pairs of frond traces that diverge from adjacent cauline bundles in a 2/5 phyllotaxis. The cortex is also parenchymatous except at the periphery, where there is a well-developed sclerotic hypodermis. The stipe is characterized by a pair of hippocampiform bundles, and ground tissues are similar to those of the rhizome. Prominent nests of large cells with black contents occur adjacent to the vascular bundles in the ground tissue of the rhizome and stipe. Roots are diarch with cortex that grades from parenchymatous at the interior to sclerotic at the periphery. The vascular architecture of this fern appears to be novel among known Filicales. There are no gaps in the stele that result from the divergence of either frond or root traces, and there is no evidence that cauline bundles anastomose. Rather, the cauline bundles extend through the rhizome independently of each other, with each cauline bundle producing successive frond traces on alternating tangents. Root traces diverge from the outer surface of cauline bundles as is characteristic of solenostelic filicalean species and dictyostelic tree ferns. Examination of the literature reveals that there is a wide range of variation in filicalean vascular architectures that traditionally has not been recognized. Although there is anecdotal evidence that this newly recognized stelar variation is correlated with patterns of systematic diversity, the overall phylogenetic significance of fern vascular architecture has yet to be fully explored. [ABSTRACT FROM AUTHOR]

An anatomically preserved leptosporangiate filicalean that combines characters of the Pteridaceae and tree ferns has been discovered in the Lower Cretaceous (Valanginian-Hauterivian boundary) Apple Bay flora on Vancouver Island, Canada. Exindusiate sori are radial, with numerous annulate sporangia diverging from a conical receptacle that is positioned below a pinnule vein. No paraphyses or other trichomes are present. Sporangia have a nearly vertical annulus that is not interrupted by the long, quadriseriate stalk. Spores are trilete and angular, with a distinctive equatorial flange and a distal deltoid structure that contacts the rim at the corners of the spore. The suture extends three-fourths of the distance to the margin and is flanked by prominent ridges. Spore walls consist of two dense layers, and the surface is psilate. Pterisorus radiata gen. et sp. nov. has characters that are reminiscent of both tree ferns and the most highly derived of modern species, providing direct evidence for the third major radiation of Filicales. [ABSTRACT FROM AUTHOR]

A distinctive new permineralized stem from marine deposits of western North America provides additional evidence for the diversity of Upper Cretaceous tree ferns. The fossil occurs in a calcareous concretion from the Late Campanian Spray Formation at Shelter Point, Vancouver Island, British Columbia, Canada. It measures 20 cm long and 7 cm in maximum diameter, with adventitious roots diverging between persistent, helically arranged fronds. Frond traces are derived from an amphiphloic dictyostele, and the stem produces no medullary or cortical bundles. The pith has a sclerenchymatous center and a parenchymatous outer zone. Sclerenchyma sheaths accompany both cauline and foliar vasculature. Frond traces diverge as six to ten bundles, most often eight. At the stem periphery, the cortex produces a homogeneous sclerenchymatous hypodermis, and is clothed by a dense ramentum of both uniseriate and large multiseriate trichomes. This novel combination of characters reveals the presence of a new genus and species of tree ferns, Rickwoodopteris hirsuta gen. et. sp. nov. Cladistic analysis of stem characters infers that R. hirsuta conforms to the dicksoniaceous grade of Cyatheaceae s.l., and further clarifies our understanding of evolutionary diversification among Mesozoic filicalean tree ferns. [Copyright &y& Elsevier]

We test competing hypotheses of relationships among Aroids (Araceae) and duckweeds (Lemnaceae) using sequences of the trnL–trnF spacer region of the chloroplast genome. Included in the analysis were 22 aroid genera including Pistia and five genera of Lemnaceae including the recently segregated genus Landoltia. Aponogeton was used as an outgroup to root the tree. A data set of 522 aligned nucleotides yielded maximum parsimony and maximum likelihood trees similar to those previously derived from restriction site data. Pistia and the Lemnaceae are placed in two separate and well-supported clades, suggesting at least two independent origins of the floating aquatic growth form within the aroid clade. Within the Lemnaceae there is only partial support for the paradigm of sequential morphological reduction, given that Wolffia is sister to Wolffiella + Lemna. As in the results of the restriction site analysis, pantropical Pistia is placed with Colocasia and Typhonium of southeastern Asia, indicative of Old World affinities. Branch lengths leading to duckweed terminal taxa are much longer relative to other ingroup taxa (including Pistia), evidently as a result of higher rates of nucleotide substitutions and insertion/deletion events. Morphological reduction within the duckweeds roughly correlates with accelerated chloroplast genome evolution. [Copyright &y& Elsevier]