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Three types of anatomically preserved vegetative shoots with features that characterize crown group Equisetum have been discovered in Lower Cretaceous deposits ([approximately equal to] 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. vancounerense 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 Equisetum 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. Key words: clade age; Equisetales; Equisetum; euphyllophyte phylogeny; fossil; Lower Cretaceous. doi: 10.3732/ajb.0800381

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 trichomes. They apparently broke open to release the tightly enclosed seeds by valves. Seeds are similar to those of the Triassic seed fern Petriellaea, but are about 100 million years younger and differ in size, vascularization, integumentary anatomy, seed attachment, and number of seeds/cupule. These new seeds are described as Doylea tetrahedrasperma 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. Key words: angiospermy; corystosperms; Cretaceous; cupule; Petriellaea; seed ferns.

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 carpel. Cladistic tests were performed to assess the strength of the 'anthophyte hypothesis' and possible relationships 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. Key words: anthophytes; Bennettitales; Caytonia; Cycadeoidea; Erdtmanithecales; Gnetales; Williamsonia.

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. Key words: Botrychium; fern; Ophioglossales: radial metaxylem; secondary cortex: secondary growth.

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. Key words: Cretaceous; fern phylogeny; Osmundaceae; Osmundastrum; rhizome; Todea.

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 quaternary 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. Key words: aquatic; Araceae; aroids; Cretaceous; Dinosaur Park; fossil plants; Pistia.

Five perminemlized seed fern stems from the Fayetteville Formation (middle Chesterian/Upper Mississippian) of Arkansas conform to the concept of lyginopterid seed ferns. However, these specimens are unlike all previously reported lyginopterids, and the name Trivena arkansana (Lyginopteridaceae) gen. et sp. nov. is proposed. The stems are up to 30 by 19 mm in diameter and have pentagonal pith and eustele of five cryptic sympodia. Secondary tissues include abundant xylem with numerous wide rays and phloem surrounded by a periderm. The cortex is parenchymatous with abundant sclerotic clusters: some clusters are randomly dispersed and some are in discontinuous rows. Sclerenchyma bands form the 'Dictyoxylon'-type outer cortex. Leaf traces diverge in a 2/5 phyllotaxy. Traces, accompanied by concentric secondary xylem, increase in size as they extcnd through the secondary xylem of the stem. The trace assumes a squat C shape at the outer margin of the secondary xylem and in the cortex divides into three discrete bundles, each surrounded by secondary xylem. Galleries within the phloem contain arthropod coprolites and exhibit wound response, suggesting plant-arthropod coevolution. The discovery of this new lyginopterid stem adds to the growing list of unique taxa described from the Fayetteville Formation and further solidifies its reputation as one of the most important Upper Mississippian plant fossil sites in North America. Key words: Chesterian; Lyginopteridaceae; Mississippian; Pteridospermales; Trivena arkansana; wound response.

Permineralized cyatheaceous sori occur among remains of conifers, fungi, and other plants in newly discovered calcareous concretions from Early Cretaceous (Barremian) marine sediments of Vancouver Island, British Columbia, Canada. Sori are superficially attached in two rows to narrow pinnules and display a globose sphaeropteroid indusium. Annulate sporangia with multicellular stalks diverge from a basal, vascularized receptacle. The nearly vertical uniscriate annulus is not interruptcd by the stalk. The sporangia bear 64 trilete spores with perispore sculpturing that ranges from irregular granulate/echinate to prominent rodlets. These specimens, described as Cyathea cranhamii sp. nov., are the first anatomically preserved tree fern sori from the fossil record. They represent the most ancient evidence for fertile structures of the Cyathcaceae and demonstrate that essentially modern species of cyathcaceous tree ferns had evolved by the Early Cretaceous. Key words: Barremian; British Columbia; Cretaceous; Cyathea cranhamii sp. nov.; Cyatheaccae; Filicales.

New ovules from the Fayetteville Formation (Upper Mississippian) of Arkansas expand our knowledge of the morphology and anatomy of Rhynchosperma and suggest it was produced by a medullosan seed fern. Rhynchosperma has been described as radially symmetrical with a two-layered integument and vascularization in the integument only. The apical portion of the integument is ribbed; the nucellus is fused to the integument and apically differentiated into a dome-shaped pollen chamber. The vascular system is incompletely known and apparently restricted to the base of the integument. The new specimens are like Rhynchosperma in external shape, size, number of ribs, and numerous histological features. However, new data reveal that the nucellus is vascularized by a sheath of tracheids, the integument is vascularized by discrete bundles, the pollen chamber has a nucellar beak, and the nucellus is attached to the integument for a variable distance from the base. In addition, the integument is tripartite with an elaborate apical region; ribs formed by the integument are more pronounced at the apex; and internally open, hollow lobes form a stellate micropylar canal. The presence of a tripartite integument, the nature of the vascular system, the nucellus-integument attachment, the pollen chamber structure, symmetry, and the association with medullosan vegetative remains suggest medullosan affinity for these ovules and strengthens the evidence for the origin of the family before the end of the Lower Carboniferous. Key words: Chesterian; Medullosaceae; Mississippian; ovule; Rhynchosperma quinnii; trigonocarpalcan.

Four anatomically preserved ovulate cycadeoid cones have been recovered from three localities in Upper Cretaceous (Turonian/Coniacian-Late Campanian) sediments of Vancouver and Hornby Islands, British Columbia, Canada. All of the specimens are preserved by calcareous cellular permineralization and are quite similar to seed cones described as several species of Cycadeoidea and Bennettites. These cones, described as Cycadeoidea maccafferyi sp. nov., consist of tightly packed interseminal scales and ovulate sporophylls with terminal ovules. Two specimens also preserve remains of a small receptacle, Interseminal scales and ovulate sporophylls are oriented parallel to one another. Ovules are distinctly stellate at the base of the micropylar tube, and the sarcotesta consists of both longitudinally oriented tubular cells and large radially elongated cells attached to the sclerotesta. The vascular strand below each ovule is highly contorted in a pattern that is characteristic of contractile tissue in the roots of living plants. These specimens are the most recent anatomically preserved cycadeoid cones yet discovered, revealing details of the reproductive biology shortly before extinction of the clade. Superb preservation of the British Columbia cones confirms that Bennettitales lack a cupule, have radial seeds, and have a vascularized nucellus (but no integumentary tracheids), and that no pollen chamber is produced. Together with a new species of Williamsonia preserved at one of the same localities, these specimens reveal a clear set of contrasting systematic characters for differentiating between isolated seed cones of Williamsoniaceae and Cycadcoidaceae. Key words: Bennettitales; Cretaceous; Cycadeoidea; seed cones; Williamsonia.

Numerous small fern trunks and dispersed osmundaceous frond fragments occur within a Middle Triassic silicified peat near Fremouw Peak in the Transantarctic Mountains of Antarctica. These specimens form the basis of a new species of osmundaceous ferns that further helps to characterize the early Mesozoic vegetation of high latitude Gondwana. Ashicaulis woolfei n. sp. consists of small, upright trunks with a persistent armor of frond bases, adventitious roots, and vegetative frond parts. In cross section the trunks are ~2.5 cm in diameter and include up to 45 frond bases. Stems range from 5 to 8 mm in diameter with a xylem cylinder of 8-9 xylem segments separated by leaf gaps. Phyllotaxy is variable, approaching 2/5 or 3/8, with 10-12 frond traces in the cortex. Stipes have parenchymatous, stipular wings that are usually devoid of sclerenchyma; fronds are pinnate with alternate-subopposite pinnatifid pinnules. Although the absence of fertile pinnules and sporangia precludes assigning the fossils to a living genus, this species demonstrates that ferns with stelar architecture and histology similar to Osmunda subgenus Osmundastrum (Osmundaceae) were present in the Southern Hemisphere by the mid-Triassic. Key words: anatomy; Antarctica; Ashicaulis; ferns; Osmundaceae; stelar architecture; stems; Triassic.

More than 200 specimens of Limnobiophyllum scutatum (Dawson) Krassilov have been recovered from lacustrine claystones in the Paleocene Paskapoo Formation near Red Deer, Alberta. The plant was a floating, aquatic angiosperm with helically arranged, ovate leaves attached in small rosettes. Rosettes are interconnected by stolons and bear simple adventitious roots as well as larger branching roots that appear to have vascular tissue. Leaves are pubescent, aerenchymatous, with 12-14 campylodromous primary veins that curve toward the apex, joining a fimbrial vein, often an apical notch. Staminate flowers with two, four-loculate stamens, are borne in the axils of second leaves. Anthers contain monoporate, globose, echinate pollen, 20-25 [[micro]meter] in diameter. The pollen wall is 0.8 [[micro]meter] thick, with a homogeneous foot layer, granular to slightly columellate infratectal layer and an echinate tectum. Pollen most closely resembles the sporae dispersae genus Pandaniidites Elsik. The completeness of L. scutatum has allowed for its inclusion in a numerical cladistic analysis to resolve relationships among taxa of the Lemnaceae, Pistia, and selected genera of Araceae. Results of the analysis indicate that the Lemnaceae plus Pistia form a monophyletic group within the Araceae. Key words: Araceae; Lemnaceae; Limnobiophyllum; Pandaniidites; phylogeny; Pistia; Spirodela.

A megasporangiate fructification has been discovered in dysoxic, offshore marine shales from Upper Pennsylvanian deposits of northcentral Texas. This specimen, described as Suavitas imbricata gen. et sp. nov., consists of imbricating, helically arranged sporophylls that diverge from a stout axis. The axis is characterized by parenchymatous pith and weakly developed vascular tissue. Sporangia are terminal with a horizontally elongated, apical dehiscence slit. There is one large functional megaspore in each sporangium, and the megaspore wall is constructed of interconnected rodlets. Parsimony analysis indicates that Suavitas may be related to rhizomorphic lycophytes. The unique combination of characters displayed by this species illustrates the central role played by extinct species in characterizing overall patterns of plant relationships, and emphasizes the uniqueness of plant communities from extrabasinal habitats during the late Paleozoic. Key words: Carboniferous; dysoxic marine; extrabasinal vegetation; lycophyte; seed analogue.

Large segments of intact plants that represent a heterosporous fern have been discovered within an aquatic plant community from the Late Cretaceous St. Mary River Formation near Cardston in southern Alberta, Canada. Branching rhizomes of Hydropteris pinnata gen. et sp. nov. are 1-2 mm wide. They produce fronds at intervals of 2-12 mm and bear numerous elongated roots. Fronds, up to approximately 6 cm long, are pinnate with subopposite to alternate pinnae that exhibit anastomosing venation. Large, multisoral sporocarps occur at the junctures of the rhizome and frond rachides. Both microsporangiate massulae and megaspore complexes occur within each sporocarp. Megaspore complexes are assignable to the sporae dispersae genus Parazolla Hall. Microspores are trilete, smooth-walled, and are embedded in episporal material of the massulae. A numerical cladistic analysis indicates that the heterosporous aquatic ferns are monophyletic, and not as closely related to either schizaeaceous or hymenophyllaceous ferns as they are to some other filicaleans. Systematic revisions are proposed to reflect newly recognized cladistic relationships within the heterosporous clade, and character originations in the evolution of heterosporous aquatic ferns are evaluated. Hydropteridaceae fam. nov. is proposed, and included with Salviniaceae and Azollaceae in the Hydropteridineae subord. nov., and the Hydropteridales Willdenow.

Meristematic activity in Stigmaria ficoides is interpreted from a combination of historical information and newly developed data on stelar diameter, wood production, and morphology of the apex. Many specimens of Stigmaria preserved as mold/casts display little or no recognizable change in the width of the stelar groove between successive forks. Thickness of the xylem cylinder in permineralized axes of similar diameters also is relatively uniform. Over a distance of 1.5 m along one axis the mean number of tracheids per radial row diminishes from 56 to 46 toward the apex. While this is a statistically significant decrease, in biological terms it is consistent with the reduction in primary growth that one would expect in a zone of apoxogenesis. Coupled with our knowledge of the morphology of the apex, these data allow us to interpret radially aligned tracheids in the steles of most stigmation axes as having been produced largely from the action of a primary thickening meristem, rather than from a secondary vascular cambium as commonly believed.

Basal parts of Botryopteris forensis have been discovered rooted within the mantle of the tree fern Psaronius. Specimens occur in Upper Pennsylvanian coal balls from near Steubenville, Ohio, USA. The Botryopteris stems branch profusely, and these shoots are intertwined with the Psaronius roots near the surface of the mantle. They also produce adventitious roots that extend among the Psaronius roots. This material demonstrates that B. forensis was a trunk epiphyte, rather than a rhizomatous terrestrial fern. The B. forensis plant is interpreted tohave branched continuously, to ramify, and to maintain itself at the periphery of the growing mantle of Psaronius roots. A new reconstruction of B. forensis is offered showing the large, globose fructifications hanging pendulously from horizontal fronds on emergent shoots. Epiphytes and lianas are common on the trunks of Psaronius, indicating that some Marattiales did not produce leaf skirts.

Fossil seeds and seedlings of a Metasequoia-like taxodiaceous conifer occur in Paleocene deposits at the Munce's Hill and Gao Mine localities of central Alberta, Canada. Compression/impression specimens are preserved in upright growth positions among seedlings of the cercidiphyllaceous dicot Joffrea speirsii Crane & Stockey. There are a large number of seeds, a few of which were buried while germinating and show a radicle or short primary root. More than 500 Metasequoia-like seedlings have been identified that have two linear cotyledons with parallel margins and rounded tips. Three specimens have been found that display three cotyledons. Slightly older seedlings show decussate pairs of leaves attached to the stem distal to the cotyledons. Still older seedlings have axillary branches that show varying sizes and numbers of opposite leaves arranged in a single plane distal to the opposite pairs. These specimens reveal that both Joffrea and this extinct taxodiaceous conifer were early colonizers of North American floodplain communities at the beginning of the Tertiary. Key words: Metasequoia; Paleocene; seedlings; Taxodiaceae.

Germination of Ginkgo biloba seeds with intact and removed sarcotesta was compared to test the role of the seed coat in germination biology. The presence of an intact sarcotesta significantly reduced total germination percentage when compared to seeds with the sarcotesta removed. Some seeds were also cold stratified. This treatment was not necessary for germination, but it did improve total germination percentage. The seeds were collected during the period of natural abscission. Contrary to the accepted literature, we found that Ginkgo seeds contain well-developed embryos at the time of dispersal. These data demonstrate that the seed coat contributes to winter dormancy of G. biloba, and that the phenology of this species is less primitive than popularly believed. Key words: dormancy; evolution; germination; Ginkgo; Ginkgoaceae; phenology.

Fossil ectomycorrhizae were found recently among permineralized plant remains in the middle Eocene Princeton chert of British Columbia. The ectomycorrhizae are associated with roots of Pinus and have a Hartig net that extends to the endodermis, a pseudoparenchymatous mantle, and contiguous extramatrical hyphae that are simple-septate. The mycorrhizal rootlets lack root hairs and dichotomize repeatedly to form large, coralloid clusters. Reproductive structures are absent. Based on the morphological characteristics, and the identity of the host, the closely related basidiomycete genera Rhizopogon and Suillus are suggested as comparable extant mycorrhizal fungi. These exquisitely preserved specimens represent the first unequivocal occurrence of fossil ectomycorrhizae and demonstrate that such associations were well-established at least 50 million years ago. Key words: Allenby Formation; ectomycorrhizae; Eocene; fossil fungi; Pinus; Princeton chert; Rhizopogon; Suillus.

Anatomically preserved Woodwardia virginica (Blechnaceae) and a newly recognized onocleoid fern are described from the middle Miocene Yakima Canyon flora of central Washington State, USA. Identification of the W. virginica fossils is based on a combination of vegetative pinnules, rhizome and stipe anatomy, and fertile pinnules with indusiate sori and sporangia like those of extant W. virginica. Fronds are isomorphic. Vegetative pinnae are elongated and pinnatifid, with a secondary vein paralleling the midvein. Secondary veins of the pinnule lobe anastomose to form primary areoles and are either simple or dichotomize toward the margin. Rhizomes have a simple dictyostele with 3-5 cauline vascular bundles and often a sclerotic hypodermis. Leaf traces contain two large adaxial vascular bundles that occur laterally and adaxially, flanking an arc of 4-6 smaller bundles. Fertile pinnules have linear sori that are somewhat embedded in the laminae and are enclosed by a thin indusium. Leptosporangia display a vertical annulus and an elongated stalk. A second fern, Wessiea yakimaensis gen. et sp. nov., is represented by anatomically preserved branching rhizomes and attached frond bases that conform to the Onoclea-type pattern of rhizome and frond-base vasculature. Rhizomes have a simple dictyostele of 4-5 cauline meristeles. Leaf divergence is helical, with paired hippocampiform rachial traces. These two ferns occur in the same matrix with specimens of Osmunda wehrii. They demonstrate that filicalean fern assemblages similar to those of extant temperate floras were well established in western North America by the middle Miocene and further emphasize the exceptional species longevity of some homosporous pteridophytes. Key words: Blechnaceae; fossil Filicales; Miocene; silicified; Wessiea; Woodwardia virginica.

A species of Pityostrobus (P. milleri Falder et al.) recently was described from calcareous nodules recovered from shallow marine sediments of Lower Cretaceous (latest Aptian: Clansenian) age located east of the Black Sea in the Caucasus Mountains in southwestern Russia. Nodules of this type also contain conifer needles, filicalean frond members, wood fragments, gastropods, bivalves, and an extremely rich assemblage of well preserved cephalopods. Additional collecting at this locality has yielded a second new species of this extinct ovulate cone genus assignable to the Pinaceae. The incomplete cone measures 8 cm long and 3.4 cm wide. The cone axis is 5 mm in diameter, with a parenchymatous pith that displays scattered sclerids. The cylinder of wood is discontinuous and does not show a growth ting. The tiny bract is united with the scale except at the tip. Bract and scale traces diverge from the stele independently, and the bract trace extends to near the tip of the organ. Resin canal architecture is distinct, but similar to that of Larix, Pseudotsuga and Picea. Ovules display a distinctly undulating surface of the integument on the side that faces the ovuliferous scale. This new species adds further to our knowledge of the explosive diversification of Pinaceae during Early Cretaceous time.

The Late Pennsylvanian flora at Hamilton, KS has yielded approximately three thousand conifer specimens including leafy shoots, pollen cones, ovulate cones, ovules and seeds, and decorticated stems that show a wide range of variation in structural features and preservational modes. These specimens display characters of external morphology, internal anatomy and cuticular detail, and are interconnected in various combinations of organs that provide a large number of characters for formulating and testing hypotheses of taxonomic diversity. These include the morphological and cuticular characters used in classical fossil conifer studies, as well as new information on anatomical and developmental variation, and reproductive biology. Based on our analyses of vegetative shoots, pollen cones, pollen, ovulate cones and ovules/seeds we have identified intergrading combinations of characters for individual organs. When the characters of organs that are in organic attachment are included, these combined analyses allow us to test our hypotheses of taxonomic diversity using multivariate techniques and cladistic methodologies.

The medullosan pteridosperms are a common group of early seed plants that extend from the Lower Carboniferous to the Permian of North America and Europe. The earliest occurrence of the genus Medullosa is from the Missippian Fayetteville and Imo Formations of Arkansas, which are equivalent to the uppermost Lower Carboniferous (Namurian A) in Europe. Four specimens of permineralized stems with diverging leaf traces have been discovered, and these represent a previously undescribed species with features that are characteristic of vine-like growth architecture. Specimens range up to 40 cm long and 2-3 cm in diameter. The number of vascular segments ranges from two to eight, with relatively equal development of centripetal and centrifugal secondary xylem. In cross sections the vascular segments vary from circular to oval to tangentially elongated, as they anastomose from level to level. The stelar zone is surrounded by a thin zone of periderm and primary cortex. Cross sections reveal that the primary cortex is subdivided into leaf bases in differing stages of divergence, and this indicates helical phyllotaxis. Within the cortex, vascular bundles, resin canals and sclerenchyma form the typical Myeloxylon histological configuration for species of Medullosa. Leaf traces to a single frond are produced over an extended vertical distance along the stem, and are relatively large at the level of separation from the stele. Traces subdivide further in the leaf base. In cross sections of the stem, traces from each protoxylem sympodium consistently diverge in two directions at the same level. This produces two emission areas in each cylinder of secondary vascular tissues. These stems represent the earliest occurrence of the genus Medullosa, and are stratigraphically equivalent to the earliest records of the family Medullosaceae.

An anatomically preserved specimen of a woody, heterosporous pteridophyte has been discovered in Upper Pennsylvania peat-forming swamp deposits of eastern Ohio. The fossil is described as Cecropsis luculentum gen. et sp. nov. It consists of a protostelic shoot tip with helically-arranged vegetative leaves, sporophylls and adaxial eusporangia. The stele is marginally mesarch, with five cauline protoxylem strands that produce leaf-trace protoxylem in a helix that approaches 2/5. Dense wood surrounds the protostele. Secondary tracheids have reticulate bordered pitting on all walls. Rays are uniseriate and 1-2 cells high. Vegetative leaves are 2-3 cm long and are pinnately-dichotomously branched into terete lobes. Sporophylls are somewhat more extensively webbed, with clusters of sporangia located above vascularized receptacles. Sporangia are sessile and globose, with a terminal dehiscence slit. Megasporangia and microsporangia appear to be intermixed. Most are empty, but a small number contain either fragments of bean-shaped microspores with asymmetrical trilete sutures, or a single radial and trilete megaspore. The presence of gymnospermous protoxylem architecture and wood in this heterosporous pteridophyte place it within the circumscription of the Progymnospermopsida. However, features of the stele, leaves, sporangia, and extreme heterospory indicate that it does not conform to a presently recognized order. The Pennsylvanian occurrence and unique features of Cecropsis leave open to question whether it is phylogenetically, or only phenetically related to other members of the Progymnospermopsida.

Vegetative and fertile frond segments of Botrychium have been recovered from Paleocene deposits of central Alberta, Canada. Specimens are preserved as coalified compressions that yield information about frond structure, sporangia, and spore ultrastructure. These fossils, described as Botrychium wightonii sp. nov., establish a megafossil record for the Ophioglossales, and demonstrate that modern-appearing species of the order were present in western North America by the earliest Tertiary. The largest vegetative fragments are up to 4.6 cm long and tripinnately compound, with opposite to subopposite branching. Ultimate segments are pinnatifid with dentate pinnules and open dichotomous venation. Fertile specimens are also tripinnately compound with a long rachis and subopposite to alternate pinnae. Sporangia are either submarginal and superficial, or marginal, and are all directed toward one surface of the pinnule. They are ovoid to subspheroidal and 0.8-2.0 mm in diameter. Some sporangia are apparently stalked, while others appear to be sessile. This variation results both from the ultimate frond segments being compressed in several different planes, and the fossils being exposed at different levels. Spores macerated from the sporangia are radial and trilete, and range 30-67 [micrometer] in diameter. Most are psilate, but some have a densely striate surface.

A rich fossil biota from a Pennsylvanian age deposit of eastern North America contains numerous vegetative and fertile specimens that conform to a single species of primitive walchian conifers. Among the specimens is a compound pollen cone that comprises closely spaced, helically arranged, leaf-like bracts with axillary dwarf shoots. The specimen looks superficially similar to an ultimate vegetative conifer shoot, but there are small appendages in the axil of each bract that represent the fertile dwarf shoots. Dwarf shoots consist of an axis that bears sterile scales and sporophylls with erect pollen sacs. Pollen found in the sacs is monosaccate and conforms to the sporae dispersae genus Potonieisporites Bhardwaj. This cone is a compound shoot system that is morphologically equivalent to the ovulate cones of conifers and to the pollen cones of Paleozoic cordaitaleans and modern gnetophytes. Therefore, it is fundamentally different from the simple pollen cones of other fossil and modern conifers. Discovery of this specimen unexpectedly supports molecular studies that predict a close relationship between Coniferales and Gnetales, and provides fossil evidence to help reconcile the discordant phylogenetic hypotheses of seed plant systematics that have been developed from morphological and molecular data. Key words: compound pollen cone; conifer; Paleozoic; seed plant phylogeny; walchian.

Ferns and fern-like plants are conspicuous vegetational components in floras that range from the Middle Devonian to the recent. As with paleontological data in general, fossil ferns provide characters and novel character combinations that are not present in living species. They establish minimum dates for the origins and geological longevity of clades, and may be used to perform stratigraphic tests of systematic hypotheses that are rendered in the form of phylogenetic trees. Fossil species have the potential to occupy positions on a tree that otherwise are 'vacant', thereby reducing the number and length of long branches. They also can be used in inclusion/exclusion experiments to help reveal whether systematic relationships determined from living species alone are representative of the overall phylogenetic pattern. Extinct species appear to make the most valuable systematic contributions when they are well known as organisms (i.e., can be scored for a majority of the characters used in an analysis), and when they represent ancient representatives of clades in which a great deal of evolution has taken place. Examples from recently completed studies and ongoing analyses support the view that the fossils are most valuable for resolving deep branches in cladistic trees, and that morphological analyses that include extinct species have great potential for resolving ancient cladogenic events that are inaccessible from other types of data.

Living gymnosperms are all long-lived woody plants that begin sexual reproduction after an extended period of juvenile vegetative growth. This growth habit has also been presumed to characterize all fossil gymnosperms, including conifers. However, in her characterization of Lower-Middle Triassic vegetation from the Buntsandstein of eastern France, Grauvogel-Stamm described seedlings and entire fertile plants of Aethophyllum stipulate, and interpreted it to be an herbaceous conifer. Reexamination of the depositional regime and structure of A. stipulare adds additional support for this interpretation, and suggests that life history patterns that include herbaceous ruderals were present among some extinct gymnosperms. Rooted seedlings and whole plants of Aethophyllum are preserved in silty clay lenses, indicating that they grew around ephemeral brackish ponds in the flood plain of the Gres a Voltzia delta. The fossils include dicotyledonary seedlings and small monoecious plants, one to two meters tall, with numerous terminal cones. Internal anatomy reveals that little or no secondary xylem was produced, except in the roots, and that the stems have a large pith with prominent lacunae. All of these characters are consistent with the interpretation that Aethophyllum represents an herbaceous conifer ruderal. If so, this would establish that at least some fossil gymnosperms had life history patterns that allowed them to rapidly colonize the temporary, usually disturbed, habitats in which plant speciation is thought to be most common.