52 research outputs found
The Fossil Record of Basal Monocots
The fossil record of basal monocots (Acorales and Alismatales) extends back to the Cretaceous in the Northern Hemisphere. While many fossils were originally assigned to these basal groups, rigorous paleobotanical studies show many of them to be misidentified. Acarus fossils have been reliably reported from the Eocene while those of Alismatales extend back to the early Cretaceous. The fossil record of basal monocots is usually represented by leaves, fruits, and seeds; however, some localities preserve stems with attached leaves and roots and even whole plants. A detailed examination of leaf venation patterns in alismatids has recently allowed the description of a new taxon from the Upper Cretaceous of Alberta based on leaves attributed to Limnocharitaceae. Anatomically preserved alismatid petioles (Heleophyton helobiaeoides) and well-preserved flowers/fruits are known from the Middle Eocene Princeton chert of British Columbia. A complete developmental sequence from flower to fruit is known, and this material has good possibilities for whole plant reconstruction. The extinct floating aquatic Limnobiophyllum (Araceae/Lemnoideae) and the genus Pistia have been the subject of morphological cladistic analyses and competing hypotheses of relationships among aroids and duckweeds. The fossil record and recent molecular studies support separate origins of Pistia and the duckweeds from within Araceae. The fossil taxon Pistia corrugata has been reexamined in light of new evidence and indicates the presence of a new genus that shows leaf morphology unlike that seen in extant Pistia, but with a similar growth habit. Fossil evidence indicates that the floating aquatic habit probably arose at least three times within Araceae
Cuticular Features and Epidermal Patterns in the Genus Araucaria de Jussieu
This is the publisher's version, also available electronically from http://www.jstor.org.The cuticular organization and epidermal features of le aves from the four sections of the genus Araucaria, growing under similar environmental conditions, were studied by scanning electron microscopy. Cuticles from these extant species and the Jurassic fossil Araucarites santaecrucis were compared by rubber replicas and examination of the fossil leaf surfaces. Two distinct groups of araucarian leaves are distinguished by cuticular features. The Columbea-Bunya species have regular stomatal rows with polar cells always oriented in the same direction, four to five subsidiary cells, and a granular inner cuticle surface on both epidermal and subsidiary cells. The Eutacta-Intermedia species have four to seven subsidiary cells with thin cuticular flanges between guard cells and subsidiary cells, a smooth inner cuticular surface on both epidermal and subsidiary cells, and thinner intercellular flanges on epidermal cell walls. Epidermal features of a raucarian leaves appear to be taxonomically useful at the section level
Studies of Paleozoic Seed Ferns: Additional Studies of Microspermopteris aphyllum Baxter
This is the publisher's version, also available electronically from http://www.jstor.org.The genus Microspermopteris is characterized as a small lyginopterid pteridosperm with a pentarch protostele, irregular cortical ridges, and multicellular trichomes. We describe the frond architecture and variability among axillary branches previously unknown for the genus. Fronds are small and delicate, exhibiting three orders of branching. Clasping V-shaped petioles produce primary pinnae alternately to suboppositely from adaxial projections. Primary pinnae in turn produce secondaries that bear two-, three-, or four-lobed ultimate laminar pinnules. Pinnules reconstructed from serial sections are morphologically similar to Sphenopteris-like compressions; however, the overall frond is reduced in size and complexity. While some axillary branches produce secondary xylem, others are composed entirely of primary tissues. Some axillary branches produce scalelike leaves in a tight helix; distally, immature buds are surrounded by flattened bud scales. Although Microspermopteris shows similarities to Heterangium in stelar and cortical anatomy, the two taxa are distinct. Microspermopteris is interpreted as a delicate, scrambling vine, liana, or shrublike plant in contrast to the more robust lyginopterids Lyginopteris, Schopfiastrum, and Heterangium
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A Lower Cretaceous (Valanginian) seed cone provides the earliest fossil record for Picea (Pinaceae)
Premise of study: Sequence analyses for Pinaceae have suggested that extant genera diverged in the late Mesozoic. While the fossil record indicates that Pinaceae was highly diverse during the Cretaceous, there are few records of living genera. This description of an anatomically preserved seed cone extends the fossil record for Picea A. Dietrich (Pinaceae) by similar to 75 Ma.
Methods: The specimen was collected from the Apple Bay locality of Vancouver Island (Lower Cretaceous, Valanginian) and is described from anatomical sections prepared using cellulose acetate peels. Cladistic analyses of fossil and extant pinaceous seed cones employed parsimony ratchet searches of an anatomical and morphological matrix.
Key results: This new seed cone has a combination of characters shared only with the genus Picea A. Dietr. and is thus described as Picea burtonii Klymiuk et Stockey sp. nov. Bisaccate pollen attributable to Picea is found in the micropyles of several ovules, corroborating the designation of this cone as an early spruce. Cladistic analyses place P. burtonii with extant Picea and an Oligocene representative of the genus. Furthermore, our analyses indicate that Picea is sister to Cathaya Chun et Kuang, and P. burtonii helps to establish a minimum date for this node in hypotheses of conifer phylogeny.
Conclusions: As an early member of the extant genus Picea, this seed cone extends the fossil record of Picea to the Valanginian Stage of the Early Cretaceous, ca. 136 Ma, thereby resolving a ghost lineage predicted by molecular divergence analyses, and offers new insight into the evolution of Pinaceae.Keywords: Seed cone, Cladistic analysis, Conifer cones, Picea, Midoriphyllum, Cretaceous, Pinaceae, Northwestern Kamchatka Peninsula, SP NOV Pinaceae, Arctic Canada, Pityostrobus, Axel Heiberg Island, Conifer, Middle eocene, Cathaya Pinaceae, Vancouver Island, Berry comb no
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Pararaucaria carrii sp nov., anatomically preserved evidence for the conifer family cheirolepidiaceae in the northern hemisphere
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 Pararaucaria, 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.This is the publisher’s final pdf. The published article is copyrighted by University of Chicago Press and can be found at: http://www.press.uchicago.edu/index.html.Keywords: Coniferales, Oregon, Pararaucaria, Seed cone, Cheirolepidiaceae, Jurassi
Integrative paleobotany: Affirming the role of fossils in modern plant biology - Introduction and dedication
If you are interested in plant evolution, try this quick exercise: take a phylogenetic tree of the plant kingdom, close your eyes, and point your finger randomly to a node of the phylogeny. Irrespective of the clade to which you are pointing, there is one thing you should know about it: the living representatives of that clade have evolved as a result of a long process in which failed attempts are the rule, and as a result, the diversity of extinct forms accumulated in the fossil record far exceeds that recorded in the extant flora. From this simple concept, Gar W. Rothwell made his career. Because of that, here is a second thing you should know about the plant clade to which you pointed at random: Gar has, more likely than not, contributed information about evolution in that clade at some point in his career. Gar was one of the principal contributors to the revival of paleobotany from a largely descriptive discipline to a vibrant field of investigation at the forefront of modern evolutionary sciences that contributes crucial insights into plant evolution, equal in importance to those provided by genetics and molecular biology. Because of this, the impact of Gar’s scientific contributions reaches far beyond the field of paleobotany, with important implications for wide areas of plant biology, including anatomy and morphology, development, systematics, phylogeny, and evolution. Gar earned a master’s degree in the laboratory of Thomas N. Taylor (University of Illinois at Chicago, 1966) studying Paleozoic seeds in the genus Conostoma (Rothwell and Eggert 1970; Rothwell 1971a). He subsequently earned his PhD degree in the laboratory of Wilson N. Stewart (University of Alberta, 1973), where he reconstructed the plants in the seed fern genus Callistophyton (Rothwell 1972b, 1975, 1980, 1981). His work was instrumental in ushering in studies of fossil plants as whole living organisms, looking at both structure and development. These early experiences launched Gar on a career in plant evolutionary biology that stretched over a half century, during which he occupied positions at the University of Alberta, University of London–Chelsea College, Ohio University, and Oregon State University. Throughout his career, Gar’s scholarly work and contributions have been recognized by numerous awards and honors: the Isabel Cookson Award, the Edgar T. Wherry Award, the Michael A. Cichan Award, the Merit Award of the Botanical Society of America, and honorary membership in the International Organization of Palaeobotany, where he served for 12 years as secretary-treasurer and president.Fil: Escapa, Ignacio Hernán. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Tomescu, Alexandru M. F.. Humboldt State University. Department of Biological Sciences; Estados UnidosFil: Dunn, Michael T.. Cameron University. Department of Agriculture, Biology and Health Science; Estados UnidosFil: Stockey, Ruth A.. State University of Oregon; Estados Unido
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Mesozoic Diversity of Osmundaceae: Osmundacaulis whittlesii sp. nov. in the Early Cretaceous of Western Canada
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 phylogeny
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.This is the publisher’s final pdf. The published article is copyrighted by the University of Chicago Press and can be found at: http://www.jstor.org/action/showPublication?journalCode=intejplanscie.Keywords: Osmundacaulis, Mesozoic, Haida Gwaii, Albian, Osmundaceae, Early Cretaceou
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Plant-Arthropod Interactions in Acanthostrobus edenensis (Cupressaceae), a New Conifer from the Upper Cretaceous of Vancouver Island, British Columbia
Premise of research. A new, morphologically distinct, anatomically preserved conifer assignable to the basal Cupressaceae, which was subject to arthropod infestation during life, has been discovered within a marine carbonate concretion from the Coniacian (Late Cretaceous) Eden Main locality of Vancouver Island, British Columbia. Methods. Specimens were studied from anatomical sections prepared using the classic cellulose acetate peel technique. Pivotal results. This plant, described as Acanthostrobus edenensis gen. et sp. nov., has helically arranged needle leaves and terminal seed cones composed of numerous helically arranged bract/scale complexes dominated by the bract. Both vegetative leaves and bracts display exceptionally long, narrow tips that may have been involved in predator deterrence. The seed cone has diminutive ovuliferous scales with free distal margins; bract/scale complexes bear two to four small, secondarily inverted ovules. Cone tissues contain arthropod feeding galleries surrounded by necrotic tissue and closing tissue (wound periderm) that proliferated throughout the specimen. Conclusions. The new plant is clearly attributable to basal Cupressaceae (Cunninghamioideae, Taiwanioideae, and Athrotaxoideae). While it shares features with extinct Jurassic and Cretaceous Cupressaceae, it exhibits a novel combination of characters that distinguishes it from previously described genera. This discovery expands our understanding of basal cupressaceous diversity and provides insight into conifer-animal interactions during the Cretaceous.Keywords: coneworm,
Dioryctria,
weevil,
Taiwanioideae,
hypersensitive response,
Caridae,
Cunninghamioideae,
AthrotaxoideaeThis is the publisher’s final pdf. The published article is copyrighted by the University of Chicago Press
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Bisexual Flowers from the Coniacian (Late Cretaceous) of Vancouver Island, Canada: Ambiplatanus washingtonensis gen. et sp. nov. (Platanaceae)
PREMISE OF RESEARCH: Anatomically preserved platanaceous inflorescences have been found in rocks of Late
Cretaceous (Coniacian) age at the Eden Main locality on Vancouver Island, British Columbia, Canada.
METHODOLOGY: Specimens occur in calcium carbonate concretions near the base of the Nanaimo Group
(Comox Formation) and are studied with the cellulose acetate peel technique and SEM.
PIVOTAL RESULTS: Inflorescences are small (<5 mm), pedunculate heads, with fewer than 30 flowers per
inflorescence. Both bisexual and unisexual flowers are present on the same inflorescence. Elongate and overarching
tepals enclose the developing gynoecium and androecium at early stages of development. More mature
specimens have individual flowers with at least two whorls of tepals fused toward the base. Flowers have a
whorl of five free stamens, each with short filaments and a sclerotic apical connective extension. In situ pollen
is small, prolate, tricolpate, 11–13 μm in polar diameter, and 8–9 μm in equatorial diameter. In flowers where
it can be observed, the staminal whorl encloses five short, conduplicate, glabrous carpels lacking differentiated
styles but bearing broad, flat apices. The ovary of these carpels is occupied by a single ovule.
CONCLUSIONS: While the Eden Main specimens display a five-parted gynoecial arrangement common in
the pistillate flowers of other Cretaceous platanoids, Ambiplatanus washingtonensis gen. et sp. nov. provides
the first fossil evidence of functional bisexuality in fossil Platanaceae.This is the publisher’s final pdf. The published article is copyrighted by the University of Chicago Press and can be found at: http://www.jstor.org/action/showPublication?journalCode=intejplanscie.Keywords: Cretaceous, Proteales, Platanaceae, Platanu
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Hubbardiastrobus cunninghamioides gen. et sp. nov., Evidence for a Lower Cretaceous Diversification of Cunninghamioid Cupressaceae
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.This is the publisher’s final pdf. The published article is copyrighted by the University of Chicago Press and can be found at: http://www.jstor.org/page/journal/intejplanscie/about.html.Keywords: Ovulate/seed cones, Lower Cretaceous, Conifer, Fossil plants, Cunninghamioid Cupressacea
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