Edith L. Taylor

The biology and evolution of fossil plants

Precambrian life fungi, bacteria and lichens algae bryophytes terrestrialization of the land the structure and organization of vascular plants early land plants with conducting tissue lycopods sphenophytes ferns progymnosperms origin and evolution of the seed habit palaeozoic seed ferns mesozoic seed ferns palaeozoic and mesozoic foliage cycadophytes ginkgophytes gymnsoperms with obscure affinities cordaites conifers flowering plants plant/animal interactions.

Fungi from the Rhynie chert: a view from the dark side

The exquisite preservation of organisms in the Early Devonian Rhynie chert ecosystem has permitted the documentation of the morphology and life history biology of fungi belonging to several major taxonomic groups (e.g., Chytridiomycota, Ascomycota, Glomeromycota). The Rhynie chert also provides the first unequivocal evidence in the fossil record of fungal interactions that can in turn be compared with those in modern ecosystems. These interactions in the Rhynie chert involve both green algae and macroplants, with examples of saprophytism, parasitism, and mutualism, including the earliest mycorrhizal associations and lichen symbiosis known to date in the fossil record. Especially significant are several types of specific host responses to fungal infection that indicate that these plants had already evolved methods of defence similar and perhaps analogous to those of extant plants. This suggests that mechanisms underlying the establishment and sustenance of associations of fungi with land plants were well in place prior to the Early Devonian. In addition, a more complete understanding of the microbial organisms involved in this complex ecosystem can also provide calibration points for phylogenies based on molecular data analysis. The richness of the microbial community in the Rhynie chert holds tremendous potential for documenting additional fungal groups, which permits speculation about further interactions with abiotic and biotic components of the environment.

The present is not the key to the past: a polar forest from the permian of antarctica.

An in situ Upper Permian fossil forest in the central Transantarctic Mountains near the Beardmore Glacier includes 15 permineralized trunks in growth position; the paleolatitude of the site was approximately 80� to 85� south. Numerous leaves of the seed fern Glossopteris are present in the shale in which the trunks are rooted. The trunks are permineralized and tree rings reveal that the forest was a rapidly growing and young forest, persisting in an equable, strongly seasonal climate—a scenario that does not fit with some climate reconstructions for this time period.

Depositional setting and paleobotany of Permian and Triassic permineralized peat from the central Transantarctic Mountains, Antarctica

Abstract Silicified peat is known from two sites in the central Transantarctic Mountains. Both are within a 2-km-thick Permo-Triassic sandstone-shale sequence that was deposited by braided streams in a rapidly subsiding foreland basin along the paleo-Pacific margin of Antarctica. Upper Permian permineralized peat occurs as scattered boulders just above a channel-form sandstone in the upper part of the Buckley Formation on Skaar Ridge overlooking the Beardmore Glacier. These boulders are erosional remnants of fine-grained deposits that accumulated in shallow lakes or swamps on a flood plain. At Fremouw Peak, the peat occurs near the top of the Fremouw Formation in strata that are probably Middle to Late Triassic in age. The peat consists of large blocks that were rafted into a sandy braided stream channel during a flood and then stranded and buried as flood waters receded. Both sites are characterized by exceptionally well-preserved plant material, although the composition and diversity of the two floras are very different. Permineralization apparently took place rapidly and was enhanced by the dissolution of siliceous volcanic detritus that is abundant in both formations.

Correlation of permian and triassic palynomorph assemblages from the central Transantarctic Mountains, Antarctica

from the overlying Fremouw and Falla Formations (Triassic) were also examined. The Buckley assemblages are interpreted as Late Permian (Australian Stage 5). Silicified peat from the Fremouw Formation (Early-Middle Triassic) yielded an assemblage indicating a possible Anisian age (Middle Triassic). Shales and shaley coals from the Falla Formation (Late Triassic) contained assemblages correlative with possible Norian (Late Triassic) sequences in Australia and Tasmania. Permian-Triassic palynofloras in Antarctica show greater similarity with Australian assemblages than with those from other Gondwana continents.

Osmunda (Osmundaceae) from the Triassic of Antarctica: an example of evolutionary stasis.

Compressed specimens of the fern Osmunda are described from the Triassic of the Allan Hills, Antarctica. The specimens consist of a once pinnate, deeply pinnatifid fertile frond as well as several sterile specimens. Six pinnae are present on the partial fertile rachis, with two sterile pinnae above four fertile pinnae. Both sterile and fertile specimens are virtually identical to the modern species Osmunda claytoniana. Entire fronds are fragmentary; the longest is 21 cm in length. Sterile pinnae are alternate and deeply pinnatifid, with slightly toothed pinnules and dichotomous venation. Fertile pinnae are 1-1.3 cm long, once pinnate, and lack vegetative lamina. Sporangia are clustered, each 300-375 um in diameter, and possess a transverse annulus 6-8 cells long; dehiscence is by a vertical slit. Fronds arise from a rhizome 4 cm long by 1 cm wide; two croziers are present on the rhizome. Two frond segments up to 6 cm long and three deeply pinnatifid pinnae are present on the uppermost part of one rachis. Pinnules are ~4 mm long and 2-3 mm wide. The presence of this Osmunda species in the Triassic demonstrates stasis of frond morphology, both fertile and vegetative, for the genus.

How Paleozoic Vines and Lianas Got off the Ground: On Scrambling and Climbing Carboniferous–Early Permian Pteridosperms

Late Paleozoic pteridosperms displayed various growth habits, including arborescent, leaning, and scrambling and/or climbing forms. This article reviews information gathered to date on vine- and liana-like forms among these plants, based on impression/compression material and cuticle preparations from the Upper Carboniferous and Lower Permian of Europe and North America. Vine- and liana-like pteridosperms used various modes of attachment for both anchorage and support. Such adaptations are very similar (and perhaps analogous) to those that exist in extant angiosperms and include hooks, leaflet tendrils, tendrils terminating in adhesive pads, and aerial adventitious roots. A number of morphological features of scrambling/climbing pteridosperms (e.g., tiny, deeply sunken stomata, marginal water pits, various types of secretory structures, and heterophylly) are considered as they relate to the autecological significance where they may be related to special physiological requirements necessary in the scrambling/climbing growth habit. We hypothesize that scrambling and/or climbing pteridosperms may have played an important role in some of the late Paleozoic coal-swamp forest ecosystems, perhaps even comparable to the role of angiospermous vines/lianas in tropical and subtropical forest ecosystems today.ZusammenfassungJungpaläozoische Pteridospermen besaßen unterschiedliche Wuchsformen; einige Taxa waren freistehende Bäume, andere Formen stützten ihre Körper durch Anlehnen, wieder andere waren Spreizklimmer oder Kletterpflanzen. Die vorliegende Arbeit gibt eine Übersicht über Spreizklimmer und Kletterer unter den Abdrucktaxa oberkarbonischer und unterpermischer Pteridospermen aus Europa und Nordamerika. Anhand von Abdruckfossilien und Kutikulapräparationen kann demonstriert werden, daß spreizklimmende/kletternde Pteridospermen verschiedene Kletterhilfen (z.B. Haken, Blattfadenranken, Haftscheibenranken, Adventivwurzeln) zur Verankerung ihrer Körper an Stützen ausbildeten, die denen heutiger spreizklimmender/kletternder Angiospermen sehr ähnlich sind und vielleicht analoge Bildungen darstellen. Auffällige Merkmale spreizklimmender/kletternder Pteridospermen (z.B. winzige, tief eingesenkte Stomata, marginale Wassergruben, verschiedene Sekretionseinrichtungen, Heterophyllie) werden im Zusammenhang mit ihrer möglichen ökologischen Bedeutung diskutiert—einige stellen offensichtlich Adaptationen an die besonderen Anforderungen und Limitationen der spreizklimmenden/kletternden Lebensweise dar. Wir vermuten, daß spreizklimmende und kletternde Pteridospermen in einigen jungpaläozoischen Sumpfwald-Ökosystemen eine wichtige Rolle gespielt haben, die vielleicht sogar mit der Rolle spreizklimmender und kletternder Angiospermen in heutigen tropischen und subtropischen Waldökosystemen vergleichbar ist.

Late Permian palynomorphs from the Buckley Formation, central Transantarctic Mountains, Antarctica

Abstract Thirty species of dispersed plant microfossils were recovered from Glossopteris -bearing shales and coals of the Buckley Formation (Permian) on Mount Achernar in the central Transantarctic Mountains, Antarctica. Palynoassemblages of variable diversity, thermal maturity and preservation were also recovered from other Buckley outcrops at Mount Picciotto, Mount Sirius and Coalsack Bluff. Although Jurassic volcanic activity in the region thermally altered all palynomorphs, they could usually be sufficiently cleared with Schulzes Solution for photomicrography and identification. Recovered taxa, some of which suggest a Late Permian age (equivalent to Australian Stage 5) for the section, include: Didecitriletes ericianus, Lophotriletes novicus, Marsupipollenites triradiatus, Praecolpatites sinuosus , Retusotriletes nigritellus, Protohaploxypinus amplus, P. limpidus, P. microcorpus, P. samoilovichii, Striatopodocarpites fusus, S. cancellatus and S. gondwanensis . These taxa provide the first palynological evidence supporting correlation of this part of the Buckley Formation with previously published Late Permian assemblages from the Nilsen Plateau, Ohio Range and Prince Charles Mountains in Antarctica.

Cataphylls of the Middle Triassic cycad Antarcticycas schopfii and new insights into cycad evolution

Cataphylls associated with the Middle Triassic stem genus Antarcticycas are described, and their impact on understanding cycad evolution is discussed. The cataphylls of Antarcticycas are triangular in outline and flattened adaxially with lateral flanges. The outer surfaces are covered with a ramentum of filamentous hairs, the epidermis is a single cell layer thick, and the ground tissue is parenchymatous with mucilage canals and sclereids. Vascular bundles form a distinct inverted omega-shaped pattern characteristic of the Cycadales observed in petioles of extant species. The structures in Antarcticycas are interpreted as cataphylls based on overall morphology, presence of straight vascular strands in the cortex of the associated stem, and lack of fascicular cambia in the vascular bundles. Because much of the overall diversity of Cycadales is represented by fossils, integrating fossil taxa into explicit phylogenetic hypotheses is important for understanding cycad evolution. Therefore, character and minimum age mapping were performed on a phylogeny of extant and fossil taxa including Antarcticycas. The results suggest that major extant lineages of Cycadales had diverged by the Permian to Triassic and that certain synapomorphies for Cycadales had evolved by the Permian. Evidence of insect feeding on Antarcticycas suggests that associations between cycads and insects are ancient.

New perspectives on the Mesozoic seed fern order Corystospermales based on attached organs from the Triassic of Antarctica

A new Triassic corystosperm is described from the Shackleton Glacier region of Antarctica. The compression fossils include cupulate organs (Umkomasia uniramia) and leaves (Dicroidium odontopteroides) attached to short shoot-bearing branches. The cupulate organs occur in groups near the apices of the short shoots, and each consists of a single axis with a pair of bracts and a subapical whorl of five to eight ovoid cupules. This unique architecture indicates that the cupules are individual megasporophylls rather than leaflets of a compound megasporophyll. A branch bearing an attached D. odontopteroides leaf provides the first unequivocal evidence that Umkomasia cupulate organs and Dicroidium leaves were produced by the same plants. Although this had previously been assumed based on organ associations, the new specimens are important in demonstrating that a single species of corystosperm produced the unique cupulate organs described here and the geographically and stratigraphically widespread and common D. odontopteroides leaf. Therefore, biostratigraphic, paleoecological, and phylogenetic studies that treat Dicroidium leaf morphospecies as proxies for biological species of entire plants should be reconsidered. Phylogenetic analysis suggests that the corystosperm cupule is an unlikely homologue for the angiosperm carpel or outer integument.