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Welcome to Paleobotany & Vascular Plant Morphology  Arizona State University

Home of the Kathleen Pigg Lab & The Fossil PlantMorphology/Anatomy Collections

dormancy

Our research is focused on studying the evolution, biogeography and diversification of angiosperms and other plants through comparative analysis of exceptionally preserved Tertiary plant fossils and their modern relatives. Currently we are concentrating our efforts on three major floras that document much of the evolutionary history of many important, mostly temperate floral elements: 1) The Late Paleocene Almont and Beicegel Creek flora of central and western North Dakota; 2) The Early Eocene Republic flora of northeastern Washington state and 3) the Middle Miocene flora of Yakima Canyon, Washington state. A common theme in our work is to glean the maximum amount of systematically significant evidence from fossils of these three Lagerstatten, or floras of exceptional preservation. We use this information, along with comparative study of nearest living relatives (NLRs) to follow the changes that occured through time in select taxonomic lineages. We thus add to and clarify aspects of the fossil record, which is an invaluable independent means by which molecular phylogenies can be tested. Information about plant habit and life history, reproductive biology, paleoecology, biogeography and character evolution can futher be inferred from what we find.


ocIn contrast to typical Late Paleocene floras that have relatively few, wide-ranging taxa, the Almont-Beicegel Creek flora has a more diverse assemblage, and considerably more fruits and seeds. In addition to the common “archaic” forms common to the Late Paleocene such as taxodiaceous conifers, Ginkgo, Nordenskioldia, Cercidiphyllaceae, and Platanaceae, Almont contains rare representatives of more tropical taxa that families like Icacinaceae and Menispermaceae that dominate younger fruit and seed floras of the Eocene thermal maximum such as the London Clay and the Clarno nut beds. Almont also documents the early evidence of taxa important to later temperate floras (Acer, Aesculus). The discovery in 2000 of a second outcrop in western North Dakota at Beicegel Creek has added even greater value to the flora because these fossils can be prepared with cellulose acetate peels to reveal greater cellular detail. The unique combination of both exceptional preservation and higher diversity that is known from the Almont/Beicegel Creek assemblage allows us a more complete view of the Late Paleocene as an important time of transition within seed plant, and especially angiosperm diversification.


The Republic flora is also significant because of its high diversity and excellent preservation of compression impression remains from upland lacustrine deposits. As the southernmost flora of the Okanogan Highlands floristic province, Republic hosts many plants with nearest living relatives that survive well in temperate zones because of adaptations such as dormancy mechanisms and shoot differenentiation. We have been documenting features such as leaf heterophylly and long and short shoot differentiation at Republic.  Occuring at the time of the Eocene thermal maximum when most of the world’s flora is of megathermal aspect, Republic was part of a higher elevation flora that was selected for its ability to withstand cooler temperatures. Other plants at Republic, including a diverse assemblage of some of the earliest members of the rose famiy, document the leaf morphological patterns we see in modern hybrid complexes, a reproductive mode common to disturbed habitats today, that may have been a significant mechanism for diversification within this group.

melia plateThe Middle Miocene Yakima Canyon flora offers a glimpse into 15.8 million year old floras of the “last gasp” of the widespread temperate floras before tectonic activities and other drivers of climate change altered the western flora into drier and cooler dconditions.  This flora has many components present today in the southeastern US bald cypress swamps such as taxodiaceous conifers, ferns (Osmunda, Woodwardia), white oaks, the sweet gum Liquidambar, the tupelo gum Paliurus, sycamores, and members of Lythraceae, Meliaceae and Typhaceae. Of slightly older age as the well known Clarkia flora of Idaho, the Yakima Canyon plants occur on the western edge of the Columbia River Basalt Group. Where the Clarkia leaf flora is lacustrine and preserves leaf cuticle, ultrastructal features and even fragments of DNA, the Yakima flora is a rare anatomically preserved fruit and seed flora that provides detailed structural features of Middle Miocene plants. Along with plant structure is evidence of galling, fungal attack, as well as caterpillar frass.

We also include Tertiary plants from additional localities, including the Eocene Princeton chert of British Columbia, and Oligocene Catahoula formation of east Texas.

In addition to these three main floras, we have a longstanding interest in the evolution of isoetalean lycopods. We have worked on isoetalean lycopods from the Late Devonian  (Clevelandodendron) and Mississippian (Lepidodendropsis-like plant), up through the Pennsylvanian (Chaloneria, Mazocarpon) and into Mesozoic (Isoetites) and have provided several reviews of this unusual pteridophyte lineage. The best known members of this lineage, the large lepidodendrid tree, that were specialized for the wettest middle Pennsylvanian coal swamps but died out as their habitat became scarce.  We have been able to help document the presence of smaller, often unbranched lycopods such as Chaloneria that were contemporaneous with the tree lycopods. These cattail sized lycopods were a major component of the Late Pennsylvanian Steubenville coal-ball flora, and are structurally quite similar in plant habit to the Triassic Pleuromeia, Annalepis and other smaller lycopods that often formed monotypic stands.  This lineage that continued to the present day as the unusual aquatic to terrestrial quillwort Isoetes

We also include some additional Pennslvanian plants, including some lyginopterid seed ferns.

Another area we have studied focuses on the anatomically preserved Glossopteris plants of the Late Permian of Australia and Antarctica. This group dominated the Southern Hemisphere and provided some of the most substantial evidence for the theory of continental drift long before the mechanisms of plate tectonics were known. We have described anatomically preserved Glossopteris leaves, each with distinctive anatomical structure that supports our understanding of these plants, often considered a possible precursor to the angiosperms. We have offered the first anatomical evidence of leaf-stem attachment and young developing twig anatomy as well as the description of fossil seeds and pollen structues, all documenting the diversity and biogeography of this important Gondwana group.

In addition to the studies on Glossopteris from Antarctica and Australia, we include a study of a Triassic seed fern frond of Dicroidium.

PLB300uIn addition to our fossil studies, we have a love of being in the woods, desert, mountains, grasslands, and present some of these favorite places and their plants under the project section. This strong interest in the morphological and anatomical diversity of extant plants, how structure mirrors adaptations to environments, has greatly informed our teaching. ASU is located in the Phoenix metropolitan area of the Southwest, in the midst of Sonoran Desert, chaparral and high country floras. Our teaching mission has included plant anatomy student projects that explore these diverse plants, as well as the subtropical to tropical forms planted as ornamentals.  In addition to Plant Anatomy, we also teach Plants and Civilization, Plant Fossils and Evolution, Plant Diversity and Evolution, and have contributed to the teaching of Arizona Flora, Organic Evolution, and a variety of participatory seminars in the plant biology seminar series. 

As part of our  duties in the curation of the ASU Fossil PlantMorphology and Anatomy Collections housed in the new off campus Alameda Facility in Tempe, we are in the process of organizing, catalouging and digitizing images of an important collection of fossil and live plant materials. Strengths include specimens supporting our own research in Tertiary flora as well as Arizona fossils from sites that are no longer available for collecting,  We have a diverse teaching collection with fossils from throughout the world. The live plant collections include research specimens of such interesting desert and higher elevation plants such as Crossosoma, and Bursera seedling development, excellent pollen and wood collections and a fruit and seed collection that is being organized.

Lastly, our interests in plants, both fossil and living grew out of a love of green and woodsy places, fields and creeks of our youth, and the occasional botanical gardens and other adventuresome places of more recent times.  So we also offer some images of our favorite places and their plants.

 

This site is under construction, so check back as new things will be appearing for some time to come.

 

For further information contact Kathleen Pigg at kpigg@asu.edu.