Paleobotanical Section, BSA mination at either end. Also present on some axes are unbranched CONTRIBUTED POSTERS conidiophores and cube-shaped arthrospores produced by seg- mentation of side branches. The fossil ascomycetes provide critical information about this unique group of true fungi, and offer impor- 285 BOYCE, C. KEVIN1*, ANDREW H. KNOLL1, tant characters that can be used in establishing a major lineage of GEORGE D. CODY2, MARILYN L. FOGEL2, AND Euascomycetes with perithecial ascocarps. ROBERT M. HAZEN2 1Harvard Botanical Museum, 26 Oxford St., Cambridge MA 02138; 283 TAYLOR, WILSON A. 2Geophysical Laboratory, Carnegie Institution of Washington, 5251 Dept. of Biology, University of Wisconsin-Eau Claire, Eau Claire, WI Broad Branch Rd., Washington DC 20015 54702-4004 The evolution of tracheids and lignification in early Assessing the earliest putative land plant remains — land plants Cambrian cryptospores natomically preserved land plant fossils from the Lower he pace of discovery of early land plant remains has broad- Devonian Rhynie Chert contain conducting tissues that ened the temporal gap between the first appearance of Arange from dark colored, elongated cells without secondary microfossils and that of megafossils. Representatives of all wall thickenings to tracheids similar to those of extant plants. T Observed differences in conducting cell differentiation may or may major categories of cryptospores (monads, dyads and tetrads) as well as minute trilete spores have been recovered from Middle not correspond to the physiological innovations of lignin biosyn- Cambrian sediments of terrestrial provenance (conservatively, a thesis and deposition. In order to evaluate the degree to which the fifty million year gap). What clues do we have to the affinity of morphological and physiological evolution were coupled in the tis- these microfossils? Those that have been examined so far with the sues of early land plants, three analytical techniques were em- TEM (Bright Angel Shale) possess a three-layered wall that sur- ployed to study anatomically preserved fossils: electron microprobe rounds each member of the unit. While this wall is morphologically analysis to obtain micron-scale resolution of elemental abundances, comparable to that seen in some modern green algal cysts (e.g., isotope ratio mass spectrometry to obtain millimeter-scale resolu- Mychonastes desiccatus, Chlorococcales), the thickness of the indi- tion of carbon isotopic abundances, and X-ray microscopy in con- vidual sporopollenin lamellae differs by a factor of two. The pres- junction with nuclear magnetic resonance spectroscopy to obtain ence of thinner fossil lamellae in somewhat younger specimens micron-scale resolution of the preservation of organic molecular suggests that preservation is not a limitation. Comparisons with functionality. Studies demonstrate that original organics are not other fossil and modern sporopollenin-containing propagules as homogenized during diagenesis and are preserved in place with well as less equivocal cryptospore remains from the Middle sufficient spatial resolution for paleobiological investigations. Tissue- Cambrian Rogersville Shale may provide some of the first clues to specific isotopic and organic chemistry of Rhynie Chert plants sug- the possible identity of these earliest land plant pioneers. gests that the anatomical evolution of tracheid secondary thicken- ings and the biochemical evolution of lignin synthesis were origi- 284 TOMESCU, ALEXANDRU MIHAIL FLORIAN* AND nally independent: the earliest vascular thickenings were unlignified GAR W. ROTHWELL and cell wall lignification may have first appeared in other tissues. Dept. of Environmental and Plant Biology, Ohio University, Porter Only later were the anatomical and biochemical characteristics Hall, Athens, OH 45701 coupled to produce true tracheids like those of all living vascular plants. Exploring the cladistic relationships of sphenopsids hylogenetic relationships of Equisetum are firmly established 286 HANSEN, AMANDA, L.* AND KATHLEEN, B. PIGG within the euphyllophytes, but more detailed resolution of Dept. of Plant Biology, Arizona State University, Box 1601, Tempe, Psphenopsid phylogeny has not been achieved. Traditional AZ, 85287-1601 paleobotanical studies recognize five groups of sphenopsids Taxodiaceous conifers from the middle Miocene including Hyeniales, Pseudoborniales, Calamitales, Yakima Canyon flora, Washington State, USA Sphenophyllales and Equisetales, but these hypothesized relation- ships have not been fully tested using cladistic methodology. natomically preserved taxodiaceous conifer remains are Sphenopsids plus cladoxylalean/zygopterid ”ferns” resolved as the described from the middle Miocene Yakima Canyon flora of sister group to lignophytes in an analysis of euphyllophytes by Acentral Washington State, USA. These remains include ovu- Rothwell (1999), but Equisetum nested among the ferns as the sis- late cones and seeds, isolated cone scales, wood, foliage and twigs ter to marattialeans in the recent analysis of living plants by Pryer et of possible taxodiaceous affinity. Some seeds contain mature al. (2001). Relationships among sphenopsid groups are equally embryos. While many specimens are contained within the chert uncertain. Whereas Equisetales and Calamitales are widely matrix, others have been weathered out and are preserved in the regarded as closely related, their relationships to Pseudobornia, round, showing external morphological features. Isolated cone Hyenia and Sphenophyllum are far less certain. Indeed, Stewart scales range from 9-11 mm high x 11-12 mm wide x 4 mm thick (1980) has hypothesized that Sphenophyllum may be more closely and bear two seed depressions on their inner surface. The apoph- related to lycophytes than to euphyllophytes. To test these com- ysis has an umbo that protrudes 3 mm from the outer surface of peting hypotheses, we have undertaken a numerical cladistic analy- the scale and a dentate margin on the apical half. Isolated seeds are sis of representative rhyniophytes, zosterophylls, lycophytes, and winged, elongate, 11.5-13 mm long x 6 mm wide x 3-4 mm high, euphyllophytes, including all of the hypothesized groups of and are triangular in cross section. Foliage shows prominent stom- sphenopsids. Relationships of these taxa are resolved using a matrix atal furrows. The taxodiaceous remains at Yakima Canyon occur of more than 100 morphological characters. Principal questions commonly with the ferns Osmunda wehrii Miller, Woodwardia vir- addressed by this analysis include the following. Do the sphenop- ginica (L.) J. E. Smith, and a third small filicalean form and are con- sids (as traditionally circumscribed) form a clade? What are the sis- siderably more abundant than the previously described pine from ter group relationships of the sphenopsid clade that includes this same site, Pinus foisyi Miller. Equisetum? And, are Sphenophyllales euphyllophytes, or do they nest within the zosterophyll/lycophyte clade? ABSTRACTS 71 Paleobotanical Section, BSA 287 HENRY, APRIL M.* AND KATHLEEN B. PIGG 289 RADTKE, MEGHAN G.1*, KATHLEEN B. PIGG1, AND Department of Plant Biology, Arizona State University, Box 871601, WESLEY WEHR2 Tempe, AZ 85287-1601 1Dept. of Plant Biology, Box 871601, Arizona State University, Tempe, AZ, 85287-1601; 2Burke Museum of Natural History and Hamamelidaceous infructescences from the Late Culture, University of Washington, Seattle, WA, 98195 Paleocene Almont, North Dakota flora Fossil Corylopsis and other Hamamelidaceae-like nfructescences of Hamamelidaceae are described from the leaves from the middle Eocene flora of Republic, Late Paleocene Almont flora of North Dakota. The study is Ibased on forty-nine specimens that are preserved morphologi- Washington, USA cally with some details of the fruit wall anatomy. The largest fossil leaf of Corylopsis Sieb. & Zucc., (Hamamelidaceae; infructescence consists of up to ten sessile fruits attached to a Saxafragoid clade) and several other Hamamelidaceae-like peduncular axis 8 cm long x 0.5 cm thick. Biloculate fruits are leaves are described from the middle Eocene (49-50 MA) roughly square in outline, around 10-12 mm in dimension, and A Republic flora of eastern Washington State, USA. The fossil have persistent, recurved styles on the distal faces of the carpels. Corylopsis leaf is similar to several extant species, particularly with Fruit walls are composed of elongate, interwoven fibrous cells sim- the presence of prominent agrophic veins and ladder-rung-like ter- ilar to those seen in extant Hamamelis. Ellipsoid to ovoid locules are tiaries at right angles to the secondaries. The leaf is 1.9 cm wide, of 5-10 mm long x 3-5 mm wide. Most specimens probably represent incomplete length, with an asymmetrical base. Teeth are concave senescent fruits lacking seeds, that may have dehisced explosively apical, straight basal, with simple apices. Several other like those of some modern Hamamelidaceae. Hamamelidaceae-like leaves present in the Republic flora are sim- ple, symmetric, range from 2.1 to 8.7 cm in length, from 0.9 to 4.3 288 MCKOWN, ATHENA D.1*, RUTH A. STOCKEY2, AND cm in width, have a L/W ratio of 2.0 to 2.3 and are generally ellip- CHARLES E. SCHWEGER3 tic in shape. Bases are typically asymmetric and cordate to 1Dept. of Biological Sciences, University of Alberta, Edmonton, AB, rounded. Leaf apices are not preserved. Venation is craspedodro- T6G 2E9, Canada; 2Dept. of Biological Sciences, University of mous with secondary veins produced