NAPC 2001

Abstracts, Br - Bu
(5/17/01)

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GRAPHIC DISPLAY OF THE UPPER DEVONIAN BIOSTRATIGRAPHY IN THE CENTRAL-SOUTHERN APPALACHIAN BASIN

BRAME, Roderic I., Dept. of Geological Sciences, Wright State University, Dayton, OH, USA

24,000 macrofossils were collected from Upper Devonian nearshore clastic marine sediments in the Valley and Ridge Province of the Central-Southern Appalachian basin in Virginia. One hundred fifty taxa were identified and cataloged. Taxa include: brachiopods (83), bivalves (39), gastropods (16), cephalopods, tentaculitids, echinoderms, and arthropods. Collections were made at eight of the most complete sections that could be found in the region. The field data were then converted into an electronic format that can be easily followed in future studies. The biostratigraphic data from each section was combined to produce a composite standard reference section. The standard reference section and additional data are displayed on an Excel spreadsheet. The spreadsheet contains the biostratigraphic elevation of each sample, the range of each taxon, the total number of individuals of each taxon for each elevation, and the total number of individuals of all the taxa for each elevation. Sixteen local biozones were chosen based on first occurrences except for zones with significant numbers of last occurrences. The graph offers a spectacular high resolution and highly detailed view of the Frasnian/Famennian extinction event. The graph shows two distinctive events just before the Frasnian/Famennian boundary that I believe are equivalent to the timing of the Kellwasser events recognized in Germany by E. Schindler (1993). 50% of the brachiopods go extinct during the two events while the bivalves do not seem to be affected. This data will be used to measure biodiversity, analyze the Frasnian/Famennian extinction, develop a sequence stratigraphic model for the Central-Southern Appalachian basin, and to develop a more regional biostratigraphic reference section.

ENVIRONMENTAL MICROPALEONTOLOGY REVISED: CHEMICO-ECOLOGICAL APPROACH

BRESLER, Vladimir, Institute for Nature Conservation Research, Dept. of Zoology, Tel Aviv University, Israel; and Valentina Yanko-Hombach, Avalon Institute of Applied Science, Winnipeg, MB, Canada

Micropaleontology discovers and describes micro- and meioorganisms of different ages. To revive these microfossils, i.e., to reconstruct the interaction between different species and their environment (environmental micropaleontology), the chemical-ecological approach was used. The experimental and field studies of eastern Mediterranean foraminifera were focused on the interaction of foraminifera with xenobiotics and ability of foraminifera to protect themselves against xenobiotics using various defense mechanisms (Bresler and Yanko, 1995; Bresler and Yanko-Hombach, 2000). This approach was based on the assumption that if anti-xenobiotic defense mechanisms fail to protect the organisms, populations, or ecosystems, the effect of xenobiotics would be shown by damage to various levels of biological structures of organisms, from molecular to ecosystems. Thus, the investigation of anti-xenobiotic defense mechanisms of foraminifera reflects the adaptation of studied species to their environment. Special devices together with molecular, biophysical, cytophysiological, biochemical and morphological vital microfluorometrical methods were used. This enabled us to evaluate the health of foraminifera and to perform early warning monitoring, environmental risk assessment and a prognostication of the studied area.

Numerous foraminiferal defense systems are similar to those of multicellular organisms. This reflects the ancient origin and evolutionary importance of foraminiferal defense mechanisms, which integrated specimens and species in ecosystems and determines their structure and stability. At least one of these defense mechanisms (xenobiotic deposition into foraminiferal test) can be examined in fossils. Thus, a further comparative study of anti-xenobiotic defense mechanisms in modern living microorganisms against the main xenobiotics in these environments may be used as reliable tool for the chemical-ecological analysis of fossils and further development of environmental micropaleontology.

APPLICATION OF MOLLUSCAN PALEOECOLOGY TO THE EVERGLADES RESTORATION PROJECT: DECADAL TO CENTENNIAL SCALE CHANGE IN FLORIDA BAY

BREWSTER-WINGARD, G. Lynn, U.S. Geological Survey, Reston, VA, USA

Molluscan assemblages from shallow sediment cores taken in Florida Bay, Everglades National Park, have provided historical data on salinity, sub-aquatic vegetation, water quality, and other environmental parameters. The historical perspective provided by traditional paleoecologic techniques is essential to restoration efforts in endangered ecosystems. The south Florida ecosystem has been profoundly affected during the last century by construction that disrupted natural water flow patterns, by increased demands on water from a booming population, and by an economy strongly dependent on agriculture and tourism. Paleoecologic data are used to delineate the natural range of variation that occurred within the system prior to significant human alteration. These data can be contrasted with changes that have occurred since the system has been altered to provide land managers with realistic success criteria for restoration.

Molluscan data indicate that significant changes occurred in the latter half of the 20th century in Florida Bay. Brachidontes exustus, a euryhaline mussel tolerant of low water quality and increased salinity fluctuations, constitutes greater than 80% of the molluscan assemblage in the upper portions of six cores. Corresponding decreases in molluscan abundance and faunal richness also have occurred during the last forty years. These findings indicate a system under stress. Furthermore, the molluscan assemblages indicate increasing salinities throughout the 20th century in the northern transition zone of Florida Bay near the freshwater outflow. The molluscan epiphytal species indicate that subaquatic vegetation has varied over the last two centuries. Patterns of change leading up to the 1987 seagrass die-off are repeated downcore, implying that die-offs have occurred prior to any significant human influence. In addition, the molluscan epiphytes in cores from isolated basins show similar patterns of change, which indicates common factors are affecting the faunas and, presumably, the vegetation they live on.

THE IMPACT OF FOSSIL CALIBRATION CHOICE IN MOLECULAR DIVERGENCE ESTIMATION

BROCHU, Christopher A., Dept. of Geoscience, University of Iowa, Iowa City, IA, USA

Recent comparisons of crocodylian fossil appearances and sequence data confirm recent suspicions that using a single divergence to calibrate a groupwide clock can be dangerous. Rate estimates for mitochondrial genes vary within an order of magnitude depending on the species-pair comparison used, with comparisons from more recently diverged species uniformly suggesting significantly higher rates of evolution and, when used to calibrate a clock, more ancient divergence time estimates throughout the group. Multiple hits per site will increase with time, causing an apparent rate slowdown when older divergences are used, and for the same species pair, the divergence time estimate can vary over 150 million years depending on whether fast or slow rates are used. Likelihood corrections to the data reduce the differences between comparisons, but do not remove them, and some unlikely divergence time estimates—sometimes predating first occurrences in the fossil record—can still result from some calibrations. There are problems when alligatorid comparisons are used as calibrations, regardless of how old the divergence is, because relative rate tests suggest higher evolutionary rates for alligatorids; moreover, some alligatorid clades are known to have significant ghost lineages, inflating molecular rate estimates. Alligatorids also demonstrate the importance of taxonomic revision when applying fossil calibrations, as phylogenetic reinterpretations more than quadruple the first appearance age for some alligatorid lineages. This highlights the importance of group-wide taxonomic sampling (including fossils) and careful consideration of known geographic or facies biases for the group's record.

PHYLOGENETIC REVISION AND FOSSIL DIVERGENCE
ESTIMATES: WHEN IS A CONFLICT NOT A CONFLICT?

BROCHU, Christopher A., and Colin D. Sumrall, Dept. of Geoscience, University of Iowa, Iowa City, IA, USA; and Jessica M. Theodor, Dept. of Organismic Biology, Ecology, and Evolution, University of California, Los Angeles, CA, USA

Different sources of temporal information—the stratigraphic distribution of fossils and molecular distances between extant species—can yield very different estimates of divergence timing. But these do not represent real "conflict" between data sets, as our temporal estimates are limited by known incompleteness (the fossil record) and labile assumptions (a priori estimates of molecular evolutionary rate). Researchers are sometimes misled by imprecise language, leading to a failure to address the same phylogenetic question with different data sets. And although all aspects of divergence timing estimation, including molecular clock calibration, ultimately rely on first appearance data from the fossil record, the standard compendia used to obtain fossil first appearance data have not always kept abreast of new discoveries or taxonomic revisions accompanying applications of new phylogenetic methods to extinct clades. Worse, rigorous phylogenetic methods have not been applied to many prominent fossil groups, forcing comparisons between molecular estimates (which are inherently phylogenetic) and nonmolecular patterns that may reflect stratigraphic distributions or a priori process expectations of evolution rather than phylogeny. This can lead to miscalibrations of molecular clocks, but it can also cause researchers to find "conflict" where none really exists, as the patterns being compared are nonanalogous reflections of very different underlying processes. Many famous cases of divergence timing "conflict" actually represent cases of miscommunication because the fossil divergence estimates were not based on hypothesis of phylogeny; real incongruence between molecules and fossils can only occur if the fossils are considered in an explicitly phylogenetic framework.

ZOOPHYCOS: STRUCTURAL AND ETHOLOGIC OVERVIEW

BROMLEY, Richard G., Geological Institute, University of Copenhagen, Denmark

Truly a complex trace fossil, the venerable ichnogenus Zoophycos is, as they say, "in need of revision." But how? We need to understand the trace fossil better, before we undertake a taxonomic revision.

The morphology of the trace fossil is highly variable, both through time and within individuals. Several names, usually considered synonyms of Zoophycos, are available for these variants, but their occurrence within single individuals is not suggestive of synonymy. Perhaps these heterogeneous individuals should be regarded as compound trace fossils.

Zoophycos also has been considered ethologically diverse, and some authors have suggested more than one behavioral style within some individual specimens. Suggestions for functions for the structures include deposit feeding, surface-detritus feeding, constructional ballast, waste disposal, cache-building, gardening—the scope is large. Some spectacular individuals will be singled out for scrutiny. Can such wide diversity, if genuine, be crowded into a single ichnogenus?

THE EVOLUTIONARY HISTORY OF THE NIMRAVIDAE (CARNIVORA) IN THE JOHN DAY BASIN OF OREGON

BRYANT, Harold N., Royal Saskatchewan Museum, Regina, SK, Canada; and Theodore J. Fremd, John Day Fossil Beds National Monument, Kimberly, OR, USA

The Nimravidae is an extinct clade of cat-like carnivorans of late Eocene to late Miocene age. The John Day Basin plays a pivotal role in our understanding of nimravid evolution because the latter stages of the initial North American radiation of this clade are best preserved in its early Arikareean depositional sequence. Six of eleven North American nimravinae species recognized in a recent systematic review are known from the John Day (Hoplophoneus primaevus, Eusmilus cerebralis, Pogonodon platycopis, Nimravus brachyops, Dinictis cyclops, Dinaelurus crassus); the latter two species are known only from this area. Although the sources of early collections from the John Day, including the type specimens of five of the above species, are poorly documented, stratigraphically controlled collecting since the mid 1980s, together with the dating of tuffs, has provided a much improved biostratigraphic and temporal framework for interpreting nimravid evolution.

The John Day sequence documents the last five million years of nimravine history (30­25 Mya), and provides an opportunity to follow evolutionary trends and extinction events in this clade within a limited geographic area. Nimravid diversity is high in the earliest portion of the early Arikareean (below the Picture Gorge Ignimbrite; >28.7 Mya); at least the first four species in the above list are present. Later in the early Arikareean, species diversity drops considerably (leaving only the Pogonodon lineage, for which there is good stratigraphic control, and possibly Dinictis cyclops and Dinaelurus crassus). With the improved temporal resolution in the John Day sequence, the involvement of possible causal factors, such as climatic and environmental change and competitive exclusion, in the extinction of the nimravine clade can begin to be assessed. Continued collecting will lead to further refinement in the timing of evolutionary events, and an increasing ability to address these issues in a rigorous fashion.

FOSSIL FUTURES: PRESERVING FOSSILS FROM PUBLIC LANDS—PANEL DISCUSSION WITH REPRESENTATIVES OF FEDERAL LAND MANAGEMENT AGENCIES

BRYANT, Laurie, and Mike O'Neill, Bureau of Land Management, USA; Lucia Kuizon, USDA Forest Service, USA; H. Gregory McDonald, National Park Service, USA; Sally Shelton, National Museum of Natural History, Smithsonian Institution, USA; and Theodore J. Fremd, John Day National Monument, Kimberly, OR, USA

Fossils from federal lands have contributed significantly to scientific research and public education for investigating and understanding the history of life on earth. Most paleontological collections originating from federal lands are housed in non-federal facilities throughout the country, and held in trust for the benefit of the public. These institutions provide expertise for the study, care and preservation of federal fossil specimens; provide access to other researchers and scientists; and make collections accessible to all segments of the public not otherwise able to view such specimens. The relationship of federal agencies with non-federal curatorial facilities, both public and private, is crucial to the continued study, availability, management, protection, and interpretation of this shared natural heritage.

Federal lands are administered by a variety of agencies created for a specific purpose, each with its own legislative mandate as to how these lands will be managed. Despite these unique mandates, Department of the Interior agencies, U.S. Forest Service and the Smithsonian Institution have made a commitment to develop a unified Federal policy for storing and preserving fossils collected from federal lands. The goals are to develop consistent standards for the professional long-term care of fossil collections that maximize the availability of fossils for research and scientific study, and to provide access to information resulting from this research to the general public in the form of exhibits and educational programs. Recommendations include new and continuing partnerships with curatorial facilities; enhanced use of online databases, images and other information technology; and an increased emphasis on stewardship opportunities.

The panel discussion will provide an open dialog that will cover differences in philosophy of the various land management agencies, their historical relationships with non-federal repositories, current legal requirements of accountability for fossils from public lands, and how these affect non-federal repositories.

EARLY EVOLUTION OF A DOMINANT CARIBBEAN REEF CORAL: MORPHOMETRICS AND PHYLOGENETIC ANALYSIS OF EARLY PLIOCENE MONTASTRAEA FROM THE DOMINICAN REPUBLIC

BUDD, Ann F., Dept. of Geoscience, University of Iowa, Iowa City, IA, USA

The early evolution of a dominant Caribbean reef coral, the Montastraea "annularis" species complex, is traced using morphometric and phylogenetic approaches on specimens collected in the early Pliocene of the Dominican Republic and the Plio-Pleistocene of Costa Rica and Panama. To distinguish species, new landmark methods are developed by comparisons with genetically characterized modern colonies from Panama. The landmarks comprise 27 spatially homologous points, which define the thickness and structure of the corallite wall and associated costosepta. Bookstein size and shape coordinates are analyzed using cluster analysis and canonical discriminant analysis, and three morphotypes are distinguished in the Pliocene and ten in the Plio-Pleistocene. Cladistic analyses are performed using characters derived partially from morphometric data. Homology is assessed using microstructure. The results reveal two or more distinct evolutionary groups. One group contains one modern species, and the other contains a second; the relationships of the third are poorly resolved.

High numbers of plesiomorphic taxa, long range extensions, and lack of agreement with genetic data indicate that the new characters alone are inadequate for interpreting evolutionary relationships. Longitudinal characters involving the dissepiments and columella offer promise for increasing resolution. Preliminary results suggest that the three modern species of the M. "annularis" complex arose prior to accelerated extinction at the end of Plio-Pleistocene faunal turnover of Caribbean reef corals, and two may have originated younger than 4 Ma. Three static and possibly ancestral species occur in the Pliocene of the Dominican Republic; whereas six or more sister species are represented in Plio-Pleistocene sequences in Costa Rica and Panama. Coexistence of predominantly pre- and post-turnover clades may have been responsible for the high diversity observed within the complex during turnover.

A NEW STEM-ARACHNATE FROM THE SIRIUS PASSET (LOWER CAMBRIAN OF NORTH GREENLAND) AND THE BASAL EUARTHROPOD PROBLEM

BUDD, Graham E., Dept. of Earth Sciences (Historical Geology and Palaeontology), University of Uppsala, Uppsala, Sweden

A new crown-group euarthropod is presented from the Lower Cambrian Sirius Passet fauna of North Greenland. It is one of the most common taxa in the present collections from the Sirius Passet fauna, being represented by some 1700 specimens out of an estimated total of 8500 fossils (19%). Much internal anatomy of the fossil has been preserved, although interpretation of the preserved structures has been hampered by their remarkably variable appearance in different specimens. A model for the internal architecture of the animal is nevertheless proposed, which recognizes the preservation of apodemes, musculature and the gut, and a complex internal skeleton, providing the most complete picture of the internal anatomy of any Cambrian arthropod. This morphology complements that preserved in the Chengjiang and Burgess Shale faunas and offers a secure basis for reconstruction of basal arthropod phylogeny, in particular in elucidating the split between crown-group euarthropods (especially stem-group arachnates) and taxa at the top of the stem group. However, the vexed question of basal head segmentation patterns in euarthropods remains open to several interpretations.

ESTIMATING BIODIVERSITY IN LIGHT OF HETEROGENEOUS SAMPLING INTENSITIES: THE RELATIONSHIP
BETWEEN TAXON-OCCURRENCE SUBSAMPLING
METHODS AND ALPHA AND BETA DIVERSITY

BUSH, Andrew M., Molly J. Markey, and Charles R. Marshall, Dept. of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA

Estimates of biologic diversity depend on sampling intensity. If within-locality abundance data are available, a two-step standardization method (an equal number of specimens per list and an equal number of lists) will best normalize for heterogeneous sampling. Several proposed subsampling methods require only presence-absence data, but it is unclear to what extent they provide reasonable standardization. We explore the relationships between the subsampling curves generated by these methods and alpha and beta diversity. Alpha diversity is here equated with the mean number of taxa over a set of lists, and beta is the total number of taxa divided by alpha (a common definition well-suited to this type of data). The relationships between the various subsampling curves and alpha and beta diversity may be demonstrated using the curve that relates beta diversity to the number of lists in a data set. Multiplying values of beta on this curve by alpha produces the by-list (unweighted) subsampling curve. Multiplying beta and the number of samples by alpha produces the by-list (weighted by occurrence) curve, which is nearly identical to the rarefaction-by-occurrence curve. Multiplying beta by alpha and the number of samples by alpha squared produces the by-list (weighted by occurrences squared) method. These relationships are exact if all lists contain an equal number of taxa. Heterogeneity in list length only substantially affects the occurrences-squared curve. We use these relationships to show how each method will respond to changes in alpha and beta diversity. If within-locality sampling intensity is constant, all methods will accurately reflect diversity changes driven by beta, but the weighted subsampling methods will damp changes driven by alpha. The unweighted method is most sensitive to changes in sampling intensity. Thus, all methods will fail under some circumstances, and these circumstances depend on the ways in which diversity structure and sampling intensity vary in time and space.

PALEONTOLOGY AND PALEOECOLOGY OF THE ARCO HILLS FORMATION (CHESTERIAN), EAST-CENTRAL IDAHO

BUTTS-MATHESON, Susan, and Peter E. Isaacson, University of Idaho, Moscow, ID, USA

Within the thick Carboniferous carbonate and siliciclastic rocks of the northern Rockies is a succession with exquisitely preserved faunas of Chesterian (Late Mississippian) age. The Arco Hills Formation yields abundant silicified brachiopods. Brachiopod assemblages show both in situ communities and biostratinomic accumulations in storm-generated packstones and grainstones. Beds with sufficient silicification and minimal dolomitization were sampled at regular intervals. Extraction with muriatic acid yielded abundant fossils, including some with all growth stages represented. These were cleaned, photographed, and cataloged. Among the abundant brachiopods are echinoderms, bryozoans, rare gastropods, bivalves, vertebrates, and trilobites.

Inasmuch as Chesterian brachiopod faunas remain poorly described, a complete taxonomic description is underway. Additionally, detailed assemblage and community analysis within the Late Mississippian Arco Hills Formation will be analyzed for the following parameters; generic and species diversity, richness, and dominance. Preliminary community analysis reveals low specific diversity Orbiculoidea, Spiriferidina/Athyrididae, and Productoidea/Davidsonioidea communities.

Associations within brachiopod communities and facies affinities will be used in biotopic analysis. With biocoenoses and taphocoenoses found, the presence of communities can result in clarity of depositional setting far exceeding that gained from lithologic analysis alone. Four factors are of paramount interest to the regional geologist: depth (storm and fair weather wave base), siliciclastic input, including the sediment source, substrate availability, and lowered oxygen levels imposed by geographic barriers or bathymetric changes. This paleoecologic work will help us to answer these questions and improve what little is known about Antler history.