NAPC 2001

Abstracts Ar - Ba
(5/17/01)

Jump to: Arens | Arnold | Aronowsky | Arpad | Ashwill | Babcock | Badgley | Baghai-Riding | Bambach | Barberena | Barnosky | Baumiller

Return to Main Abstracts Page

LOSS OF LOCAL ANGIOSPERM SPECIES RICHNESS
PRECEDES THE CRETACEOUS/TERTIARY BOUNDARY:
PALYNOLOGICAL EVIDENCE FOR INCREASED HABITAT HETEROGENEITY

ARENS, Nan Crystal, and Anna Thompson, Dept. of Integrative Biology, University of California, Berkeley, CA, USA; and A.H. Jahren, Dept. of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA

Understanding the biological context in which the terminal Cretaceous bolide impact occurred is important to explaining its biotic effects. We report palynological data from Russell Basin, McCone County, northeastern Montana. In this section, the Cretaceous/Tertiary (K/T) boundary is bracketed biostratigraphically, and diagnosed by a ­2 per mil carbon isotope excursion in terrestrial organic carbon. We recognized a decline in palynological species richness (the number of distinct forms) beginning approximately 3.5 m below the Hell Creek-Fort Union formational contact. Species richness declined from 85 species 3.5 m below the formational contact to 10 species at about ­1 m. Most of the species lost were triaperturate forms, produced by dicot angiosperms. Relatively low species richness floras (26­34 pollen taxa) persisted across the K/T boundary. Only about 10 percent of palynospecies present in the uppermost 1 m of Cretaceous sediment had last occurrences at the K/T boundary. Similar patterns of local species richness loss in the uppermost meters of the Cretaceous have been reported throughout Canada. However, these do not represent pre-K/T boundary extinctions; instead taxa lost at one locality commonly persist at another. This suggests that the cosmopolitan late Cretaceous flora was becoming regionally heterogeneous during the interval represented by the last 3 m of the Cretaceous.

DISTRIBUTION, DIVERSITY, AND LIGHT ISOTOPE SIGNAL IN BENTHIC FORAMINIFERA ON A SEAMOUNT NEAR THE EAST PACIFIC RISE; EFFECTS OF THE EAST PACIFIC OXYGEN MINIMUM ZONE

ARNOLD, Anthony J., William C. Parker, and Xiaoli Liu, Dept. of Geological Sciences, Florida State University, Tallahassee, FL, USA

Seamount 7 is about 30 km from the axis of the East Pacific Rise at 102° 30' W, 13° 25' N at depths ranging from 730 to 3,353 m below MSL; at its summit Seamount 7 penetrates into the East Pacific oxygen minimum zone (OMZ) thus affording an unusual opportunity to investigate the effects of oxygen deprivation on benthic foraminiferal communities in an open marine environment. Bottom water oxygen concentrations vary from near-microxic (about 0.1 ml/l) at the top of Seamount 7 to dysoxic (0.1 to 1 ml/l) at about 1,100 m below the summit. At greater depths, the bottom waters would be considered oxic. The likely presence of the OMZ at Seamount 7 (as well as at two other seamounts in the area) was reported in 1987 based on foraminiferal diversity, test ultrastructural evidence, and relative species abundance data consistent with other reports of foraminiferal response to oxygen deprivation. Later studies focused on macrofaunal and physio-chemical characterization of Seamount 7 with special attention to the effects of oxygen concentrations, and provided an excellent background for understanding foraminiferal distribution patterns. The present study focuses exclusively on Seamount 7 in the context of that background data and using a new and more comprehensive suite of samples with the following goals in mind: (1) to test the hypothesis that stable light isotope signals, particularly ¹²C/¹³C, should reflect the presence of an oxygen minimum, and (2) to refine and quantify our understanding of the effects of oxygen deprivation on the foraminiferal populations in this area with respect to distribution, diversity, abundance, and test ultrastructure. Shannon-Weaver diversity values are significantly lower within the OMZ. This is primarily caused by the high dominance of cassidulinids, while Ehrenbergina spp showed high abundances and unusually thin shells. Relatively elevated frequencies of bolivinids and uvigerinids were also noteworthy in the OMZ. Elevated diversities were characteristic of the ecotone separating the OMZ from oxic conditions.

NATICID GASTROPOD DRILLHOLES: AN INTEGRATIVE APPROACH INVOLVING RE-ANALYSIS OF PUBLISHED DATA, EXPERIMENTAL TESTS, AND INTERNAL BIOLOGY

ARONOWSKY, Audrey, Dept. of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA, USA

Naticids are infaunal predatory gastropods that drill holes in the shells of their molluscan prey. Because these drillholes are beveled, they have two diameters, an inner-boring diameter (IBD) and an outer boring diameter (OBD). In a seminal paper, Kitchell et al. (1981) reported a positive correlation of OBD with the shell length of the drilling naticid. This correlation is thought to represent a relationship between the size of the predator and its inflated accessory boring organ (ABO) diameter. Re-analysis of the Kitchell et al. (1981) data suggests that this relationship is more tenuous than previously thought. For example, an OBD value of 3.25 mm can yield shell length values ranging from 29­52 mm. In addition, the Kitchell et al. (1981) data are derived from the analysis of a single naticid species, Polinices duplicatus.

Experimental studies on other naticid species will test whether the shell length:OBD correlation is valid for other taxa. Laboratory studies will maintain individual naticids with prey of varying morphology to examine the range of drillhole geometries produced by an individual predator. This technique will provide a more rigorous investigation into the relationship between naticid size and drillholes produced. Subsequent dissection of these same predators will permit the investigation of the ABO:OBD relationship. Currently, categorization of naticid drillholes (fossil or recent) below the family level is problematic and will only be elucidated through analysis of many naticid species.

ACTIVITY OF PREDATORY GASTROPODS ON THE SHELLS OF LATE-OLIGOCENE (EGERIAN) MOLLUSCS (WIND BRICKYARD, EGER, HUNGARY)

ARPAD, David, Karoly Eszterhazy College, Dept. of Geography, Eger, Hungary

The clay-pit of Wind Brickyard at Eger is the stratotype of the Egerian Stage. Sequence of the profile is: glauconitic sandstone; molluscan clay; marine silty sandstone; marine limonitic sandstone; alternation of coarse sand and carbonaceous clay. These formations are rich in molluscan fossils. 22,065 specimens were examined, belonging to 189 species. Shells of bivalves, gastropods and scaphopods showed traces of predatory gastropods belonging to the families Naticidae and Muricidae. Mode of life, feeding habits of the prey molluscs, and distribution of successful, unsuccessful and unfinished borings were investigated and compared. The molluscs examined have been found in the following layers: molluscan clay, marine silty sandstone, marine limonitic sandstone, alternating coarse sand and carbonaceous clay. Naticid boreholes were examined on the shells of molluscs collected from three different layers of the exposure. Traces of naticid predation occurred on the shells of bivalves, gastropods and scaphopods. Mainly gastropods were attacked by naticids, producing 998 boreholes on 944 shells, with successful borings the most frequent. The rate of bored specimens is 4.44% in the samples of the Molluscan Clay. Increasing number of naticid borings were observed in molluscs of the other layers. Multiple naticid borings and "cannibalism" have also have been found. Suspension feeders and scavengers are dominant among the prey species of naticids. Occurence of muricid drillholes on the shells of molluscs collected from four different layers of Wind Brickyard was examined. Traces of muricids were found on the shells of bivalves and gastropods, with 220 borings observed on 201 shells. Gastropods were the most common prey; successful borings were dominant. The number of boreholes was low on the molluscs collected from the Molluscan Clay with increased numbers in the upper layers. The only layer where the number of unfinished borings was higher than the two other boring types was the uppermost layer. Suspension feeders and scavangers were the main prey items of muricids.

THE ENTOBIA ICHNOGENUS IN HUNGARIAN TERTIARY FORMATIONS

ARPAD, David, Monika Brecz, and Judit Horvath, Karoly Eszterhazy College, Dept. of Geography, Eger, Hungary

Occurrence and distribution of Entobia ichnospecies at eight Hungarian Tertiary localities have been examined. The age of the localities are middle Eocene (Lutetian), early Miocene (Egerian, Ottnangian, Carpathian) and middle Miocene (Badenian). Oyster shells, gastropod tests and abrasion pebbles served as firm substrate for the Clionid larvae. One hundred twenty epoxy-casts have been made from the collected material (5­15 from each locality). From these epoxy casts, seven Entobia ichnospecies have been identified. They include the following: Entobia cateniformis Bromley et D'Alessandro, E. geometrica Bromley et D'Alessandro, E. laquea Bromley et D'Alessandro, E. megastoma (Fischer), E. ovula Bromley et D'Alessandro, E. paradoxa (Fischer), and E. retiformis (Stephenson). The most frequent ichnospecies are E. geometrica, E. cateniformis and E. megastoma. Idiomorphic forms are rare in the oyster valves. Depth of the trace fossils is shallow. Clionid borings also occur in the inner side of the valves in most cases. From our observations, we found no correlation between the thickness of the oyster valves and the depth of the Entobian borings. "D+" growth phase occur only in the Entobia ichnospecies observed in the tests of gastropods. Growth phases from "A" to "D" occur in the case of the Entobians of the abrasion pebbles. Forms are idiomorphic in each case. Based on our observations, Clionid sponges played a significant role in the destruction of shelly substrates and calcareous rocks during the Tertiary of Hungary.

OCCURENCE AND DISTRIBUTION OF GASTROCHAENOLITES ICHNOGENUS IN MIDDLE MIOCENE (CARPATHIAN) AGE ABRASION PEBBLES OF TWO LOCALITIES— A COMPARISON (NAGYVISNYO & DEDESTAPOLCSANY BÜKK MOUNTAINS, HUNGARY)

ARPAD, David, and Rozalia Fodor, Karoly Eszterhazy College, Dept. of Geography, Eger, Hungary

Abrasion pebbles from two localities (Nagyvisnyo, abandoned limestone quarry and Dedestaapolcsany, pebble quarry) have been examined for the presence, abundance and distribution of Gastrochaenolites ichnospecies. The Gastrochaenolites ichnogenus is formed by boring bivalves in calcareous substrates. Their characteristic club-shaped trace fossils are dwelling structures (domichnia). The age of the black Permian limestone and dolomite pebbles is middle Miocene (Carpathian) and belongs to the Egyhazasgerge Formation. Epoxy casts of pebbles from both localities were made: 36 from Nagyvisnyo and 43 from Dedestapolcsany. Among the number of observed bioerosional traces of boring bivalves, these could be attributed to the following taxa: G. lapidicus, G. cor, G. cluniformis, G. orbicularis, G. torpedo and G. turbinatus. The frequency of G. lapidicus and G. torpedo is significant at both localities. The high number of G. orbicularis in the pebbles collected at Dedestapolcsany is also remarkable. Differences in the length of G. lapidicus and G. torpedo at the two localities is attributed to paleoenvironmental alternations; in the case of Dedestapolcsany locality the fossil rocky shore was richer in nips and uneven surfaces.

TWO FLORAS IN THE UPPER JOHN DAY FORMATION NEAR MADRAS, CENTRAL OREGON

ASHWILL, Melvin S., Madras, OR, USA

Two fossil floras in the upper John Day Formation, one well collected, the other reconnaissance collected, add to the understanding of this poorly documented gap in the paleobotanical record of the early Miocene in central Oregon. The data presented tend to corroborate previous observations about the drying and cooling climatic change that took place there between early Oligocene and late Miocene times. The gradual replacement in the niche once held by the dominant Metasequoia ("dawn redwood") by Taxodium (swamp cypress) is relected in these floras.

INTERPRETATION OF BIOLOGICAL AND ENVIRONMENTAL CHANGES ACROSS THE NEOPROTEROZOIC-
CAMBRIAN BOUNDARY: DEVELOPING TOOLS FOR
PREDICTING THE OCCURRENCE OF BURGESS SHALE-TYPE DEPOSITS

BABCOCK, Loren E., Dept. of Geological Sciences, The Ohio State University, Columbus, OH, USA

The fossil record of biotic change from the late Neoproterozoic through the Middle Cambrian resulted from an interplay of biological and environmental factors. By the Early Cambrian, biological conditions underway in shallow shelf seas included rapid diversification, experimentation with new body plans, and a shifting of ecological setting away from mat-dominated communities to more burrowed sediment surfaces. High eustatic sea level, high tidal ranges, areas of rapid sedimentation, and interfaces between conditions of contrasting seawater chemistry afforded opportunities for the exceptional preservation of nonmineralizing organisms at a rate exceeding that for any other interval of the Phanerozoic.

Understanding the conditions under which exceptional preservation occurred during the Early and Middle Cambrian provides a framework for exploring for previously unknown sites of exceptional preservation. For the most part, Burgess Shale-type deposits were developed in tropical to subtropical paleolatitudes where sedimentation was relatively rapid, and commonly episodic. Exceptional preservation seems to have occurred most commonly in late phases of transgressive systems or in highstand systems tracts. Such preservation is typically associated with thin bedding of clay- or silt-sized grains. Rhythmic bedding patterns in some localities suggest tidally influenced deposition. Oxic-anoxic, saline-hyposaline, and potentially saline-hypersaline, conditions are inferred to have inhibited scavengers, microbial biodegraders, and bioturbators, thus providing sufficient time for burial prior to the occurrence of substantial breakdown of organic remains. Following burial, geochemical conditions, including establishment of dysoxic or reducing microenvironments, would have promoted exceptional preservation of nonmineralized remains.

DATABASES FOR RECENT MAMMALS AND MAMMALIAN FAUNAS

BADGLEY, Catherine, Museum of Paleontology, University of Michigan, Ann Arbor, MI, USA; and David L. Fox, Dept. of Earth Sciences, University of California, Santa Cruz, CA, USA

Databases for modern mammalian faunas were created to address questions in community ecology, biogeography, and paleoecology. Mammals are well documented in terms of taxonomy, ecology, and geographic distribution, and thus are well suited to coverage in databases and synoptic analyses. We constructed three kinds of database. One is a species file that records taxonomic and ecological information for individual species. Individual species have multiple records when their ecological attributes show high geographic variation, as in species with clinal variation in body size. Second is a locality file based on sites where comprehensive faunal surveys occurred. This database records geographic, ecological, and climatic information about each locality. The third database contains quadrats from a grid system that covers continental regions. For each quadrat, we recorded latitude, longitude, and topographic and climatic data. The species database is linked to the site databases through a relational file that expresses species occurrences at particular sites. We used these databases to quantify the relationship between environmental variables and ecological diversity of modern mammalian faunas. For example, we studied the ecological biogeography of all 721 extant species of North American mammals. Five climatic and topographic variables explain 88% of the geographic variation in species density, including the latitudinal and longitudinal gradients in species density. Five environmental variables explain 76% of the variation in mammalian ecological diversity, as expressed by size and trophic structure. Evaluating how much these patterns reflect ecological sorting of species ranges since the last deglaciation versus geographic variation in speciation and extinction will require linking our research goals and databases with those focusing on Quaternary and Neogene mammals, vegetation, and environments. We also see opportunities for productive links with databases serving biogeographic or conservation goals for extant organisms and environments.

AN ANALYSIS OF PALYNOMORPHS OF THE AGUJA FORMATION (CAMPANIAN), BIG BEND NATIONAL PARK, BREWSTER COUNTY, TEXAS

BAGHAI-RIDING, Nina L., Dept. of Biological and Environmental Sciences, Delta State University, Cleveland, MS, USA

Exposures of the Aguja Formation (84­74.5 m.y.a.) at Big Bend National Park contain deltaic sequences that were deposited on the southwestern margins of the Western Interior Seaway. Near-shore marine and paralic sandstone units interbed lignite, carbonaceous shales and mudstones. Well-preserved assemblages of palynomorphs provide greater resolution of the two-progradational deltaic cycles than are reflected by sedimentological and stratigraphic data. The microfossil flora also provides an accurate assessment of subtropical to warm temperate paleoclimates and concurrent plant communities that once prevailed in this region.

Palynomorph samples, collected and processed from six measured and correlated stratigraphic sections from the northwestern and northeastern part of Big Bend, include a diverse assortment of freshwater protists, dinoflagellates, fungi and vascular and nonvascular plant taxa. Quantitative counts and analysis of 54 samples revealed 134 various form genera: 28 dinoflagellates and freshwater algae, 16 fungi, 37 ferns and mosses, 13 gymnosperms and 40 angiosperms. The lower shale member, which accumulated largely in coastal marshes and freshwater swamps, possesses a more diverse array of fungi, ferns, mosses and angiosperms than the upper two shale units. The thin, middle shale unit contains a larger assortment of dinoflagellates at its base that reflects a marginal marine influence. The upper shale unit, which was deposited in coastal floodplains, freshwater swamps and continental floodplains, contains many tricolporate and tricolpate pollen grains, not found in the other horizons. Common genera are Deflandrea, Palaeohystrichophora (dinoflagellates), Schizosporis (freshwater algae), Cyathidites, Deltoidospora, Gleicheniidites (ferns), Cycadopites, Inaperturopollenites (gymnosperms), and Liliacidites, Momipites, Plicapollis, and Proteacidites (angiosperms).

WALKER AND BAMBACH 1971 REVISITED: AT LAST WE ARE RELEVANT

BAMBACH, Richard K., Dept. of Geological Sciences, Virginia Tech, Blacksburg, VA, USA

Walker and Bambach 1971 (a GSA meeting discussion paper in the days before poster sessions) was inspired by the difficulty in communication between biologists and paleontologists that characterized the Penrose Conference on marine ecology and paleoecology held in December, 1970. The biologists were skeptical that ecologically useful information could be obtained from accumulations of non-contemporaneous specimens, yet that is the stuff of fossil assemblages.

Times have changed. Time-averaged assemblages are now recognized as having impressive environmental fidelity. Because time-averaging reduces the variability that short-term patchiness and response to disturbance generates, time-averaged assemblages often resolve environmental gradients in greater detail than can be detected with sedimentological analysis alone. Since the fossils preserved in a time-averaged deposit lived (and died) during the interval after the underlying bed was deposited and before the end to disturbance and deposition marked by the bed in which the fossils are preserved, the fossils in a time-averaged deposit actually record information from the time otherwise concentrated in bedding-plane diastems. Dating of individual shells by amino-acid racimization and calibration from radiocarbon dating permits segregation of different age shells from time-averaged deposits in the sub-Recent and Recent. This offers the opportunity of monitoring isotopic patterns and following environmental change even during intervals of time-averaging. Environmental patterns on century to millennial scales may become available from deposits that mix shells from disparate times together in such time-averaged, reworked and redeposited assemblages. Time-averaged but little mixed assemblages are now recognized as having great utility in understanding biologically relevant phenomena in the past.

A NEW FAUNA OF VERY MAMMAL-LIKE CYNODONTS FROM THE LATE TRIASSIC OF BRAZIL

BARBERENA, M.C, and J.F. Bonaparte, Federal University of Rio Grande do Sul, Porto Alegre, Brazil; A.W. Crompton, Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA; J.A. Hopson, Dept. of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA; and C. Schultz and R. Rubert, Instituto de Geociencias, Universidad Federal de Rio Grande do Sul, Porto Alegre, Brazil

Very small cynodont therapsids of the Late Triassic have long been assumed to have given rise to mammals. However, with the exception of Therioherpeton cargnini, described from an incomplete skull from the Santa Maria Formation of Brazil and isolated teeth of uncertain affinities from Europe and North America, such small cynodonts have been unknown. A new fauna of extremely mammal-like cynodonts has recently been discovered in the Caturrita "Formation" in Rio Grande do Sul, Brazil. This fauna is associated with sphenodontids and procolophonids and is considered to be of early Norian Age.

Several skulls with associated lower jaws of a primitive ictidosaur, Riograndia quaibaensis, recently described by Bonaparte et al., and a collection of partial skulls, lower jaws and postcranial elements representing very small mammal-like cynodonts are briefly discussed.

Riograndia appears to be related to the classic South African ictidosaurs (the trithelodontids Pachygenelus, Diarthrognathus and Trithelodon), but it is both more primitive in cranial anatomy and divergently specialized in its dentition.

The remaining cynodonts are much smaller, with more slender delicate skulls and lower jaws. Their postcanine teeth resemble those of Morganucodon and other basal mammalian forms, but they lack certain diagnostic features seen in Early Jurassic mammaliformes. These Late Triassic non-mammalian cynodonts appear to be more closely related to mammals than either the trithelodontids or tritylodontids.

The entire cynodont fauna is currently being studied with cooperation between the Federal University of Rio Grande do Sul and the Natural Science Museum of Buenos Aires, while the species of "ictidosaurs" are being studied in cooperation with the paleontologists from the University of Chicago and Harvard.

MIOMAP: A RELATIONAL AND SPATIAL DATABASE FOR RESEARCH ON EVOLUTION, ECOLOGY, AND BIOGEOGRAPHY OF MIOCENE MAMMALS

BARNOSKY, Anthony D., and Marc A. Carrasco, Museum of Paleontology and Dept. of Integrative Biology, University of California, Berkeley, CA, USA

The Miocene Mammal Mapping Project (MIOMAP) has the primary goal of casting light on the question: How do large-scale physical-environmental perturbations affect the evolution and biogeography of mammals? The intent is to apply the fossil record to help delineate what is natural for the mammalian component of ecosystems to assess as accurately as possible the environmental effects of human induced global change. MIOMAP is a relational database in PARADOX 9 designed for incorporation into a GIS analytical tool (ARC/INFO 8.0). It includes all published Miocene mammal species of the United States, and as time and resources allow, will also include well-identified, unpublished specimens represented by voucher specimens in museums. Information associated with each species occurrence includes latitude, longitude, relevant taxonomy, geologic age, depositional environment, taphonomic attributes, bibliographic information, and numbers of specimens, among other relevant data. The data structure parallels that for the FAUNMAP project, with which complete compatibility is envisioned. A later phase of the project also calls for exploring interfaces that would easily link MIOMAP with other relevant datasets. The immediate research application of MIOMAP is to test hypotheses about how global warming and a tectonic event ~17 Ma ago affected faunal turnover, species richness, and biogeographic patterns in the western US. Analyses so far have focused on comparisons of the Pacific Northwest, Northern Rockies, and northern Great Plains. Preliminary results indicate that alpha diversity and faunal turnover rates in the northern Rockies may have increased as a result of the environmental perturbations and that beta diversity may have remained the same or decreased. However, the results highly depend on analytical method. In addition, the three areas seem to have retained biogeographic integrity throughout the Miocene intervals that were studied; modern biogeographic patterns may therefore be deeply rooted in time.

COST-BENEFIT ANALYSIS AS A GUIDE TO THE ECOLOGY OF DRILLING PLATYCERATIDS

BAUMILLER, Tomasz K., Museum of Paleontology, University of Michigan, Ann Arbor, MI, USA

Boreholes in Paleozoic crinoids and blastoids have been hypothesized as parasitic based on the presence of: (1) multiple and healed borings, which indicate that drilling was not fatal, (2) attachment scars, which imply a long-term association between host and parasite. It has also been argued that these boreholes were made by platyceratids because examples of platyceratid infested blastoids and crinoids are known, and one example of a platyceratid positioned over a borehole on a crinoid tegmen has been reported.

To further explore the platyceratid parasitic drilling hypothesis, a cost-benefit analysis was performed comparing the quality of various crinoids as hosts and as edible prey. Platyceratid energetics were modeled on the marine snail Polinices, for which experimental data on drilling and metabolic rates exist. The value of crinoids as prey was calculated using the empirical relationship between calyx soft tissues and calyx size, and data on caloric content of soft tissues in extant crinoids. The value of crinoids as hosts was evaluated assuming snails "stole" unused captured nutrients directly, or through coprophagy. Crinoid nutrient capture was modeled for a range of filter morphologies, concentrations of particles in seawater, and current velocities, using previously developed models for passive suspension feeders.

Results indicate that under realistic environmental conditions pelmatozoans with high solidity filters (pinnulate or highly branched) (1) could capture sufficient nutrients to host kleptoparasitic snails, (2) provided a greater energetic return as hosts than as prey items, and (3) provided a greater energetic return as hosts than would be available for snails preying on contemporaneous brachiopods. This may partly explain the host preferences of platyceratids (associated only with pelmatozoans with high-solidity filters) and the apparent failure of these snails to exploit the predatory potential of drilling.