NAPC 2001

June 26 - July 1 2001 Berkeley, California

Abstracts, Ra - Ru

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RAHMAN, Yasmin J., Dept. of Integrative Biology, University of California, Berkeley, CA, USA; and Jane Mason, Museum of Paleontology, University of California, Berkeley, CA, USA

Gelatinous animals have long been considered to be ephemera in the geologic record. However, use of some common vertebrate paleontology preparation techniques allows recent invertebrate remains and traces to be preserved and compared to those in the fossil record. The contrast of surface details on such specimens can be augmented by use of tinted silicone, ammonium chloride "smoking," dry brushing, washes, and peels.


RAISOSSADAT, S. Naser, Dept. of Geological Sciences, University College, London, UK

The Kopet Dagh basin is situated in the northeast of Iran and southeast of Turkmenistan. The ammonite biostratigraphy of the Sarcheshmeh and Sanganeh Formations has been studied (Raisossadat, 2000). A preliminary account of the ammonite paleobiogeography is given here.

From a biopaleogeographical point of view the presence of Heteroceratidae, Desmoceratidae and Ancyloceratidae at the Upper Barremian confirm a connection to the Mediterranean via the Caucasus. Turkmenicerasis apparently endemic to the Kopet Dagh Basin.

Deshayesitesspecies in the basin are similar to those from the Caucasus, Eastern Europe and even England. This proves that there were seaway connections and similar environmental conditions predominated.

The Kopet Dagh basin was influenced by representative genera of the Ancyloceratidae, Desmoceratidae, Phylloceratidae and Oppeliadae families during the Lower Aptian. The Parahoplitidae are closer to those from Mangyshlak, Caucasus and Germany than from other parts of the world. The presence of the Cheloniceratidae and Douvilliceratidae in the Upper Aptian-Albian may indicate the influence of the Boreal Realm.

During the Albian, the Kopet Dagh Basin was a part of the hoplitinid Province. The ammonite biogeography indicates that, the Kopet Dagh Basin during the Upper Barremian-Upper Aptian was situated at the north margin of Tethys and was a part of the Sub-Mediterranean Province. Its paleogeographic position and ammonite faunas prove its close relation to the Caspian and Caucasus regions. From the Upper Aptian to the Cenomanian the basin was open Boreal faunas.

Raisossadat, S.N. 2000. Lower Cretaceous ammonite biostratigraphy of the Sarcheshmeh and Sanganeh Formations in the Kopet Dagh Sedimentary Basin in the northeast of Iran. 6th International Cretaceous Symposium, Vienna, Austria (abstract with program).


REGA, Elizabeth A., Dept. of Anatomy, Western University of Health Sciences, Pomona, CA, USA; and Ken Noriega, Dept. of Biology, California State University, San Bernardino, CA, USA

Sailback forms are known from pelycosaurian-grade synapsids in seven genera distributed between two families. While the precise function of the sail remains disputed, most researchers agree in assuming the presence of soft tissue in the form of webbing between the elongate neural spines. An isolated fragment of neural spine from the early Permian of Baylor County in North central Texas has been assigned to Dimetrodon sp. based upon its diagnostic dumb-bell shaped cross-sectional outline and associated fragmentary specimens assigned to the same genus. This fragment shows clear evidence of a completely healed fracture. The fracture is very well resolved, with no evidence of malalignment in the form of subluxation, torsion or lateral bending. The lack of deformation provides indirect evidence of the presence of the soft-tissue sail webbing, in that it would have provided a biological splint to neural spine fractures, thus promoting alignment during healing.


RETALLACK, Gregory J., Dept. of Geological Sciences, University of Oregon, Eugene, OR, USA

Neogene expansion of the climatic and geographic range of grasslands at the expense of woodlands is now revealed by studies of paleosols, fossils and their stable isotopic compositions. The spread of this uniquely coevolved ecosystem of grasses and grazers has been attributed to global climatic cooling and drying created by the uplift of large mountains and the slowing of oceanic thermohaline circulation. Here I propose the opposite view that grasslands coevolved as a biological force for climatic drying and cooling that stimulated mountain uplift by glacial incision and isostatic uplift, and that curtailed thermohaline circulation by the growth of sea ice. Grasslands are important sinks for atmospheric green house gases, carbon dioxide, methane and water vapor, because grassland soils are richer in organic matter than the dry woodland and desert soils they replaced, and when eroded their crumb peds form sediment unusually rich in organic matter. Grasslands also promote export of bicarbonate and nutrient cations to lakes and oceans where they stimulate productivity and carbon burial, because grasslands preferentially exploit fertile young soils in the first flush of weathering and their crumb structure has a very high internal surface area for weathering. Grasslands also promote regional climatic drying by virtue of their higher albedo and lower transpiration that woodlands of comparable regions. Labile pools of carbon in grassland soils and their accelerated weathering rates early in soil development may also account for increased climatic instability through the Cenozoic. Unidirectional, stepwise, long term climatic cooling, drying and climatic instability may have been driven not by tectonic forcing, but by the coevolution of grasses and grazers.


RIDING, Robert, Dept. of Earth Sciences, Cardiff University, Cardiff, UK

Thin (<150 micron) micritic veneers lining crypts in Paleozoic and Mesozoic reef, microbial, and bioclastic carbonates resemble modern uncalcified bacterial biofilm in dimensions and architecture. Morphologic attributes include rounded aggregate nanofabric, internal channels, external swellings, mushrooms and plumes. All can be interpreted as characteristics of attached bacterial communities: aggregates as microcolonies, originally embedded in a matrix of extracellular polymeric substances (EPS); channels as water conduits and/or uncolonized nutrient-poor spaces; external protuberances as results of localized growth; plumes as surface streamers curved by fluid flow. Cryptic habitat favored pristine biofilm preservation by precluding disturbance and overgrowth, and suggests formation in aphotic and anoxic conditions. These examples show that detailed morphologic criteria for biofilm recognition can be preserved in protected habitats in a wide range of Phanerozoic carbonates.


RINDSBERG, Andrew K., Geological Survey of Alabama, Tuscaloosa, AL, USA; and Anthony J. Martin, Dept. of Environmental Studies, Emory University, Atlanta, GA, USA

Compound trace fossils, defined by Pickerill (1994) as "those [trace fossils] comprising separate parts that collectively form the whole," are problematic for ichnologists for several reasons. Some compound traces (CTs) are made by individuals of one species, whereas others are made by symbionts of different species. Where made by one species, CTs force us to reconsider previous taxonomic distinctions, e.g., between Ophiomorpha and Thalassinoides, and to establish a more credible taxonomy. In some cases, the concept of ichnotaxa is expanded by considering their possible origins by multiple tracemakers. Where made by different species, CTs reveal new information about symbiotic relationships. Indicators that a CT was made by one species include attachment, cooccurrence, similar dimensions, similar components, and morphologic intergradation. Notably, trace size and inferred tracemaker are important to the study of CTs, which is seemingly contrary to the principle that morphology is paramount in ichnotaxonomy.

Arthrophycus serves as an example of a trace fossil whose compound nature has made for taxonomic difficulties. Hall (1852) diagnosed it as consisting of "stems simple or branching, transversely marked by ridges or articulations." Some later workers recognized that the simple and complex burrows of Arthrophycus were made by the same animal, but considered the fans to be functionally equivalent to Phycodes Richter, 1849, reserving the name Arthrophycus for simple burrows with endoconic fill. But Arthrophycus is not endoconic; its fill consists of truncated cones surrounding an internal cylinder. Endoconic burrows should be reassigned to another ichnogenus, and Arthrophycus should include simple and complex burrows. This suggestion is encouraged both by consistencies in trace size and by interpretation of an arthropod (trilobite?) tracemaker for Arthrophycus from the Early Silurian of Alabama and West Virginia.


RINDSBERG, Andrew K., Geological Survey of Alabama, Tuscaloosa, AL, USA; Anthony J. Martin, Dept. of Environmental Studies, Emory University, Atlanta, GA, USA; and Nicholas D. Pyenson, Dept. of Biology, Emory University, Atlanta, GA, USA

The term fossil-lagerstätte is often restricted to body fossils, but is also appropriate for extraordinary assemblages of ichnofossils. Strata at the Union Chapel Mine in north-central Alabama have such a lagerstätte, which is represented by abundant vertebrate and invertebrate tracks above the Mary Lee coal seam, constituting an important new Carboniferous tracksite. Hundreds of specimens were recovered recently by the Birmingham Paleontological Society and were cataloged cooperatively by this amateur group and scientists from the Geological Survey of Alabama, Alabama Museum of Natural History, and Emory University.

Tracks are preserved in laminated gray shale that was likely deposited on an upper estuarine tidal flat. The most common vertebrate tracks are Cincosaurus, probably made by amphibians. Limulid trackways are assigned to Kouphichnium; invertebrate burrows (Diplocraterion, Planolites, Treptichnus) and plant debris are also abundant. Vertebrate tracks range from 1 to 12 cm wide. Although most tracemakers were small (perhaps juvenile), some measured 1.5 m long, based on glenoacetabular distances and track sizes. An amphibian tracemaker is inferred from five digits on each foot (with bulbous terminations on digits) and an elongated pes digit IV. Some trackways also show dozens of sequential strides, turning motions, tail drags, and at least one specimen indicates a sideward shuffle. Abundant specimens of Kouphichnium also provide an estimation of limulid population dynamics. Some of these traces show intrastratal locomotion (burrowing along a shallow horizontal plane), as well as locomotion on the sediment-water interface. With regard to tiering of the ichnofossil assemblage, previous expectations hold that vertebrate tracks are relatively superficial. However, in this assemblage the vertebrate tracks penetrate more deeply than invertebrate traces, supporting a different ichnofossil tiering hypothesis.


RODE, Alycia L., and Bruce S. Lieberman, Dept. of Geology, University of Kansas, Lawrence, KS, USA

Invasive species, species that enter a region and expand their geographic ranges to the detriment of endemic species, are one of the primary causes of the current biodiversity crisis. Although modern invasive species are often introduced by humans, the same phenomenon has occurred in the geologic past due to the breakdown of geographic or ecological barriers. Increases in extinction rates due to invasive species have been well documented by biologists, but invasive species may also impact evolution by altering speciation mode and depressing speciation rates. Like the modern biodiversity crisis, the Late Devonian mass extinction is associated with geographic range expansions and a decline in faunal endemism.

To examine the role of invasive species in the geologic past, the Phyllocarida, an important macroarthropod group during the Middle and Late Devonian, was examined as a case study. Speciation and extinction rates were calculated and mode of speciation was inferred from biogeographic analysis within a phylogenetic framework. These results were compared to mean species geographic range as determined from GIS analysis. Within Devonian phyllocarids, expansion of geographic range, a hallmark of the invasive species phenomenon, is associated with a decrease in regional-scale vicariant speciation and a relative increase in speciation by dispersal. In fact, no regional-scale vicariant speciation was observed during the entire Late Devonian. Local scale-vicariant speciation also declines during the Late Devonian as geographic ranges expand.

The observed relationship between geographic range and speciation mode in Devonian phyllocarids has implications for conservation biology and the modern biodiversity crisis. By approaching the problem of modern species invasions with the improved understanding that the ecological impact of invasive species is not limited to increasing local extinction, but also results in suppression of vicariant speciation and an overall decline in speciation rate, a more effective approach to conservation biology can be developed.


ROOPNARINE, Peter. D., and Shelly Willard, Dept. of Invertebrate Zoology and Geology, California Academy of Sciences, Golden Gate Park, San Francisco, CA, USA

A significant number of studies support observations that the predatory drilling behaviors of naticid and muricid gastropods are often highly stereotyped. Stereotypy has been demonstrated for prey size selection, prey shell thickness, and location of the drill hole. These stereotypes are probably not determined solely by the behaviors and strategies of the predatory cohort, but also by the interaction between the behaviors and prey morphology. The purpose of this study is to explore the effects of prey morphology on drilling behavior, with a morphometric analysis of morphology and drilling of tropical American venerid bivalves. It is hypothesized that such a study will reveal patterns of predation related to prey morphological diversity, as well as environmental patterns such as productivity, temperature and substrate type. It is further hypothesized that these patterns will reflect changes in predator diversity and the taxonomic composition of the predatory cohort.

Preliminary analyses have been performed on the chionine (Veneridae: Chioninae) species Chione californiensis in the Gulf of California. Naticid-type drilling of this species in the Gulf is highly stereotyped, and is influenced primarily by depth of the pallial sinus (= burial depth in this shallowly burrowing species) and orientation of the posterior adductor muscle (or associated, non-preserved, soft visceral structures). Muricid-type drilling is significantly more variable, but exhibits considerable stereotypy at any given locality. It remains to be seen how these patterns vary with increasing geographic scale, and increasing morphological diversity as multiple prey taxa are examined.


ROOPNARINE, Peter D., Dept. of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA, USA; and Michael Murphy, Nancy Buening, and Paul Fitzgerald, Dept. of Geology, University of California, Davis, CA, USA

The Pa element of the conodont "Ozarkodina" wurmi is abundant at many levels of the SPVII section, central Nevada, permitting analysis at high resolution within the Lochkovian, Lower Devonian. The SPVII section spans much of the Lochkovian, to the base of the Pragian, and specimens of "Ozarkodina" were collected from a series of deeper water turbidite deposits. The interval measured is expressed in composite stratigraphic units resulting from graphic correlation, and represents approximately five million years.

Several morphological features were assessed morphometrically and meristically, including denticle number, expressed as a function of size, and morphology of the basal profile in lateral view. The latter was quantified using a standardized cubic spline method, and both characters were subsequently compared among stratigraphically ordinated samples. The morphological data revealed the presence of two separate lineages in the section, one possessing a relatively flat element and referred to as Type I, and the other possessing a highly arched element, termed Type II. Type II specimens are present, but are rare even in very large bulk samples of more than 50 kg.

Application of a computational technique appropriate to the analysis of stratophenetic data reveal that the Type I species exhibits a significant degree of constrained stasis throughout the section. The rarer Type II lineage exhibits an equivocal morphological trend, but the current numbers of samples and specimens are too low to confirm this. Further work will increase the resolution of the section, as well as extend to the Upper Silurian, and test the potential sister-taxon status of the Type I and Type II species.


ROSS, Charles A., Dept. of Geology, and June R.P. Ross, Dept. of Biology, Western Washington University, Bellingham, WA, USA

A biological species is "a population of genetically compatible, randomly interbreeding individuals that are morphologically similar and produce viable offspring." Because in paleontology we can only work with the "morphologically similar" part of this definition, estimates and assessments of the variability of similar specimens in a population in one sample, or among a set of samples, form the concept of a morphological (paleontological) species. This paleontological species is construed in the "eye of the paleontologist" to be similar to the morphological variation which that paleontologist might expect to see in an interbreeding species population. Discontinuities in a morphological continuum are widely used to separate different populations into paleontological species. Charles Darwin noted nearly 150 years ago that the paleontological record is very incomplete. Recent studies of depositional sequence stratigraphy and sequence boundaries have illustrated that indeed the stratigraphic record has a multitude of significant depositional breaks and hiatuses. Studies of paleosols and depositional environments associated with the hiatuses at depositional sequence boundaries show that the time breaks commonly are of much longer duration than most stratigraphers, biostratigraphers, and paleontologists have taken into account. As shown by a number of well documented examples, the concept of "sequence evolution" and "sequence extinction" takes into account that morphological discontinuities observed across breaks in the sedimentary succession of fossil phylogenetic lineages (i.e., through time) are usually perceived by paleontologists as serving to distinguish different species.


ROTHWELL, Gar W., Dept. of Environmental and Plant Biology, Ohio University, Athens, OH, USA

Ferns have been important components of North American vegetation throughout the Cenozoic. Homosporous species comprised the principal ground cover in many early Paleogene landscapes, and radiated to occupy diverse niches in multistoried tropical forest communities. At the generic level, the diversity of heterosporous water ferns has remained constant throughout the Tertiary, and these species are probably as important in wetland habitats today as they were at the end of the Mesozoic. The diversity of terrestrial species is more difficult to estimate. The herbaceous growth form of most ferns contributes to their significant under representation in the most common fossil leaf floras. In contrast, representatives of selected living families, genera and even species are present throughout the Tertiary. These suggest that mean species longevity for ferns may be much greater than for seed plants, particularly angiosperms. Several depositional regimes preserve relatively complete floristic pictures of some habitats, and these provide revealing insights to the ecological roles of ferns throughout the Tertiary. Emergent or floating members of aquatic communities are often preserved more or less in situ, as are wetland species that have been inundated by floods. Some of the most revealing evidence for the roles of ferns in Tertiary plant communities derive from in situ assemblages associated with volcanism. Included are compressed floras buried by ash falls and permineralized chert biotas. An evaluation of these data suggests that ferns have been replaced by flowering plants in prairie biomes of the Neogene, Quaternary and Recent, but otherwise may have maintained important ecological roles through Tertiary and Quaternary time.


ROY, Kaustuv, and Deborah P. Balch, Section of Ecology, Behavior and Evolution, Div. of Biology, University of California San Diego, La Jolla, CA, USA; and Michael E. Hellberg, Dept. of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA

Ongoing studies of biotic response to Pleistocene climate change have either, focused on ecological aspects such as changes in species associations or on genetic changes. The phenotypic consequences of global climate change have remained surprisingly neglected despite the excellent Pleistocene fossil record of many vertebrate and invertebrate taxa. Molecular phylogeographic analyses in conjunction with phenotypic measurements from living and fossil assemblages can provide important insights into the evolutionary responses of species and populations to climate change. Such integrative analyses not only provide insights into the evolutionary process but also have important implications for conservation of many species and populations. We used mitochondrial sequence data in conjunction with morphological measurements from living and Pleistocene assemblages to quantify the evolutionary responses of two northeastern Pacific marine gastropods to late Pleistocene climatic changes. The results show that exclusive dependence on genetic markers, as is the practice in most phylogeographic studies, only provides an incomplete picture of how the populations responded to environmental change. However, combining population level phylogenies with information from the Pleistocene fossil record reveals geographic areas where populations have seen rapid morphological evolution since the late Pleistocene. In the case of one gastropod, such areas may also harbor populations that are currently being threatened by other introduced species and may be in need of protection. Clearly, a better understanding of how species respond to climatic changes requires that we integrate ecological, genetic, morphological and paleontological data.


RUBIDGE, Bruce S., Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, Johannesburg, South Africa; Sean P. Modesto, Dept. of Paleobiology, Royal Ontario Museum, Toronto, ON, Canada; and Romalo Govender, Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, Johannesburg, South Africa

The Karoo of South Africa preserves a wealth of therapsid amniotes which have been utilized in the biostratigraphic subdivision of the Beaufort Group. Systematic fossil collecting from the rocks of the paleoshoreline contact zone between the Beaufort and Ecca groups has revealed the diachroneity of this contact and the presence of a new biozone (Eodicynodon Assemblage Zone) below the Tapinocephalus Assemblage Zone, which was previously considered the lowermost biozone of the Beaufort Group. Our results show that faunal changes occur within the Tapinocephalus Assemblage Zone and that it may be possible to subdivide this biozone.

Although sparse, a new diverse fauna of primitive synapsids have been discovered along the Beaufort-Ecca contact. These include a relatively well-preserved specimen of the varanopseid Elliotsmithia, Patranomodon and Anomocephalus, the most basal anomodonts known, and the primitive dicynodont Eodicynodon. Dinocephalians include the primitive anteosaurid Australosyodon, and Tapinocaninus, the most basal tapinocephalid. The fully articulated skeleton of the latter genus reveals much new information on the postcranium of basal therapsids. In addition, a number of new primitive dicynodonts are currently being described. These discoveries of basal therapsids suggest that Gondwana, rather than Laurasia, was the center of origin and radiation for many basal therapsids.