NAPC 2001
June 26 - July 1 2001 Berkeley, California
Abstracts, Ra - Ru
(5/22/01)
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GELATINOUS ANIMAL REMAINS: MIMICKING THE GEOLOGIC
RECORD
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.
LOWER CRETACEOUS (UPPER BARREMIAN-LOWER
ALBIAN) PALEOBIOGEOGRAPHY OF THE KOPET DAGH BASIN IN NORTH EAST OF IRAN
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).
INDIRECT EVIDENCE OF SAIL PRESENCE FROM A HEALED
SPINOUS PROCESS FRACTURE IN DIMETRODON
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.
DID GRASSLANDS SPREAD WITH CENOZOIC DRYING
AND COOLING, OR VICE VERSA?
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.
BIOFILM ARCHITECTURE OF CRYPTIC MICRITE VENEERS
IN CARBONATE SEDIMENTS
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.
ARTHROPHYCUS AND THE PROBLEM OF COMPOUND
TRACE FOSSILS
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.
ICHNOFOSSIL-LAGERSTÄTTE IN ALABAMA:
A WORLD-CLASS CARBONIFEROUS (WESTPHALIAN A) TRACKSITE
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.
ASSESSING THE ROLE OF INVASIVE SPECIES IN MEDIATING
MASS EXTINCTIONS: A CASE STUDY USING DEVONIAN PHYLLOCARIDS
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.
BIVALVE PREY MORPHOLOGY AS A GUIDE TO DRILLING
STEREOTYPY OF NATICID AND MURICID GASTROPODS: VENERIDS, MURICIDS AND NATICIDS
IN TROPICAL AMERICA
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.
A MORPHOMETRIC ANALYSIS OF MICROEVOLUTIONARY
MODE IN THE LOWER DEVONIAN CONODONT LINEAGE "OZARKODINA"
WURMI
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.
THE CONCEPT OF SEQUENCE EVOLUTION AND SEQUENCE
EXTINCTION
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.
CENOZOIC FERNS OF NORTH AMERICA: PRESERVATION,
ECOLOGY AND EVOLUTION
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.
MOLECULES, FOSSILS, CLIMATE CHANGE AND EVOLUTION:
EXAMPLES FROM MARINE GASTROPODS
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.
BASAL THERAPSID FAUNA FROM SOUTH AFRICAIMPLICATIONS
FOR THERAPSID ORIGINS
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.
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