NAPC 2001
June 26 - July 1 2001 Berkeley, California
Abstracts, La - Ly
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DEPOSITIONAL ENVIRONMENTS IN THE TYPE AREAS
OF THE CHADRONIAN, ORELLAN, WHITNEYAN, AND ARIKAREEAN NALMAS, NEBRASKA,
USA
LAGARRY, Hannan E., James B. Swinehart, and Leigh Anne LaGarry, Conservation
and Survey Division, University of Nebraska, Lincoln, NE, USA
This paper summarizes recent 1:24,000-scale geologic mapping of the type
areas of the Chadronian (Peanut Peak Mbr., Big Cottonwood Creek Mbr.,
Trunk Butte beds, Chadron Fm.), Orellan (Orella Mbr., Brule Fm.), Whitneyan
(Whitney Mbr., Brule Fm.), and Arikareean (Sharps beds, Brule Fm.; Ash
Creek beds; Monroe Creek Fm.; Harrison Fm.; Coffee Mill Butte beds; Harrison
Fm.; Upper Harrison beds) North American land mammal ages (NALMAs). These
NALMAs were originally defined as geochrons bounded by prominent marker
beds (e.g., "upper purplish-white layer"). However, our map
units are based on lithology and allow a more refined understanding of
the sequence and distribution of depositional environments across the
region during late Eocene through early Miocene time. The Chadronian NALMA
is represented by deposition of eolian and fluvially reworked volcaniclastic
silts over broad, relatively stable uplands and lowlands with incised
valleys, intermittent lakes, and evaporitic basins. Orellan time was marked
by a changed to fluvially dominated environments with repeated incision
and backfilling of small valleys. During Whitneyan time eolian volcaniclastic
silts were deposited over the entire region. Fine-grained eolian deposition
continued into early Arikareean time. In early Arikareean time, three
E-W drainages were incised, backfilled by coarse-grained sediment, and
buried by eolian volcaniclastic sands. At least three ergs existed in
the region during this time. These occasionally stabilized ergs were followed
by the deposition of additional valley fills; burial by volcaniclastic
eolian silt, and intermittent landscape stability. This work was supported
by the 19962000 Conservation and Survey Division STATEMAP program.
REVISED PALEOGEOGRAPHY OF BASAL WHITE RIVER
GROUP STRATA (EOCENE), NORTHERN GREAT PLAINS, USA
LAGARRY, Leigh Anne, Conservation and Survey Division, University of
Nebraska, Lincoln, NE, USA; Mary Anne Holmes, Dept. of Geosciences, University
of Nebraska, Lincoln, NE, USA; and Hannan LaGarry, Conservation and Survey
Division, University of Nebraska, Lincoln, NE, USA
Based on geologic mapping and lithologic correlations of basal White
River Group strata in NW Nebraska and adjacent areas, we expand the geographic
extent of the Chamberlain Pass Formation (CPF). The CPF consists of pedogenically
modified white channel sandstones and extensive red and green overbank
silty claystones deposited on a broad, shallowly incised, well-drained,
heavily vegetated stable landscape supporting deciduous hardwood open
canopy and riparian forests in a humid, strongly seasonal climate. We
have mapped or observed facies of the CPF west to the Sherrill Hills of
eastern Wyoming, north to the Railroad Buttes and Big Badlands of South
Dakota, and east to Keya Paha County in north-central Nebraska. Previous
workers identified similar beds at Lance Creek, Wyoming, Slim Buttes,
South Dakota, and in the Little Badlands of North Dakota. Reinterpretation
of subsurface data suggests that the CPF filled a >61 m deep NW to
SE trending paleovalley across the Nebraska panhandle and extends south
to Morrill County, Nebraska. Vertebrate fossils from the areally extensive
overbank facies of the CPF are rare due to the long duration of surface
exposure and acidic environments of soil formation. Fossils recovered
from the channel sandstones include a lower jaw, associated upper teeth,
and postcranial elements of a brontothere more primitive than those in
Chadronian faunas. Destruction of bone by severe pedogenic modification
makes correlation of the CPF based on fossil mammals nearly impossible,
but earlier workers assumed a Duchesnean age for the sandstone facies.
Our reexamination of this unit suggests that the CPF represents a time
of widespread landscape stability and is the earliest preserved regionally
extensive Tertiary deposit of the northern Great Plains. This work was
funded by The University of Nebraska-Lincoln Conservation and Survey Division
STATEMAP project and the Nebraska National Forest. Fossils discussed here
are housed in the University of Nebraska State Museum.
LATE WHITNEYAN, ARIKAREEAN, AND EARLIEST HEMINGFORDIAN
OREODONTS (MAMMALIA: ARTIODACTYLA: AGRIOCHOERIDAE AND OREODONTIDAE) FROM
THE JOHN DAY FORMATION OF CENTRAL OREGON
LANDER, E. Bruce, Paleo Environmental Associates, Inc., Altadena, CA,
USA; and Theodore J. Fremd, John Day Fossil Beds National Monument, Kimberly,
OR, USA
Based on the shared occurrences of age-diagnostic agriochoerid and oreodontid
species and subspecies, stratigraphically superposed land mammal assemblages
in the John Day Formation (JDF) can be correlated with taxonomically similar
land mammal assemblages in the upper White River, the Arikaree, and the
lower Hemingford Groups (WRG, AG, HG, respectively) in the central Great
Plains (CGP). Late Whitneyan assemblages in the lower Turtle Cove Member
of the JDF are dominated by Agriochoerus antiquus guyotianus and
Eporeodon occidentalis occidentalis, which also occur in Whitney
B/C intervals and/or in the Leptauchenia beds of the Brule Formation
of the WRG, and by the endemic Eucrotaphus trigonocephalus.
Earliest Arikareean assemblages of the JDF are dominated by E. occidentalis
major and also contain Oreodontoides oregonensis, A. a. guyotianus,
and E. trigonocephalus. With the exception of E. trigonocephalus,
these taxa also occur in the Brown Siltstone member of the Brule Formation
and/or in the Gering and Sharps Formations of the AG. Late early Arikareean
assemblages, which occur above the Deep Creek Tuff in the JDF, are dominated
by Merycochoerus superbus and also contain E. o. major, O. oregonensis,
and Merycoides pariogonus, all of which also occur in the upper
Gering and Sharps Formations and in the Monroe Creek Formation of the
AG.
Assemblages of presumed early late Arikareean age in the JDF contain
Merycochoerus chelydra chelydra, which also occurs in the Harrison
Formation of the AG. Latest Arikareean assemblages of the JDF are dominated
by the endemic Paroreodon parvus and contain Hypsiops breviceps,
which also occurs in the upper Harrison Formation and probably the Upper
Harrison Beds of the AG.
Earliest Hemingfordian assemblages in the Haystack Valley Member of the
JDF contain Merycochoerus matthewi, Merychyus elegans arenarum,
and possibly Merycoides longiceps, which also occur in the lower
Runningwater Formation and the Upper Rosebud Beds of the HG.
HETERASTRIDIUM: A PLANKTONIC INVERTEBRATE
IN THE UPPERMOST TRIASSIC
LARSEN, Martin C., Dept. of Geology, University of Montana, MT, USA
Restricted to the uppermost Triassic strata, Heterastridium are
spherical fossils hypothesized to have increased in size during their
evolution. Further, they are postulated, based on functional morphology
and wide paleogeographic distributions, to have exploited a pelagic-planktonic
mode of life. To test the first hypothesis, measurements of the diameters
were made, along with the ages of each specimen correlate with age based
on ammonoid and conodont biochronology. A clear trend of size increase
through geological time follows Cope's rule and makes this taxon useful
in biostratigraphic classification and dating. The specimens for the project
consist of material in the Research Collection at the University of Montana,
the U.S. Geological Survey's collections, and specimens from a parallel
study at the University of British Columbia, Vancouver. To test the mode
of life a suitable program was required in order to determine the original
porosity of the aragonitic skeleton. Thin sections of the specimens were
studied to assess the porous construction of the aragonitic coenosteum,
which consist of numerous radial series, zooidal tubes and coenenchyme.
These observations, Heterastridium's occurrence in nearly all marine
facies, and its worldwide distribution, support the pelagic-planktonic
hypothesis.
THE CENOZOIC EVOLUTION OF ANTARCTIC RADIOLARIAN
FAUNAS
LAZARUS, David. B., Museum fuer Naturkunde, Berlin, Germany
Antarctic radiolarian faunas today are moderately diverse and highly
endemic, and differ radically in composition from adjacent faunas of temperate
waters. Fossil faunas are well preserved in deep sea sediments and provide
a record of evolutionary change that can be compared to paleoenvironmental
changes.
Mid-Eocene and older faunas from the Southern Ocean show some
endemism but are largely dominated by temperate water cosmopolites. Beginning
in the late Eocene endemism increases. This appears to be in response
to the development of a distinct Antarctic water mass and polar circulation
system, caused by the separation of southern Australia from Antarctica.
The endemic fauna spreads from relatively near the continent in the late
Eocene to a broad region comparable in area to the modern Southern Ocean
by the early Oligocene. Later Oligocene and Neogene faunas appear to evolve
largely in situ, although there are several shorter lived episodes
of decreased endemism caused by the influx of "warmer" water
species. Late Neogene to Recent faunas are dominated by extinction and
the overdominance of just a few species, notably those of Antarctissa.
Although tectonics plays a major role in triggering water mass changes,
most radiolarian evolution appears to be more directly driven by changes
in the water masses and currents themselves. The late Neogene decrease
in diversity appears to be linked to reduced Southern Ocean productivity,
possibly the result of increases in sea-ice coverage. Lastly, many Cenozoic
species in the Antarctic appear to have had closely related sister taxa
in either low-latitude upwelling areas, or in north polar regions, suggesting
that allopatric speciation between polar regions has been important as
well, with upwelling regions serving as stepping stones for faunal transfer.
EVALUATING THE ACCURACY OF DRILLING FREQUENCY
AS AN ESTIMATE OF PREY PREFERENCE AND PREDATION INTENSITY
LEIGHTON, Lindsey R., Dept. of Geology, University of California, Davis,
CA, USA
Studies of drilling predation often use drilling frequency, the percentage
of individuals of a given taxon or community that have been drilled, as
an estimate of (a) the predator's prey preference, and (b) the intensity
of drilling predation in a given community. Estimations of prey preference
assume optimal foraging by the predator. Encounters between most drilling
predators and their prey are sequential; upon encountering potential prey,
the predator's choice is, either to attack, or continue searching. For
optimal foragers, the decision whether to take a prey type is based on
whether the available prey will provide more net energy per unit time
than the average of other taken prey types in the system; the encounter
rate with these other prey must be considered. The predator maximizes
net energy over time when a given prey type is always ignored or always
taken: the zero-one rule. This result implies that all taken prey types
should have similar drilling frequencies; drilling frequency is not indicative
of prey preference. Observed differences in drilling frequency may be
due to differences in encounter rate, or to time-averaging.
Analysis of pooled drilling frequencies of communities, as a means of
assessing relative predation intensity, holds promise, but may be questionable
in systems in which the predator need not drill its prey. For example,
naticid gastropods do not need to drill Ensis; the prey can be
penetrated through a gape. As prey that do not require drilling probably
cost less energy to kill, they usually will be among those prey taken.
Optimal foraging models reveal that the abundance of such prey not only
effect overall pooled drilling frequency, but also the pooled drilling
frequency for drilled prey. Practical examples from the Devonian and the
Neogene demonstrate this phenomenon.
PALEOBIOLOGY AND PALEOBIOGEOGRAPHY OF CORUMBELLA,
A LATE NEOPROTEROZOIC EDIACARAN-GRADE ORGANISM
LESLIE, Stephen A., Dept. of Earth Sciences, University of Arkansas at
Little Rock, Little Rock, AR, USA; Loren E. Babcock, Dept. of Geological
Sciences and Byrd Polar Research Center, The Ohio State University, Columbus,
OH, USA; Anne M. Grunow, Byrd Polar Research Center, The Ohio State University,
Columbus, OH, USA; and Georg R. Sadowski, Instituto de Geosciencias, Universidade
de São Paulo, São Paulo, Brazil
Corumbella werneri Hahn et al., 1982, is the most abundant macroscopic
body fossil in the Tamengo Formation (Corumbá Group; upper Neoproterozoic)
of Mato Grosso do Sul, Brazil. Recent collecting in Mato Grosso do Sul
has yielded new material that sheds considerable new light on the morphology
of this organism and its phylogenetic affinities. Comparison with Corumbella
from the western United States provides important support for a late Neoproterozoic
age for the Tamengo Formation of Brazil, and potentially for a relatively
close juxtaposition of the Amazon craton and the Laurentian craton during
the latest Neoproterozoic. The morphology and phylogenetic affinities
of Corumbella werneri, type species of the genus, is reinterpreted
based on the new material from the Tamengo Formation. Corumbella
secreted a narrow, elongate, tetraradially symmetrical tube. Reinterpretation
of tube morphology and new evidence of reproduction by means of budding
indicate close affinities with the present-day coronate scyphozoan cnidarian
Stephanoscyphus, and possibly the Paleozoic-Mesozoic conulariids.
Corumbella may have value for interpreting paleogeographic relationships
between terranes rifted from the most recent late Neoproterozoic supercontinent
(Rodinia or Pannotia). Corumbella species are known from only two
Neoproterozoic localities: western Brazil and western United States. We
recognize that paleogeographic interpretations based on such limited data
must be viewed with caution. However, the shared presence of Corumbella
on both the Amazonian and Laurentian cratonic areas is consistent with
the hypothesis that these areas were in relatively close juxtaposition
at the close of the Neoproterozoic. Likewise, the shared presence of Cloudina
in western Brazil and the western United States further supports the hypothesis
of a relatively close paleogeographic position between the Amazonian and
Laurentian cratons.
THE CAMBRIAN EXPLOSION: MOLECULAR DIVERGENCE
TIMES, PROBABILITIES, AND SIMULATIONS
LEVINTON, Jeffrey, Dept. of Ecology and Evolution, SUNY at Stony Brook,
Stony Brook, NY, USA; Lindsey Dubb, Dept. of Genetics, University of Washington,
Seattle, WA, USA; and Gregory Wray, Dept. of Biology, Duke University,
Durham, NC, USA
The fossil record is currently consistent with a model approximating
a near basal rapid Cambrian divergence of animal groups. In concordance
with the estimate of Wray, Levinton, and Shapiro (1996) most molecular
estimates of the Protostomata-Deuterostomata divergence time are considerably
older than the Cambrian, centering around 800900 million years ago.
These estimates, however, are widely scattered and it is possible that
a number of biases make molecular divergences unreliable. But if they
are unreliable then a paradox arises: The order of molecular divergence
estimates of protostome-deuterstome, echinoderm-chordate, and agathan-gnathostome
fishes can be recovered with highly improbable accuracy relative to a
null model (p = 10(-5) to 0.03, depending upon assumptions).
If the divergences occurred in a very short time, as indicated by fossil
occurrences, and if the molecular clock is so inaccurate, then why are
the divergence orders recovered so faithfully? We are conducting simulations
of evolutionary radiations, varying the ratio of the time of divergence
to subsequent evolution using various molecular evolution models. Parameters
incorporating an extreme Cambrian explosion time (ca. 10 my) or a slightly
more prolonged time (ca. 30 my) do not permit accurate phylogeny reconstruction.
Success did not exceed 80 percent at the time of the Cambrian without
an extended divergence time interval of at least 100 my. Using larger
numbers of taxa (25) the proportion of clades that were correct was quite
small unless very large divergence times were used. This seems inconsistent
with our success in getting such estimates of order of divergence time
from actual data. Our results militate against the likelihood of an Early
Cambrian or slightly longer explosion of the animal phyla, as apparently
recorded by the fossil record.
THERE'S NOT MUCH MEAT IN A BRYOZOAN ZOOID: SMALL
PREDATORS AND BOREHOLES VERSUS BIG INDUCTIVE REASONING IN CHEILOSTOME
BRYOZOANS
LIDGARD, Scott, Dept. of Geology, Field Museum of Natural History, Chicago,
IL, USA
One major evolutionary trend in cheilostome bryozoans is the broad secular
increase of calcified armament of the frontal wall of the zooid, in all
likelihood to protect the soft tissues inside from predators or mechanical
stress. An inductive explanation uses the observation that variation in
zooid calcification is greatest in the exposed frontal wall, not in the
lateral, transverse or basal walls. Fossil drilling predation is evidenced
by small, centrally located and uniformly positioned boreholes. Yet, this
fossil evidence is actually quite sparse. Reports of modern predators
are dominated by omnivorous fishes and macroinvertebrate grazers, and
from nudibranchs at the shallow extreme of bryozoan depth ranges. A broad
survey of reported bryozoan predators reveals that zooid-scale boring
and demineralizing predators do exist, including turbellarians, nematodes,
errant polychaetes, and both juvenile and adult prosobranch and opisthobranch
gastropods. Some of these predators' feeding behaviors also circumvents
skeletal armament by attacking fleshy everted polypides or boring through
uncalcified zooid operculae without leaving skeletal boreholes. Skeletal/non-skeletal
weight ratios and mechanical resistence to puncture suggest that for some
drilling or demineralizing predators, dining on thickly calcified zooids
may be overpriced energetically relative to uncalcified zooids. Species
with uncalcified frontal walls make up a disproportionately large percentage
of all cheilostomes reported in these predators' diets. Lastly, fossil
skeletal evidence of frequent reparative zooid budding in taxa with uncalcified
frontal walls supports the probable existence of zooid-scale predators
from the earliest stages of cheilostome diversification. Small predators
have probably been grossly underrepresented by collecting and observation
biases.
MARINE ANGIOSPERM PATELLOGASTROPODS FROM THE
DOMINICAN REPUBLIC NEOGENE: A SPATIAL-TEMPORAL WAY POINT BETWEEN EOCENE
EUROPE AND RECENT NORTH AMERICA
LINDBERG, David R., W. Brian Simison, and Emina Begovic, Dept. of Integrative
Biology and Museum of Paleontology, University of California, Berkeley,
CA, USA
Specialist herbivores are rare in marine systems, and often specialist
species thought to be more likely to become extinct. Marine sea grass
limpets first appearance in the Eocene of the Paris Basin with a high
morphological diversity that is correlated with fossil sea grass leaf
widths. Today there are four species in North Pacific, one extinct species
in Northwestern Atlantic, and one species in Australia. In the North Pacific
the distribution of plants and limpets are not congruent. There are two
patterns: In the NorthLottia alveus and Lottia angusta track
the northern range of Zostera marina, while in the southLottia
depicta occurs only on southern populations of Zostera marina and
Lottia paleacea occurs on southern populations of Phyllospadix
spp. A molecular phylogeny of these taxa was necessary to resolve relationships
because of possible homoplasies in sea grass morphology. Both COI and
16s mDNA genes produce a phylogeny that suggests two distinct radiations
of sea grass limpets in North PacificLottia alveus in the North
and Lottia depicta and Lottia paleacea in the south. The
lineage of Lottia depicta and Lottia paleacea was tropical
and present in the continuous Panamic-Caribbean region. The ancestral
clade is likely represented in the MiocenePliocene fossils of the
Dominican Republic and shell structure data connects these taxa back to
the Eocene Paris Basin fauna. Without phylogeny the ecological scenario
of adaptive radiation associated with habitat diversification would have
remained plausible, but untested.
EOCENE ANGIOSPERM REMAINS FROM VANCOUVER
ISLAND
LITTLE, Stefan A., and Ruth A. Stockey, Dept. of Biological Sciences,
University of Alberta, Edmonton, AB, Canada
Large numbers of permineralized angiosperm remains have been recovered
from the Late Eocene Appian Way locality from Vancouver Island, British
Columbia. Fossils are represented by water washed fruits, seeds, leaves
and toredo-bored wood remains in calcareous concretions containing numerous
gastropods that help to date the sediments. Fossils are studied using
the cellulose acetate peel technique. The angiosperm remains are found
in close association with those of cupressaceous/taxodiaceous conifers
and at least three types of ferns. Some of the most prominent recognizable
fruits and seeds include those of Juglandaceae, Annonaceae, Cornaceae
(Mastixioideae) and Magnoliaceae. Fruits and seeds are closely comparable
to the London Clay Flora of southern England and the Clarno Nut Beds Flora
of western North America. At least 14 kinds of undescribed fruits and
seeds have been preliminarily identified from Appian Way. Due to the large
number of specimens, there is much promise for future study despite the
apparent transport of these plant parts prior to deposition and preservation
in a shallow marine environment.
DIVERSITY PATTERNS OF CRETACEOUS CORALS
LOESER, Hannes, Estación Regional del Noroeste, Instituto de Geología,
Universidad Nacional Autónoma de México, Hermosillo, Sonora,
México
Variation in specific and generic richness of corals through the Cretaceous
is presented using an extensive computer database of worldwide Cretaceous
coral indications. After an increasing number of taxa in the Early Cretaceous,
which ceased in the Early Aptian, a phase of extinction took place that
lasted until the Early Cenomanian. During the Cenomanian many new genera
and species appeared, but became rapidly extinct and were replaced by
Turonian taxa. A second phase of evolution started in the Coniacian and
continued into the Santonian, but was overlapped by an extinction phase
from the Late Santonian that ceased at the K/T boundary. The phases are
represented by different taxonomic groups. Whereas the Early Cretaceous
is dominated by genera that originated in the Middle to Late Jurassic,
the Late Cretaceous is characterized by genera that became established
during the Early and Late Cretaceous. Generally, genera and species were
long-lived. The endemism of species is extremely high; faunas of the European
Boreal, Tethys, the Asian Tethys and Caribbean provinces have a high number
of joint genera but also show numerous endemic genera and many endemic
species.
Species richness and evolutionary changes are compared to the sea level
changes and the abundance of continental-margin anoxic events. The richness
of taxa correlates with a high sea level and the absence of anoxic events,
but there is no clear evidence that these conditions have also influenced
the evolution of the organism group. The coral diversity patterns are
finally compared with these of rudist bivalves and foraminifers.
TIME-DELAYED PLANT EXTINCTION AFTER THE END-PERMIAN
ECOLOGIC CRISIS
LOOY, Cindy V., Johanna H.A. Van Konijnenburg-Van Cittert, and Henk Visscher,
Laboratory of Palaeobotany and Palynology, Utrecht University, The Netherlands;
David L. Dilcher, Paleobotany Laboratory, Florida Museum of Natural History,
University of Florida, Gainesville, FL, USA; and Richard J. Twitchett,
Dept. of Earth Sciences, University of Southern California, Los Angeles,
CA, USA
Irrespective of climatic zonation or floral provinciality, terrestrial
vegetation was dramatically affected by the end-Permian ecological crisis.
The expanded nature of the Permian-Triassic siliciclastic sedimentary
record in East Greenland provides a unique opportunity for a high-resolution
palynological analysis of the vegetation dynamics associated with ecosystem
collapse and initial recovery. Six successional steps are recognized:
(a) rapid decline of closed gymnosperm woodland; (b) proliferation of
opportunistic herbaceous lycopsids; (c) establishment of high-diversity
open shrubland vegetation; (d) renewed lycopsid proliferation; (e) extinction
of typical late Permian gymnosperms; and (f) establishment of cosmopolitan
low-diversity open shrubland vegetation, characteristic for the beginning
of the Mesozoic. This succession reveals some unanticipated patterns.
There exists a significant time lag, possibly with a duration of 0.50.6
million years, between terrestrial ecosystem collapse and selective extinction
among late Permian plants. Furthermore, ecological crisis resulted in
an initial increase in regional plant diversity instead of a decrease.
These patterns resemble modeled "extinction debt" responses
of multi-species metapopulations to progressive habitat destruction.
DEEP SEA BENTHIC FORAMINIFERA AND SURFACE OCEAN
BIOPRODUCTIVITY: WHAT MORE DO WE NEED TO KNOW?
LOUBERE, Paul, Dept. of Geology and Environmental Geosciences, Northern
Illinois University, DeKalb, IL, USA
Relative abundances of benthic foraminiferal taxa in deep-sea assemblages
have long been generally associated with bioproductivity of the overlying
surface waters. Over the past 5 years, specifically developed statistical
tests have quantified this association on a global basis for surface sediments.
The result was transfer functions for estimating past surface-ocean bioproductivity
from fossil assemblages. These transfer functions have now been tested
in the eastern equatorial Pacific. Tests include comparisons to benthic
foraminiferal d13C, changing patterns of carbonate preservation,
surface ocean nutrient-tracers and geochemical tracers of productivity
such as Ba/Al and Al/Ti ratios. In all cases, the tests support the transfer
function estimates. Our ability to estimate surface ocean bioproductivity
with benthic foraminiferal assemblages is surprising because variations
in the flux of organic carbon to the seabed are relatively small at water
depths greater than 2000 m. We have the empirical evidence that this small
difference has an important effect on assemblage formation; but the reasons
for this are unclear. There is benthic community theory, which explains
general ecologic stucture at the seabed, but a specific model for foraminiferal
community response to changing organic carbon flux in the deep sea is
lacking. Confident use of the benthic foraminiferal bioproductivity proxy,
and its application to time periods preceding the late Pleistocene, requires
the development of such a model.
RELATIONSHIPS OF MAJOR MESOZOIC MAMMALIAN CLADES
LUO, Zhe-Xi, Section of Vertebrate Paleontology, Carnegie Museum of Natural
History, Pittsburgh, PA, USA; Zofia Kielan-Jaworowska, Instytut Paleobiologii
PAN, Warszawa, Poland; Richard L. Cifelli, Oklahoma Museum of Natural
History, Norman, OK, USA
We propose a phylogeny of 40 lineages of Mesozoic mammals, plus three
lineages of non-mammalian cynodonts, based on a parsimony analysis of
255 osteological and dental characters. Mammals (mammaliaforms of some
authors) are monophyletic. Within mammals, Sinoconodon is the most
primitive taxon; and Sinoconodon, morganucodontids, docodonts,
and a new early Jurassic taxon are successively closer to the mammalian
crown group. Within the mammalian crown group, there is a division of
an australosphenidan clade of Gondwana and a boreosphenidan clade of Laurasia.
Within our phylogeny, allotherians (haramiyids and multituberculates),
eutriconodonts, australosphenidans, and therians (including boreosphenidans)
form a very robust clade. However, there can be two alternative placements
for allotherians: either allotherians are sister-taxon to the clade of
the stem and living therians by strict consensus of the parsimony analysis;
or alternatively and with several additional steps, allotherians are placed
outside the mammalian crown group by a topological constraint that is
consistent with the traditional emphasis on the uniqueness of allotherian
dentition. The difference between the two alternatives in tree statistics
is small, given our dataset. There are also two alternative positions
of the "eutriconodonts" in the Mesozoic mammal phylogeny, contingent
on the placements of other clades such as allotherians, although we favor
a monophyletic eutriconodont group nested within the mammalian crown group.
Our phylogeny indicates that the "obtuse-triangle" symmetrodonts
are paraphyletic, and they lack any unambiguous synapomorphies.
A NEW, PRIMITIVE GENUS OF SEA TURTLE FROM THE
MIOCENE OF THE CENTRAL VALLEY OF CALIFORNIA
LYNCH, Shannon C., and James Ford Parham, Dept. of Integrative Biology,
University of California, Berkeley, CA, USA
Although the history of California's sea turtles extends into the Late
Cretaceous, specimens are extremely fragmentary and rare. An important
exception is material from the middle Miocene (Barstovian NALMA) Sharktooth
Hill locality, Round Mountain Silt Formation. in Kern County, California.
In addition to bearing numerous enormous leatherback (Dermochelyidae)
fossils, Sharktooth Hill has yielded a handful of hard-shelled sea turtle
(Cheloniidae) specimens.
Here we present a new member of the Cheloniidae that is unlike all other
Neogene cheloniids, but bears a striking resemblance to Erquelinnesia
from the Eocene of Europe. The material of this middle Miocene turtle
includes a curiously primitive femur, humerus and cranium, and several
lower jaws. In order to understand its phylogenetic relationship with
other members of Cheloniidae, cranial and postcranial characters were
cladistically examined. Based on our analysis, this new turtle is the
last surviving member of a clade of durophagous cheloniids that originated
in the Late Cretaceous and, until now, was thought to have gone extinct
in the early Eocene.
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