Climate models as well as the distribution and migration patterns of land plants and articulate brachiopods from the Early and Middle Carboniferous suggest that Visean latitudinal temperature gradients were relatively weak, and that the high latitudes may have been warmer than they were during the late Namurian and Westphalian. Biogeographic analysis of middle Visean brachiopod genera from Laurussia and North China supports these conclusions. Cluster analysis, multidimensional scaling and principal components analysis reveal longitudinal differentiation among brachiopod assemblages from Laurussia and the North China plate. Based on their faunal similarity, localities from the east coast of Laurussia (Urals, Moscow Basin, Donets Basin) and North China group together; localities from south central coast of Laurussia (Maritime Canada, England, Ireland and Belgium) group together, and localities from the southwest and west coast of Laurussia (Canada and the United States) group together. On recent Early Carboniferous reconstructions, the east Laurussian localities lie in equatorial, subtropical, and middle latitudes, but exhibit no paleolatitudinal differentiation. This may be the expected result for a biogeographic unit on the east coast of a large paleocontinent during an interval with a well-developed circum-equatorial current. On recent Early Carboniferous reconstructions, all of the localities from south central Laurussia lie near the paleoequator.

West Laurussian assemblages show paleolatitudinal differentiation, which may be the expected result for a biogeographic unit along the west coast of a large paleocontinent influenced by high-latitude westerlies. Within the cluster analysis, assemblages from the Appalachians, Midwest, and Southwest clustered separately from Cordilleran (Idaho, Utah, Montana, Wyoming and Nevada) assemblages. Recent paleogeographic reconstructions for the Early Carboniferous suggest that the Cordilleran localities were paleoequatorial and that the Appalachian, Midwestern and Southwestern localities lay in the southern paleo-subtropical belt. However, the relative diversity of assemblages from these two clusters suggests that the Early Carboniferous paleoequator lay to the south of the Cordilleran localities. Throughout the Early and Middle Carboniferous, individual assemblages within the Appalachian-Midwest-Southwest cluster have higher diversities than individual assemblages within the Cordillera cluster.

We have avoided a hierarchical ranking of these biogeographically distinct groups of assemblages into realms and provinces pending species and community level-analyses of Visean brachiopod communities which are in progress.

Lipids from a suite of 12 representative samples from the Lower Oxford Clay (LOC) and from the Middle and Upper Oxford Clay (MUOC) were extracted with organic solvent, separated, and analyzed qualitatively and quantitatively using gas chromatography-mass spectrometry (GC-MS) and isotopically using isotope-ratio-monitoring gas chromatography-mass spectrometry (irmGCMS). Determination of molecular structures allowed identification of compounds which retained enough chemical structural information to be recognizable as having a biochemical origin related to a specific organism or group of organisms (biomarkers). By allowing assignment of each compound to a portion of the local carbon cycle (production, sedimentation, and alteration), isotopic analyses of individual compounds provided further information regarding their origins. The 12 samples were chosen to represent the various macrofaunal assemblages define by Duff (1975) and to cover the total range of variability of the bulk geochemical parameters measured on sediments from LOC and MUOC (Kenig et al., this symposium).

A relatively high content of unsaturated hydrocarbons, as well as the abundance of biogenic forms of molecular stereoisomers such as ββ hopanes and ααα steranes and other molecular indicators, confirms the low level of maturity of organic matter in the LOC. Contributions from the two main sources of sedimentary organic matter already identified from bulk geochemical data, marine phytoplankton and terrestrial organic matter, can be recognized in the saturated hydrocarbon fraction of all the samples analyzed. However, contributions from these two sources vary as a function of the TOC content, the HI, and the δ13C of organic matter. Saturated hydrocarbon fractions of high-TOC samples, formed during periods of high marine productivity, are mainly dominated by pristane and phytane and by tetra- and pentacyclic biomarkers. This dominance decreases with the TOC content and the 13C abundance. Conversely, the relative abundance of compounds indicative of terrigenous input increases. In samples with lower TOC, n-alkanes with a strong odd-carbon preference, peaking at C27, are particularly prominent in the saturated hydrocarbon fraction.

Biosynthetic products with n-alkyl carbon skeletons are found in nearly all organisms. Accordingly, sedimentary n-alkanes are likely to derive from multiple sources. These can be partly distinguished by isotopic analysis of individual n-alkanes. In particular, marine and terrestrial sources can be resolved. Considering the variation of their relative abondance and of their isotopic composition as a function of TOC, δ13C of total organic matter and hydrogen index, the origins of n-alkanes, pristane and phytane as well as those of other biomarkers will be discussed. The paleobiological assemblage responsible for the production and alteration of the organic matter will be tentatively reconstructed.

To understand the processes controlling production, accumulation, and preservation of organic matter in the Lower Oxford Clay (LOC), we determined the hydrogen index (HI), the oxygen index (OI), the Tmax (from Rock-Eval), the content of total organic carbon (TOC), total carbon and total sulfur, and the carbon isotopic composition of bulk organic matter from 160 samples collected from 6 different quarries and one continuous core. With concentrations of TOC varying between 0.5% and 16.6%, the LOC is an organic-rich shale. For samples dominated by organic matter of phytoplanktonic origin, the hydrogen and oxygen indices and the Tmax (~418°) indicate low levels of maturity, and, thus, the shallow burial of the LOC through geologic time.

Two main sources of organic matter can be distinguished: a major phytoplanktonic source with high HI and low OI and a minor terrestrial source with low HI and high OI. A third group, represented by samples with low HI and low OI, consists mainly of altered materials from the Middle Oxford Clay and the LOC. Selection of samples for chemical analysis was based on the macrofaunal assemblages defined by Duff (1975). These various biofacies are characterized by specific organic geochemical features indicating the relationship between conditions affecting faunal assemblages and those controlling accumulation and preservation of organic matter. For example, Duff's ‘deposit feeder shales', which are dominated by epifaunal bivalves and are depleted in infaunal organisms, exhibit the highest concentration and best preservation of marine organic matter, with an average TOC of 6.8% for 56 samples analyzed. The preservation of such organic matter requires a dysaerobic water column and a high sedimentation rate.

Carbon isotopic compositions within the ‘deposit feeder shale’ biofacies (−27.6 to −23.2±) appear to have been controlled by the intensity of primary productivity. The highest-TOC, marine-dominated, 13C-rich samples reflect photosynthetic drawdown of dissolved-CO2 level, and, thus, originated in highly productive environments. On the other hand, variations in the carbon isotopic composition of organic matter in shell beds (−27.5 to −26±) probably reflect heterotrophic reworking of the organic matter, winnowing of the sediments, and mixing with a source of organic matter enriched in 13C, such as wood (δ13C from −25 to −23±). Such mixing phenomena may also explain the high variability of the carbon isotopic compositions of TOC-depleted and altered samples from the Middle and Upper Oxford Clay.

The environment of deposition of the LOC would be characterized by the alternation of two major conditions: 1) periods of high productivity, dysoxic water column and high sedimentation rate leading to the development of organic-rich shales dominated by phytoplanktonic organic matter, and 2) periods of low productivity, oxic water column and high current activity implying winnowing and alteration of organic matter, and leading to the formation of shell beds where marine and terrestrial organic matter are mixed.

What controls the diversity of life? Is it the randomness of historical contingency or the deterministic constraints of adaptive design? Several recent studies of colonial animals have suggested that nonrandom macroevolutionary patterns are common in the fossil record. These patterns generally consist of long-term, interspecific improvements in the biomechanical design and/or ecological success of some lineages over others. The problem with these previous studies is that they simply censused morphology through time. That is, they read the stratigraphic record directly. What this study does is examine macroevolutionary morphologic patterns within a phylogenetically well-defined lineage of lower Paleozoic trepostome bryozoans.

17 species of ramose trepostomes ranging from the Middle Ordovician to the Upper Silurian were examined. 16 ingroup species were analyzed: 7 species of halloporids (including species belonging to Hallopora, Parvohallopora, and Tarphophragma) and 8 species of bimuroporids (including species belonging to Bimuropora and Champlainopora). Two species of Eridotrypa were chosen for the outgroup. These ingroup taxa were selected as they are united by several synapomorphs strongly suggesting this lineage is monophyletic. Phylogenetic hypotheses were constructed from a cladistic analysis of 40 multistate, qualitative, morphologic characters using outgroup analysis and the parsimony principle. This led to a single most parsimonious cladogram of 78 steps with a consistency index of 0.641.

Within this lineage, species were examined for changes in the distribution of calcite across the colony by measuring a single, continuously varying, quantitative, morphologic character. Calcite distribution across cylindrical branching colonies has been shown theoretically by Wainwright et al. and empirically by Cheetham to affect branch strength. Calcite distribution was measured by exozone width. The exozone is the peripheral part of the colony where most of the calcite is precipitated due to the thick zooecial walls there. Exozone width is proportional to branch strength. This morphometric character is relatively independent of the qualitative characters used in the cladistic analysis.

Exozone width was measured using a personal computer-based, digital, image analysis system. To minimize operator and system error as well as to ensure that intracolony and intraspecific variation was sufficiently represented, exozone width was measured 10 times per colony. These values were then averaged to obtain colony means. The colony means were averaged to obtain species means. A total of 261 colonies belonging to the 17 species were measured.

Macroevolutionary patterns were quantified by comparing the mean exozone width for each species to 3 different evolutionary metrics derived from the most parsimonious cladogram: number of branching events each species has undergone from the base of the cladogram, number of character state transformations each species has undergone from the base of the cladogram, and the mean manhattan distance between each species and the 2 outgroup species.

Regardless of which measure of evolution is chosen, the results indicate that exozone width has significantly increased through this lineage. Linear regressions revealed that these 3 trends are significant at P = 0.05. That is, the evolutionary history of this lineage reveals a progressive, nonrandom increase in branch strength. Many more species within this lineage need to be analyzed. This pattern is significant with 17 species; it may or may not be when the project is completed with the estimated 100 species that will eventually be measured. It must also be remembered that the patterns observed are dependent on the cladogram used which is dependent on the characters chosen for the phylogenetic analysis. Though these results are very preliminary, it raises the interesting question of are progressive macroevolutionary patterns more common in colonial organisms.

Skeletal concentrations are common foci for paleontologic collecting, yet vary widely in their expected levels of taphonomic bias, particularly temporal resolution and biological fidelity. Basic concentration types include: (1) simple event-concentrations composed of anything from autochthonous-census, entirely exotic, or entirely remanié assemblages (e.g., shelly tempestites, shell-lined burrows); (2) composite concentrations of many stacked to complexly amalgamated events, accumulated in normal to expanded thickness (e.g., bioherms, shell banks & fans); (3) stratigraphically condensed hiatal concentrations having an even greater minimum degree of assemblage-level taphonomic bias (e.g., transgressive shelly sands, sediment-starved bone beds); and (4) lag-concentrations formed by erosion/corrosion of significant section and composed typically of highly culled and time-disordered skeletal material. Detailed field study of three temperate to subtropical basins in North America and reconnaissance of other basins at similar and lower paleolatitudes indicate that these four concentration types are distributed systematically within unconformity-bounded sequences and, moreover, that marine sequences vary qualitatively both in their stratigraphic anatomy (e.g. Van Wagoner et al., 1990; Einsele & Bayer, 1991) and skeletal taphonomy as a function of long-term subsidence.

I. Basins of moderate subsidence (total 10's cm/ka maintained over 1–10 ma) are characterized by “textbook” sequences composed of discrete upward-shallowing parasequences in transgressive and highstand/regressive marine phases. Taphonomically, sequences in these settings typically contain a variety of concentration types, and therefore require careful taphonomic differentiation. In the shale-rich Cretaceous Ostracode Zone (Alberta foreland basin; Banerjee & Kidwell, 1991), for example, composite shell beds mark the tops of parasequences near the basin margin, event-beds of granulated shell mark the bases of parasequences further offshore, and diagenetically complex, shell-poor hiatal limestones mark maximum flooding surfaces in the most distal areas.

II. Basins of high subsidence (total 100's cm/ka maintained over ≥1ma) are typically characterized by expanded sequences with vague parasequences; sedimentary cyclicity is linked more clearly to local tectonism and autocyclic environments than to eustasy. Taphonomically, these records are dominated by comparatively straightforward event- and composite concentrations. In the Mio-Pliocene Salton Trough (Gulf of California rift basin), for example, oyster bioherms and shell-ridges cap upward-shallowing delta-front cycles, and coral-bearing bioclastites occur along the distal toes of coastal alluvial fans and are banked against inter-fan rocky shorelines. Hiatal concentrations are poorly developed, even along downlap surfaces, and laterally extensive lags are rare.

III. Basins of low subsidence (total ≤ few cm/ka maintained over 1–10 ma) are characterized by stratigraphically telescoped sequences with poorly developed (and locally deepening-up) “parasequences”; transgressive surfaces largely coincide with sequence boundaries. Hiatal and lag concentrations are relatively common and close-spaced stratigraphically; these may be taxonomically diverse even in temperate latitudes owing to environmental condensation, and in all instances are taphonomically complex. In the Miocene Chesapeake Group (outcropping U.S. Altantic passive margin), 4 transgressive hiatal shell concentrations lie within 40 m of section; each contains up to ~100 species and rests directly on a 3rd-order sequence boundary. A starved hiatal bone bed with high microplankton diversity marks the major 2nd-order downlap surface; lags of comminuted bones, teeth, and mollusk steinkerns mantle shallow-water unconformities near lap-out.

Analysis of Frasnian conodont sequences in the Montagne Noire, southern France, results in the recognition of a conventional zonation consisting of thirteen zones. Graphic correlation of eight Montagne Noire sections with a total of 11 sections in the Alberta Rockies, the Hay River-Trout River areas of the southern Northwest Territories, Canada, the Midcontinent and New York sequences in the United States, and the Canning Basin, Western Australia divides the Frasnian into 34 composite standard units. Most of these sections are dominated by conodonts of the outer-shelf to basinal Palmatolepis biofacies, but those of Hay River-Trout River are occupied by the quite contrasting inner-shelf Polygnathus biofacies. Correlation of the latter with the Montagne Noire zonation is effected only through graphic correlation. The taxonomy of many of the critical species involved in the correlations is based on shape analysis and multielement taxonomy of Palmatolepis.

Prevailing opinion is that the Frasnian was a time of cosmopolitanism as exemplified both by benthic organisms, especially corals and brachiopods, as well as conodonts. This contrasts with the Early and Middle Devonian which was a time of significant endemism in benthic fossils and in conodonts. The high point in conodont endemism according to the zone-by-zone analysis of the Early and Middle Devonian (Klapper and Johnson, 1980) was the early Eifelian when there were about 70% endemic species. Although endemism did not reach this high in the Frasnian, analysis of a limited number of intensively collected and studied sections in the Montagne Noire, U.S. and Canada, Western Australia, and the Russian Platform demonstrates levels of endemism ranging from about 30 to 45% in three composites of two zones each. Endemic species occur in both the Palmatolepis and Polygnathus biofacies. Using the Probabilistic Index of Similarity of Raup and Crick (1979), the null hypothesis of randomness is rejected for some paired comparisons between localities representing different biofacies, as would be expected, but it is also rejected between some localities representing the same biofacies on different continents. Although the explanation of significantly dissimilar faunas can be accepted at 95% confidence levels in only a limited number of instances, there are dissimilarities of somewhat lesser magnitude among various paired comparisons. This seems to indicate that the Frasnian was not a time of conodont cosmopolitanism even within the Palmatolepis biofacies.

The Lower Devonian Haragan Formation of Oklahoma has well preserved odontopleurid trilobites found in repeated calcarous mudstones. These layers (5–9cm. thick) represent distal tempestites that rapidly buried and preserved completely articulated odontopleurids which provide important paleobiological information. The genal and pleural spines of Leonaspis williamsi and Dicranurus hamatus elegantus of the Haragan Formation are examined and compared.

In Leonaspis the ventrally directed genal and pleural spines are straight and lay flat. The first pleural spine is the longest followed by progressively shorter pleural spines. Several collected and prepared enrolled specimens have the spines radiating outward. In an enrolled position the spines would protect Leonaspis from a large predator.

The pleural spines of Dicranurus have a very different pattern from Leonaspis. The first three spines are short and laterally directed, the fourth, sixth and seventh are very long, curved and directed ventrally, the eighth, ninth and pygidial spines are short and decrease in length toward the pygidium. There is no pleural spine on the fifth thoracic segment and the genal spine is very long and curved. On these spines at many growth stages there is direct and indirect evidence of being encrusted based on the following: (1) Epibionts such as bryozoans, brachiopods and a crinoid; 2) Endoliths (25–150 microns in diameter) of unknown origin are found all over Dicranurus but are predominantly on the spines; 3) Pyrite (now limonite) coating the spines apparently formed from the decay of organic matter. If the source of the organic matter came from the trilobite, then pyrite would be found all over Dicranurus. However, it is only found randomly on the spines. This pattern is like some of the encrusting bryozoans suggesting that the source of the organic matter may be from an encrusting organism.

It is doubtful that the pleural spines of Dicranurus would be adapted for resting on the bottom when bryozoans are found encrusting the entire surface of the spine. However, the very long pleural and genal spines with attched organisms would break up the outline of Dicraurus making it less conspicuous to a predator.

As demonstrated by Silurian Konservat Lagerstätten from North America, not all Lagerstätten represent living associations but are biased taphonomically, and the conditions necessary for exceptional preservation are environmentally, temporally, and areally diverse.

The early Silurian (late Llandovery-early Wenlock; Brandon Bridge strata) Lagerstätte from Waukesha, Wisconsin, was deposited under peritidal conditions in a thin, narrow zone adjacent to a karst-formed paleoscarp during transgression. Anoxic conditions resulting from restricted circulation and eutrophication are indicated by sediment lamination, shell decalcification, absence of sessile benthos, coiling of worms, absence of Chondrites (ubiquitous elsewhere), and presence of Pacytheca alga. Although anoxia, which was neither widespread nor long-lived, excluded most benthonic organisms, arthropods are abundant and diverse. These are mainly exuviae as suggested by consistent lack of specific body parts, extreme compaction, monotaxic size-sorted assemblages, absence of trackways and escape traces, and absence of enrollment in response to anoxia. This then is not a living association, but a taphonomic accumulation of mostly arthropod exuviae that were concentrated hydrodynamically.

Arthropods (mainly eurypterids and phyllocariids) dominate late Silurian (Ludlow-Pridoli; various units) Lagerstätten that were deposited in hypersaline peritidal lagoons surrounding the Michigan Basin in the U.S. and Canada. Although less diverse, these biotas were more widely distributed and of longer duration than the Waukesha Lagerstätte. Hypersalinity inhibited bacterial decomposition and lowered oxygen solubility, further excluding benthos by creating interstitial anoxia. These compose another example of taphonomically biased Lagerstätten, consisting chiefly of arthropod exuviae.

The late Silurian (Ludlow, Racine Dolomite) Lecthaylus Lagerstätte was deposited in deeper water on the shelf or slope of the Michigan Basin in northeastern Illinois. The limited biota, dominated by a single worm taxon (Lecthaylus) includes phyllocariids, graptolites and inarticulate brachiopods. Worms are outstretched and grouped in an orientation that suggests in situ burial. Laminated strata are succeeded by bioturbated sediment in cyclic repetition, indicating recolonization by wormlike burrowers (Lecthaylus?) following rapid sediment influx and burial of the biota under interstitial anoxic conditions. This is probably an autochthonous biota; sessile benthonic organisms may be absent as a result of soft substrate consistency or high sedimentation rate.

These Silurian Lagerstätten show that anoxia required for early diagenetic mineralization and exceptional preservation may be established in different amounts of time and in various ways (stagnant sediment trap, hypersalinity, obrution) and settings from peritidal to shelf/slope. Identification of these variations is important for prediction of additional Lagerstätten sites. Although arthropods in exuviae-dominated Lagerstätten may accurately reflect their true taxonomic diversity, they are probably present in greater numbers and in higher dominance relative to other taxa than in living associations.

The Vendian interval (ca. 610–540 Ma) links Proterozoic and Phanerozoic worlds of sharply contrasting character. Despite decades of study, the nature of this transition remains unclear, in part because of our limited ability to correlate Vendian successions or evaluate shifts in global environments. New data on secular variations in the C and Sr isotopic compositions of Vendian carbonates (and organic matter) provide an improved stratigraphic and biogeochemical framework for understanding latest Proterozoic biological and environmental evolution.

Biologically, the Vendian interval is best known for the Ediacaran radiation of macroscopic animals, but this event is set within a broader Neoproterozoic diversification of higher eukaryotes. All three principal groups of multicellular algae radiated well before the beginning of the Vendian, as did a host of unicellular protists. In particular, successions deposited immediately after the Varanger Ice Age (ca. 610–590 Ma) are characterized by a high diversity of large and morphologically complex acritarchs; most of these forms disappeared after the first appearance of Ediacara-grade metazoans but before the eponymous fauna preserved in South Australia.

Stratigraphic ordering of the earliest faunas is made possible by chemostratigraphy. Contrary to some published expectations, the morphologically complex petalonemids and skeletalized cloudinids of the lower Nama Group, Namibia, appear to predate, perhaps significantly, the classic faunas of South Australia, eastern Siberia, and elsewhere. Zircon ages for tuffs promise an absolute chronology for biological and biogeochemical events. The presence in pre-Cambrian rocks of Cloudina, calcareous algae and (?)siliceous discs comparable to chrysophyte scales demonstrates that eukaryotic calcite, aragonite, and silica biomineralization all predate the beginning of the Cambrian; however, sedimentological and petrographic features of carbonates and cherts suggest that skeletons first emerged as globally significant components of the carbon and silica cycles with the basal Cambrian radiation.

Vendian evolution must also be evaluated within a broader context of environmental change. The Sr and C isotopic data that enhance stratigraphic correlation also record patterns of hydrothermal emission and organic carbon burial that must have affected pO2. Independent models by Derry and others and Knoll and Walker suggest that latest Proterozoic reductions in the hydrothermal flux of reduced materials into the oceans coupled with high burial rates of organic carbon resulted in a significant increase in global oxygen levels immediately prior to the great Ediacaran radiation.

Many questions about Vendian evolution remain unresolved. Some will surely require fresh insights into the development and functional morphology of early metazoans, but it is becoming increasingly clear that a satisfactory accounting of Ediacaran animal diversification will not be achieved without a better understanding of the stratigraphic, environmental, and biological context in which it occurred.

Land mammal faunas changed dramatically from the late Paleocene to the Eocene. This interval was marked by substantial paleoceanographic changes, including marine warming, and mass extinction of benthic foraminifera. Yet study of the impact of marine events on continental climates and faunas is problematic, due to imprecision in marine/continental correlation.

Oxygen isotope measurements of paleosol carbonates, mammals, and bivalves from the Paleogene Bighorn Basin can be used to estimate mean annual temperature (MAT). The δ18O of paleosol carbonate is controlled by two factors: the δ18O of the groundwater from which it crystallizes, and the temperature during crystallization. Because mammals and bivalves secrete mineral in a biologically-restricted range of temperatures, their isotopic compositions serve as proxy indicators of surface water δ18O. The difference in δ18O between these proxy indicators of water and paleosol carbonate is used to calculate MAT through application of standard oxygen isotope thermometry relationships. Calculated temperatures vary significantly throughout the interval, with high values (>20°) in the late Paleocene, lower values in the earliest Eocene (10–20°), and renewed warmth later in the Early Eocene.

In modern temperate regions, MAT and the δ18O of precipitation are closely correlated. Estimates for Paleocene/Eocene surface waters from tooth apatite and bivalves range from −8 to −12± (SMOW). Today, precipitation with values this low is usually found in cold regions (0–10°). These temperature estimates are too low in light of other isotopic and paleobotanical indicators, which suggest very warm temperatures in the Bighorn Basin during the Paleogene. We hypothesize that vapor transport to the region was substantially different than at present. A potential model may be Amazonia, where wet season air masses lose up to 80% of their water vapor as they move across the basin, resulting in 18O-depleted rainfall despite a warm climate.

Variations in δ13C provide a tool for marine/continental correlation. Carbon in tooth apatite and soil carbonate is derived from plants, which fix atmospheric CO2. Atmospheric CO2 is, in turn, in isotopic equilibrium with marine carbonate. Because of these links, marine carbonate, land plants, land mammals, and soil carbonate should exhibit coupled carbon isotope variations. In the Paleogene, when C3 plants dominated floras, isotopic variations due to shifting floral composition, such as those documented in the Miocene Siwalik Sequence, could not occur. Paleogene continental and marine carbon isotope records are tightly coupled. In particular, there is an unusual marine carbon isotope excursion immediately preceding the Paleocene/Eocene boundary, which corresponds precisely to the major paleoceanographic changes and the extinction of benthic foraminifera. Tooth apatite and soil carbonate from the Paleogene Bighorn Basin also record this excursion, which occurs at the base of the Wasatchian, where perrisodactyls, artiodactyls, and modern primates first appear. Carbon isotopes allow tight marine/continental correlation of the Paleocene/Eocene boundary, and demonstrate that major biologic and climatic events at this time were globally synchronous.

The isotopic composition of oxygen in the phosphate (δ18Op)was determined in 159 fish bones and teeth from museum collections throughout the world. The fossils were both marine and fresh-water ranging in age from the Devonian to the Recent. In 45 of those we also determined the isotopic composition of oxygen and carbon of the lattice carbonate in apatite (δ18Oc and δ13C). In most cases the isotopic results are compatible with previously available geological information: the difference between marine and fresh water, the indication of previously known warm and cold time periods, and the ranking of fishes from warm to cold according to their inferred life habitat.

Three fish specimen from the Devonian of the Orcadian Basin in Scotland yield results which are compatible with the thermal structure of a stratified lake. The isotopic analysis of Inocentrus vulgaris, a fish found inside Cretaceous inoceramids, yields normal marine δ18Op. Hence we favor the suggestion of Tourtelot and Rye (1969) that 18O depleted inoceramids did not deposit their shells in isotopic equilibrium with sea water.

The relationship between δ18Op and δ18Oc suggests early diagenetic replacement of an originally phosphatic phase by carbonate fluor apatite (CFA). This conclusion is in accord with REE studies of fish fossils. The correlated latitudinal variation in δ18O of meteoric water and temperature should result in a small variation of δ18Op in fresh water fish. The large range in δ18Op of Recent fish is the outcome the “altitude effect” (Dansgaard, 1964) i.e. of the existence of Recent high altitudes, and sharp morphological gradients.

Interpretations of geologic history would be enhanced if taphonomic processes, including color changes in shells, were better known. This study deals with the origins and alteration of post-mortem colors in podocopid ostracodes. Modern shells were subjected to elevated temperatures and pressures in reactor vessels with sediments, simulating some burial conditions. Fossil shells from outcrops and boreholes were heated and treated with solvents, in an attempt to identify the coloring agent(s).

Modern marine shells are white to pale yellow (Munsell 5Y 8/1 – 2.5Y 8/4). Upon heating at atmosphere, up to about 650°, they became slightly redder, slightly darker, and less color saturated, but never dark (Munsell “value” less than 5). From 650-850° they became yellower and lighter, and above 850° chalky and more yellow. Shells at elevated temperatures and pressures (T-P) with organic-poor sediments and/or iron compounds developed higher color values and lower chromas; they did not become dark. Thus, modern ostracode shells subjected to elevated T-P changed colors, but alone never attained the dark colors seen in many fossils. Only those heated in matured organic-rich sediment and/or crude oils became dark (dark grays, browns, and blacks), like some fossils. Fossil ostracodes from boreholes in Mesozoic and Cenozoic sedimentary rocks showed downhole color differences similar to those from experiments. That is, the colors of fossils are different in hue, value and chroma in different thermal zones and ostracode color appears to be broadly indicative of thermal history.

Fossils near igneous intrusions are dark, while the lowered values and chromas of those in metamorphics also are correlatable with paleotemperatures. Reheated dark fossils lightened at about 375-450°, eventually becoming pale yellow to white, apparently indicating that organic coloring agents were driven off. This, and the fact that modern ostracodes develop dark colors only when heated in organic-rich substances, support the contention that the dark color originates from extrinsic organic materials. Pyritized shells become weak red (Munsell 10R 4/4) upon heating; thus, they can be distinguised from those colored by organics.

Therefore, ostracode colors appear to be diagnostic of T-P and present the potential for use in paleotemperature reconstructions. A wide range of fossils, including conodonts, phosphatic brachiopods, scolecodonts, and palynomorphs are known to show recognizable and useful evidence of thermal maturation and it is proposed that ostracodes be added to the list.

The question of the response of endolithic reef communities to changes in primary framework builders that serve as hosts prompted a study to compare two different types of frameworks from two formations, one Cretaceous and the other Oligocene, from Puerto Rico. The primary framework builders from the Cretaceous Cotui Formation of western Puerto Rico are rudistid bivalves, with corals and stromatoporoids also serving as supporting organisms to a lesser extent. Both larger endolithic organisms such as lithophagid bivalves and smaller endoliths such as clionid sponges are common throughout the study area. All three framework types serve as hosts. However, actual densities of endoliths, especially the bivalves, are low per host.

Corals are the primary framework builders in the Upper Oligocene Lares Formation of northwestern Puerto Rico. In the study area, two types of coral frameworks were observed. The main reef was composed of massive coral heads, while facies interpreted as lower-energy patch reef and lagoonal environments were comprised of more delicate branching poritid-like corals. Oysters were common in both facies. Few larger endoliths were found in the branching coral. By contrast, boring bivalves including lithophagids, occurred in high densities in many of the massive coral heads. Some of the oysters were riddled by clionids.

The comparison revealed that while the composition of the two endolithic communities was similar, the abundances and differences in density of the individual endolithic organisms was markedly different. This is attributed primarily to differences in the host substrates themselves. Hosts were abundant in both the Cotui and the Lares. However, the exoskeletons of rudistids differ considerably from corals, as do stromatoporoids. External influences such as environment, may have had some impact as well.

A considerable amount of research has been devoted toward evaluating the impact of the Cretaceous/Tertiary extinction on terrestrial life. This research has focused primarily on terrestrial vertebrates (primarily dinosaurs), marine invertebrates (notably molluscs and foraminifera), and to a lesser extent, terrestrial vascular plants. Terrestrial arthropods, especially insects, have seldomly been investigated, principally because of an alleged depauperate fossil record. Nevertheless, within the past two decades, some of the most productive and taxonomically diverse insect faunas have originated from Cretaceous amber- and compression-fossil deposits from every continent. Whereas it was once thought that the Cretaceous represented an unknown void in the understanding of insect evolution, now it appears that many extant lineages are traceable to Cretaceous precursors.

Three approaches are available for determining the extent of the effect of the terminal Cretaceous extinction event on insects. Assessed for the interval from the Early Cretaceous to the Early Paleogene, these approaches are: (1) establishing the secular pattern of familial- and generic-based taxonomic diversity (macroevolution); (2) recognizing the persistence or eradication of specific insect/vascular plant interactions, such as leaf-mining, wood-boring and pollination (behavior); and (3) establishing temporal trends in the range of mouthpart design, as an indicator of faunal disparity or structural diversity (morphology). These three operationally separate but complimentary approaches allow the advantage of using distinct data bases to bear on a common question. The body-fossil record of insects provides primary data for the taxonomic expansion, steady-state, or contraction of insect faunas. The trace-fossil record of those insect interactions that are coevolved with plant hosts reveals the temporal continuity of highly stereotyped and taxonomically obligate behaviors. Both of these are contrasted to an assessment of insectan structural disparity, herein determined from a robust data base of 30 modern insect mouthpart classes that are traced back in geologic time.

A preliminary analysis of each of these three approaches indicates broad agreement–namely that insects were not dramatically affected by the terminal Cretaceous extinction event. First, insects experienced only a modest decline in diversity, about 9 percent at the family level. (The generic level is not yet analyzed.) Second, although the data base is limited, there is no indication of the extinction of major leaf-mining, wood-boring, pollinating or other plant-specific behaviors at the end of the Cretaceous. In fact, leaf-mine morphologies for three lepidopteran families with Cretaceous occurrences are apparently indistinguishable from their modern descendants. Last, of the 30 mouthpart classes occurring during the Paleogene, 28 are represented during the Cretaceous. These data provide strong evidence for a largely uninterrupted continuum of insect faunas across the Cretaceous/Tertiary boundary as measured by taxonomic diversity, coevolved behavior, and structural disparity.

Because of abundant and often intimate associations between insects and flowering plants, these results are consistent with a gradual and not catastrophic change in terrestrial floras across the Cretaceous/Tertiary boundary. Acceptance of a catastrophic extinction of flowering plants during the terminal Cretaceous would necessitate an unprecedented level of host-switching by coevolved insects on contemporaneous plants. This is unlikely, based on evidence from the prolific literature on modern insect/plant interactions. These studies indicate the ubiquity of obligate insect specificity for various secondary chemicals on many flowering plant species.

Four types of septal necks are present in the Ammonoidea: (1) retrochoanitic (entirely projected adapically), (2) modified retrochoanitic (projected adorally or both adorally and adapically on the dorsal side and adapically on the ventral side), (3) amphichoanitic (projected both adorally and adapically), and (4) prochoanitic (entirely projected adorally). Each septal neck is continuous with the rest of the septum and consists primarily of a nacreous layer. A spherulitic-prismatic deposit called the auxiliary deposit commonly appears on the adoral side of the septal neck and covers the inner surface of the nacreous layer. Another spherulitic-prismatic deposit (cuff) may also occur on the adapical side of prochoanitic necks. In all of the Paleozoic suborders except Goniatitina (Prolecanitina, Bactritina, Anarcestina, Agoniatitina, Clymeniina, Gonioclymeniina and Tornoceratina), type 1 necks are present throughout ontogeny (1→1). In the Goniatitina as well as in the Ceratitina, type 1 necks either persist throughout ontogeny (1→1) or develop into type 2 necks (1→2). In the Phylloceratina, type 1 necks are present in early to middle ontogeny, later developing into type 3 necks (1→3). In the Lytoceratina, type 1 necks are only present in very early ontogeny and are immediately replaced by type 4 necks (1→4). In the Ancyloceratina and Ammonitina (with few exceptions), only type 4 necks occur (4→4). Type 1 necks evidently represent the primitive condition. Variation among suborders in the ontogenetic timing of the transformation from the primitive condition to one of the three more derived conditions may be the result of heterochronic processes such as acceleration or predisplacement. However, the pattern of septal neck transformation within suborders is more or less stable and was probably established at the time each suborder originated.

Biothems are regional wedge- or lens-shaped bodies of strata that are: bounded shelfward or cratonward by paleontologically recognizable unconformities; generally thicken on marine shelves, where they are typically conformable with underlying and overlying biothems; are commonly thinner or represent “starved” sequences further basinward; and in their most basinward extent, are either bounded by biostratigraphically recognizable unconformities or are conformable with underlying and overlying biothems. Biothems are practical units whose definition and degree of refinement are dependent on the quality and availability of biostratigraphic control. As recognized to date, biothems have a logical distribution of faunal and floral components, as well as facies groupings that represent internally consistent and logical sequences of depositional environments. The use of biothems as primary sequence stratigraphic units places the emphasis on relative time in a stratigraphic framework.

A west-to-east transect within the North American Mississippian System, which extends from the Basin and Range Province, across the Transcontinental Arch (TA) and into the Anadarko Basin, was constructed to demonstrate the regional distribution and tectono-stratigraphic significance of biothems relative to the axis of the TA. The relationships portrayed on the transect, tied to an understanding of North American Mississippian paleogeography, imply that biothems deposited during relative highstand events on one flank of the TA are time-equivalent to biothems deposited during relative lowstand events on the opposite flank of the TA. This distribution is interpreted to have been controlled by intraplate tectonic events that formed “piano-key” basins along the flanks of the TA. The spatial patterns of these basins are not consistent with published models of basin evolution. A further conclusion is that the lack of transgressive or regressive coincident Mississippian biothems on either flank of the TA suggests that it is inadvisable to impose the Mississippi Valley-derived eustasy curve on western flank depositional sequences.

Cyclocrinitids are considered to be calcareous green algae closely related to, or members of, the dasycladacean algae. Cyclocrinitids are characterized by a globular thallus 1-5 cm in diameter consisting of whorls of calcified meromes borne from a tubular or spherical central axis. The species Cyclocrinites darwini is distinguished from other cyclocrinitids by the presence of lateral branches arranged in a stellate pattern at the distal end of each merome.

C. darwini is restricted to strata of the Cincinnatian Series. Specimens are commonly found in shale-filled channels cutting through nodular, irregularly-bedded limestones within the Mt. Auburn Formation and the lower Sunset Member of the Arnheim Formation. Numerous specimens are also known from the Bellevue Member of the Grant Lake Formation at Maysville, Kentucky. Each of these units has been interpreted to be the top of separate shoaling-upward, third-order cycles. These facies are abundantly fossiliferous, often consisting of broken, abraded, and reworked material.

The modern dasyclad Neomeris is cited for its structural similarity to the cyclocrinitids and ecological parallels have been postulated as well. Neomeris and a similar dasyclad Batophora, thrive while attached to pieces of coral rubble at depths of less than 3 m in the high-energy conditions associated with a reef crest environment at Key Largo, Florida.

It is likely that C. darwini lived under similar conditions, attached to rubble in shoaling areas. Preservation only occurred in instances when thalli were broken off from their holdfasts and swept into ripple troughs or downslope channels cutting across the shoals. It has been suggested that the presence of cyclocrinitids is indicative of relatively quiet environments below wave base. For Cyclocrinites darwini, the opposite would appear to be the case.

Radiolarians are the most diverse of the 4 major fossil forming plankton groups, with several hundred living species, and an equally diverse range of biologic specializations for planktonic existence. Studies of radiolarian evolution are mostly from the Cenozoic, where the opaline silica skeletons of radiolarians are well preserved in most areas of the world's oceans. Cenozoic radiolarian skeletons are mostly too small (50-150 μm) and delicate to easily manipulate individually. Washed sieved skeletons are strewn at random orientations onto glass microslides and viewed in transmitted light. At the required magnifications, most skeletons cannot be viewed in their entirety within a single focus-plane. Many (perhaps the majority) of taxonomic characters in radiolarians are not visible in the skeleton outline, but are internal. These characteristics make normal image analysis techniques more difficult to employ. Computer assisted manual digitizers (one version working in 3 dimensions) have sometimes been used to measure skeletons. Distance, angle, area, and shape outline measurements have all been used to quantify radiolarian morphology.

Radiolarian skeletal growth is determinate, and relatively little ontogenetic or within-population allometric variation is seen. Geographic variation in radiolarian species morphology is common, but little studied. Perhaps due to the effort involved, most ordinary taxonomic work does not employ morphometric data: its use has largely been in species-level evolutionary studies. Phyletic trends in size, shape, and in other characters have long been used to delineate stratigraphically useful chronospecies, and some of these anagenetic series have been morphometrically measured. Cladogenesis has also been morphometrically quantified in a few cases. Most studies of both cladogenesis and anagenetic evolution have documented gradual rates of morphologic change.

Integrated studies of paleogeographic variation and temporal change are still needed, as is better information on modern radiolarian biology. Much more efficient measurement tools are also needed, to handle the very large number of specimens required by integrated studies.

Planktonic foraminifera first evolved in the middle Jurassic but did not experience a major radiation until the mid-Cretaceous. The mid-Barremian to late Aptian was characterized by a steady increase in species richness and by the appearance of new morphological forms including planispiral coiling, clavate and radially elongate chambers, and culminating in the first appearance of taxa with complex apertural structures and the keeled morphotype in late Aptian time. This broad interval of radiation was abruptly ended by evolutionary turnover and low diversification rates in the latest Aptian and early Albian prior to a second explosive episode of radiation in the middle and late Albian. The evolutionary history of mid-Cretaceous calcareous nannofossils generally parallels the trends observed in planktonic foraminifera, although the latest Aptian-early Albian turnover event is not as pronounced. Reef communities in the Caribbean/Gulf of Mexico and Mediterranean provinces show a change in dominance from coral-algal-rudist reefs in the Barremian-early Albian to rudist domiance by the late Albian time. These changes in calcareous plankton and reef communities are related to complex oceanographic changes of the mid-Cretaceous including structure of the upper water column, productivity, sea level, atmospheric and oceanographic circulation, and changes in the chemistry of the ocean.

Changes in eustatic sea level influenced many of these factors including nutrient delivery to the oceans, climate, sites and rates of deep water formation, and ocean chemistry. What is the relationship between changes in sea level, as expressed by major seismic sequence boundaries, and the changes observed in marine biota? We have compared major changes of eustatic sea level within this interval of generally rising global sea level (Scott et al., 1988), with equivalent sequence boundaries (Haq et al., 1988) and the records of calcareous plankton (Roth, 1987; Leckie, 1989) and reef communities (Scott, 1988). What is most striking about these relationships is the apparent lack of direct correlation between sequence boundaries and turnover events in the marine biota. The calcareous plankton alternate in phase between relatively high rates of diversification and low rates of diversification, with the major sequence boundaries falling within intervals of change rather than at intervals of change. However, we acknowledge the potential of missing or condensed intervals in deep sea settings which may influence the record of evolutionary rates (e.g., Loutit, et al., 1988). Only the basal Albian sequence boundary appears to correlate with a major turnover event in the planktonic foraminifera, and the rapid change in Gulf Coast reef communites between the middle and upper Albian may correlate with a eustatic sea level change and a major sequence boundary. Based on high-resolution calcareous nannofossil, planktonic foraminiferal, sedimentologic, and geochemical data of Bralower et al. (submitted), the lower Aptian, basal Albian, and lower upper Albian sequence boundaries appear to correlate more closely with widespread oceanic dysoxic/anoxic events OAE1a, OAE1b, and OAE1c, respectively. The correlations between evolutionary events, anoxic events, and sequence boundaries must be considered tentative at this time because major disparities exist between the correlation of calcareous plankton zones and mid-Cretaceous chronostratigraphic units used by Haq et al. (1988) and Bralower et al. (submitted).

An abrupt change in the composition of graptolite faunas just below, and at, the Wenlock-Ludlow boundary has recently been demonstrated in southeastern Germany and Kirgizistan. JAEGER (1991) terms that changeover the “Big Crisis”.

On a global scale, throughout all but the uppermost Wenlock, Monograptus (s.s.), Cyrtograptus, and plectograptine retiolitids are moderately diverse and very abundant. This fauna is abruptly replaced in the uppermost Wenlock by an acme of simply thecate Pristiograptus dubius types and “pristiograptids”, and a marked increase in the diversity of the plectograptines. The succeeding earliest Ludlow fauna, which too appears abruptly, is marked by a mostly new fauna of plectograptines and new forms of monograptids the earliest of which include Lobograptus, Neodiversograptus and Bohemograptus. Two “crises” are therefore manifest, the earlier one being more profound.

The Cape Phillips Formation of the Arctic Islands, Canada, yields a superb late Wenlock and early Ludlow graptolite, fauna. The late Wenlock lundgreni-testis Biozone has yielded isolated specimens of about 15 species of monograptids (including Monograptus (s.s.); especially M. testis), Cyrtograptus (several species), and at least seven species of plectograptines. About half of the fauna continues from the underlying zone. The overlying uppermost Wenlock ludensis Biozone is markedly different. Pristiograptus (of the P. dubius type) and “Pristiograptus” (Pseudomonoclimacis?) with novel thecal and sicular development (four or five species) are very abundant, and ten species plectograptines, only two of which continue from the underlying zone, appear abruptly. Cyrtograptus and Monograptus (s.s.) are totally absent.

The succeeding earliest Ludlow is also characterized by rather abrupt appearances, again of several or more species of plectograptines, most very small, as well as monograptids with new thecal/rhabdosomal styles; these include Lobograptus. Neodiversograptus, Bohemograptus and Colonograptus, and slightly later, Saetograptus and the reappearance of Monograptus (s.s.). Plectograptines apparently become totally extinct by about mid Ludlow.