Although many fossil epibiont assemblages have been described, the taphonomy of these assemblages is poorly understood. In an effort to investigate the percentage of epibiontic organisms that would likely be preserved in the fossil record, and the contemporaneity of epibionts on a particular shell, I investigated the epibionts on live and dead Chlamys hastata and C. rubida from around San Juan Island, Washington. Using a video imaging system, over 300 shell surfaces were examined and the percent covers of epibionts in eight taxonomic categories were calculated.

The left (upper) valves of live Chlamys had an average epibiont cover of 75% that was composed primarily of sponge, or a combination of barnacles and sabellid annelids. The preservable portion of this assemblage (18%) was significantly less than that of epibionts on the exteriors (68%) and interiors (87%) of dead valves. On dead shell surfaces, sponge coverage is <1%, and there are higher proportions of cheilostome and cyclostome bryozoans, and serpulid and spirorbid annelids.

On upper surfaces (left valves) of living Chlamys, 10% of the epibiont cover was composed of dead organisms. An even greater percentage of dead epibiont cover existed on lower valves of live individuals (25%), and on dead valves (37-47%). During the study, no unambiguous examples of competitive interactions were found except for barnacles overgrowing barnacles and other epibionts. Numerous other overgrowths were observed, but these resulted from growths over dead organisms, or growths over mineralized skeleton, not living tissue.

These results suggest that exact contemporaneity between epibionts should not be assumed in paleoecological studies.and that soft bodied and agglutinating organisms may have been important constituents of some paleocommunities. Encrusting epibiontic sponge actually protects shell surface ornamentation and may be evidenced in the fossil record by particularly clean and unfouled shells.

Xenophyophores are large, agglutinating protozoans whose modern distribution is limited exclusively to the deep sea (> 500 m water depth). Test morphologies vary from simple discoidal forms to elaborately folded or reticulated forms. Often specific particle sizes or minerals are selected for test construction. Tests are typically 1-5 cm in diameter, but some species may be up to 25 cm in longest dimension. Xenophyophores have been reported from a wide variety of soft- and hard-substrate deep-sea settings, including foram sands, calcareous and hemipelagic oozes, manganese nodule beds, fresh basalts, and hydrothermal oxides. They appear to obtain highest densities (often > 1/m2) on sloped substrates such as occur on seamounts, continental slopes, canyons, and trenches. Most xenophyophores live as epifauna on the sea floor and feed by actively or passively capturing suspended particles, but several species live as infauna and are presumed to be deposit feeders. It has been proposed that xenophyophores may garden bacteria within tests to provide an additional food source. Xenophyophores are distinguished from foraminifera by the occurrence of: (1) protoplasm encased within an organic membrane, (2) barite crystals within the protoplasm, and (3) tightly packed strands of fecal pellets (stercomare) within an organic membrane in the test.

Xenophyophore tests and surrounding sediments are known to be hotspots of metazoan activity in a variety of settings. Tests provide habitat and presumably refuge for many invertebrate groups, and sediments beneath epifaunal xenophyophore tests often exhibit elevated densities of macrofauna and meiofauna. Radiochemical studies suggest that xenophyophore tests are sites of enhanced particle flux to the seabed. Associated metazoans may be taking advantage of elevated food supplies in the vicinity of tests, or may be passively trapped by xenophyophore tests during dispersal stages.

Xenophyophores are not known from the fossil record. A resemblance between the infaunal xenophyophore Occultammina profunda and the trace fossil Paleodictyon has been noted by Swinbanks. Similar structures have been observed on the mid Atlantic ridge, but their identification as xenophyophores has not been confirmed. Maybury and Evans report a strong resemblance in external morphology, fine structure and barite content between modern xenophyophores in the genus Psammina and some Carboniferous phylloid algae, but fall short of suggesting a systematic relationship. Broader knowledge of xenophyophore morphology and ecology among ichnologists may lead to discovery of possible fossil antecedents. In addition, confirmation of xenophyophore presence could provide valuable information concerning paleohabitats.

Shell concentrations have constituted an important and conspicuous part of the stratigraphic record since the Early Cambrian. The paleontological and stratigraphic significance of shell beds is well understood, primarily from Mesozoic and Cenozoic examples. Lower Paleozoic fossil concentrations, however, have not received much attention. The Cambrian and Ordovician evolutionary radiations were two of the most significant events in the history of life and established the Cambrian and Paleozoic faunas respectively. In order to determine the effect of these radiations on the development of fossil accumulations, a systematic study of early Paleozoic shell beds was conducted in the Great Basin areas of California, Nevada, and Utah.

In order to minimize taphonomic variations in original chemical and physical conditions, shell beds were compared from strata deposited in similar depositional environments from similar tectonic settings. Preliminary analysis of the shell beds from relatively pure carbonate facies and mixed carbonate and siliciclastic facies shows: 1) that shell concentrations became a significant stratigraphic feature in the later Early Cambrian; 2) the thickness and lateral extent of the shell beds increase from Early Cambrian to Middle Ordovician; 3) the abundance and internal complexity of the shell beds increase from Early Cambrian to Middle Ordovician; and 4) the Cambrian and Early Ordovician shell beds are primarily, if not exclusively, dominated by trilobites whereas the Middle Ordovician shell beds are dominated by brachiopods and ostracodes.

These data show a temporal trend in the development of the early Paleozoic shell beds. The nature of the Cambrian and Ordovician shell beds differs qualitatively and quantitatively. There is an increase in physical scale, abundance, and internal complexity through time. The thickness and abundance of the trilobite beds increase through the Cambrian. Interestingly, although trilobites were still diverse and abundant, they did not commonly generate thick trilobite beds after the Late Cambrian. The early Middle Ordovician is a critical time in the development of early Paleozoic shell beds. A variety of monotaxic and polytaxic shell beds, including 6m thick composite beds, first appeared at this time. While the brachiopods and ostracodes generate laterally extensive, commonly monotaxic, shell beds, the gastropods and bryozoans only formed lenticular concentrations.

The cyclostome and cheilostome bryozoan clades diversified at different times and consequently in different ecological contexts. Cyclostomes began their rebound from a Permo-Triassic bottleneck in the early Jurassic, prior to increases in bioturbation, durgophagous predation, and other ecological changes commonly termed the Mesozoic Marine Revolution. Cheilostomes did not appear until the latest Jurassic and rapid diversification began only in the mid-Cretaceous, when the Mesozoic Revolution was well under way. We compared the radiations of these clades to test for similarities reflecting general patterns in the origin of within-clade novelties, and for differences that might be due to ecological context or clade attributes. We examined the timing and environment of first occurrence of eight morphological novelties that evolved convergently in both clades (ovicells, cylindrical arborescent colony, multilayered encrusting growth [frontal budding s.l.], bilaminate erect colony, fenestrate colony, articulated colony, calcified operculae, avicularia), as well as novelties unique to cheilostomes (cribrimorph and ascophoran grades, and lunulitiform colonies) or to cyclostomes (apertures arranged in fascicles). First occurrences were traced from the literature, BMNH collections, and unpublished data provided by Prof. Dr. E. Voigt; environments were inferred within an onshore-offshore gradient using the protocol of Jablonski and Bottjer (1990).

As seen for other invertebrate groups, within-clade novelties were not concentrated in onshore settings for either bryozoan clade, in contrast to the origination patterns at the ordinal level (including the Cheilostomata). Differences in sequence or environment of first occurrence were not obviously related to the Mesozoic Revolution, or to the distinction between zooid- and colony-level characters. Novelties showed a weak tendency to originate in similar sequence and in similar environments for both clades, but these numbers are small. Differences in sequence may partly reflect clade-specific constraints: for example, opercula are considered a prerequisite for the development of avicularia, so that cyclostomes needed to evolve that precursor before avicularia could appear, whereas opercula are primitive (though uncalcified) in cheilostomes and thus did not constitute such a constraint. If avicularia are omitted, the rank-order correlation of novelties becomes marginally significant (p = 0.05, Spearman rank test). The most striking difference is in the temporal pattern of novelty acquisition. In cyclostomes, these are rather evenly spread over 100 Ma, whereas in cheilostomes six of the novelties appeared in the Late Albian-Early Cenomanian during a period of rapid diversification. Despite a slow start, the cheilostome radiation enters an explosive phase that may characterize successful establishment of clades founded late in the Phanerozoic.

This analysis examines the evolution of the greater diversity of non-planktonic species relative to planktonic species in the turritellid gastropods. Two mechanisms for generating diversity gradients in larval types have been proposed in the literature. The first, species selection or the effect hypothesis, focused on the population biology of larval types. The second proposed that factors in development were responsible. Turritellids have been cited as a classic example of species selection. In order to test the validity of these mechanisms for the evolution of the turritellids two phylogenetic models are formulated. One is constructed to fit the predicted evolutionary results if species selection or the effect hypothesis are the operative processes driving diversification. The second model is constructed as if developmental constraints prohibiting the origination of planktonic species in non-planktonic lineages were responsible for the relative increase in non-planktonic species.

In order to test these two proposed mechanisms a phylogenetic analysis of the turritellids using molecular sequence data was performed to determine the evolution of larval types in this clade. This is compared to the phylogenetic patterns predicted by the two models. The model asserting the control of species selection or the effect hypothesis is rejected. It is predicted that species with non-planktonic larvae will increase at the expense of planktonic species because planktonic organisms are developmentally more open to change, while developmental change is buffered in the non-planktonics. Once a lineage has become non-planktonic, there is little chance for it to undergo subsequent changes in larval style through phylogenetic time. The process producing this pattern is termed the cell-lineage effect, and it is a mechanism governing changes in the timing of germ line sequestration in organisms. Thus, the fossil and recent turritellid biota will show a bias towards non-planktonic forms due to biases and constraints in development.

In 1925 Rudolf Ruedemann described a remarkable Silurian biota dominated by noncalcified plants and animals from the Lockport Dolomite of western New York State. Ruedemann stated that the biota was confined to a single lens of interreef strata exposed at a Gasport, New York quarry; hence, he referred to the deposit as the Gasport Channel. Apart from a brief taxonomic treatment of the biota, this deposit remained largely unstudied, principally due to the destruction of the fossil site (by quarrying activity) shortly after the publication of Ruedemann's report. Recently, several new exposures of this fossil-bearing interval were discovered, prompting renewed interest in this unusual occurrence.

The stratigraphic relations of this fossil occurrence reveal that it is not a lenticular interreef channel deposit, as indicated by Ruedemann, but is instead a thin (10 cm on average), laterally continuous unit that overlies the bioherms. Based on the great lateral extent of this unit (over 100 km), and the abundance of the noncalcified dasyclad alga Medusaegraptus mirabilis within, this interval has been termed the Medusaegraptus epibole.

The biota of the Medusaegraptus epibole is dominated by dendroid graptolites and noncalcified algae. Several well preserved worms (Protoscolex) have been recovered, as well as fragments of probable terrestrial plants. A typical Silurian shelly marine biota of brachiopods, bryozoa, corals, trilobites and crinoids is almost completely absent, although shelly material is represented by rare internal and external molds. Apparently, the Medusaegraptus epibole does not present a taphonomically biased view of a “typical” Silurian community, but instead presents a picture of an entirely different kind of Silurian association.

Based on the sedimentology and paleontology of the Medusaegraptus epibole, this unit was likely deposited in rather shallow (10–20 m), stagnant marine water. The fossil-bearing beds represent a series of tempestites with sharp, slightly erosional bases and distinct internal grading; fossil material is concentrated near the tops of these graded beds.

Other, quite similar Ludlovian Konservat-Lagerstätten from North America (basal Mississinewa Shale, Lecthaylus Shale) apparently were deposited concomitant with the Medusaegraptus epibole. Synchronous deposition of these widespread units suggests that a large-scale mechanism, such as the emplacement of dysaerobic water on the craton, may be at least partly responsible for the formation of these Silurian Konservat-Lagerstätten.

The 17–20 million year old Miocene locality at Clarkia, northern Idaho, has become renowned as the first site to yield amplifiable DNA of geological age. This discovery has opened up the possibility of phylogenetic studies on fossil tissue using preserved DNA. However, the conditions required for DNA preservation in the fossil record are not understood. An organic geochemical study of fossil tissue and sediments has been undertaken at the Clarkia site to assess the preservation of other less labile compounds, such as leaf waxes, structural polysaccharides, cutins, lignins and chlorophyll pigments. Previous organic geochemical studies have developed an understanding of the behaviour of these compound classes in different environments. The relative behaviour of the compound classes and the preservation of individual compounds within each class can therefore help in the interpretation of the biogeochemistry of this site which may in turn shed light on the reported preservation of fossil DNA.

Leaf waxes are preserved but a selective loss of long chain esters has occurred, and microbial degradation products of triterpenoids have been identified. Structural polysaccharides and cutins have been lost from the leaf tissues. A highly resistant aliphatic polymer is preserved in the mesophyll and epidermal regions of the leaves, with lignin identified in leaf vein tissues. Various degradation products of chlorophyll have also been identified. The organic geochemical results are all consistent with microbial degradation within the leaf tissues and sediment. Excellent morphological preservation is not accompanied by mutual chemical preservation. The survival of DNA in this environment is extremely surprising. However, preservation of plant polyphenols may provide an answer to this anomaly.

Planktonic foraminifera grow by adding chambers to their shells, increasing shell size and changing shell shape. Shell development can be distinguished from shell size either by counting the chambers or by measuring the allometry associated with developmental shape changes. It is necessary to make this distinction when trying to understand the life history adaptations of planktonic foraminifera to their environment because there is wide variation in shell size among individuals at the same stage of development.

While the life cycle of many species of planktonic foraminifera is adapted to the monthly lunar cycle, certain deep-living species such as Globorotalia truncatulinoides and G. hirsuta are adapted to the annual cycle of late winter nutrient upwelling and spring bloom, the mechanism that drives primary productivity in subtropical latitudes. These deep-living species grow while sinking from the surface ocean through the upper 500 to 1000m of the water column and then reproduce at depth. Juveniles must somehow return to surface waters.

For such a life cycle, size may affect reproductive success in two opposing ways: while the number of gametes produced is directly proportional to size, the bouyancy of the offspring and so the likelihood that they will reach surface waters are inversely proportional to size. The balance between the reproductive benefits of large size and the difficulty of returning large juveniles to surface waters can be altered by vertically mixing the water column. The deep mixing that brings nutrients to surface waters can also help juvenile foraminifera reach the surface.

Today the largest shells of G. truncatulinoides are found in populations growing on the poleward margins of the subtropical gyres, areas where the scale of mixing is greatest. As the vertical scale of this mixing decreases toward the tropics, shells at each stage of development shift toward smaller average sizes. This apparent acceleration in development reflects a loss of large shells, which decreases both the average size and the overall abundance of the species.

The relationship of apparent developmental rate to the scale of vertical mixing produces the previously reported “ecophenotypic cline” in which G. truncatulinoides changes from a compressed biconvex form in high latitudes to a highly conical form in the tropics. By design, the study reporting this observation was based on shells from a narrow range of size in an attempt to minimize any developmental sources of morphologic variation. Paradoxically, this strategy focussed observations on the systematic shift in the relationship between shell size and development caused by differences in upper ocean mixing. The apparent cline consists of shells of the same size but at different stages of development. A similar explanation may account for the apparent gradual “evolution” observed in G. truncatulinoides during the Late Pleistocene.

A comprehensive review of the stratigraphic and geographic distribution of the advanced, non-mammalian cynodonts (traversodontids, tritylodontids and tritheledontids) and the Late Triassic-Early Jurassic mammals indicates that: (1) traversodontids were a wholly Triassic group that disappeared during the Rhaetian; during the late Carnian-early Norian they were rare but widespread components of Pangaean land-vertebrate faunas; (2) tritylodontids first appeared in Europe during the Rhaetian, were a cosmopolitan group by the Sinemurian/Pliensbachian and disappeared during the Bathonian; (3) tritheledontids ranged in age from late Carnian to Sinemurian/Pliensbachian and were mostly a New World group; and (4) the oldest mammal is of late Carnian age from West Texas, but there is at least a 10-million-year gap between it and the next oldest mammals from the late Norian of Europe.

Advanced cynodont and mammalian distributions of the Late Triassic-Early Jurassic do not suggest Late Triassic paleoprovinciality, but they do support the notion of a cosmopolitan vertebrate fauna during the Sinemurian/Pliensbachian. Proponents of a tritylodontid ancestry of mammals must explain away a 15-million-year-long absence of tritylodontids from the Late Triassic fossil record. In contrast, proponents of a tritheledontid ancestry of mammals need offer no such explanation since tritheledontids and mammals appeared simultaneously during the late Carnian.

An abundant and unusual fauna is associated with deep-sea hydrothermal vents on the crest of the global mid-ocean ridge system. Precipitation of metal sulfides, silica, iron-oxyhydroxides and other minerals at these vents encrusts and replaces the remains of dead organisms to form fossils that may be preserved in the geologic record. For example, molds and casts of tubiculous polychaete and vestimentiferan worms are abundantly preserved in Recent hot spring deposits on the mid-ocean ridge crest, and similar worm molds also have been found in Tethys ophiolite sulfide mineral deposits of mid-Cretaceous age. The aragonitic and calcareous shells and tests of other vent species are also good candidates for fossilization by encrustation and replacement of their carbonate constituents with hydrothermal minerals.

Recent and ongoing studies of the ecology and mineralization of vent organisms at active hot spring sites on the mid-ocean ridge in the eastern Pacific provide knowledge needed for gleaning paleoecological information from fossiliferous marine hydrothermal deposits in the geologic record. At modern vents, intact larval shells (prodissoconchs or protoconchs) are present on the surfaces of many juvenile molluscs. Preservation of these larval shells by hydrothermal mineralization may provide a powerful paleoecological tool for interpretation of the life history strategies of many sessile invertebrates associated with ancient submarine hydrothermal vents. Bacterial mats that grow on the outer surfaces of sulfide mineral structures have been preserved by silica deposition in inactive deposits on the East Pacific Rise (EPR) axis at 9°27'N. Studies of the ecology and growth history of this bacterial species at active vents are in progress.

Preservation of ridge crest vent fauna within volcanic rock units can occur when lava erupts on the ridge crest near hydrothermal vent communities. Along the axis of the EPR at 9°50.6'N, vent mussels and vestimentiferan worms were found partially buried by lava flows and volcanic collapse rubble. Animals trapped beneath eruption-associated rubble may be coated or replaced by hydrothermal minerals precipitating from fluids circulating in the cooling rocks. In addition, worm-tube molds were created at the EPR 9°50.6'N site where lava quenched around living vestimentiferans (analogous to the formation of tree-molds in Hawaiian lava flows). These lava molds contained pyritized remnants of the chitinous tubes of the vestimentiferans.

The Bighorn Basin of Wyoming and its northerly extension, the Crazy Mountains Basin of Montana, contain a continuous record of the middle Paleocene through early Eocene mammalian biota. This interval, spanning some eight million years, is subdivided into 18 faunal zones. Durations of the zones, ranging from 0.3 to 0.75 million years, are extrapolated from intrabasinal depositional rates and correlated with the early Tertiary paleomagnetic reversal record. This stratigraphic resolution allows us to document in detail regional diversity and turnover.

In the Bighorn and Crazy Mountains basins, standing generic richness (estimated number of genera at the midpoint of an interval) decreased slightly between the Torrejonian and Tiffanian (middle and late Paleocene), increased from the latest Tiffanian and Clarkforkian (latest Paleocene) to the early Wasatchian (early Eocene), and declined during the later Wasatchian.

Changes in diversity reflect first and last appearances (including originations, extinctions, and dispersal). Because first and last appearance rates are in part dependent on diversity and the duration of each interval, we plot generic turnover as rate quotients, ratios of observed to expected first or last appearances. Expected turnover rates are calculated from multiple regression of turnover on duration and generic richness. Turnover rates are evaluated in relation to the quality of the fossil record for each interval. Rate quotients show that the slight decline in generic richness in the Bighorn and Crazy Mountains basins between the Torrejonian and Tiffanian resulted from a higher than expected disappearance rate at the end of the Torrejonian. Lower than expected disappearance rates and higher than expected appearance rates in the early Clarkforkian and, particularly, the earliest Wasatchian contributed to the increase in richness during this period. The middle through late Wasatchian decline in generic richness resulted from surprisingly low appearance and high disappearance rates.

There was little change in taxonomic composition of faunas between the middle and late Paleocene; faunas from this interval were dominated by archaic groups (e.g., “condylarths”, multituberculates, plesiadapiforms). In contrast, faunal composition changed markedly during the latest Paleocene and the early Wasatchian, with the introduction of major modern groups (e.g., rodents, artiodactyls, perissodactyls, primates) and the decline in diversity of the archaic forms that dominated earlier Paleocene faunas. There is strong evidence that this faunal change was influenced by global climatic factors: climatic warming, beginning in the latest Paleocene, opened new routes for intercontinental dispersal, and had a major effect on worldwide patterns of faunal composition and diversity, including those of the Bighorn and Crazy Mountains basins.

Studies of loop ultrastructure reveal much about both the processes and patterns of loop growth in brachiopods. Such studies also provide useful insight into evolutionary relationships between various main loop-bearing brachiopod taxa. At least five different loop types, two short-looped and three long-looped, are recognisable in Cenozoic Terebratulida.

Loop development in short-looped forms is relatively unspectacular and of limited value for evolutionary studies. It consists of the growth of either an undulating transverse ribbon extending between two short crura (in the Family Terebratulidae) or, where crural processes are united (as in most Cancellothyrididae), a ring. In all short-looped forms the loop is derived from, and hence supported solely by, the crura throughout ontogeny.

The early stages of loop development in the great majority of post-Paleozoic long-looped brachiopods are similar. A septal pillar, located centrally in the dorsal valve floor, appears generally very early in ontogeny. Rudimentary descending branch elements are generated both from the crura and the flanks of the septal pillar. Rudimentary ascending elements develop at either the ventral or posteroventral edge of the septal pillar and consist firstly of an inverted or steeply inclined and continuously expanding cone or hood which, through resorption of its posteriorly located apex, becomes transformed into a ring. Further growth sees firstly the fusion of the anterior extremeties of adjacent ascending and descending loop elements followed by their progressive anterolateral separation from the septal pillar.

Contrasting modes of growth characterise the later stages of loop development in the three main groups of long-looped brachiopods. In Dallinidae, ascending and descending elements detach from the septum to give rise to a long, reflected loop supported only by the crura. In Terebratellidae, a pair of narrow, laterally directed but anteriorly migrating struts anchor the the descending branches to the median septum. These struts, in structural continuity with the median septum, are built up entirely from secondary layer fibres. In Laqueidae, in addition to a pair of septal struts, a pair of anterolaterally migrating vertical bands spanning the gap between adjacent ascending and descending branches provide further support. Unlike the septal struts but like the remaining ascending and descending loop elements, the vertical bands are constructed from both primary and secondary shell layers. Growth line discordancies at the junctions between the vertical bands and contiguous ascending and descending elements indicate the structural integrity of the vertical bands.

Quantitative analysis of a high resolution latest Maastrichtian through Danian planktic foraminiferal database reveals that degrees of endemism characterizing tropical Tethyan and both northern and southern high latitude faunas throughout this interval are much lower than previously supposed. In terms of temporal patterns in the relative abundance of cosmopolitan species, the transition from the diverse globotruncanid-dominated late Maastrichtian assemblage (I), characterizing the lower portion of the A. mayaroensis / P. deformis zones prior to the base of Chron 29, to the diverse globigerinid-dominated Danian assemblage (V) found in Zone P1c and above, takes place through the successive rise and fall of at least three intermediate faunal associations. These include: a mixed assemblage (II) that delineates an interval from the base of Chron 29 to lowermost Danian Zone PO and is dominated by heterohelicids, hedbergellids, and globigerinelloids; a guembelitrid-dominated assemblage (III) that ranges through lower Danian zones P0 - P1a; and a chiloguembelinid-dominated assemblage (IV) that characterizes lower Danian zones P1a through P1b.

Species whose differential relative abundances identify them as more or less endemic to a northern high latitude biogeographic province include Guembelitria danica (assemblage III), Chiloguembelitria waiparensis (assemblage IV), and Eoglobigerina danica (assemblage V), while southern high latitude forms with endemic abundance acmes include C. waiparensis (assemblage III) and several globigerine species (e.g., Globigerina extensa, Igorina spiralis, Globigerina aequiensis, Globigerina chasconoma). Tropical tethyan abundance endemics include Heterohelix navarroensis and Pseudoguembelina costulata (fauna II), along with both Parvularugoglobigerina eugubina and Woodringina hornerstownensis (assemblage IV). Overall, levels of planktic foraminiferal endemism were quite low throughout the upper Maastrichtian A. mayaroensis / P. deformis zones, across the K/T boundary, and into the Danian Zone P0. Endemism increased gradually throughout zones P1a and P1b with the addition of species to both northern high latitude and tropical tethyan biogeographic provinces, and then increased much more substantially in Zone P1c with the addition of the southern high latitude globigerine species.

Our analysis has also uncovered several instances of dramatic abundance increases for individual taxa occurring significantly earlier in the southern high latitudes (e.g., Chiloguembelina waiparensis). Associated with these diachronous relative abundance patterns, stable isotopic studies indicate that environmental conditions (e.g., temperature, organic productivity) over this K/T transition interval were more stable in the southern ocean than in tropics. Finally, our data reveals a distinct difference and mirror-image ordering in both the disappearance and successive reappearance of the planktic foraminiferal test morphotypes (e.g., keeled trochospires, globigerine trochospires, forms with serially arranged chambers) that prevailed in each faunal assemblage. We believe that these data can best be accounted for by accepting a causal model of geographically heterogeneous deterioration and subsequent restructuring of marine planktic habitats that took place over an extended interval of time and was ultimately driven by a synergistic combination of climatic (global cooling), oceanographic (sea level change) and tectonic factors.

The inference of locomotor mode in Paleogene mammalian faunas has traditionally been based on qualitative comparisons between fossil postcranial skeletal elements and those of modern forms whose range of locomotor behavior is known. Recently, Van Valkenburgh (1987) has shown that detailed functional interpretations can also be obtained by using a series of geometric indices to quantitatively assess correspondences between Oligocene carnivores and a predominately carnivorous assemblage of modern mammalian species. We generalize and extend Van Valkenburgh's morphometric approach by focusing on the analysis of ungual phalanx and proximal radial head outlines using a variant of the eigenshape procedure.

Results of the phalanx analyses show that the geometric consideration of the lateral outline is, for the most part, sufficient to discriminate among modern arboreal / scansorial, fossorial, and cursorial species. In modern mammals, this skeletal element displays a wide range of variational modes (e.g., relative thickness of the proximal phalanx shaft, curvature of the ventral margin, degree of both lateral and dorso-ventral compression, relative differentiation of the extensor tubercle) that appear to reflect differences among the various locomotor guilds involving relative degrees of phalanx robustness along with both the precision and strength of phalanx movement. While a separate analysis of modern mammal phalanx shape in dorsal view failed to reveal a similar degree of variation among the various locomotor guilds, our study did uncover an intriguing geometric conservatism in this aspect of phalanx morphology that appears to cut across both taxonomic and adaptive classifications. Two-dimensional outline analyses of modern mammal proximal radial heads indicate that this skeletal element can ordinate taxa on the basis of relative ability to supinate the forearm that, in turn recognizes functional distinctions between arboreal / scansorial and fossorial / cursorial taxa. Finally, our results reveal that when modern mammalian taxa are grouped by geometric correspondences among these two skeletal character complexes, the consequent associations of taxa are almost invariably polyphyletic, indicating widespread evolutionary convergence on a relatively small number of alternative morphotypes.

In order to test the feasibility of using an outline-based morphometric approach for the inference of locomotor behavior in fossil mammals, ungual phalanx and proximal radial head outlines from a suite of Paleogene species were projected into their respective modern mammal shape spaces, thereby allowing these morphologies to be directly compared with those of modern morphological analogues at highly detailed levels of shape resolution. These results indicate that Cantius, Chriacus, Kopidodon, Nannodectes, Plesiadapis, Thyptacodon, and Vulpavus ungual phalanx and/or radial head outlines are similar to those of modern arboreal / scansorial mammals; Bunophorus, Diacodexis, Pachyaena, Prolimnocyon, and Oxyaena appear to be morphologically similar to modern ambulatory or cursorial forms; and Palaeanodon exhibits a strong shape correspondence with modern fossorial taxa. In each case, our outline-based functional diagnoses are consistent with independent interpretations based on qualitative studies of other skeletal character complexes and associated paleoenvironmental evidence.

Permineralized plant remains occur individually and in small mats within anoxic and dysoxic marine black shales deposited seaward of the Wedington delta (Fayetteville Formation, Middle Chester) in northwestern Arkansas. Plant debris and associated cephalopods occur within 20 km of offshore bars that developed at the mouths of delta distributary channels. The bars were produced by longshore paleocurrents flowing eastward among the southwestern margin of the Ozark Dome. The flora includes several genera of arborescent lycopods, zygopteridalean ferns, filicalean ferns, calamites, medullosan seed ferns and seed fern remains with features that are characteristic of the Lyginopteridaceae. Among the lyginopteridalean stems are specimens that have been described as Megaloxylon wheelerae, an arborescent form, as well as several undescribed species.

Two stems with prominent leaf scars represent one species of a new genus. The stems measure 35 cm and 34 cm long, and are approximately 2.5 cm in diameter. Leaf arrangement is helical, approaching a 3/8 phyllotaxis, with internodal lengths of about 3 cm. Stems are eustelic with a polygonal primary body 3-4 mm in diameter. Each leaf trace diverges from the cauline bundle as a single strand. The strand trifurcates in the cortex to produce a distinctive configuration of two c-shaped lateral bundles separated by a tangentially elongated central strand.

Pith cells are large with prominent walls. Some show internal contents suggestive of secretory substances. The primary body is surrounded by a distinctive zone of wood 3-4 cm wide. Large rays 2-5 cells wide and more than 8 mm high separate wedges of tracheids that typically are 2-4 cells wide. Secondary tracheids display multiseriate oval bordered pits on the radial walls. Vascular cambium and secondary phloem are present, but incompletely preserved. The cortex is differentiated into an inner parenchymatous zone with horizontally elongated “sclerotic” nests, and an outer zone of alternating bands of vertically elongated sclerenchyma and parenchyma.

This material significantly increases our knowledge of Namurian floras inhabiting non peat-forming environments, and emphasizes the systematic diversity among hydrasperman gymnosperms at the base of the Upper Carboniferous.

Clusters of ammonoid embryonic shells have been discovered in several carbonate concretions from a dysoxic, relatively deep water shale (Heebner Shale-Oread Formation) of Virgilian (U. Carboniferous) age near the community of Pomona, Kansas. The concretions from a single outcrop display four distinct units. Unit 1 is the lowest unit and has an evenly laminated fabric with scattered embryonic and juvenile ammonoids, gastropods, and bivalves. The bedding fabric of this unit is interrupted and truncated by a series of pits that form the base of Unit 2, which is a sharply bounded discontinuity. Within the pits there are embryonic ammonoid clusters up to 2.5 cm thick containing as many as 250 individuals per cm3. Some juvenile ammonoids and shell fragments (mostly of ammonoids) are also present. These clusters are capped by Unit 3 which has a gradational boundary with Unit 2. Unit 3 consists in places of a packstone of fossil debris including ammonoid body chamber and phragmocone fragments, three genera of juvenile ammonoids, embryonic ammonoids, and more rarely brachiopods, bivalves, and orthoconic nautiloids. Elsewhere, fossils of Unit 3 are well separated by matrix, which lacks the bedding fabric characteristic of Unit 1. The ammonoids in Unit 3 include mature to sub-mature fragments of Aristoceras and sub-mature phragmocones of Glaphyrites and Shumardites. The brachiopods (articulate and inarticulate) and the bivalves are probably sub-mature or mature. Planktonic bivalves are extremely rare. The number of shell fragments of embryonic and postembryonic ammonoids and other shell fragments decreases upwards from the upper contact of Unit 2. The boundary of Units 3 and 4 is more-or-less gradational; Unit 4 has a sedimentary fabric and faunal content like that observed in Unit 1.

One set of hypotheses to explain the embryo clusters in Unit 2 emphasizes sedimentological processes such as selective transportation and accumulation by currents, turbidity transport and storm deposits. Another set of hypotheses favors biological activities such as reproductive activity and egg-laying. If this second set of hypotheses is correct, these clusters would provide the first documentation of ammonoid reproductive activity and would represent a find as significant in its way as that of the nests of embryo bearing dinosaur eggs.

A diverse (>200 specimens representing more than 20 taxa) Famennian echinoderm fauna has been collected from the Hongguleleng Formation, Junggar Basin, Xinjiang, Uygur Autonomous Region, Peoples Republic of China. Famennian faunas are relatively poorly known on a global basis, Famennian echinoderm faunas in general are very poorly known, and echinoderm faunas of any age from China are virtually unstudied. Echinoderms are highly endemic, which makes them relatively poor for global biostratigraphy, but excellent for use in biogeographic studies. Because Frasnian and Famennian faunas are noted for their general lack of endemism, echinoderms may be critical, sensitive indicators of Famennian biogeographic provinces. Preliminary analysis indicates that this Chinese Famennian echinoderm fauna is dominated by blastoids and inadunate, small-calyx camerate, and flexible crinoids, many of which show morphological characters that are intermediate in nature at higher classificatory levels between older Devonian and younger Carboniferous taxa. The taxonomic composition of this fauna clearly indicates that diversification and re-radiation in the aftermath of the Frasnian-Famennian extinction event was well underway before the close of the Famennian. The most similar faunas are from Famennian rocks of England and, possibly, Germany. Brachiopods, corals, and trilobites of this age also show similarities between northwestern China and western Europe. These two areas were high latitudinal and tropical, respectively, during deposition, therefore their similar composition may represent latitudinal contraction associated with global cooling or a nearshore migratory pathway between the two areas via Kazahkstan and Poland.

The present day distribution of crocodilians appears to be climatically controlled, at least in part, with the group restricted to tropical through sub-tropical regions. Studies have shown that although crocodiles may be able to withstand sub-zero temperatures they can do so for only limited periods. By analogy the presence of fossil crocodilians in the geologic record has been interpretated as indicating warmth. However previous studies have generally been of limited scope. This study uses global paleodistributions of the crocodilians to map gross global climate for the last 100 million years.

A comprehensive database of published occurrences of fossil crocodilians from the late Cretaceous to the Present has been constructed. Taphonomic and collection biases have been addressed using ‘control groups', these are respectively the Testudines and the vertebrates in general. Problems of taxonomic inconsistency have been dealt with by ‘accepting’ a standard published taxonomic scheme (Carroll, 1988). Geographic and temporal uncertainties and imprecisions are coded on the database to facilitate sorting; this allows the analyses to be run at different levels of precision and provides an opportunity to understand the way biogeographic and hence paleoclimatic interpretations may be influenced by both the nature of the geologic record itself and by a priori decisions made by the worker. The database also includes lithologic, stratigraphic and environmental information on some 3300 localities and includes specimen information for the taxa entered (>14000 separate entries assembled from 1000 references).

Preliminary analyses of paleolatitudinally reconstructed localities reveals the following trends: an overall equatorward movement of the poleward limit of the crocodiles from the late Cretaceous to the present; this is punctuated by an abrupt equatorward excursion of almost 10° during the Oligocene and another of similar magnitude at the end of the Miocene, with an apparent Miocene ‘recovery’ in between (this trend is shown most clearly by the families Alligatoridae and Crocodylidae). At the suborder level the Mesosuchians (excluding the Sebecidae) show a distinct equatorial shift from the Campanian through to the middle Eocene when they disappear; inclusion of the Sebecidae in the Mesosuchia gives rise to a sudden poleward expansion in the middle Eocene of some 20° paleolatitude. Map reconstructions, especially for North America, reveal an eastward shift of crocodilian localities as the Tertiary progresses, perhaps due in part to a taphonomic artifact, viz., the migration of the locus of sedimentation. With the late Miocene the crocodilians disappeared completely from the continental interior record, a transition which seems tied to increased aridity (as indicated by the development of caliches in many areas) and increased seasonality of temperature. This pattern is also seen in the southern ‘U.S.S.R’.

The distributions of the Crocodylia through time therefore reflect and support established views concerning late Cretaceous through Tertiary climate with a general cooling trend from the late Cretaceous to the present punctuated by abrupt coolings in the Oligocene and around the Miocene-Pliocene boundary.

Recently there have been increasing efforts to integrate morphological, molecular and paleontological data in assessing evolutionary relationships. In some instances molecules appear more reliable than morphology. For example, a DNA-DNA hybridization phylogeny of clypeasteroid echinoids appears superior to conflicting morphological phylogenies, because: 1) Of all the nodes on the morphological tree, the one drawn into question by the DNA data is the least supported (the characters are few and of relatively low quality; character quality was judged using Remane's a priori homology recognition criteria). 2) A case can be made for the conflicting characters being functional correlates. 3) The morphological tree only finds support in 1% of 500 bootstrap analyses of the DNA data. 4) On the DNA tree sister groups occupy the same paleobiogeographic realm while on the morphological tree sister groups occupy completely disparate paleobiogeographic realms.

However, in other instances morphology appears more reliable than molecules. For example, a recent 18S rRNA phylogeny of amniotes unites birds and mammals to the exclusion of crocodiles. Paleontologically this result seemed highly unlikely and it was suspected that some sort of substitution bias was responsible for the 18S rRNA result. Not only were pronounced substitution biases found, but when the 18S rRNA sequences were analyzed with an algorithm designed to deal with substitution biases a paleontologically more ‘reasonable’ tree resulted (birds were closer to crocodiles, not mammals).

By comparing independent data sets, it appears that both morphological features and molecules may evolve less than parsimoniously. More significantly, in these cases the unanticipated parallel evolution has an identifiable biological 'signature’. It is perhaps disappointing that the evolutionary process may produce more parallel evolution than is implied by most-parsimonious trees. But when analyzed carefully there appears to be a coherency to the unanticipated parallel evolution, a coherency that may help us understand the structure of the adaptive landscapes within which evolutionary innovation arises.

Conventional palaeontological methodology over the last one hundred years has revealed a complex and intricate food web in the Jurassic Lower Oxford Clay of central England; we are able to identify the top carnivores (pliosaurs) down to the primary producers (coccolithophoroids) within the water column. In some cases it is even possible to identify individual prey preferences for different taxa.

What conventional palaeontology cannot do satisfactorily is determine the quantities of food processed through the food web, the source of the nutrients, and how much and where recycling of nutrients took place. Consequently we here combine the results of extensive fossil collecting, begun in the 1890s, with data obtained from organic geochemical analysis and isotopic analysis of Oxford Clay sediment and its preserved biota (shells and bones). Examples follow:

Palaeotemperatures derived from vertebrates show that ichthyosaurs, plesiosaurs and crocodiles were calcifying in waters with temperatures in the range (190 – 220). In addition, the giant filter feeding fish Leedsichthys also yields palaeotemperatures in this range, suggesting that it was a pelagic filter feeder exploiting a rich surface plankton source.

Direct evidence for tetrapod diet in the form of preserved stomach contents indicates that hookleted cephalopods formed an important food source for macrovertebrates (Martill 1986). Isotopic data indicate that belemnites (believed to have been hookleted) were living in the lower water column (T = 150). We suggest that perhaps belemnites migrated to surface waters for feeding (probably at night) where they were predated upon by marine reptiles.

Duff (1978) suggested that the bivalves Bositra and Meleagrinella lived attached to seaweed rather than living directly on a dysoxic, probably soupy, sea floor. Isotopic data gives palaeotemperatures from these bivalves in the range 16-18 C, comparable with the range 15-18 C derived from the definitely benthic bivalve Gryphaea. Clearly if Meleaqrinella and Bositra lived attached to seaweed then the bottom of the Oxford Clay Sea lay within the photic zone. Organic geochemical analysis indicates high nutrient input, and this is reflected in an extremely high abundance, and diversity peak, for Boreal Jurassic nannofossils.