Because of their abundance, composition, and widespread occurrence throughout the Phanerozoic, microfossils are ideal subjects for teasing apart the ecological, evolutionary, geochemical, and taphonomic controls on the fossil record, and for testing hypotheses of evolutionary paleoecology against secular change in ocean chemistry as evidenced by patterns of fossil preservation. The history of calcareous plankton is one of interaction between the evolutionary innovation of regulatory pathways in hardpart construction and the paleochemistry of the seas. Diversification of ancestral shelfal calcareous plankton lineages in the Mesozoic was related to sea level transgression, water column stratification, and habitat diversity, as evidenced by major expansions of these groups in association with Oceanic Anoxic Events. In the case of coccolithophorids (calcareous Haptophyceae), the origination of calcified lineages also appears to have been related to nutrient resuspension from bottom sediments and anoxic waters (which may have promoted calcification) advected into the photic zone over shallow shelves during transgressions. Invasion of pelagic habitats by Foraminifera was facilitated by the evolution of test secretory mechanisms (beginning in the Late Paleozoic) that conferred greater cellular control over shell microstructure and density. The beginnings of calcareous nannoplankton, however, are traceable to microfossil “Lagerstätten” that hint at the first attempts at calcification by naked haptophycean lineages much earlier in the Paleozoic. During the Early-Mid Paleozoic greenhouse phase, calcareous nannoplankton assemblages were unlikely to be preserved because high levels of atmospheric (and therefore oceanic) CO2 and extraction of CaCO3 in epeiric seas by calcareous biota resulted in a very shallow CCD. With the advent of the Late Paleozoic icehouse phase (and associated sea level fall), the locus of biogenic limestone deposition shifted seaward and the CCD deepened. Significant accumulations of calcareous pelagic sediments followed in the Late Jurassic in response to diversification of calcareous plankton. As deep pelagic oozes began to accumulate, a new component was added to the global carbon cycle: the metamorphic decarbonation of pelagic limestones that controls long-term (i.e., tens to hundreds-of-millions of years) global warming.

Two skulls representing new forms of carnivorous cynodonts were discovered recently in the Upper Triassic (Carnian) Ischigualasto Formation of northwestern Argentina. These specimens are the first complete carnivorous cynodonts described from the Late Triassic of Argentina, and provide critical evidence for the evolution of cranial form between well known Middle Triassic cynodonts, such as Probainognathus, and the first mammals in the latest Triassic.

The first skull (PVSJ 422) is proportionately long, with a posterior skull width only 35 per cent of basal skull length (9.5 cm.). Other distinctive features of the skull include the form of the postcanine crowns, which have two cusps posterior to the principal cusp and fine serations on their leading edges, and which overlap each other in an imbricate pattern. Postcanines 5-7 are subequal in size, overlap the dentary laterally, and are substantially larger than postcanines 2-4. The dental formula in the upper jaw is I4-C1-PC7, with the small first postcanine separated fore and aft by small diastemas. As in other advanced eucynodonts, no pineal foramen is present. Some postcranial elements, as yet unstudied, were also found with this specimen.

The second skull (PVSJ 411) has broader proportions, the width between quadrates almost half that of basal skull length (7.5 cm.). These proportions, in combination with deep, curved zygomatic arches, resemble other Middle Triassic cynodonts such as Probelesodon. Distinctive features of this skull include bicusped postcanines in the upper jaw similar to those of Probelesodon, and a mandibular symphysis that extends back to the level of the fourth postcanine. The dental formula in the upper jaw is I4-C1-PC6. As in the first skull, a pineal foramen is absent.

Several advanced cranial features, such as a fused mandibular symphysis, occur in both skulls and strongly suggest that these new forms belong within the Eucynodontia (Hopson, 1991). Other advanced features, such as the absence of a pineal foramen, further suggest that these new forms are closer to mammals than are traversodontid cynodonts. In contrast, other characters appear to be curiosly primitive, such as a short hard palate in the first skull. These new cynodonts thus may introduce previously unseen features and character combinations to the study of cynodont cranial evolution.

Polyploidy, the condition where an organism has more than two complete sets of chromosomes, is a common and important evolutionary phenomenon in flowering plants (angiosperms). Estimates of the percentage of angiosperms (approximately 250-300,000 living species) derived from polyploids range from 47-90%. The historical development of polyploidy is currently very poorly understood and whether polyploidy is a major causal factor in angiosperm diversification is widely debated.

Many questions about the base chromosome number of angiosperms (important for establishing the extent of polyploidy) and the origin of polyploidy can be addressed using fossil plants. One of the physical effects of polyploidy is a general increase in cell volume; the size of guard cells (leaf epidermal cells that control the opening and closing of the gas exchange pores [stomata]) has been used successfully to determine the relative number of chromosomes present or ploidy level in living Carva (hickories), Betula (birch), Magnolia, and Pvrus (pear). At least two previous studies have used guard cells to estimate ploidy level in fossil taxa (Metasequoia, Sequoia, and Paleorubiaceophyllum).

The base haploid chromosome number in angiosperms generally has been assumed to be between n=7-9, but this is apparently based either on the dubious assumption that the most common condition is likely to be primitive (cf. egg laying in mammals) or the inference that because this number is found in many different clades it is likely to be basic in each of these groups. The Gnetales (the living gymnosperms most closely related to angiosperms) have a haploid basic number of 7, but Donoghue and Doyle (1989) find that it is almost equally parsimonious to assume the base number is n=12-14 because of uncertainties over the chromosome number of certain critical extinct outgroups. My guard cell measurements of three angiosperm families (Platanaceae, Magnoliaceae and Lauraceae) provide additional empirical support for the n=7-9 hypothesis and suggest that extinct diploid members existed in the mid-Cretaceous and early Cenozoic floras. These results also falsify the hypothesis that polyploidization triggered the angiosperm radiation in the Cretaceous in these families. Other hypotheses regarding the historical timing of major increases in polyploidy are being tested. These include climatic deterioration and associated modification and mixing of plant distributions during the Eocene and Pleistocene. It may be that polyploids survive major disturbances at a higher rate than diploids because they often have broader ecological tolerances and wider geographic ranges. Thus the accumulation of polyploids in plant families may not occur because they are speciation prone as usually inferred but because they are extinction resistant. My preliminary results in Platanaceae support an increased level of polyploidy after major disturbances.

Transgressive-regressive cycles involve environmental change and therefore, under the predictions of the theory of natural selection, biological response is expected. The nature, magnitude, and instrumentation of that response is, however, less well understood and difficult to predict. Generally the magnitude of biological response would be expected to be a direct function of the magnitude of the environmental change produced by alterations in sea level. However, this may not be the case. Moreover, the magnitude of environmental perturbation seen may itself not be a direct function of the magnitude, range, or even rate of sea level rise or fall.

Biological responses to transgressive-regressive cycles are highly variable, yet may be empirically demonstrated. Although the reality of faunal changes can be observed, the precise forcing mechanism or mechanisms driving those changes may be hypothetical at best. The observed iterative morphological series seen in shallow water Jurassic ammonites, for example, appear to be produced by a complex interplay of species adaptation to changes in local habitat and response to immigration from oceanic realms, both of which are ultimately driven by relative sea level. Likewise, changes in diversity and species composition in Devonian shallow marine communities appear to be produced by the effect of variable sedimentation rates and shifts in the oxygen minimum zone, both of which also are related to changes in relative sea level.

Published onlap-offlap sequence curves, as such, may offer very little to the paleobiologist interested in the evolutionary behavior of marine organisms. Additional geographic and areal data are required if any rigorous quantitative relationship between relative sea level and evolutionary biology is to be formulated. In the Devonian, for example, it can be demonstrated that a total lack of correlation exists between the evolutionary biology of major benthic marine organisms (brachiopods) and relative sea level as projected from onlap-offlap curves. It could be hypothesized that the rate of change of sea level is more important to organisms than relative sea level itself, though most hypotheses concerning the biological effect of sea level are explicitly framed in terms of relative sea level (usually invoking the species-area effect). Again, onlap-offlap curves alone offer little in testing such a rate hypothesis, as it can also be demonstrated that no correlation exists between the derivative of the Devonian relative sea level curve and the evolutionary biology of the Brachiopoda.

The Lower Ordovician through Upper Jurassic record of the phylum Bryozoa consists almost entirely of the class Stenolaemata, excepting a very few Gymnolaemata (ichnofossils of the order Ctenostomata and, in the uppermost Upper Jurassic, Pyriporopsis, which is the oldest known Cheilostomata). Along with the decline to eventual extinction of most Paleozoic stenolaemates beginning with the end-Permian crisis, the stenolaemate order Cyclostomata radiated in Late Triassic and Jurassic to include the diversity of growth forms and locally the abundance common for Paleozoic bryozoan faunas. By late Cretaceous, however, cheilostomes had diversified and had come to dominate in bryozoan faunas; they have continued to dominate to the present.

In the abundant and diverse bryozoan fauna of the northern Adriatic Sea, cheilostomes are four to five times as diverse and are orders of magnitude more abundant than are cyclostomes. Within this fauna, encrusting sheet-like cheilostomes consistently overgrow adjacent encrusting cyclostomes. Different ontogenetic patterns of skeleton and organs, as well as larger zooid sizes at colony margins, produce patterns of feeding currents that allow cheilostomes to deliver their filtered water to and to overtop competing cyclostomes at interacting margins. These Bauplan differences apparently constitute a key evolutionary innovation characterizing the Cheilostomata. Along with higher growth rates in most cheilostomes, this key evolutionary innovation should have given cheilostomes a competitive edge since the origin of multiserial colonies within the clade in Early Cretaceous. It is hypothesized that superior overgrowth capability of cheilostomes has been an important factor in their success and the relative decline of cyclostomes.

In the Proterozoic Clemente Formation at Cerro Rajon, south of Caborca, Sonora, we have collected sandstone beds that contain many small, sediment-filled structures. Each structure is a thin-walled, elongate sack, about 1.5 cm tall, oriented perpendicular to bedding. The sacklike structures are laterally flattened and roughly elliptical in transverse section, with the major axis of the ellipse measuring several mm and the minor axis 2-3 mm. The walls are not mineralized and consist of a thin layer of cryptocrystalline clay. One or both walls of each specimen is undulatory with a wavelength of 3-4 mm. The sacks are closed at the bottom, but appear to be open at the top, like an uninflated toy balloon. On the bottom surface of the sandstone bed, beneath each vertical sack structure, is a prolate ellipsoid-shaped sole mark. The long axis of each ellipsoid sole mark is parallel to the long axis of the associated sack structure, and the sole marks are oriented sub-parallel to one another on the surface of the bed. We tentatively interpret these structures to be the holdfasts of gregarious, attached, benthic organisms oriented sub-parallel to one another on the sea floor.

A preliminary study of carbon and oxygen isotope stratigraphy was carried out on the 2 km-thick Proterozoic through Lower Cambrian section at Cerro Rajon. Samples were collected every 50 m, and analyses were done in the laboratory of J.M. Hayes at Indiana University, whose assistance is gratefully acknowledged. The isotope record shows a primary signature for most of the section. Although the wide spacing of sample collection does not permit an unequivocal intercontinental correlation, a prominent negative δ13C excursion near the base of the Papalote Formation may correlate with similar excursions at the Vendian-Cambrian boundary on several continents. This would place the base of the Cambrian of the Caborca area several hundred meters lower than previously thought, but still several hundred meters above the possible body fossils of the Clemente Formation.

The thin-shelled pteriid bivalve Halobia is widely distributed in Upper Triassic (Carnian-mid Norian) marine strata throughout the circum-Pacific region with significant occurrences along the western and arctic margin of North America, northeast Russia, China, Japan, Indochina, islands of the western Pacific, and New Zealand. Halobiids are commonly associated with deep water, black shale facies typically devoid of macrobenthos. This facies occurrence and a thin-shelled, flat-valved morphology suggests an autecology (possibly pseudoplanktic) in contrast to modern benthic pteriids. High speciation and extinction rates of halobiids not only provide an excellent means for dating rocks lacking ammonoids, but they give an independent view of rapidly evolving lineages during Carnian-Norian time.

A composite halobiid succession with nearly complete coverage from the earliest Carnian through the late mid Norian is constructed from numerous North American sequences and localities with ammonoid control. Although differences in nomenclature rather then endemism make correlation of the North American succession with other circum-Pacific regions difficult, similar (and quite possibly homologous) morphologies allow limited correlation between these regions. The early Carnian is typified by H. zitteli, which occurs in predominantly boreal strata of Canada and Siberia. By later Carnian time, a variety of similar morphotypes (probably conspecific) belonging to subspecies of H. superba, H. radiata, and several other species are known throughout the circum-Pacific. The earliest Norian Kerri ammonoid zone is recognized by the first appearance of H. beyrichi in North America, and H. styriaca in Asia. In North America and the rest of the circum-Pacific, the latter part of the early Norian is marked by a rapid diversification of forms, including H. cordillerana and H. fallax. By late mid Norian time diversity reached a maximum 5 species. The mid Norian species H. fallax, H. halorica, and H. plicosa are particularly wide-spread; they occur throughout the circum-Pacific where they coexisted with the earliest Monotis. As in the Alpine-Mediterranean region, the remaining halobiids went extinct by the end of the mid Norian.

Halobiid speciation and extinction rates exceed other Late Triassic macrofauna except ammonoids. The average North American species duration is fewer than three ammonoid zones (ca. 2.5 MY). The late early Norian is a period of pronounced diversification, whereas the middle early Norian and late middle Norian are times of accelerated extinctions. Instead of catastrophic extinction at the Carnian-Norian boundary, North American halobiids exhibit complex taxonomic turnover. Similar diversity patterns are recognizable in other circum-Pacific halobiid sequences.

In the evolution of morphology, the importance of both historical constraints and selection for adaptive design has been widely acknowledged, but the relative efficacy of these internal (historical or phylogenetic) and external (selective or functional) factors has been much debated. Innumerable examples can be selected to make a case either way, but disinterested evaluation requires study of instances in which the relative degrees of functional and phylogenetic control are not already known. The vertebral column is an appropriate case: as the central structure for vertebrate locomotion and support, it ought to be subject to strong selection for functional design, yet it is also deeply generatively entrenched in vertebrate development, and therefore, arguably, ought to be less plastic than other structures.

For this analysis, I applied three shape metrics to the vertebral column. The metrics are univariate and measure shape as functions of degree of differentiation within a column. (The metrics were developed in another context as measures of morphological complexity.) Then, a series of tests was conducted: in each, mean shape values for a group of functionally similar mammals (e.g. aquatics) and values for a group of phylogenetically related mammals (e.g. carnivorans) were compared independently with values for a test case, a mammal which belongs to both groups (e.g. aquatic carnivoran, otter). In almost all instances in which differences in resemblance were significant, the test cases more closely resembled their functional kin than their phylogenetic kin, suggesting a predominance of functional control. Results of standard cluster analyses (unweighted-pair-group method) supported this conclusion.

Plant fossils including silicified wood, amber and a diverse suite of palynomorphs were recovered from beds of the Rhems and Williamsburg Formations of the Black Mingo group. The Rhems beds are Danian in age and the Williamsburg is Thanetian. Both formations constitute prograding delta sequences. The palynomorph assemblage was recovered from the Rhems Formation and consists of 112 species of pollen and spores of angiosperms, gymnosperms and cryptogams as well as 32 species of fungal spores. Silicified wood represents 10 taxa and the amber is suggestive of two but precise stratigraphic position of these latter fossils is uncertain.

An analysis of the ranges of palynomorph taxa within the Rhems Formation yields three assemblages. An assemblage concentrated in the lower, pro-delta beds of the unit is felt to represent a coastal community, a group concentrated in the upper delta-front and topset beds is representative of an inland assemblage and a third group ranges throughout the section. The coastal assemblage is dominated by palms with gymnosperms also being abundant. The inland assemblage consists primarily of a diverse array of dicots associated with the Normapolles group. The long ranging assemblage is associated with both the above groups in about equal numbers. A habitat mosaic consisting of xeric to mesic and hydric elements within the coastal and inland community zones is inferred. Analysis using the modern affinities of the palynomorphs suggests a subtropical, summer dry climate near its meteorological boundary with the tropical zone such as that found in parts of coastal southeast Asia today.

Wood taxa from the site include specimens assignable to Podocarpoxylon, Myrica, Fagaceaoxylon, Magnoliaeoxylon, Ulminium, Liquidambar, Nyssoxylon, the Olacaceae, Apocynaceae and possibly the Icacinaceae. Calculated “V” values and anatomical details of these woods correlate well with the habitat mosaic and paleoclimatic implications suggested by the palynomorphs.

Infra-red spectra of the ambers suggest affinities of these fossils with the Caesalpiniaceae and the Araucariaceae. Pollen that might be attributable to these groups includes Margocolporites, Rhoipites, and Classopollis (Pagiophyllum).

The fungal palynomorphs are both abundant and diverse in some samples from the site. These fossils include both hyphae and conidia in place in the silicified wood and dispersed spores.

To understand the evolutionary significance of apparent temporal trends in global biotic diversity, it is important to delve beneath the umbrella of synoptic, global-scale compilations. Specifically, when evaluating a measurable increase or decrease on a global diversity curve, we must determine whether it reflects a transition that was truly global in scope and space-transcendent, or, alternatively, whether it is the manifestation of change associated with particular geographic or environmental regime(s).

Previous analyses of the Ordovician faunal radiations have suggested that an onshore-offshore environmental overprint was associated with the diversity increase: trilobite-dominated biotas, which were ubiquitous during the Cambrian, became progressively restricted to deepwater through the Ordovician as diversifying, articulate brachipod-dominated faunas came to dominate shallower, open marine settings. At the same time, a less rapid proliferation of mollusc-rich biotas enabled them to become particularly diverse in nearshore settings. Additional analyses of diversification conducted for post-Paleozoic biotas have yielded onshore-offshore signals associated with diversification of a variety of taxa, suggesting the existence of a general evolutionary pattern associated with marine diversification that transcends taxonomy and time.

However, to date, evaluations of Ordovician onshore-offshore patterns have been based on data limited primarily to North America, and, thus, to the Paleozoic continent of Laurentia. Thus, it is reasonable to ask whether this pattern was unique to Laurentia, or whether diversification proceeded similarly in Ordovician seas around the world.

To analyze possible patterns of environmental and geographic selectivity associated with episodes of Ordovician diversification and extinction, I am currently compiling a database on the paleogeographic and paleoenvironmental distributions of Ordovician genera. Although this compilation is still in its infancy, preliminary analyses suggest that, in aggregate, paleoenvironmental patterns exhibited elsewhere are comparable to those recognized for Laurentia. However, the data remain scanty for many parts of the world; as the database grows, a province-by-province analysis of diversification patterns will be conducted. This analysis will not only permit determination of the degree to which onshore-onshore patterns transcended paleogeographic boundaries, but, more generally, will enable exploration of the relationship between local diversity trends and global-scale trends already documented for the Ordovician with synoptic data.

The Muricidae constitute a taxonomically and morphologically diverse family of marine gastropods. The subfamily Muricinae is the largest in the family with over 180 Recent species recognized. Modern representatives typically are strongly sculptured and possess pronounced axial thickenings (varices) and varical spines. Early fossil representatives of the subfamily generally do not display the strong ornamentation that is characteristic of more modern forms. A study of Recent and fossil muricines in museum collections was made in order to document quantitatively the morphological evolution of this group. Morphometric data were obtained from oriented photographs, X- radiographs and actual specimens. These data were supplemented with limited measurements made from published plates. A preliminary analysis of these data has revealed the following:

1. Neogene and Recent representatives are significantly more ornamented than those of the Cretaceous and Paleogene. Neogene and Recent forms typically have thicker varices and a greater number of well developed varical spines. The diversity of varix and spine morphologies also increases through time. Intervarical nodes also become more developed during the Neogene. A less pronounced trend towards increased spiral ornamentation is also indicated. Similar patterns are observed in both Europe and the western Atlantic and a preliminary analysis of Indo - Pacific fossil taxa suggests that the trend exists in this region as well.

2. Although the appearance and diversification of higher taxa contributes to the above pattern (eg. Chicoreus, Murex), similar patterns are also observed within previously existing taxa.

3. Elongated siphonal canals become more prevalent in the Neogene, although this pattern is largely the result of the diversification of new higher taxa (eg. Murex, Haustellum, Chicoreus (Siratus)).

4. The range of gross shell morphologies described by Raup's coiling parameters increases during the evolution of the subfamily. Taxa with relatively high rates of whorl translation and relatively high whorl expansion rates appear later in the history of the group. However, at the subfamilial level, no obvious directional trend exists and this pattern may be explained as an increase in morphological variance. Nevertheless, the possibility that this pattern is the result of a number of independent unidirectional trends at a lower taxonomic level can not yet be discounted.

5. Mean shell size within the family increases during the Cenozoic.

6. The Miocene appears to be an interval of increased morphological and taxonomic diversification.

Although the function of the diverse sculpture expressed in muricids remains poorly understood, features such as thick varices, spines and spiral ribbing are known to play a role in resisting durophagous predators. Increased size has also been implicated as a means of avoiding predation. It is likely that some varices and spines perform other functions as well and there are indeed morphologies within the Muricidae that do not comfortably fit an anti - predation interpretation. However, the directional patterns of morphological change observed in the Muricinae are broadly consistent with an “arms - race” scenario and strongly suggest that durophagous predation was an important driving force in the morphological evolution of this subfamily.

The growth records of spongiomorph and colonial skeletons have great potential for revealing the short-term depositional dynamics of ancient shallow marine environments. The utility of such skeletons for understanding the type and frequency of physical disturbance is illustrated by chaetetid-bearing limestones from Pennsylvanian (Desmoinesian) cyclothems of southeastern Kansas. Individual chaetetids frequently contain growth-interruption surfaces that are marked by clay partings or encrusting overgrowths of epibionts. Such interruptions occur irrespective of the growth form of the chaetetids, although they are more conspicuous in laminar and domical growth forms with ragged margins. Growth forms with smooth margins and fewer interruptions are more commonly high domical to columnar. The latter occur in cleaner carbonates with higher rates of carbonate accumulation and little siliciclastic influx.

Interruption surfaces, which may be accompanied by reorientation of skeletal growth, record significant depositional and erosive events during the life history of the chaetetids. Similar surfaces have been described from a variety of other organisms including stromotoporoids, fistuliporoid and trepostome bryozoans, and favositid corals. In most environments, physical disturbance events of this time scale are invariably destroyed by subsequent bioturbation or current reworking. For this reason, chaetetid skeletons provide a valuable means of inferring the frequency and intensity of physical distubance and the rate of sediment accumulation.

The temporal significance of growth interruptions must be determined before their environmental significance can be assessed. Geometry of calicle growth at these surfaces is critical for recognizing the manner in which growth was reestablished. Colonization by the settling of larvae on a dead surface has a much different implication than rejuvenation from surviving calicles. The former could occur on long dead skeletal hardgrounds, and the latter indicates physical disruptions during the life of a single chaetetid. Clay partings and clay-filled calicles record mud burial events resulting in partial mortality, followed by rapid rejuvenation and overgrowth of the sediment. Encrustation of growth-interruption surfaces by auloporid corals, and more rarely bryozoans and stromatolitic algae, indicate prolonged exposure of the skeletal surface and subsequent recolonization. Interestingly, auloporid encrustation appears to be more common in clay-rich carbonates having evidence of more frequent and higher-energy disturbance events. Evidence of dissolution or biocorrosion of the skeletal surface may imply an even longer period of exposure between disturbance and recolonization.

Local development of chaetetid mounds and biostromes also permits larger-scale environmental fluctuations to be recognized. Changes in growth form, typically associated with changes in clay content of the enclosing carbonates, appear to reflect fluctuations in clastic sediment influx and water turbidity. Subtle clay-rich intervals and unconformity surfaces are recognized within chaetetid-bearing units only a few meters thick. The thin sedimentation units thus defined appear to be correlative between outcrops separated by tens of kilometers.

Close examination of spongiomorph and colonial skeletons therefore has the potential to shed light on depositional processes and environmental changes at time scales of tens to thousands of years normally inaccessible to paleoecologists.

What is the relationship, if any, between soft-bodied infaunal animals and shell accumulations? Do shell layers negatively affect infaunal animals and have they in the past? To determine whether this type of taphonomic inhibition may have operated in Ordovician infaunal communities, we evaluated extent of burrow penetration of shell-rich layers in shallow-water limestones of the Lebanon Formation, central Tennessee. Most of the analyzed shell layers, which are a few mm to 15 cm thick, are not cut by burrows. No burrows occur in shell layers in slabs containing 67% of the total area examined (5500 cm2), although burrows are common above and below the shell-rich layers.

Most of the few shell-rich layers that are burrowed occur in wackestones in which skeletal fragements are arranged in a loose/dispersed fabric (Kidwell and Holland, 1991). Where burrow diameter is greater (1 cm) than maximum dimension of most shell fragments (2-4 mm), shells outline the burrow, suggesting that the animal pushed them aside during burrow construction. Where burrow diameter is less (2-3 mm) than length of shell fragments (0.5–2 cm), the burrows occur between the fragments, which show no signs of biogenic reorientation. In the single case where grainstone consisting of densely packed skeletal fragments (3–5 mm in longest dimension) is penetrated, burrow diameter (1 cm) exceeds fragment size.

Shell layers penetrated by burrows originated variably as storm deposits, current winnowed accumulations, and dense shell pavements. No layers with vertically imbricated shells are burrowed; they probably were deposited in a high energy environment inimical to burrowers. With this exception there is little evidence that mode of origin of shell bed exerts strong control over subsequent penetration by burrowers.

Although limited, these data suggest that Ordovician soft-bodied infaunal animals avoided burrowing through shell-rich layers. Those shell layers that were penetrated are loosely packed. Characteristically, in burrow-penetrated shell layers the ratio of fragment size: burrow size is either very low (animal pushed fragments aside) or very high (animal moved between shell fragments). Thus, abundance and character of shell-rich layers may have been an important factor controlling the composition and structure of Ordovician infaunal communities.

This symposium will cover new developments in the ecology and paleoecology of deepsea organisms, based largely on advances in the study of protists, metazoan associations, and biogenic sedimentary structures. Bringing together ecologists and paleoecologists will establish a bridge between workers who have devoted their attention exclusively to the modern biota and those who have only considered fossil evidence from pelagic, turbidite, and related deep basinal rock sequences. Contributors will emphasize patterns and processes from historical or developmental perspectives as well as from experimental or actualistic perspectives, and will attempt to identify the promising directions for future research.

Specifically, attention will be focused on benthic organisms and associations, and on biogenic structures, because these entities make up ecologic patterns that are most accessible to study by both biologists and paleontologists. On the biologic side, contributors will review the significance of new discoveries and theories, present summaries of path breaking work on foraminiferids and xenophyophores, and characterize modern organism-sediment interactions and trace associations. Paleontologists will emphasize processes requiring large areas of seafloor and long time spans in their review of the origins of deepsea communities and ichnofacies, large-scale dispersal patterns, long-term ecosystem dynamics, and taphonomy and time-averaging of deepsea fossil deposits. This is the first attempt to bring ecologic and paleoecologic efforts into closer coordination in order to identify the most significant themes in the historical biology of deepwater marine organisms.

Some examples of research issues amenable to this kind of coordinated approach include: 1) origination of deepsea inhabitants from shallow marine sources vs. elaboration and diversification of taxa already established in deepwater; 2) importance of small-scale, frequent disturbance vs. large-scale, rare events (turbidity currents, anoxia episodes) in shaping the deepsea biota; 3) taxonomic replacements and invasions at varied spatiotemporal scales; 4) biotic interactions vs. environmental pacing as mechanisms producing community structure; 5) evolutionary importance of allochthonous vs. autochthonous food supplies; 6) relationships between trace fossil assemblages and the development of deepsea ecosystems; 7) the nature and history of linkages between deepsea ecologic systems, and terrestrial and shallow marine systems; and 8) preservation potential of the dominant benthic organisms, and their symbionts or traces, and its implications in paleoecologic reconstructions. In general, combining biologic and paleontologic information should result in more realistic and useful interpretations of ancient biotas (rather than simply the description of more unique fossil finds), as well as an increased awareness of the long-term development of the modern biota (rather than attention directed exclusively to living organisms, short-term processes, and small-scale patterns).

Fusion (soft tissue merger and coordinated growth) of conspecific colonies originating from different larvae (i.e., homosyndrome) occurs rarely among a wide variety of benthic colonial organisms, including cnidarians, bryozoans and tunicates. Whether or not individuals fuse upon contact is determined by similarity in their histocompatibility complex. Among higher invertebrates fusion is genetically controlled and largely restricted to close kin (parent-offspring and sib-sib pairs).

Two large collections of three-dimensionally preserved graptolites, etched out of Upper Ordovician limestones, contain three homosyndrome colonies. In each a sicula (B) fused with the distal portion of a somewhat more mature but still small rhabdosome (A). In the two Geniculograptus pygmaeus homosyndromes, B passes through the lateral wall of A, and is enveloped by its periderm, including a secondary cortical layer that is continuous across the suture between A and B. The interthecal septa of one A colony (which ordinarily attach to the nema) are instead inserted on B. The B colony of the Orthograptus quadrimucronatus homosyndrome is a mature sicula and immature first theca that incorporated the nema of A in its structure as it developed.

Unlike previously reported homosyndromes, these graptolites were planktonic. This, the consistent age difference between A and B colonies, and fusion compatibility studies of other invertebrates together indicate that the B colonies were offspring of the A colony. The most likely scenario for their formation is that a mature larva, brooded within the central lumen of the parent colony, moved out along the colony's nema. There, rather than swimming off into the surrounding water as usual, the larva underwent metamorphosis within or near the open growing end of the parent colony. Subsequent growth of parent and offspring lead to fusion (see figure).

In one of the G. pygmaeus homosyndromes the nema of A terminates against B at the level of the fourth thecal pair. The nema in this species ordinarily projects about 0.9 mm beyond the growing edge of the colony. If B in this homosyndrome represents a daughter larva that metamorphosed at the growing tip of the nema, then the parent colony must have begun sexual reproduction when it comprised no more than five zooids. Large colonies of G. pygmaeus commonly contain 30 to 50 zooids. Thus, sexual reproduction in this species may have commenced at a quite early age. Early onset of sexual reproduction, and the resultant high population growth rates, is consistent with sedimentological evidence that suggests both species typically occurred as ephemeral, monospecific swarms within relatively shallow water.

Among modern colonial organisms these graptolites appear most similar ecologically to thaliacean tunicates. Both are planktonic, colonial organisms that exhibit low levels of zooid specialization. Both display a combination of depth and water mass specificity in their habitat preferences and frequently occur in swarms. Thus, it is likely that graptolites, like thaliaceans, were primarily opportunist suspension feeders, with high inherent population growth rates as an adaptation to tracking plankton blooms. The multiple macroevolutionary trends toward reduction in colony size and complexity, which pervade graptoloid macroevolution, accordingly become interpretable as a common response to selection for accelerated sexual reproduction and enhanced rate of population increase.

In mammalian assemblages, size distributions reflect conditions of vegetation and climate as well as biotic interactions among mammals. Paleogene (Wyoming/Montana) and Neogene (Siwalik) mammalian faunas depict strikingly different size distributions in the cenograms below (rank v. size of herbivorous and omnivorous species), because evolutionary increase to substantial size did not become widespread among lineages until the middle Eocene (after our record).

In the Paleocene to early Eocene, substantial faunal turnover with accompanying change in guild structure occurred with little change in size distributions. While maintaining relatively small sizes, lineages of modern mammalian orders replaced species from archaic groups. However, most mammalian lineages experienced size increase, especially through the Wasatchian (early Eocene).

From the middle to late Miocene, significant size increases occurred upsection within several families of Siwalik carnivores, artiodactyls, and rodents. Families of insectivores, primates, proboscideans, and perissodactyls exhibited little change in species sizes despite changes in species composition and number. The trend toward increasing size preceded the widespread development of C4 grasslands in the Siwaliks, suggesting that biotic rather than abiotic factors influenced the size increase.

This study explores an excellent mid-latitude Oligocene calcareous neritic succession that spans the Eocene/Oligocene boundary to the Miocene. Rapid changes in sea level and climate should have a palpable influence on macroevolution and the Eocene-Oligocene transition marks one of the most substantial changes for the Cainozoic.

Stratigraphic ranges of some 130 benthic and 20 planktic species occurring in two contrasting marine environments, one relatively restricted (low plankton - Murray Basin) and another more open (high plankton - Otway Basin) to oceanic processes, were identified and correlated with signals derived from changes in the physical environment. The signals include: the ‘Exxon’ sea-level curve, deep sea stable isotope curves, and prominent lithological changes.

There is a significant turnover of species at the Eocene/Oligocene boundary. This event impacts on all assemblages and correlation metrics indicate that there is an ‘across-the-board’ response. Interestingly, the turnover corresponds to a local Saint Vincent Basin lithological change from the grey-green, organic rich facies of the Blanche Point Formation to the red-yellow-brown, well oxidized, quartz and bryozoa rich facies of the Port Willunga Formation. This switch is in turn coincident with the saltatory positive deviation in the δ18O top and bottom water curves derived from oceanic sections.

The turnover pattern is not repeated at the major sea level fall predicted for the mid Oligocene (at 30 million years), neither is there any comparable lithological transition. Geographically widespread species (common to all environments) cross this supposed prominent type one sequence boundary, there is a signal but the impact on the fauna is less than that detected for the Eocene/Oligocene boundary. Those faunas that were more restricted to open ocean processes exhibited shorter stratigraphic ranges and appeared to be controlled primarily by sea level fluctuation and salinity changes. There is evidence to suggest that foraminiferal faunas of the more restricted environment in southern Australia were less responsive to the well mixed, thermohaline driven ocean of the Oligocene. Generally, Oligocene benthic assemblages are dominated by Cibicides, Notorotalia and Buliminid species in consistently high numbers, indicating a high dominance of relatively few taxa, that is, large populations and low diversity. Faunas of open ocean assemblages demonstrate relatively subdued turnover patterns compared to those of more restricted environments.

The Late Eocene displays parallel patterns of foraminiferal turnover and the Oligocene is characterised by inter-basin contrasts. In comparison to the Eocene, faunas appear to be more robust in the psychrosphere constrained ocean of the Oligocene. It is proposed that these patterns indicate that the Latest Eocene was dominated by species adapted to a specialist life strategy while the Oligocene reflect patterns more often associated with opportunist colonization.

In evolutionary paleontology of terrestrial biotas, the Miocene is the most important age especially for evolution of hominids and mammalian faunas. The modern mammalian fauna appeared from the end of this age in Eurasia. In Sub-Saharan Africa, the assemblage of the late Miocene mammalian faunas was very poor, and these faunas were represented by only few faunas. Therefore, this incompleteness of the late Miocene East African faunas, it is very difficult to analyze faunal turnover of Sub-Saharan mammalian faunas and compare with Eurasian and Sub-Saharan faunas of this age.

The paleontological contribution of the Japan and Kenya joint expedition to the Samburu Hills, northern Kenya covered this gap of mammalian evolution in Sub-Saharan Africa.

In this work, the Miocene mammalian faunas in Sub-Saharan Africa is examined the half-life (Kurtén 1959, 1972, 1988) of each faunal assemblages (sets).

Assemblage of the mammalian faunas from early Miocene was comparatively stable and had long half life in Sub-Saharan Africa on the basis of the results of this work.

However, mammalian assemblage changed drastically at the middle Miocene (Astaracian) in Sub-Saharan Africa.

A great number of early to middle Miocene mammalian taxa were extinct and the modern mammalian taxa appeared in this period. The half life of middle and late Miocene mammalian faunas is shortened compared with the early Miocene faunas in the East Africa. This geological event of faunal turnover occurred by the immigration and divergence of open land taxa.

It is evident that the rise of open land taxa is related to the environmental change for the plateau phonolite and basalt volcanism in the middle Miocene East Africa (Pickford 1981) and the worldwide warm and arid event (savannitisation) of continental temperate zone in the middle to late Miocene (Liu 1988). In the middle Miocene (16 Ma) Pacific region, it has been proposed that the tropical event is recognized from shallow marine faunas of the Southwestern Japan (Tsuchi 1986). African and Eurasian land connection was also established before the middle Miocene (16 Ma±) (Bernor et al. 1987).

The Astaracian faunal turnover in Sub-Saharan Africa is considered to be caused by immigration and diversity of open country mammalian taxa and that was related to the worldwide middle Miocene warm event and the plateau volcanism in middle Miocene East Africa. Furthermore, the Pleistocene and modern taxa and their direct ancestors of Sub-Saharan Africa appeared from the late Miocene faunas of East Africa. It has been made clear that the Namurungule Fauna is the forerunner of the modern Sub-Saharan mammalian fauna of savanna environments.

As mentioned before, the Hominid Fossil was found from the Namurungule Formation (late Miocene) of northern Kenya. The savannitisation in the Sub-Saharan Africa began in middle Miocene. The origin of hominid bipedalism seems to be closely related to the environmental change from forest to open land (Foley 1984). Human evolution in East Africa is accelerated by the savannitisation of Sub-Saharan Africa which commenced earlier than that of Eurasia and continued throughout the Neogene.

Although most occurrences of Ediacaran fossils are from shallow-shelf deposits, taxonomically-similar assemblages have recently been described from a 2.5 km-thick succession of dark mudstones and turbiditic sandstones in the Windermere Supergroup of the Mackenzie Mountains, northwestern Canada. The paleogeographic position (20-40 km seaward of the shelf edge), abundant evidence of mass flow, and the complete absence of in situ shallow-water features imply that deposition took place on a slope considerably below storm wave-base. Ediacaran fossils were not observed in axial trough deposits (lower parts of the Twitya and Sheepbed formations), but megafossils occur sporadically in lower to middle slope deposits higher in the same formations. Megafossils and trace fossils are present in upper slope settings (Blueflower Formation) at the top of the Ediacaran succession. The megafossil assemblage varies stratigraphically, but in all formations is dominated by discoid forms (e.g. Cyclomedusa, Ediacaria, Nimbia); frondose forms and vendomiids are very rare.

Megafossils are preserved mainly as positive features on the soles of thin turbidite beds. Most fossiliferous beds begin with the rippled layer of the turbidite (Tc), but a few begin with the graded (Ta) or parallel-laminated (Tb) layer. Consistent orientation and high relief of individuals, evidence of mutual deformation during growth of adjacent organisms, and other taphonomic features imply that virtually all of the taxa represent benthic polypoid and frond-like organisms (not jellyfish). Slump structures occur commonly in the sandstone fill of fossils, suggesting that many of the organisms were buried alive by the turbidite and later decomposed. Other individuals, even on the same bedding plane, exhibit graded to laminated fill identical to that of the overlying turbidite bed, indicating that the depressions on the sea bottom produced by these individuals were empty at the time of turbidite deposition. Escape structures are absent, suggesting that the Ediacaran organisms were not capable of burrowing up through even thin layers of sand.

Ediacaran megafossils are invariably preserved on black, wrinkled surfaces similar to those elsewhere interpreted as microbial mats. Molding of delicate features (including tentacles), preservation of open molds as negative epireliefs, and sedimentological evidence of considerable cohesion of these surfaces relative to the underlying turbiditic muds (Td,e) supports this interpretation, and suggests that microbial mats were as important in the preservation of these deep-water Ediacara faunas as they were in their shallow-water equivalents. The presence of the wrinkled mats and their associated Ediacaran fossils almost exclusively in the pyritic intervals of the succession suggests that both may have lived under exaerobic conditions in this deep-water setting.

The regular and irregular echinoid fauna of the Northern Bay of Safaga (Red Sea, Egypt) has been investigated within the framework of an actuopaleontological study of the flora, fauna, sediments and facies. The distribution of echinoids has been compared to grain size parameters as well as to the distribution of other organisms.

The study area (ca. 10 × 7 km) was investigated using SCUBA-diving techniques along 55 transects with a total length of 126 km. Echinoid presence was quantified using weights of fragments (2 mm) originating from 67 standardized bulk samples distributed throughout the Bay. The complex morphology of the echinoid test and the spines allow the identification of fragmented material upon comparison to complete specimens. The resulting data was analyzed using correlation techniques as well as Q and R-mode multivariate statistical analysis. This method counters the difficulties originating from the cryptic habitats and patchy distributions.

The results of the analysis show that echinoid distribution can be analyzed for both regular and irregular wchinoid taxa despite taphonomic bias and restrictions imposed by the analytic method. Time averaging in fact counters the difficulties arising from the patchy distributions of echinoids. There is a close correlation of echinoid distribution to sedimentary and bottom facies as well as to grain size parameters and other environmental factors. The distribution of irregular echinoids is highly differentiated with coarse coastal sand dominated by Clypeaster sp., Echinodiscus auritus, Fibularia ovulum, and Lovenia elongata; muddy sands by Laganum depressum, Clypeaster sp. and Echinocyamus crispus; and muds by members of the Schizasteridae. Regular echinoids, mostly Eucidaris metularia, Echinometra mathaei, Tripneustes gratilla, Heterocentrotus mammillatus and Diadema setosum, dominate the sediments found within, or near reefs, coral carpets and patch reefs.

The methodology used in this actuopaleontological investigation should be useful in recognizing the distribution patterns of ancient echinoid faunas, especially in light of the significance of regular echinoids in the bioerosion of reefs and irregular echinoids in the bioturbation of sediments.