Middle-Late Wolfcampian phylloid algal/Tubiphytes biohermal complexes have been found exposed in western outliers of the Hueco Mountains of far west Texas. Paleogeographically, the bioherms are located along the fault-controlled shelf margin between the Late Paleozoic Diablo Platform and Orogrande Basin. Although Virgilian and Early Wolfcampian phylloid algal mounds are well-known from the Hueco and Sacramento Mountains, outcropping Middle-Late Wolfcampian bioherms have not been described previously from the Orogrande Basin area.

The biohermal complexes are exposed in three large outliers that lie about 3 miles west of the main Hueco Mountains and extend for about 12 miles in a north-south direction. The shelf margin complexes are in the Hueco Canyon Formation and correlate to well-bedded shelf facies in the main Hueco Mountains based on fusulinid biostratigraphy.

The phylloid algal/Tubiphytes shelf margin bioherms contain an upward shallowing facies succession, which consists of, in ascending order: (1) phylloid algal wackestone-bafflestone, (2) phylloid algal bafflestone-packstone, (3) phylloid algal-fusulinid bafflestone-packstone, and (4) Tubiphytes boundstones and Tubiphytes-fusulinid-phylloid algal packstones and grainstones. Unlike some previously described Wolfcampian phylloid algal buildups, the phylloid algal mound facies in these buildups contain only rare calcisponges, heliosponges, and marine radial fibrous cements. On the crest of the southern outlier there occurs a rather different type of bioherm, which contains nodular boundstones that are composed of encrusting red algae and bryozoans, and in which calcisponges are common. That bioherm is thought to be slightly younger in age than the phylloid algal/Tubiphytes bioherms, and it might also have been formed in a deeper-water setting.

Bordering the phylloid algal/Tubiphytes bioherms on the seaward side are overlapping tongues and channels of lithoclastic-skeletal debris and skeletal grainstones and packstones. Some of these forereef units extend seaward into slope facies, which consist of dark-gray cherty limestones that generally lack skeletal fossils, but contain a rich ichnofossil assemblage in the shallower upper slope beds. Backreef facies consist mainly of skeletal-peloidal packstones and wackstones.

The Hueco Mountains outlier exposures are significant because: (1) they establish the presence of a Middle-Late Wolfcampian shelf margin with distinct topographic relief in the southern Orogrande Basin, and (2) they provide an easily accessible field laboratory to study Middle-Late Wolfcampian shelf-to-basin facies relationships and shelf margin bioherms. Middle-Late Wolfcampian shelf margin bioherms are of particular interest because they represent an important transitional stage in the evolutionary history of Late Paleozoic reef communities, and because they form important petroleum reservoirs just to the east in the Delaware and Midland Basins.

Biological parameters, in addition to physical parameters, are important in determining past ecology, taphonomy and the effects of human intervention. Research conducted on a Recent community of gastropods and two late Pleistocene fossil assemblages from Puerto Penasco, Mexico, reveal a complex pattern of interrelationships among gastropod shell users. First, shell representation is biased in the intertidal of Puerto Penasco, Mexico, because of a complex mosaic of secondary shell occupants. Hermit crabs (five species) represent almost half (47%) of the intertidal gastropod shell resource available throughout the year. Living snails are represented by 17 out of the 32 gastropod taxa. Additionally, hermit amphipods (three species) occupy ten gastropod taxa. Hermit crabs and hermit amphipods retain the shells in anomalous habitats (that differ from the living snail). Second, physical factors act as a temporal component which affects shell use and availability during the seasons at Puerto Penasco. Late winter storms mix-up the intertidal distribution of living gastropods and hermit crabs. Subtidal to low intertidal shells appear in the high intertidal; living snails are buried under a thick bed of sand. Most importantly, empty shells become available, and the hermit amphipod population peaks. Thus, physical factors contribute to the demise of living snails (i.e, burial by sand) and the mixing of shells. However, the organisms (hermit crabs and amphipods) maintain this motif by retaining the shells in the anomalous habitats.

Third, all hermit crab species (Paguristes anahuacus, Pagurus lepidus, Paguristes roseus), except for one (the high intertidal, Clibanarius digueti), have epi-and endobionts associated with the gastropod shell. More than 20 species of invertebrates bore into or encrust the hermitted shells at Penasco. Of these, the encrusting bryozoans Hippothoa, Hippopodinella adpressa, ?Floridia antiqua, Lichenopora, Antropora tincta and the boring spionid polychaetes (Polydora commensalis, Polydora, Boccardia) and spirorbid polychaetes (Spirorbis; Serpula) are important bionts to use in recognizing hermit crab shell use in the fossil record of the northern Gulf of California. The encrusting bryozoans (H. adpressa and A. tincta) are present on Pleistocene gastropods at the unusual Pelican Point terrace deposit (large gastropod shells preserved among large bryozoan encrusted cobbles) indicating hermit crab inhabitation. These bryozoans appear to protect the gastropods from taphonomic alteration.

Finally, reworked fossil shells occur within the hermit crab guild and the beach drift assemblage. Hermit crabs retain fossil shells of the moon snail, Polinices, (n=two occurrences) and Turritella (n=3 occurrences). These species are common in the coquina beach rock which makes up the intertidal substrate of Puerto Penasco. However, reworking of fossil coquina is quite substantial in the beach drift assemblage. Three sampling periods (=150 samples) indicate the following: three species of fossil bivalves (Chione, Trachvcardium and Glycimeris) and five species of fossil gastropods (Oliva, Polinices, Muricanthus, Nassarius, and Turritella) dominated the beach drift assemblage (over 16, 600 fossil whole shells/fragments). Fossil Chione represented the most shells (958 valves;>15,557 fragments). Recent bivalves were represented by 1115 shells/fragments (representing 12 species) and Recent gastropods contained mostly fragments (1069 pieces; 30 species). Additionally, the fossil gastropods were large, unlike the species that occur today, which have been picked over by humans. Thus, a large part of active beach deposition at Puerto Penasco contains late Pleistocene shells, taphonomically altered by secondary occupants and beachcombers.

A synthesis of current research suggests several trends in deep sea taphonomy. First, epibiosis (the condition of having bionts on exoskeletons that is not obligate) appears to decrease with increasing depth. Epibionts, such as serpulid polychaetes and barnacles that take advantage of ephemeral hard substrates offered by crab exoskeletons, sea urchin spines or gastropod shells, appear to be more diverse and common at depths of less than 500 m. At abyssal depths, microbial communities on living shells are common and may contribute to the breakdown of molluscan periostracum. These communities may also have patchy distributions.

Second, shell-inhabiting symbionts, such as sea anemones uniquely associated with shells of pagurid crustaceans, are most common from 300 to 700 m. These unusual sea anemones cover hermit crab-inhabited gastropod shells with a chitinous material (Dunn et al. 1980) that may affect shell longevity. While gastropod shells without a periostracum may degrade quickly in calcium-poor waters, the chitinous covering secreted by the anemone may increase the postmortem longevity of the shell.

Third, deep sea gastropods usually have eroded apical whorls but buttress this weakness with internal calcium plugs (J. McLean, pers. comm., 1992). In addition, not all deep sea gastropods, like buccinids, have thick periostracal layers. How differing periostracal thicknesses affect taphonomy is undetermined.

Finally, deep sea gastropod fossils occur throughout the Cenozoic from many geographic localities: Eocene (Oregon, United States), Upper Oligocene (France), Miocene (New Zealand, Japan), Miocene/Pliocene (Australia), and Pleistocene (Italy). Sedimentary deposits containing these gastropods vary from thin interbedded sediments within oceanic basalt (e.g., Eocene, Oregon), volcanic breccia with bathyal sediments (e.g. Miocene, Japan), turbiditic sequences (Neogene, Japan) and bathyal clays (Pleistocene, Italy). Fossil quality varies from poorly preserved internal molds with altered shell material, to excellently preserved specimens with calcareous layers intact. We will discuss how this record bears on the geographic and preservational differences among the various deep sea gastropod fauna.

Brachiopods contain several classes of intracrystalline molecules, secreted during the growth of the organism, and subsequently incorporated in the shell during biomineralization. The function of these molecules is not clear, although in the Mollusca, molecules in similar sites are thought to be involved with biologically controlled mineralization. The order of amino acids, and hence the quantity of each amino acid in proteins is determined by the genome of the organism, and study of such molecules should reveal information regarding the genomes of the fossil organisms.

Previous studies of fossil molecules from brachiopods have concentrated on the web of intracrystalline molecules which surrounds the crystallites of the secondary fibres of the shell. Work with Recent articulate brachiopods has shown that this web decays in less than a year, and hence any remnants of this web in the fossil record are likely to be highly degraded and unrepresentative of the original composition of the protein.

In contrast to this, intracrystalline molecules will be protected, encased within the calcium carbonate of the shell and analogous in many ways to fluid inclusions found in inorganic minerals. In such sites, contaminant and degradative factors such as microorganisms and large concentrations of water will be excluded and the effects of the enclosing sediments negated. Any breakdown of the molecules will be in situ, and the detectable products analysed.

In this study, intracrystalline molecules have been extracted from the shells of Recent and fossil brachiopods from the Plio-Pleistocene South Wanganui Basin, New Zealand. The molecules were analysed for free and peptide bound amino acids from both the soluble and insoluble fractions. The state of preservation of the molecules and their taxonomic specifity were analysed.

It was found that, even in these protected sites, individual amino acids were up to 90% in the free state i.e. that the proteins had mostly been hydrolyzed by the action of time and any water remaining in the shell structure after 0.12 Ma. Amino acids which are particularly sensitive to degradative reactions, such as serine and threonine were totally lost from the soluble fraction. However, the use of multivariate statistical analyses on data from the soluble remains of the protein indicates that decay does not render the molecules useless for taxonomy; groupings can be made on the basis of analyses alone.

Progressively older samples tend to have lower yields of amino acid in the soluble fraction, and this tends to correspond with an increase in the relative proportion of intracrystalline insoluble compounds. Although there is no direct linear relationship between the age of a sample and the proportion of insoluble compounds, older samples tend to have more insolubles. It is clear that other factors must play a part in the formation of these insoluble compounds. Preliminary studies of their amino acid composition indicates the presence of sensitive amino acids such as serine, indicating the stabilising effects of these diagenetic compounds.

The degradation of amino acids follows complex decay pathways, with some decaying to non-amino compounds and others to other amino acids, the most common being alanine from the dehydration of serine. The increasing concentrations of these amino acids can be a distorting factor in molecular taxonomy from fossil molecules.

ACKNOWLEDGEMENTS. This work was completed during the tenure of a UK NERC studentship to DW (GT4/89/GS/42) and funding from the Royal Society to GBC.

The late Miocene Chinese hipparions are morphologically diversified showing similarity to both western Old World's and North American forms. Two Chinese taxa that are phylogenetically related to western Old World's forms are Hipparion fossatum (= H. forstende) from Baode (Shanxi) and H. hippidiodus from Qingyang (Gansu) and Baode. The former is related to H. mediterraneum and the latter to H. urmiense - platygenys from the Turolian localities in the western Old World. H. fossatum and H. hippidiodus are associated with the “dorcadoides” (open-land) and “mixed” faunas in northern China. Hipparion fossatum that is characterized by POF located close to the orbit co-occurs with large and morphologically specialized form, H. dermatorhinum in Baode (Loc.30). H. hippidiodus with reduced POF is discovered with smaller H. coelophyes in Loc. 43, 44 (Baode) and Loc. 115 (Gansu).

The hipparions associated with the “gaudryi” (forest) fauna are characterized by well defined and small POF located far from the orbit. Those forms are: H. platyodus from Loc. 70; H. ptychodus from Loc. 73; H. tylodus from Hsi-Liang in Yushe - Wuxiang basins; and H. sefvei from Loc. 12 at Xin-an in Henan province. H. coelophyes from Baode (Loc.43 & 44) and Qingyang (Loc. 115) also show similar facial morphology to the these forms, although it has small size and shallow POF. Those forms are similar in facial and dental morphology to Hipparion sensu stricto and some species of Cormohipparion in North America.

The assemblages of Chinese hipparions are composed of two groups whose members are phylogenetically similar to the forms from both western part of Eurasia and North America. The “gaudryi” fauna is considered younger than the other two on the basis of faunal analyses. The similarity in hipparionine taxonomy between northern China and North America in the latest Miocene is an evidences for possible faunal interchange(s) occurred during that period, as suggested by taxonomic analyses on carnivores and proboscideans in eastern half of Eurasia and North America.

Because Late Cenozoic land life in the Americas is best represented in temperate latitudes, it has long been standard practice for paleontologists to infer the history of the Great American Interchange from the classic mammalian sequences in western United States and in Argentina. In this record it is also clear that interchange genera in South America (ultimately of northern origin) make up about half of the modern land-mammal fauna, in contrast with a very limited success on the part of the reciprocal cohort of interchange genera.

On the other hand, tropical biologists at least since the days of A. R. Wallace have known that the Amazon Basin was a very rich center of tropical diversity and that this Neotropical richness had spread northward at least to the latitude of Oaxaca and Veracruz in Mexico. Thus, mammalian paleontologists claim a victory for north temperate forces spreading south, whereas much of the modern biota seems to register a countervailing victory for south tropical forces spreading north.

Current paleontological research in tropical latitudes, especially in the western Amazon Basin, indicates the manner in which these two different views of interamerican biotic movements can be reconciled. In effect both views are true, because they represent alternating modes of interamerican interchange. Perhaps simplistically, we recognize a “glacial arid phase” and an “interglacial humid phase”. During the former phases savanna habitats predominated even at tropical latitudes, as the western Amazonian records of the late Pleistocene strongly indicate. Because the source area in the temperate north was six times as large as that in the south, the great success of northern land mammal groups is explained. On the other hand, during interglacial humid phases, the principal biotic movement was from the vast Amazonian rainforest reservoir through the tropical latitudes of Mesoamerica. We review some of the new evidence of land mammals from tropical America in the late Pleistocene.

Stratophenetics has been widely adopted in paleontology to reconstruct phylogenetic trees. Despite the easy access to powerful computing facility amongst paleontologists, there is a shortage of integrated statistical procedures in such approach. This report is to (1) introduce a pattern recognition technique, Soft Independent Modeling of Class Analogy (SIMCA), for an objective stratophenetic approach, and (2) demonstrate its applicability by tracing two planktic foraminiferal lineages through a deep-sea sedimentary sequence.

Stratophenetics proceeds in three steps: (1) recognizing phena (groups of morphologically similar specimens) from each stratigraphic sample, (2) ordering stratigraphic levels in each local section, and (3) linking phena in adjacent chronostratigraphic intervals on the basis of overall morphological similarity. The Plio-Pleistocene planktic foraminiferal sequence of the Globorotalia (Globoconella) puncticulata-inflata plexus obtained from the Deep Sea Drilling Project site 588 serves a good illustration case. This sequence, dated at 3.66 Ma to the Recent, is relatively complete and furnished with a good chronostratigraphy. It records the branching history of G, inflata form the G. puncticulata lineage. The gradation nature of the divergence and the enormous morphological variability in G. inflata have caused difficulty in achieving a consensus of taxonomy and phylogeny in this plexus.

Typical specimens of the two species, G. puncticulata and G. inflata, were identified from a stratigraphic level dated at 2.76 Ma. Principal component models were built to characterize the morphometric patterns of the two morphotypes using SIMCA. The Globoconella specimens of the two adjacent stratigraphic intervals, one above and one below (dated 2.74 Ma and 2.83 Ma, respectively), were evaluated against the models and classified into one of the two morphotypes. The newly classified specimens were then used to build new models for further tracing specimens in the next adjacent stratigraphic levels. Progression such training and classification procedures through the stratigraphic intervals resulted in a reconstruction of the evolutionary patterns of the two lineages. The cladogenesis is inferred to occur at about 3.5 Ma and is characterized by a gigantism in the G. inflata lineage. The two lineages differ only in size and show similarity in all other characters in the beginning of the divergence, A disparity in allometric heterochrony further differentiated the two lineages after 2.8 Ma and the trend continued until G. puncticulata became extinct at 2.35 Ma.

Coevolutionary links between plants and herbivores, often cited as examples of adaptive response of one group of organisms to another, have been much studied from both neontological and paleontological perspectives. The most commonly cited case of coevolution from the latter viewpoint is the radiation of grassland grasses and grazing mammals during the mid-Tertiary. Other promising examples are also beginning to emerge, among them the radiation of ornithischian dinosaurs and early angiosperms during the Cretaceous.

Preliminary studies (Weishampel and Norman 1989) analyzed the temporal distribution of trophic groups among Ornithischia (and other herbivorous tetrapods) across the Mesozoic. Trophic groups were based on a mixture of monophyletic and paraphyletic taxa assigned to assorted taxonomic rank. Speciation, extinction, and turn-over rates were calculated from stratigraphic data to identify co-evolutionary “hot spots” between herbivores and contemporary plants: times of evolutionary perturbation between these two groups of organisms within the Mesozoic.

The present study reanalyzes Ornithischia from the perspective of ecosystem richness and phylogeny. As in the previous study, trophic categories are assessed on the basis of tooth morphology, occlusal patterns, and jaw construction. All ornithischians appear to orally process food in ways ranging from orthal pulping (ankylosaurs, most pachycephalosaurs) to orthal slicing and transverse grinding (euornithopodans, ceratopsians, some pachycephalosaurs).

During the Early Cretaceous, relative species-level trophic diversity (as expressed as percentages) for ornithischians consists of a subequal mixture of herbivores with a transverse power-stroke (euornithopodans) and orthal pulpers (ankylosaurs, rare pachycephalosaurs). Toward the end of the Early Cretaceous, orthal slicing herbivores (ceratopsians) have their earliest record. At the end of the Cretaceous (Santonian-Maastrichtian), the transverse-chewing euornithopodans contribute somewhat less toward relative diversity, while the orthal slicing ceratopsians diversify and orthal pulpers decline (mostly due to reduced ankylosaur diversity).

The pattern of acquisition of feeding/chewing styles among Cretaceous ornithischians is determined by mapping trophic categories on the phylogeny of the clade. With this in mind, our knowledge of the phylogeny of ornithischian tropic organization is in part a product of the completeness of the fossil record of these animals. Errors that may accrue because of a patchy record can be partially corrected by combining phylogenetic and stratigraphic information. This approach calls for the identification of ghost lineages, as well as their calibration using minimal divergence times (MDTs). Thus, diversity counts based on monophyly and evolutionary continuing can be augmented for yet-to-be-discovered species. Using ghost lineages and MDTs, a fuller picture of the pattern of acquisition of different jaw systems (and hence trophic organization) among ornithischian will become available.

Cells of Emiliania huxleyi are surrounded by ‘coccoliths', minute, elegant scales of calcium carbonate. In all the oceans, particularly at mid-latitudes, this species forms gigantic blooms, readily visualized by satellite imagery. Coccolith-bearing organisms, of which E. huxleyi is by far the most abundant representative, are the major contributors to the ocean floor limestone sediments, and this in turn is the largest long-term sink of inorganic carbon on earth. In addition, E. huxleyi blooms emit vast amounts of dimethyl-sulphide (DMS), a gas which, on oxidation, is a dominant source of cloud nuclei. The profusion of E. huxleyi and its intimate involvement with the global biogeochemical cycles of both carbon and sulphur make it a key component of the greenhouse effect (CO2), natural acid rain and albedo regulation.

E. huxleyi blooms are often almost monospecific. They can be visualized by satellite imagery and leave highly characteristic skeletal and macromolecular markers which accumulate on the deep-sea floor as a long-term record of their history. The organism is easily cultured in the laboratory and molecular genetical, biochemical and physiological studies are underway.

We focus on Emiliania huxleyi as a model organism to study interactions between oceanic plankton and climate. Benefits of this approach are: (1) to highlight the idiosyncratic non-linear character of these interactions; (2) to reveal the intimate coupling of the oceanic carbon cycle and DMS productivity; and (3) to allow an integrated modelling and experimental approach, integrating multi-disciplinary studies that range from the global down to the macromolecular level and through geological time. E. huxleyi coccoliths and specific biomarkers preserved in the geological archive not only provide information on the distribution of this organism in the geological past. The connection with extensive neontological research offers a unique opportunity to reconstruct the development of the entire E. huxleyi system, including its multifarious climatic interactions, through geological time.

The ‘Global Emiliania Modeling Initiative’ (GEM), started in 1990, is a European research program intended to investigate and model the Emiliania huxleyi system.

Declining importance of trilobites was a key feature of Ordovician community “evolution”. Previous work has shown that replacement of trilobite-dominated communities by mollusc- and brachiopod-dominated communities was diachronous, occurring initially in nearshore settings. The processes responsible for these changes remain unclear, although many previous discussions have invoked some form of displacement of dominants of one community by those of another.

New data from more than thirty large collections made from nearshore facies at five localities in Canada and the northern United States indicate that, in this setting, trilobite species diversity maintained a constant low level (mean and mode of 3 species) between the Early Upper Cambrian (Marjuman) and the Late Middle Ordovician (Blackriveran). Reorganization of nearshore communites proceeded by addition of new elements, especially molluscs, from the Late Cambrian (Sunwaptan) onwards. Decline in the relative importance of trilobites was a case of dilution as species of new clades accumulated, rather than actual displacement. Trilobites appear to have been passive bystanders in Ordovician nearshore community “evolution”. Towards the end of the Ordovician, trilobites vacated nearshore environments in the Appalachian region. However, this appears to be related to environmental changes associated with progradation of clastic wedges during the development of the Taconic foreland basin.

A process of dilution may at least partly explain the offshore retreat of trilobite-dominated assemblages during the Ordovician. Offshore trilobite assemblages reached much greater species diversity than those of nearshore settings, so that their dilution via the addition of species of newly radiating clades would have proceeded more slowly. That is, trilobite-dominated paleocommunities may have persisted into the Ordovician in the outer shelf simply because this was the region in which, historically, they attained maximum species richness. Moreover, given the existence of a general pattern of increasing total species diversity of communities from nearshore to offshore sites, the tendency for newly radiating clades to attain maximum species richness offshore is not surprising: they are merely conforming to a general, environmentally-related diversity gradient that has existed throughout the Phanerozoic.

A sample of over 170 hand, wrist, forearm and upper arm bones, from Olorgesailie DE/89 Horizon B and from Olduvai Gorge, was examined in this study. Elements include a trapezoid and centrale, capitates, hamates, scaphoids, lunates, pisiforms, triquetra and second, third, fourth and fifth metacarpals, ulnae, radii, humerii and scapulae.

The fossils are different in several functionally significant ways from modern papionids. The angulation between the dorsal and palmar halves of the scaphoid is less acute. The helicoidal facet of the hamate, for articulation with the triquetrum, is radio-ulnarly shorter than in modern cercopithcoids; this would limit ulnar deviation. The hamulus is disto-proximally shorter, relative to the hamate body, than in digitigrade cercopithecoids, knuckle-walkers or fist-walkers. The distal hamate surface has the division into distinct, separate fourth and fifth metacarpal facets that is present in palmigrade cercopithecoids. Intermetacarpal facets are generally bissected by deep grooves, indicating strong intermetacarpal ligaments. The facet on the capitate for articulation with the second metacarpal, and the corresponding facet on the metacarpal, indicate that there was a functional division between the second and third metacarpals. The two extremes of retroflexion of the medial epicondyle of the humerus are present in the sample of humerii; some specimens closely resemble the angulation found in arboreal Colobus guereze and Cercopithecus albogularis, while others are similar to terrestrial Papio and Erythrocebus. The extremes of bifurcation and angulation of the radial notch are present in the sample of ulnae. Some specimens have the arboreal condition of a single, basically lateral-facing facet; others have the terrestrial split radial notch. The terrestrial condition is found where movement is confined to the parasaggital plane, with the arm in full pronation. The more lateral orientation of the radial notch appears to indicate more capacity for pronation/supination. The retroflexed olecranon is indicative of terrestriality; all of the examined ulnae have the short, grooved, angled olecranon typical of terrestrial monkeys. The associated specimens from MCK II illustrate that the features can appear as a mosaic: “terrestrial” olecranon, retroflexed medial epicondyle but “arboreal” radial notch. The brachialis mark is more anteriorly-oriented than in modern cercopithecoids.

All classes of extant vertebrates have lithophagic species. The debate about why animals eat stones has quietly raged for over a century. Except for a documented physiological need in a few Recent bird and fish species, few can agree why they are ingested, but they have figured in scientific literature since the 1600s. Gastroliths have been used as stratigraphic indicators for geologists. They have been used as clues to biomechanics and feeding behavior for biologists. The presence of gastroliths in primitive archosauromorphs dates to the Jurassic mesosuchia and can be traced to Recent euschia. Gastroliths found in sauropodomorphs and ornithischians have been alleged to indicate higher levels of metabolic processes. Two large groups of sauropterygians, the younginoids and the plesiosaurs are rarely found without a clutch of stones with their skeletons. Gastroliths have been discovered in Permian and Triassic amphibians, Miocene and Recent pinnipeds, and many Recent reptiles. The presence of gastroliths in a fossil specimen is an important indicator of ontogenetic and phylogenetic characteristics that should be considered in tandem with the associated osteological material.

Soft-tissues replaced by hydroxyapatite are exceedingly abundant in fossil fish from the Santana Formation (Lower Cretaceous) of Ceara, NE Brasil. A number of tissues are often phosphatized within an individual specimen and may include portions of the alimentary tract, skeletal muscle, dermis, gill apparatus and ovaries. The level of structural detail displayed by these tissues varies considerably between individual fish but is relatively constant within any single specimen. In some, sub-cellular resolution is the norm, whilst in others only gross morphological detail is preserved.

Frequently, certain tissues such as gill filaments and their secondary lamellae; epithelial cells of the gut wall; and, striated muscle fibres, preserve a number of different morphologies. In the latter for example, a continuum exists between homogeneously mineralized fibres which are almost indistinguishable from living muscle, and muscle which is disrupted by exceptionally well developed and irregularly spaced banding. In the same specimens, both the sarcolema and cell nucleii may display varying degrees of distortion. These characteristic morphologies reflect the gradual loss of structural integrity accompanying a period of post-mortem decay prior to and/or during permineralization.

High resolution TEM and SEM studies of structures produced at progressive stages of soft-tissue decay in modern fish, confirm the necrolytic origin of these morphologies. The timing of their appearance under specified conditions is remarkably reproducible. Certain parameters such as the ambient water temperature and salinity appear to have considerable influence over the rapidity of decay, whereas others, including the levels of oxygen and the presence of an established bacterial community have less, especially over short periods.

By cross-referencing certain taphanomically produced structures, estimates of both the timing of phosphatization and the likely bottom water conditions of the Santana Formation “lagoon” may be made.

Estimates of evolutionary rates require measurement of amounts of change and the period of time over which such change has occurred. Many methods of estimating amount of morphological change are available (including phenetic and morphometric measures) but in cladistics the unit of change is the step or transformation.

For a given cladistic data set the length (total number of steps) of the most parsimonious cladogram gives a lower bound estimate of the amount of evolution that has occurred within the clade. This measure is correlated with numbers of characters and taxa (and other internal parameters) in the data sets and so cannot be used to compare amounts of evolution in different clades where data set sizes vary. Further, the number of characters incorporated into cladistic studies varies widely and is likely to be a poor basis for an estimate of overall amounts of change.

One approach to the measurement of amounts of change which avoids some of these problems is to focus upon comparative levels of homoplasy rather than total amounts of morphological evolution. Most parsimonious cladograms provide lower bound estimates of the amount of homoplasy measured as extra steps.

Maximally homoplastic data provides the theoretical upper limit to the amount of homoplasy that can be estimated for a particular data set. Combining this with estimates of group duration derived from the fossil record or from molecular clocks provides an estimate of maximum rates of homoplastic evolution that can be measured using cladistic parsimony and discrete data.

Randomly permuted data provides a measure of the amount of homoplastic evolution that would be reconstructed by parsimony analysis for character data that is independent of phylogeny. Combining this with estimates of group duration provides estimates of rate of homoplastic evolution that would be sufficient to render the application of parsimony to the problems of phylogeny reconstruction inappropriate.

Comparative estimates of the rates of homoplastic evolution in different clades can be used to test macroevolutionary theories.

The 3-km thick Neogene Siwalik Group (Himalayan foredeep in northern Pakistan) and the 2-km thick Paleogene Fort Union/Willwood Formations (Bighorn Basin, Wyoming) both preserve long records of fluvial deposition adjacent to rising mountain belts. Depositional environments and associated habitats change with spatially varying physiography and deposition by river systems that may differ greatly in size, sediment loads, depositional rates, drainage of adjacent floodplains, and taphonomy of organic remains. At times, some environments may not be preserved; for example, avulsion of channels to low areas removes more deposits of channel-distal environments as avulsions increase relative to net sediment aggradation rates. Recognition of such large-scale biases is important because they represent time scales over which long term paleoecological change is reconstructed, and requires knowledge of how drainage systems changed in time and space within these evolving basins.

The Siwalik Group was deposited by large rivers that filled a basin extending at least 1000 km along its axis and 150–250 km away from the mountain front. Despite the scale of these rivers relative to Siwalik exposures, transitions between different fluvial systems have been recognized. For example, a 1-km thick sequence bridging the boundary between Chinji and Nagri formations records displacement of a smaller river system (width < 2 km; depth 5-10 m; discharge 1000-1500 m3/s) by a larger system (width <5 km; depth 15-30 m; discharge at least 5,000-10,000 m3/s), with an associated upsection increase (30 to 70%) in the proportion of channel sandstones, increased mean sediment accumulation rates (150 to 300 m/my), decrease in poorly drained floodplain deposits and well developed paleosols, marked decrease in abundance of faunal remains, and a major change in faunal composition. Stratigraphically higher (Dhok Pathan Fm.), there is a lateral transition between deposits of dissimilar, coeval river systems with corresponding differences in local paleoenvironments and vertebrate taphonomy. Although upsection changes in environments and vertebrate faunas may generally reflect extrabasinal controls such as tectonism and climate change, our studies emphasize the importance of recognizing deposits from different contemporaneous river systems before inferring such large-scale controls on paleoenvironmental change through time.

The Bighorn Basin is an intermountain foreland basin extending 200 km along its axis and about 80 km across. A large portion of this basin is exposed, and thus it is possible to reconstruct the distribution of river systems and the spatial paleoenvironments in more detail than in the Siwaliks. The Bighorn Basin was traversed along its axis by an early Eocene, north-south flowing river that was joined by smaller rivers flowing transverse to the axis. The proportion of channel sandstones decreases upsection (50 to 25%) from the Fort Union to the Willwood Fm. The proportion of channel sandstones and the abundance of well developed paleosols decrease with increasing net sediment aggradation rates. Although channel deposits are concentrated along the basin axis in a more complex way in some stratigraphic intervals, it is unclear to what extent these changes reflect deposition by different rivers versus extrinsically controlled changes within individual river systems.

Nearly autochthonous plant fossil assemblages are abundant in a variety of fluvial sub-environments in the Fort Union and Willwood Fms. of the Bighorn Basin (BHB), including abandoned channel fills, channel margins, levees, splays, and floodplain backswamps. Heterogeneity in the stratigraphic and geographic distribution of plant-bearing deposits limits our ability to resolve temporal change in floras and climate because depositional environment strongly affects floral composition, and must be considered in any analysis of floral change.

Plant-bearing levee, splay, and backswamp strata are common through much of the Fort Union Fm. in both the central and northern BHB. In the central basin, such deposits are abundant in the lower 200 m and upper 150 m of the Willwood Fm. with a gap from 350 to 620 m. In the northern BHB, the Willwood Fm. is almost entirely devoid of such plant-bearing deposits. Abandoned channel fills are scattered throughout the Fort Union and Willwood Fms. with the exception of the upper Willwood in the northern BHB and the 460-620 m interval of the Willwood in the central BHB. Deposition of plant-bearing floodplain backswamps was probably controlled by rates of aggradation, and the proximity and stability of major channels, as well as by regional climatic change. The formation of plant-preserving ponds was probably controlled less by climate than by the rate of channel cut-off and the degree to which channels reworked previous floodplain deposits. At a larger scale than these local depositional settings are sub-regional scale environments, including coal swamps, lakes, and conglomerate fans, that have a stratigraphic distribution controlled largely by tectonic activity.

Samples of fossil floras matched for depositional environment and sampling effort reveal several long-term patterns. One, the greatest number of species and fastest rate of turnover are seen in the alluvial ridge environments; backswamp samples have fewer species and slower rates of turnover. Two, floristic change during the Paleocene was relatively slow, and the Paleocene/Eocene (Clarkforkian/Wasatchian) boundary is marked by just a few extinctions and originations. The most pronounced turnover in the BHB sequence occurred between the early and late Wasatchian, probably as a result of climatic drying. Three, species number decreased from the early to mid-Paleocene, then increased steadily from 8 spp./sample in the late Clarkforkian to >12 spp./sample in the late Wasatchian.

Physiognomic analysis of floras indicates a rise in mean annual temperature from about 10° C in the Tiffanian to about 13° in the Clarkforkian and more than 18° in the early late Wasatchian; this may have been a major factor in the increasing diversity of the flora. Recent correlations of Bighorn Basin sections to standard marine zonations show that this warming trend was synchronous with global warming indicated by the oxygen isotope record.

Calcimicrobes dominate the earliest reef-ecosystems in the Precambrian and Cambrian. The Archaeocyatha, an early Cambrian group of calcified sponges, were the first skeletal metazoans to be associated with reefs but their role in the overall buildup form was generally subsidiary. The solitary nature of many archaeocyaths explains some of their previously supposed apomorphies - thus there are few modern analogies for their ecology. However, archaeocyaths, with irregulars in particular, show the progressive acquisition of low integration modularity in several different lineages through time. This trend is interpreted to be an adaptation to the reef-building habit and continues right up to the final extinction of the group. This suggests a relative immunity to extinction presumably on account of ecological response. Supposed species may be facultatively modular, with modular ecophenotypes always dominating biohermal settings. Modular organisation confers many ecological advantages in reef-building settings, such as indeterminate growth leading to larger size, greater powers of regeneration, and an ability to encrust and gain secure attachment to substrates. This confirms the widespread adaptive significance of integration in clonal organisms. Even though high integration, skeletally simple stromatoporoid-like forms developed in irregulars, low integration, branching morphologies were by far the most successful. This is suggested to represent adaptation to the particular conditions of the early Cambrian tropics - conditions of relatively high turbulence, sedimentation rates and possibly nutrient levels. However only genera possessing porous septa show any development of modularity, suggesting that an initially well-integrated soft-tissue is a prerequisite for acquisition of the habit. Increasing integration and simplification of the skeleton can be correlated with an increase in soft-tissue flexibility. Modularity is an advanced condition in sponges and we suggest that paedomorphosis facilitates its acquisition in archaeocyaths.

The Phanerozoic history of marine carbonate sedimentation shows considerable variations in both extent and style. Changes in nutrient flux have recently gained popularity as explanations for such variation, especially in the control of benthic production and reef-formation in tropical areas. Variations in nutrient flux can to some extent explain the general global patterns seen in the ecological style and systematic composition of reefs since the appearance of the habitat in the early Cambrian. Several convergently evolved organisations of reef-building organisms can be distinguished, most of which re-occur throughout the Phanerozoic. Such organisational types appear to favour different ambient nutrient concentrations: Solitary and low-integration forms together with considerable algal development are found in areas of relatively high nutrient levels, sedimentation rate and turbidity, whereas high integration forms with photosynthetic symbioses predominate in low nutrient conditions, with low rates of sedimentation and little turbidity. Therefore, the relative abundance of such forms, together with analysis of the associated biota, sediments and early diagenetic alteration, might be used as an indicator of changing nutrient levels in carbonate regimes throughout the Phanerozoic. Such studies highlight the extrinsic environmental constraints which may have controlled sedimentation in the carbonate regime and the evolutionary diversification of associated marine biotas.

Biostratigraphically significant samples have been collected from six localities in post-Neocomian terrestrial deposits of the central Andean Main Range (34° 50 S latitude), Chile. Localities are distributed over an area of 13 km by 5 km, and span more than 2500 m of section.

Two eastern localities occurring lowest in the sequence yield a diverse suite of more than 20 taxa indicative of a new biochronologic interval between the Mustersan (?middle Eocene) and Deseadan (?late Oligocene-early Miocene) South American Land Mammal Ages (LMA); speculatively it also is older than the enigmatic Divisideran “LMA”. Noteworthy occurrences include the first South American appearance of rodents, argyrolagoid marsupials, and interatheriine interathere and advanced notohippid Notoungulata, as well as the last appearance of polydolopid marsupials, and notopithicine and notostylopid Notoungulata. Four K-Ar and Ar40-Ar39 analyses on a flow and tuff which directly underlie one locality yield ages between 35.6 ± 0.9 and 37.56 ± 0.14 Ma; the fossiliferous unit itself has produced four Ar40-Ar39 dates between 31.7 ± 0.3 and 31.37 ± 0.08 Ma in one locality. Therefore, the new biochronologic interval appears to be earliest Oligocene in age, and is the oldest sequence representing Simpson's “Second Faunal Stratum”. The “Tinguiririca” assemblage is the oldest South American mammalian fauna dominated by herbivores (in a diversity of taxa) with high-crowned or evergrowing teeth, documenting major changes caused by interaction between a major phase of tectonic uplift in the central Andes and global climatic changes near the Eocene-Oligocene boundary.

We recently recovered about one dozen skulls and jaws from several sites some 10 km west of, and 2500 m stratigraphically above, these lowest localities. The fauna from these new western sites appears advanced over the localities to the east, and probably is younger than about 20 Ma, based on stratigraphy and Ar40-Ar39 dates from units overlying the eastern localities. The new faunas should help resolve controversy concerning the younger limit of the Deseadan LMA.

Discovery of the mammal faunas has profoundly altered understanding of central Andean geology: 1) we identified an unconformity between Jurassic marine/late Cretaceous clastic units and volcaniclastic mid-Tertiary deposits, indicating that a dramatic episode of volcanism previously attributed to the late Mesozoic is in fact 30 m.y. younger; 2) consequently, the late Cretaceous/early Tertiary is characterized by non-deposition or erosion, rather than by volcanic deposition as had been hypothesized earlier; and 3) our paleomagnetic results also indicate previously unrecognized, but significant post-Miocene clockwise tectonic rotation (up to 20°) of units in this part of the Andes.

The recent discovery of Tertiary plant fossil DNA from the Clarkia Miocene lacustrine deposits, northern Idaho, has raised concerns of the taphonomic conditions of preservation of fossil biotas with soft tissues and the further prediction of such occurrence in ancient lake deposits. The exceptionally preserved Clarkia fossil biota is compared with the Shanwang biota in Shandong Provence, eastern P.R.China, another example of Miocene conservative fossil lagerstatten. The comparison shows following similarities between the two extraordinarily preserved Miocene fossil biotas: (1) both were deposited under similar age, geological background, and depositional environment; (2) humid, warm-temperate paleoclimate was inferred in both areas; (3) both deposits contain diverse fossil biotas with soft tissues but having limited benthic organisms; (4) higher similarity coefficient exists between fossil diatoms, higher plants and insects at genus or higher taxonomic levels; and (5) overall similar taphofacies exists between the two fossil biotas.

However, following differences appear between the two areas: (1) diverse vertebrate fossils in Shanwang site are sharply contrasted with the Clarkia biota in which terrestrial vertebrates are absent; (2) comparison of taphonomic signatures shows slightly different patterns between the two; (3) the two Miocene lakes originated in different manners, thus differences appear in configuration, stratification, and other paleolimnologic parameters between the two ancient lakes.

The comparison of the two extraordinary fossil biotas, coupled with geologic, sedimentologic, paleoecologic and paleobiochemical studies, demonstrates that the formation and preservation of such fossil biotas with soft tissues in ancient lake deposits were strongly controlled by various paleolimnologic, paleoclimatic, taphonomic and compositional parameters.

The present day vegetation types on the earth are to a large extent controlled by climatic conditions that are mainly reflected in variations in moisture availability and temperature through the annual cycle. Therefore, fossil plants can be used as a tool to elucidate both spatial and temporal climatic changes. The global climates of the Jurassic can be interpreted with fossil floras because many parts of world have yielded abundant floral localities. Those records not only provide a strong basis for the qualitative depiction of vegetation patterns, but also provide quantitative data for the reconstruction of paleophytogeographic provinces and climatic changes. The computer program known as “Detrended Correspondence Analysis” written by Hill (1979) was used in this study. The floral data for this quantitative approach was assembled at the generic level mainly from the published literature. By definition, it is a method based on ordination scores, that is, the species ordination scores are averages of the sample ordination scores, and vice versa.

The scatter diagrams of the first two axes of genera and sample sites derived by detrended correspondence analysis were obtained for the intervals of Early, Middle, and Late Jurassic. The gradient variations of both genera and sample sites are reflected by the scores along axis 1 and 2 because axis 1 and axis 2 maximize the correlation of species and sample sites according to this technique. In the ordination score diagrams, the genera in similar climatic environments and the sample sites in similar paleogeographic regions are relatively close to each other along axis1 and axis2.

One of characteristics of the Jurassic vegetation is the taxonomic stability through the period compared with other periods of time. Therefore, the generic scores of axis1 for the Early and Middle, Middle and Late, and Early and Late Jurassic can be plotted against each other. The regression line can be used to assign the scores to the ordered genera. This is the technique used to complement the ordered genera from the gradient score diagrams and to eliminate the effect of some local genera. The genera adjacent to the regression line can be reliably used to reflect climatic gradients. The gradient changes were used to define biomes and to determine phytogeographic patterns on a global scale.

The quantitative analysis clearly shows that the use of floral data can achieve fast and satisfactory results in paleoclimatic studies of the Jurassic. For example, the cool-wet temperate climate is reflected by a ginkgophyte dominated deciduous flora, such as Ginkgo, Czekanowskia, Phoenicopsis, and Baiera, whereas the subtropical warm and drier climate is represented by cycad dominated floras, such as Anomozamites, Nilssonia, Pterophylum, Ptilophyllwn, Ctenis, and Otozamites. The general conclusion of earlier workers that Jurassic floras were especially uniform through the earth is true in the relative sense only, and the ordination study allows for the subdivision of the rather shallow gradients that do exist.