Cambrian trilobite faunas from northern India provide data critical for assessing earliest Phanerozoic paleogeography and for constraining tectonic models of Himalayan evolution. Previous investigations suggest that Indian Middle Cambrian trilobite faunas, collected from basins 500 km apart, are strikingly different. The Kashmir fauna, in the west, shows supposed faunal affinities with northern China, while the Spiti fauna, in the east, was considered of European affinity. This counterintuitive faunal distribution in adjacent basins might suggest that the area was made up of several micro-contininents during Cambrian time. Although frequently neglected, this interpretation has major implications for models of Himalayan mountain building, as most models assume a passive northern margin of India throughout the Phanerozoic.

Original type material from Kashmir and Spiti and fresh collections from intermediate localities in the Zanskar valley have been evaluated using a new statistical/computer-graphic method which removes the effects of tectonic deformation. Results show that the supposed taxonomic distinctness of the Kashmiri and Spiti faunas is largely superficial. Previous lack of appreciation of deformation has lead to: 1. over-estimation of the number of taxa present; 2. misidentification of many taxa; 3. spurious correlations with other faunas; 4. inaccurate age estimates. The revised assessment indicates that: 1. approximately 12 species of polymerid trilobites are present in the Middle Cambrian of north India; 2. 3 polymerid trilobite species are common to both Kashmir and Spiti faunas; 3. much of the Spiti fauna is significantly older than the Kashmiri fauna; 4. faunal differences between coeval deposits from the two basins are best explained as biofacies differences related to an offshore proximality trend; 5. species show patterns of developmental flexibility similar to that recently reported in other Cambrian trilobites. The faunas do not suggest that Kashmir and Spiti were part of separate continents during the Cambrian.

The morphology of Middle Cambrian faunas from Kashmir, Zanskar and Spiti suggests that all polymerid species were benthic and share morphotypes characteristic of trilobites from slope environments. Lithologic evidence suggesting that Kashmiri faunas were deeper water than those from Spiti is complimented by the presence in Kashmir of the atheloptic trilobite Bailiella, which is characteristic of deeper waters. Faunas from Kashmir, Zanskar and Spiti, which lie within the Tethyan belt of the Indian Himalaya, share closest affinity with those described from north China, north Vietnam and south China. They also show affinity with faunas from Iran. This pattern is consistent with recent paleogeographic reconstructions which place these regions in close proximity and at similar latitudes. Most of the Cambrian within the Tethyan Himalaya is of middle Middle Cambrian age.

The recognition of developmental flexibility as a general characteristic of Cambrian trilobites suggests many groups may be taxonomically over-split. Over-splitting may have lead to widespread over-estimation of faunal provinciality during Cambrian times.

Most recent workers have identified a major extinction of nonmarine tetrapods during the Late Triassic at the Carnian-Norian boundary. However, this identification is based principally on the stratigraphic distribution of tetrapods where there either is a major facies change at the Carnian-Norian boundary (Germany) or a significant unconformity that spans much of the early Norian (Argentina). Instead, we have examined the stratigraphic record of tetrapods in the western United States (Chinle Group) where there is a relatively continuous, nonmarine depositional and fossil record across the Carnian-Norian boundary that does not encompass major facies changes. The Chinle Group, because of its great area of exposure, more than one century of extensive collection and relatively complete publication, contains the world's best record of tetrapods across the Carnian-Norian boundary.

The tetrapod record from the Chinle Group does not record a significant tetrapod extinction at the Carnian-Norian boundary. Instead, it documents a staggered extinction of some taxa during the late Carnian and the persistence of most taxa across the Carnian-Norian boundary. Thus, rhynchosaurs become extinct at the end of the early-late Carnian, whereas dicynodonts become extinct somewhat later, during the latest Carnian. Among metoposaurids, only the large taxa (Buettneria) disappear at the end of the Carnian. Other groups - phytosaurs, aetosaurs, rauisuchians, trilophosaurs, etc. - only exhibit some generic turnover at the Carnian-Norian boundary. The first appearance of dinosaurs, linked by some to a Carnian-Norian tetrapod extinction, is well in advance of the end of the Carnian. Thus, we conclude that the highest resolution tetrapod record of the late Carnian and early Norian does not document a significant tetrapod extinction at the end of the Carnian.

Evolutionary novelties do not originate randomly in time and space, but geographic patterns have not been investigated systematically. The present-day latitudinal diversity gradient, manifest at many taxonomic levels, has been taken to suggest that most evolutionary novelties originate in the tropics, but differential extinction could have been as important as differential origination in the accumulation of taxa at low latitudes. Further, a clade's Recent diversity pattern need not reflect its initial geographic distribution. For example, several marine genera that are widespread or mainly tropical today have their oldest representatives recorded as fossils in high paleolatitudes. Are the tropics, in Stenseth's words, a cradle or a museum?

The question requires an empirical analysis of the fossil record, but preservation and sampling are highly uneven across the globe over the Phanerozoic. As a first attempt to detect robust patterns, I compared the geographic distribution of the 26 post-Paleozoic marine invertebrate orders having high preservation potential to two datasets likely to reflect preservation and sampling bias (Jablonski and Bottjer 1991): (a) first occurrences of poorly preserved orders (having flimsy or easily disarticulated skeletons, e.g. notaspidean gastropods and comatulid crinoids, n = 16), and (b) all published records of Triassic-Bajocian echinoids (n = 887, first third of Paleozoic-time, with most ordinal originations). First occurrences of well-preserved orders were evenly distributed above and below 30° absolute paleolatitude, contrasting significantly with the poorly preserved orders, which are predominantly extra-tropical in first occurrences (p 0.001, G test). Despite the much more intense collecting and description of fossils at higher paleolatitudes, the Triassic-Bajocian peak in the first occurrence of well-preserved orders falls below 30° paleolatitude, significantly different from the contemporaneous echinoid records, which do appear to reflect collecting intensity (p< 0.005, G test; p < 0.05 for frequency distributions using 10° blocks, Kolmogorov-Smirnov test). The difference increases if the echinoid superorder Microstomata (which contains primitive taxa bearing novelties related to an important shift to deposit-feeding, but not assignable to any presently recognized order) is used instead of its oldest named order, the Cassiduloida; and remains significant if the Lower Triassic is ignored owing to especially poor sampling (p < 0.02). Low paleolatitudes, then, contain significantly more first occurrences of marine invertebrate orders than would be expected from a null hypothesis of sampling and preservation: major novelties appear to have originated preferentially in the tropics. Still unknown is whether the tropics have a higher per-taxon rate of novelty production, but the apparent discordance between within-habitat diversity and ordinal origination along bathymetric gradients sugqests that a simple probabilistic explanation may be inappropriate.

Molluscs are the most diverse and abundant tropical American macrofossils, but their distributions and evolution are not well understood. Classic studies by Olsson and Woodring documented a rich Late Miocene to Early Pliocene “Gatunian” fauna throughout the Caribbean and tropical Eastern Pacific, with many species in common between the oceans. This fauna was divided by formation of the Isthmus of Panama, and diverged into distinct Pacific and Caribbean faunas sometime thereafter. Diversity also decreased by about half in the Caribbean. However, the timing, rates and correlation of these major biological changes with changes in environmental conditions have not been resolved because of imprecise dating and taxonomy and failure to consider problems of sampling and biofacies in biological comparisons. We used the newly revised late Neogene stratigraphy for Panama and Costa Rica to date for the first time the radiation and extinction of molluscs on opposite sides of the Isthmus. Data include occurrences throughout tropical America for nearly 100 species of the Strombina-group (Gastropoda, Columbellidae) and for more than 500 gastropod and bivalve genera from 240 Late Miocene to Pleistocene isthmian collections.

All evidence suggests that final closure of the Isthmus of Panama occurred between 3.5 and 2.5 My. Subgeneric divergence between the oceans was well developed, and trans-isthmian species were rare by the Early Pliocene, at least 2 Ma before final closure. Caribbean diversity remained high until 1.8 to 1.5 Ma when massive but selective extinction occurred. This was at least 1 Ma after final closure of the Isthmus, and may be correlated with onset of slightly cooler Caribbean sea surface temperatures in the Pleistocene. In contrast, Eastern Pacific diversity did not decline, and even increased during the Pleistocene.

Resolution of deep evolutionary problems, including the origin of the metazoa and the morphologic evolution of higher taxa within the metazoa, have long been sought in the developmental sequence. Haeckel's gastraea theory is perhaps the best example of this endeavor. Since Haeckel's time it has become apparent that the early evolution of animal life cannot be read directly from the developmental sequence. Ontogeny itself evolves making it difficult to even identify homologies in the early development between many phyla and classes. However, all may not be lost; during metazoan development gene expression must be localized in order to differentiate cell types in the body during development. It is this regionalized transcription and translation to protein product that differentiates cell types, organ systems, and the morphologic features that we can identify in the fossil record. The functional importance of the genes in question, and the fact that portions of the protein products of these genes must bind to DNA in order to perform their switching function, leads to extreme sequence conservation. This permits the identification and comparison of homologous genes important in the development of divergent taxa even after the passage of the entire Phanerozoic. If these genes retain a pattern of expression in development as well as conservation of the DNA sequence, then we can identify a homologous process derived from the development of the shared ancestor of the two taxa.

This approach can be used to address the homology of metameric units. Preliminary results indicate that the segmentation gene engrailed is expressed in chiton trochophores in associated with each of the developing plate fields. The engrailed gene is known to control segmentation processes in arthropods and annelids. Evidently the plates in chitons evolved from serial features in a shared ancestor of annelids, arthropods and molluscs. This indicates that the serial features found in molluscs are ancestral (plesiomorphic), and that the evolution of the mollusca has involved the loss or reduction of serial features rather than their de novo evolution in chitons and monoplacophorans as has been suggested by a number of neontologists. The fossil record suggests successive reduction of serial features in molluscs. This paleontological interpretation now finds support in developmental genetics.

Developmental genetics also provides a basis for evolution of body plans. Unusual preoral appendages have evolved in chelicerates, Burgess Shale arthropods such as Yohoia and Leanchoilia, and non arthropod forms such as Opabinia and Tullimonstrum. The differentiation of the vertebral column of vertebrates and the segments of arthropods are controlled by homologous genes that are expressed in a anterior to posterior sequence. Out of place (ectopic) expression of posterior genes in the anterior region produces posterior features in the antennal field of arthropods and in the most anterior vertebrae of the vertebrates. This potential for conversion of anterior features was present in the shared ancestor of vertebrates and arthropods. Thus evolution of novel anterior features resulting from ectopic expression could occur in both deuterostomes and protostomes and may account for a range of novel fossil forms. This suggests that parallel evolution of unusual anterior features could occur, and the presence of these features may not be the best character to use in a phylogenetic analyses.

The Neogene of North American represents a time of climatic change from an initially warm, non-arid climate to one with the development of increasing aridity, with warming temperatures through the early part and fluctuating (but basically cooler) temperatures through the later part. This reflects the classic story of a vegetational change from woodland to savanna and eventually to prairie. Note that the transition to true savanna in the Late Miocene was considerably earlier than the first savannas in the Pliocene of the Old World. The evolutionary trends in mammals reflect these climactic and vegetational changes.

Some general broad trends are as follows: the replacement of terrestrial and subfossorial moles and geomyid rodents with more specialized fossorial ones; a decrease in the diversity of brachydont rodents and an increase in the diversity of hypsodont ones (including saltatorial forms), and a late Neogene diversification of microtines and deer mice; a decline in the diversity of tree squirrels and terrestrial beavers, and an increase in diversity of ground squirrels and aquatic beavers; the replacement of carnivores belong to more archaic families by more modern types; taxa and an increase in body size, leg length, and hypsodonty in most ungulate taxa, including oreodonts, protoceratids, camelids, antilocaprids, rhinos and equine horses although a couple of taxa show an apparent reversal of these trends: dromomerycids (cervoids) and some anchitherine horses show other morphological changes that suggest progressively more woodland-adapted (rather than savanna-adapted) forms. Tapirs and (to a lesser extent) peccaries seem little affected by the Neogene changes, and persist until the Recent.

The Neogene was also punctuated by immigration events (primarily from Asia) and extinctions. The start of the Neogene shows surprisingly little change, with many Paleogene “holdovers”: some new forms appear as either the result of evolution in situ (e.g. equine horses and osteoborine dogs) or as immigrants (e.g. chalicotheres and hemicyonine “dog bears”). The initial major immigrations are during the late Early Miocene, marked by the Asian appearances of true felids (replacing the “false saber-tooths” or nimravids), pecoran ruminants (replacing the hypertragulids), more derived rhinos (replacing the diceratherine rhinos), neomustelids and procyonids. Archaic suoids such as anthracotheres and entelodonts become extinct at this time, and only the more derived ticholeptine oreodonts survive this period. The start of the Middle Miocene is notable for the appearance of proboscideans and deer mice. The Late Miocene sees the decline and eventual disappearance of hedgehogs, archaic carnivores (hemicyonine bears and amphicyonids), most browsing ungulates (oreodonts, protoceratids, many camelids, anchitherine horses, dromomerycids, merycodontine antilocaprids, hornless ruminants, chalicotheres, bunodont gomphotheres), and rhinos. New taxa appearing including ursine bears (immigrants), oversized camels and more derived gomphotheres (in situ evolution). The Pliocene marks a new wave of immigration: microtines, hyenas, true saber-tooths, and cervids come in from Asia; ground sloths (two families appearing in the Late Miocene), glyptodonts, armadillos and capybaras come in from South America. Most mammals that survived the end Miocene extinctions persist, but for many of them (such as horses, camels and antilocaprids) the generic diversity is greatly reduced.

Both insoluble (particulate) and soluble (molecular) sedimentary organic matter carry signatures of physical, chemical, and biological processes. These signatures may reflect (a) primary age-diagnostic, organism-specific, and environmentally-sensitive processes; (b) secondary factors related to mode of transportation, deposition, and preservation; and (c) tertiary agents that indicate post-burial alteration of the organic matter. Application of any or all organic matter data recorded in rocks can be used to solve geologic problems.

Organic stratigraphy may be applied to hydrocarbon exploration. Our example uses both particulate and molecular data to reconstruct the age relations of Cretaceous-Lower Tertiary sediments in Wyoming, to determine the age of thrust fault motion, and to demonstrate constraints on the timing of upward petroleum migration to available trapped reservoirs.

Another perspective helps establish chronostratigraphic frameworks for correlations of global sea-level change. Our example from Antarctic sediments that span the Cretaceous-Tertiary boundary reflects perturbations in relative sea-level and the consequential changes in the distribution of organic particulates from marine and terrestrial regimes. These data can be compared to age-equivalent data from other parts of the world, and test global sea-level change.

Both of these applications demonstrate the versatility of organic matter in solving geologic problems. Data from contemporaneous land plants, freshwater and marine organic-walled micro-organisms provide clues on their lifestyle and subsequent afterlife alteration. Organic stratigraphy represents a long anticipated integration of several paleontological disciplines. It combines aspects of palynology, organic geochemistry, paleobotany, and coal petrography into a coherent science, with an enhanced capability to provide significant applications in the future.

The introduction of cladistic techniques in phylogenetic systematics have revolutionized many concepts in mammalian taxonomy: most notably, many early groups have been relegated to the status of paraphyletic or polyphyletic assemblages (e.g. the “Condylarthra” or “stem ungulates” and the “Proteutheria” insectivorans.). While it is important to recognize truly polyphyletic groups (e.g. the “Amblypoda” or Paleogene “pachyderm” analogs), all non-monophyletic groups are now commonly assigned to a similar “wastebasket” status, rendering all events associated with their evolution as “pseudo-events” on the grounds of taxonomic impurity.

I am uncomfortable with this tendency for two reasons. The first is philosophical. Monophyly is a time-dependent system of classification: all taxa were monophyletic at their inception and the more successful (i.e. generative) ones must inevitably pass into paraphyly. Cladistic taxonomy claims to be independent of stratigraphic bias, but seemingly has no problem with using an arbitrary cut-off point in the geological record (the Recent) as a means of imposing taxonomic nomenclature. The second is for practical reasons concerning information contained in many of these paraphyletic taxa that is relevant to issues other than phylogenetic systematics.

I examine closely the evolutionary histories of early Paleogene “miacoid” carnivores and late Paleogene “gelocid” artiodactyls. The extinction of miacoid species in the Late Eocene (giving rise to families of larger, apparently more actively hunting carnivores) and the extinction of gelocid species in the Late Oligocene (giving rise to families of larger ruminants apparently better equipped to ingest and process fibrous vegetation) were both coincident with major climatic and environmental changes. The change from non-seasonal to seasonal climates in the Northern hemisphere in the late Eocene may have influenced a change in predator adaptive strategies; likewise, the drying trend and spread of more open habitats in the early Neogene may have influenced ruminant foraging strategies. I submit that while not all paraphylectic groups may be useful in this fashion, at least in the above instances much paleobiological information is lost if these groups are dismissed because of their paraphyletic status: their demise reflects not artificial “pseudoextinction” but rather a real loss of archaic adaptations in a changing world.

Three rhynchonellid brachiopod genera, Hiscobeccus, Lepidocyclus, and Hypsiptycha, are the most diagnostic elements of the Lepidocyclus fauna of North America in Late Ordovician time. These are characterized by relatively large, strongly biconvex to globular shells with coarse imbricating growth lamellae and, internally, with septiform cardinal processes in brachial valves. Among the three genera, Hiscobeccus appears the earliest, now known from rocks of late Trentonian-Edenian age in the Canadian Rocky Mountains and Mackenzie Mountains. Morphologically, Hiscobeccus is distinguished from the other two genera by its open delthyrium in the pedicle valve. Early forms of Hiscobeccus show close morphological similarity to Rhynchotrema in their non-globular biconvex shells covered by strong growth lamellae only in the anterior portions. It has been suggested that Hiscobeccus evolved from the Rhynchotrema wisconsinense stock through increase in shell size, globosity, and strength of growth lamellae. Earliest species of Rhynchotrema has been documented convincingly from rocks of early Trentonian age, and the derivation of Hiscobeccus most likely took place during the mid-Trentonian. Lepidocyclus and Hypsiptycha evolved from either Rhynchotrema or Hiscobeccus by developing a pair of deltidial plates covering the delthyrium.

Rhynchotrema and other rhynchonellids that evolved before mid-Trentonian time are common to the North American (Laurentian) and the Siberia-Kazakhstan paleocontinents. In contrast, Hiscobeccus, Lepidocyclus, and Hypsiptycha that evolved after the mid-Trentonian are virtually restricted to Laurentia. Therefore, Rhynchotrema marked the last successful intercontinental migration of rhynchonellids during their Llandeilian-Caradocian cosmopolitanism. The pronounced provincialism of the North American Lepidocyclus fauna may have been caused by a number of factors. Facies control is not likely the explanation because these rhynchonellids occur in nearly all the inland and marginal platform seas of Laurentia and commonly are found together in the same types of rocks. Plate tectonics and sea-level changes are considered major causes. The Ordovician rhynchonellids lived in shallow marine (intertidal-subtidal) environments and were incapable of crossing vast, deep oceanic barriers because of their sedentary mode of life and short-lived motile larval stages. The widening of the ocean between North America and Siberia, coupled with high sea-level stand, may have created a sufficiently wide oceanic barrier to interrupt faunal mixing between the two paleocontinents by late Trentonian time. Moreover, the rise in sea level would have resulted in the disappearance of island faunas, which could have served as stepping stones for intercontinental migration of shallow-water benthic faunas during low sea-level stand.

Lithistid sponges are an important component of many Ordovician faunas and form some of the earliest reef communities of the Paleozoic Evolutionary Fauna, yet they have received relatively little attention. Fossiliferous strata with abundant sponges occur at many horizons and localities within the Lower and Middle Ordovician Pogonip Group of the Great Basin. One of the best-known occurrences is near the middle of the Antelope Valley Limestone in central Nevada, where sponge-bearing units occur within the lower Whiterockian Stage. Lithistid sponges and associated species were also examined within the Shingle Limestone of eastern Nevada, where the sponge communities occur as small reef mounds about 55 m below the top of the formation in beds corresponding to the uppermost Ibexian Series. To acquire a more regional view of the environments and faunas present in Nevada during the Ordovician, contemporaneous units in the Pogonip Group were examined elsewhere in Nevada and in the Ibex area of western Utah.

The general depositional setting of the Great Basin at this time was that of a carbonate ramp in the upper Ibexian developing into a carbonate platform during the Whiterockian. The sponge mounds in the Shingle Limestone, forming in water 1 to 15 m deep, may have participated in this development by interfering with water circulation along the outer portion of the carbonate ramp. The mounds are several meters in size and are often stacked, with grainstone-filled channels cutting through the mounds in several places. The mounds themselves have muddy cores and are flanked by well-sorted echinoderm grainstones. The reef trend extends for nearly two kilometers before being faulted out, and was probably even more extensive during its development. Besides sponges, the assemblage contains abundant calcareous algae and cyanobacteria, as well as trilobites, brachiopods, echinoderms, and other groups characteristic of the Paleozoic Fauna. These mounds are very similar to those found in the Wahwah and Juab Limestones of the Pogonip Group, suggesting that these latter buildups also formed in very shallow water.

The younger sponge communities in the Antelope Valley Limestone at Ikes Canyon probably formed in about 20 to 40 m of water along the uppermost slope of a carbonate platform. The sediments consist of interbedded wackestones, mudstones, and shales with occasional hardgrounds. Some of the sponges have root tufts, indicating that they settled on soft substrate. Besides lithistid and heteractinid sponges, the unit contains a diverse assemblage of metazoans and occasional receptaculitids and other algae.

Estimates of relative species abundances were calculated for random samples from the sponge-bearing units. The Shannon Diversity Index for the Antelope Valley Limestone fauna is 3.24 with an equitability value of 0.68, while the Shingle Limestone community has values of 3.44 and 0.74, respectively. Thus, not only were both communities diverse, but the species within each community were comparable in abundance. These values compare favorably with those of modern marine communities, especially when the effects of preservational bias are considered, and suggest that well-integrated ecological communities with substantial amounts of biotic interaction had evolved by the Middle Ordovician.

The sponge communities of the Antelope Valley Limestone and Shingle Limestone are thus quite similar, yet only in the latter did the organisms build bioherms. The sucession of communities within these buildups indicate that the greater abundance of cyanobacteria and calcareous algae in the Shingle Limestone probably helped to bind and stabilize the sediment, creating a firm substrate. This was then settled by cylindrical and branching lithistid sponges and other species that not only acted as bafflers, causing mud to accumulate, but produced additional sediment when they died. As the mounds grew, the communities diversified, with cup-shaped lithistids becoming dominant as the bioherms approached sea level. The importance of calcareous algae and cyanobacteria in determining whether mud mounds developed in this depositional setting suggests that factors controlling the distribution of algae, primarily substrate, turbidity, and water depth, also control the distribution of mud mounds. This is probably true not only for these sponge mounds, but for mud mounds throughout the Paleozoic.

Stable carbon and nitrogen isotopes in fossil ostrich eggshell (OES) proteins have the potential to provide paleodietary information on ostriches through the Late Pleistocene in arid and semiarid regions of the Old World. Carbon isotopes may be used as a monitor for floral composition (C3 vs. C4 plant abundance), for example. The stable isotope composition of the organic matter in modern OES and Middle Holocene fossil OES samples from Bir Tarfawi (an archaeological site in southern Egypt) are presented, as well as the nature of modern proteins in OES and the degree to which they are preserved in the fossil samples.

The organic fraction was extracted from OES samples and subsequently desalted by (1) decalcification in 0.5 N EDTA, followed by dialysis against water in >6-8,000 molecular weight cut off (MWCO) tubing, or (2) hydrolysis in 6N HCl for 20 minutes at 153°, followed by the addition of concentrated HF to facilitate the precipitation of CaF2. There is good agreement between the stable isotope results of the two organic fractions from modern OES samples (δ13C = −23.51±±0.76 and −23.53±±0.39, and δ15N = +6.23±±0.15 and +6.42±±0.33 for the >6-8,000 MWCO and HF preparations, respectively). A 2± and 4± enrichment between ostrich diets and the organic fraction was found for carbon and nitrogen, respectively. These relationships support a vegetarian diet comprised almost exclusively of C3 plants. Result from the HF preparation show higher variability in both the δ13C and δ15N values in the fossil samples than in the modern. This increased variability may be due to isotopic fractionation accompanying protein degradation or to inadequate methodologies for isolating the bulk organic matter. These effects could be minimized by analyzing individual molecules throughout the study.

The >6-8,000 MWCO fraction of the modern and fossil OES samples were electrophoresed on SDS polyacrylamide gels. The modern sample shows predominant bands corresponding to apparent molecular weights of 14 kilodaltons (kD), 28 kD, and 35 kD, and a light smear at the top of the gel. Preliminary results of the fossil sample show a pronounced band corresponding to an apparent molecular weight of 80 kD, and a light smear over the whole gel. Results of an enzyme linked immunosorbent assay (ELISA) on the modern material demonstrate a positive antibody-antigen reaction between the >6-8,000 MWCO fraction and osteocalcin, osteonectin, and albumin.

Due to the “closed-system” nature of the ostrich eggshell matrix and the ease with which it can be accurately dated through the Late Pleistocene, it provides an ideal medium for studying protein diagenesis. Subsequent isotopic analyses, using the newly developed technologies of GC/IRMS, offer an alternative method for using the paleodiets of ostriches as a tool for paleoenvironmental reconstructions in Africa and Asia.

A dynamic interplay of tectonics and eustasy controlled the development and distribution of Cretaceous carbonate platforms, and subsequently influenced patterns of gene flow among tropical reef-forming rudist bivalves of the Caribbean Province. Mediterranean faunas first entered the Caribbean during the Valanginian, via trans-Atlantic larval drift. Larval drift distance was exceeded during the mid-Cretaceous opening of the Atlantic, and resulted in isolation of rudist gene pools and an Albian burst of endemism, the first of two for the Cretaceous. Following a Cenomanian, Turonian and Coniacian diversity drop, Caribbean endemism climbed again during the Santonian, Campanian and Maastrichtian. This second explosion of endemism is attributed, in part, to vicariance biogeography as Caribbean terranes split and became isolated, and in part to biotic factors (competition, niche partitioning) as terranes collided when the Caribbean plate moved eastward from its Pacific Ocean origin. Paleobiogeographic maps were compiled per stage of the Cretaceous, with substage resolution for the critical Albian, Campanian and Maastrichtian. Data utilized were 58 genera and 214 species of rudist bivalves plotted on Recent mercator projections and on 119, 100, 95, and 80 million year plate tectonic reconstructions. Diversity trends and indices of similarity were analyzed in drawing paleobiogeographic divisions. Generic plots delineated regions of tropical carbonate sedimentation, the northern and southern limits of reef building, and fluctuations of this reef line through time. Generic plots also identified areas with the greatest generic diversity per stage, and defined the timing and regional extent of the postulated Supertethyan climate zone. Paleobiogeographic plots revealed that Tropical reef-building in the Caribbean Province was wholly north of the paleoequator - a major paleoclimatic dilemna. Species plots mimicked those of genera for the Valanginian, Barremian, Turonian, Coniacian, and Santonian, but provided important new details of the movements of terranes, dispersal pathways, and isolation of rudist gene pools for the Aptian, Albian, Cenomanian, Campanian and Maastrichtian. These detailed data, the first to combine Cretaceous Tropical paleontology with Caribbean tectonic reconstructions, provide a framework for testing rates, patterns, and causes of evolution among Tropical bivalves.

Though long suspected to be critical to the understanding of the evolution of the pelecypod subclass Pteriomorphia, the mid-Palaeozoic family Rhombopteriidae was too poorly known to allow clarification of its relationships. Furthermore, numerous species were assigned to the nominate genus, Rhombopteria, many of which belong in other genera or even other subclasses. Consequently, the morphologic concept entailed by Rhombopteria was confused as were functional morphologic investigations.

Silicified rhombopteriids discovered in the Lower Devonian of Australia are referred to a new genus, and reveal internal shell characters essential for understanding rhombopteriid relationships. The family Rhombopteriidae is revised to include only three genera, Rhombopteria, Prantliella and the new Australian genus.

New data provided by the Australian material indicate that rhombopteriids were non-byssate, dimyarian pteriomorphs that lived pleurothetically on the left valve as do gryphaeid oysters. The Rhombopteriidae are assigned to the Ostreina and are the sister group of all other ostreinans including the Ostreoidea, Pseudomonotidae and Terquemiidae. Important characters common to rhombopteriids and gryphaeid oysters include: 1) left-sided pleurothetic habit; 2) absence of byssal notch or sinus throughout ontogeny; 3) Quenstedt muscle scar; 4) proximal gill weal; 5) circumferential curb; 6) commissural shelf; and 7) posteroventral palliobranchial fusion as evidenced by a branchitellum and posterior radial fold and sulcus. Outgroup comparison with Umburridae indicate that characters 1–4 are symplesiomorphic for the Order Ostreoida. Characters 5–7 are autapomorphies for a clade including the Rhombopteriidae, Pseudomonotidae, Terquemiidae and Ostreoidea.

Rhombopteriids were probably derived from left-sided pleurothetic, umburrid-like ancestors which, in turn, descended from primitive, equivalved, orthothetic prionodonts. Thus, a right-sided pleurothetic stage was never part of the evolutionary pathway of oysters. The inequivalved shell of eupteriomorphs evolved initially for a left-sided pleurothetic semi-infaunal habit. Retained as an adaptation in rhombopteriids and oysters, the inequivalved shell is an exaptation in Pterioida (winged shells), Pectinina (scallops) and Pseudomonotidae, having been coopted for a right-sided pleurothetic orientation, and having the effect of enhancing stability in an epifaunal habit. Evolution of right-sided pleurothetic pteriomorphs, including the Pseudomonotidae, Pectinina and Pterioida, from separate left-sided pleurothetic rhombopteriid-like or umburrid-like ancestors, is explicable by paedomorphic retention of the byssus and epifaunal habit of the early post-larva. A right-sided pleurothetic orientation would follow ‘automatically’ owing to hydrodynamic and mechanical constraints on the already evolved, inequivalved shell, byssally attached by the anterior margin on the substrate surface.

The Machaeridia is an enigmatic marine fossil group which has been variously allied with the cirripedians, molluscs, annelids, and echinoderms. Although machaeridians have previously been unreported from rocks younger than earliest Pennsylvanian (late Namurian), members of the machaeridian order Turrilepadida are now found to be locally abundant well into the Permian. New occurrences of turrilepadidan sclerites are reported from the Late Pennsylvanian of Texas and the Early Permian of Texas and Nevada.

Turrilepadidan sclerites are common in marine shales of Missourian and Virgilian age in north-central Texas. Well preserved turrilepadidan sclerites have been found in the Wolf Mountain Shale (Missourian) and in the Colony Creek, Finis, and Necessity Shales (Virgilian) of north-central Texas. A few sclerites have a high number of closely spaced rugae and are similar to those of Turrilepas, but the most common types of sclerites have relatively few, widely spaced rugae, and many of these show radial ornament like that found on sclerites assigned to the genus Clarkeolepis. Although most forms would be placed in the family Turrilepadidae, a partial specimen from the Finis Shale appears to be a lepidocoleidid sclerite.

Silicified sclerites of Permian age have been found in two marine carbonate units: the upper part of the Bird Spring Formation (late Wolfcampian or early Leonardian) of southern Nevada and in the Cathedral Mountain Formation (Leonardian) of West Texas. Although their details are generally poorly preserved, these sclerites appear to be representative of members of the family Turrilepadidae with a different taxon found at each of the two localities.

The paleoecology of turrilepadidans is not well known, but each of these occurrences is from a locality that represented an area with a muddy bottom, a slow rate of deposition, and an unusually diverse fauna. The fauna at each horizon is dominated by a large number of brachiopod and mollusc species, many of which were conspicuously encrusted or bored during life or afterwards. Although a few of the sclerites show postmortem encrustations on their inner or outer surfaces, the overall lack of borings or encrustations suggests that the turrilepadidans were mobile, possibly infaunal organisms.

Before opening of the Japan Sea, the Japanese islands were attached to the eastern margin of the Asian continent. The Southern Kitakami Belt is regarded as a micro-continent in an accretional complex of the islands, that accreted before the Early Cretaceous. But its tectonic setting and location between the belt and the Asian continent is still an unresolved argument.

Permo-Triassic sequences in the Southern Kitakami Belt are composed of shallow to off-shore deposits. These deposits are composed of clastics, carbonates with volcaniclastics. But there was no volcanic activity in the belt in the Middle to Late Permian. From the viewpoint of the sedimentary character and history, the Middle Permian to Middle Triassic sequences differ from their previous and their following successions in the belt. And the sedimentary basin of Middle Permian to Middle Triassic was bounded by transform faults. Magmatic arc was replaced by passive margin as hinterland of the Southern Kitakami Belt during the Middle Permian to Middle Triassic. It means that the sedimentary basin moved from the margin of Yangtze Platform to Sino-Korean Platform at that time.

There are essentially three major crinoid faunas of the Paleozoic: 1) the lower Paleozoic (Ordovician) fauna dominated by disparids and diplobathrid camerates; 2) the middle Paleozoic (Silurian-middle Mississippian) fauna dominated by monobathrid camerates, cladids, and flexibles; and 3) the upper Paleozoic (middle Mississippian-Permian) fauna dominated by cladids. Change from the middle Paleozoic fauna to the late Paleozoic fauna, at or near the Osagean-Meramecian boundary, was characterized by Laudon (1948) as “one of the most remarkable faunal breaks in the entire Paleozoic era”. The monobathrids that had reached their zenith in the Osagean (Tournaisian-Visean) became a very minor component of late Paleozoic faunas. Conventional thinking has implied that a mass extinction of crinoids occurred at the Osagean-Meramecian boundary.

We have biostratigraphically subdivided the late Osagean and early Meramecian into four zones (times A-D, oldest to youngest, all within the Gnathodustexanus zone) in order to study the origination and extinction of all crinoid species during the changeover from the middle to upper Paleozoic faunas. Rather than a mass extinction, a monotonic turnover of species fits a pattern of gradual extinction as extinctions outpaced originations. Data are based on 216 species (taxonomically updated) from 69 localities and are as follows:

The pattern of originations and extinctions for monobathrids is very similar to the pattern for all crinoid species.

The above data have maximum diversity during Time B of the late Osagean followed by declining diversity in times C and D into the early Meramecian. Late Meramecian crinoid faunas (after time D) were less diverse with a maximum of about 45 species. The gradual decline of crinoids across the Osagean-Meramecian boundary cannot be explained as sampling bias (Signor-Lipps effect), because ranges of crinoids thought to be extinct at the boundary are extended into the early Meramecian as well as disappearing at various tinles prior to the boundary.

The decline in diversity and the monotonic turnover of species are hypothesized to be the result of habitat reduction as the Eastern Interior Basin of North America was gradually infilled with clastic sediments at the end of the Acadian Orogeny. Most notable in this regard was the smothering of the Keokuk Limestone carbonate bank. Changes in sea level also contributed to habitat reduction. Lowering of sea level at the end of the Osagean caused restriction of open marine environments. A transgression in the early Meramecian was followed by shoaling and restriction during deposition of the late Meramecian Salem and St. Louis limestones.

Pseudoplanktic life modes have typically been invoked to explain the presence of abundant fossils belonging to normally low-oxygen intolerant taxa within oxygen-deficient black shales facies (e.g., bivalves, crinoids, barnacles, serpulid worms, brachiopods, gastropods, bryozoans, foraminifers, corals, hydrozoans, and sponges). The same explanation has been used for exceptional paleobiogeographic distribution of benthic species. However, detailed paleoecologic, population, and taphonomic analyses of numerous black-shale biotas in conjunction with recently published models for oxygen-deficient basins suggests that this hypothesis is no longer required to explain the distribution of these taxa in supposedly non-viable habitats. Actual examples that could be interpreted as evidence for pseudoplanktic life habit (i.e., colonization on both sides of ammonites) are very rare. For example, less than 2% of the encrusted ammonites (N = 1240) in the Jurassic Posidonienschiefer show pseudoplanktic colonization patterns. These could be interpreted as flipped specimens within the benthic zone. The remainder are stable “shell-island” substrates with ammonites (and large bivalve shells) colonized on one side only. Most logs believed to be colonized on the lower surface by bivalves and/or crinoids in floating position actually have evidence for benthic encrustation on the tops and sides of the logs, and have obvious current shadows of dead shells.

The data show that: 1) the abundance of these taxa greatly exceeds the expectations of pseudoplanktic rain as well as the number of potential hosts; 2) they commonly occur as short-term event communities rather than as the normal populations expected of continuous pseudoplanktic rain; 3) specimens are commonly found in epibenthic life position; 4) their occurrence patterns show strong facies control usually reflecting benthic oxygen gradients; 5) many preserve a large prodissoconch or protoconch suggesting a long-term planktotrophic larval stage. Most of these “pseudoplanktic” groups appear to have had a benthic life habit.

Moreover, most oxygen-deficient environments disappeared by the end of the Cretaceous along with some of the dominant pseudoplanktic taxa. Drifting logs and seaweeds are common today, but generally lack specific “pseudoplanktic” faunas, with the exception of boring bivalves, gooseneck barnacles, serpulid worms, and bryozoans. Epibenthic bivalves and crinoids are very rare to absent on potential “pseudoplanktic” hosts in modern seas, yet are the main groups of organisms designated as pseudoplankton in the fossil record.

High-resolution stratigraphic analysis of Cretaceous strata in the Western Interior Basin (WIB) of North America has allowed definition of numerous disconformity-bounded, eustatically and/or tectonically driven sequences and their systems tracts at 2nd- through 4th-order scale, as well as 5th- to 7th-order climate-induced cycles. Integrated event chronostratigraphy and biostratigraphy allow detailed regional tracing and facies analysis of these sequences, leading to three-dimensional modeling of facies evolution. Whether driven by relative sealevel changes or smaller scale climate cycles, Cretaceous sequences and their bounding disconformities reflect dynamic changes in many factors which moderate biological systems (e.g. sealevel and paleobathymetric changes, changes in current velocity and in erosion/sedimentation rates and patterns, watermass temperature and chemistry, etc). Predictable biological responses (patterns) to varying environmental conditions and different systems tracts are expected in sequence stratigraphy. Once defined within well-studied systems, these patterns can then be used as an independent tool for sequence stratigraphic analysis. To date, our research has focused on the development of paleobiological criteria which aid in the recognition of sequence stratigraphic frameworks, especially in basinal facies where sequence boundaries and systems tracts may be subtly defined in the physical stratigraphy. Such criteria may include the identification of sequence boundaries and other omission surfaces by punctuated character displacement in evolutionary series, by condensation or omission of biostratigraphic zones, by mixed or time-averaged community elements and biozones, and by selective colonization by firm substrate-dependent benthic communities. Gradients within and between systems are characterized by different community composition, biofacies, taxonomic and community diversity patterns, adaptive bauplans among resident taxa, taphonomic signatures, and bioevents that allow predictive biological characterization in sequence stratigraphy. Once established and correlated, sequence stratigraphic systems among different basins provide a chronostratigaphic and environmental framework within which the regional dynamics of ancient populations and communities can be evaluated, leading to the analysis and modeling of relationships between sealevel changes and biogeographic migration patterns, and the rates and patterns of evolution and extinction.

Thin-shelled, weakly articulated, epifaunal byssate to free-living flat clams characterize Devonian-Cretaceous dark, organic-rich shale facies. Convergent evolution on the flat-clam morph occurs among several families of Bivalvia. Flat clams regularly occurred in dense populations, dominating low diversity, inequitable communities for which they were commonly the pioneer species and formed shell islands for the colonization of smaller, firm-substrate dependent invertebrates. The unique flat-clam dominated ecosystem, as well as the widespread environments to which they were adapted, disappeared at the end of the Cretaceous. Although locally, low-oxygen benthic muds exist through the Cenozoic to Recent, they do not support large populations of flat clams, whose ecological niche was never filled after the Cretaceous. Flat clams underwent an exponential increase in size and apparent growth rates through the mid- and Late Cretaceous, reaching over 3 m in diameter (Inoceramidae). Most of this increase in shell size also involved expansion of mantle tissue and probably gills, relative to the size of the visceral mass. This suggests specific adaptations to colonization of oxygen-poor benthic habitats with hydrogensulfide enriched substrates, which broadly characterized Paleozoic and Mesozoic epicontinental seas, during greenhouse intervals. Such conditions were particularly well-developed during Cretaceous Oceanic Anoxic Events, at which time flat clams thrived.

Functional morphology, geochemistry, and facies associations suggest that many flat clams were chemosymbiotic and/or had greatly expanded oxygen-absorption surfaces. These adaptations allowed them to be opportunistic in chemically stressed benthic environments; growth rates also seem to be enhanced in these environments, a characteristic of living chemosymbiotic species. Many lines of evidence prove that flat clams lived in these environments and do not represent pseudoplanktic rain. A combination of factors seems to have been responsible for their disappearance near the end of the Cretaceous; i.e., mass extinction, loss of primary habitats, and major radiation among bottom-feeding bivalve predators.

The Cambrian explosion witnessed the formation of a large number of the higher taxa extant today. The higher taxa are said to have “filled in” from the top down, with species that found phyla giving rise to daughter species which found classes, then orders, and so on. During the Permian extinction, in contrast, 96% of all species go extinct. During the rebound, a large number of new families are created, a few new orders are created, but no new phyla are created. The higher taxa are said to have “filled in” from the bottom up. The profound asymmetry between the Cambrian and Permian has been a deep puzzle. I shall suggest that this asymmetry is a nearly inevitable consequence of adaptive evolution on rugged, multipeaked fitness landscapes.