Mass extinctions profoundly affect patterns of diversification and skeletal innovation in the succeeding radiation. For instance, promising adaptations may be removed permitting traits of the few survivors to proliferate. Consequently, patterns of survivorship could control directions of radiation following the extinction event. Alternatively, selection during radiation may be quite different from extinction conditions. The founders may be quickly superseded by taxa with wholely new innovations that are built upon, but are distinct from, the founding morphologies.

Planktic foraminifera nearly became extinct at the end of the Cretaceous. Of the two or three lineages that survived, perhaps only one founded the bulk of the Paleocene radiation of Globigerinacea. In addition, there was little habitat diversification within the surviving lineages. Nearly all the morphological and ecological innovations occur in a single clade that diverged rapidly from the ancestral stock.

Neither of the best known surviving lineages diversified much after the Cretaceous. Hedbergella monmouthensis is the ancestor of Danian Globanomalina archaeocompressa. The two taxa are nearly identical in both morphology and in isotopic signature. Significantly, the globanomalinids displayed very little diversification, like their Cretaceous ancestors before them. Instead, species were replaced one after another in an anagenetic trend and consistently occupied a moderately deep-water habitat. Similarly, triserial Guembelitria gave rise to only a modest radiation of biserial species in the earliest Danian primarilly within near surface water habitats.

Cladistic analysis suggests that the major part of the Cenozoic radiation was founded by one or two Cretaceous taxa. Most Danian trochospiral species abruptly radiated into two main stocks in the earliest Danian. All of them are probably derived from Hedbergella, but they rapidly became morphologically differentiated from this Cretaceous survivor. Alternatively, many of the features of the Danian species may have been inherited from another Cretaceous survivor–possibly a species of Rugoglobigerina–as suggested by comparative studies of early ontogeny. In either case, the group split rapidly into two main lineages. One, rooted in non-spinose ‘Morozovella’ taurica, led to the major diversification of the muricate-walled morozovellids. Isotopic data suggest this lineage spread from a moderately deep water habitat into the near-surface waters where the major diversification occurred. The other lineage developed spinose wall texture and gave rise to the diverse subbotinid radiation. Stable isotopic data suggests the subbotinids grew consistently in the coldest and presumably deepest waters. Their spinose wall texture suggests they were at least partly carnivorous, by analogy with living spinose taxa.

These patterns of morphological and ecological diversification suggest that the immediate survivors did not radiate markedly but retained the evolutionary rates and habitats of their Cretaceous ancestors. Most of the radiation occurred in a clade whose innovations evolved during the Danian, rather than simply retooling traits of their founder. Likewise, the radiation occurred principally in surface and deep water habitats, both largely vacated by the extinction event. The intermediate depth habitats were continuously occupied by the persistent hedbergellid-globanomalinid lineage. Their habitat was not invaded by other radiating clades. Evidently, survival alone does not confer the capacity for subsequent diversification upon a founding species. Innovation seems to be the key to dominance rather than mere persistence through an episode of heightened extinction.

Because of their prodigious abilities for rapid calcification, corals today and in the past have been principal reef builders. The mere mention of corals evokes colorful and vivid image of tropical settings, swaying palm trees, and the crash of waves against the coral-dominated, biologically complex edifice we call the reef. Most geologists, educators, and students are aware of new developments in ecology and evolution of modern and ancient reefs, but they are probably less aware of studies of corals that build reefs. Understanding ancient examples rests on a foundation of modern coral biology and taxonomy. This volume summarizes the 1996 Paleontological Society Short course “Paleobiology and Biology of Corals.” Twelve international authors present current and cutting-edge topics in coral research.

It was 17 years ago this month, 1980 in Atlanta, Georgia, that the first short course on echinoderms was held. The conveners were Johnny Waters and Tom Broadhead. The Sunday short courses had been started only two years before, in 1978, with the mollusks being the first short course and arthropods the second. Neither of these first two short courses had accompanying printed notes. Thus, we echinodermers were the ones who began this tradition of short course notes that has continued to this day.

Those participants in that 1980 short course who are also on the program today are, in addition to Johnny Waters, a convener of both short courses, Dave Meyer, Jim Sprinkle, Bill Ausich, and Ron Parsley. Many new names and faces have appeared in the study of fossil echinoderms or those who study living echinoderms in such a manner that their work has bearing on the ancient record of these animals.

Organisms from all five phylogenetic kingdoms form minerals. No less than 60 different mineral types are known, to date, to be formed by organisms and these are located at a wide variety of tissue sites and fulfill a host of different functions (Lowenstam and Weiner, 1989). A prominent and well known function of biogenic minerals is to provide mechanical strength to skeletons and often at the same time to act as a reservoir for the supply of ions necessary for vital metabolic functions. A characteristic of the mineral component of most skeletons is that it is formed under unusually well controlled conditions, such that the mineral form bears no morphological resemblance to its inorganic counterpart. This is, for the most part, achieved by inducing the minerals to precipitate in preformed spaces located by complex assemblies of macromolecules or vesicles or in some cases by combinations of both.

It seems likely that I was invited to contribute to this course because I am a renegade geologist. Many years ago I was lured by the attractions of living animals and switched to zoology. Later I became interested in the possibility of using immunological methods to assess evolutionary relationships among shrews, moles, hedgehogs, tree-shrews, elephant-shrews, otter-shrews, golden-moles and tenrecs, and I set a graduate student onto this project. We also sought to explore the relationships between these so-called ‘Insectivora’ and other orders of mammals, using immunological techniques to estimate crude biochemical distances between the serum proteins of representative species.

Foraminifera (forams for short) are single-celled organisms (protists) with shells or tests (a technical term for internal shells). They are abundant as fossils for the last 540 million years. The shells are commonly divided into chambers that are added during growth, though the simplest forms are open tubes or hollow spheres. Depending on the species, the shell may be made of organic compounds, sand grains or other particles cemented together, or crystalline CaCO3 (calcite or aragonite).

The past decade has seen many advances in research on vertebrate faunas of the Triassic period. The end of the Triassic now is cited widely as the dawn of modern terrestrial ecosystems, and currently the earliest mammals, turtles, lissamphibians (frogs, toads and salamanders), lizards, and crocodiles are all documented from this period. Admittedly many of these early members of present day higher order taxa were very different from their modern counterparts. For instance, the earliest crocodiles were highly active cursorial forms (e.g., Crush, 1984), and the mammals were very different to the living placentals and marsupials. Nevertheless, they possessed many of the key morphological characteristics that diagnose the group and that may well have contributed to their ultimate success. However, the Triassic was also a time of bizarre and enigmatic tetrapods, some of whose relationships are the subject of considerable debate. Indeed, in the last year this debate has reached new heights with suggestions that certain rather unusual Triassic non-dinosaurian tetrapods may have more bearing on bird origins than theropod dinosaurs. This debate has been fueled by the discoveries of feathered dinosaurs from China which, on the face of it, one might expect to dampen the search for alternative hypotheses regarding bird origins.

It is generally accepted that the extraordinary preservation of fossils in the Burgess Shale is at least partly due to the exclusion of large metazoan scavengers through rapid burial in an inimical environment. Disruption of individual organisms appears to have been largely the result of mechanical processes and/or microbial decay. The absence of bioturbation through much of the classic section, including Walcott's Phyllopod Bed, supports these arguments. However, macroscopic traces are known from other horizons within the Burgess Shale section and from lateral equivalents in the Stephen Formation a short distance south of the main locality.

The sparse ichnoassemblage includes bedding-plane exposures of portions of compacted, parallel-sided burrows containing skeletal debris comprising fragmented and disarticulated hyoliths, small trilobites, and bracniopods. Walcott originally figured one such trace as Planolites sp. ? and noted, but offered no evidence for, an association with the archaeopriapulid Ottoia prolifica. This notion was subsequently rejected by Conway Morris.

A recently collected specimen, from talus south of the main locality, contains a poorly preserved but recognizable body fossil of Ottoia within the outline of a “Planolites”. Although this juxtaposition may be accidental, a number of features of the association, and a consideration of the burrowing behaviour of modern priapulids, suggest that Ottoia could have been the generator of “Planolites”-like traces.

The oldest-known dinosaurs (Herrerasaurus, Pisanosaurus) occur within the Ischigualasto Formation. Recent work in the formation has brought to light significant new material, including the complete skeleton of a new primitive dinosaur. We sketch below the paleoenvironment and faunal succession during the range of these early dinosaurs, and review some of the taphonomic factors that shaped their fossil record.

The Ischigualasto Formation (Carnian?) is included within the Agua de la Peña Group, a series of continental Triassic deposits exposed in the Ischigualasto-Ville Union Basin of northwest Argentina. Ischigualasto sediments rest unconformably upon the carbonaceous fluvial/lacustrine Los Rastros Formation; this contact is characterized locally by marked angular discordance. The upper contact is gradational into red-beds of the Los Colorados Formation. Medium- to coarse-grained conglomeratic sandstones, siltstones, and silty mudstones dominate the section. Sand bodies are characterized by medium- to large-scale trough cross-stratification and broad lenticular/narrow sheet geometries, and are interpreted as deposits of shallow, low-sinuosity streams. Siltstones and mudstones show pervasive evidence of soil development, including root traces, nodular caliche horizons, and pedogenic slickensides. Deposits attributable to lacustrine/paludal sedimentation are scarce, and freshwater vertebrates and invertebrates are extremely rare. These data suggest an upland depositional setting on a low-relief alluvial plain with seasonal climate.

The Ischigualasto vertebrate fauna includes archosaurs, rhynchosaurs, traversodontid and carnivorous cynodonts, and temnospondyl amphibians. Rhynchosaurs dominate (relative specimen abundance) in the lower half of the section, but are absent from the upper half. Traversodontid cynodonts occur throughout the formation, but are much more abundant up-section. Archosaurs, carnivorous cynodonts, and particularly temnospondyls are rare throughout, with dinosaurs limited to the lower half. No major stratigraphic or sedimentologic changes occur up-section, and there is no evidence for significant shifts in physical or chemical taphonomic processes. Thus, trends in relative taxon abundance likely record a true biotic signal (e.g., local extinction, immigration) rather than a taphonomically-driven preservational bias.

Fossils are preserved as isolated carcasses or disarticulated elements, most often in fine-grained overbank facies. Bone beds and microsites are conspicuously absent. Temnospondyl remains were found within a local carbonaceous lens developed upon a sand body, suggesting autochthonous burial in an abandoned-channel setting. Isolated skulls, particularly those of the traversodontid Exaeretodon, are extremely common. Fifteen isolated crania of this cynodont were mapped in a single stratum with limited areal exposure. Abundant preservation of isolated therapsid crania has also been reported in the Beaufort Series (Permo-Triassic) of the Karoo Basin, South Africa (Smith, 1980). Post-disarticulation hydrodynamic sorting (enhanced by scavenging?) of an areally dispersed mass-mortality assemblage may explain this unusual occurrence.

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.

Study of the stratigraphic ranges of reef coral species in scattered sequences (Dominican Republic, Bahamas, Costa Rica, Jamaica, and Florida) suggests that a major episode of faunal turnover occurred in the Caribbean region between early Pliocene and mid Pleistocene time. In a data set composed of all reef corals except the families Mussidae and Oculinidae and the genera Cladocora and Madracis, approximately 90% of the Mio-Pliocene fauna, composed of as many as 65–70 species, became extinct during this time interval. Ten of 27 genera became extinct. Despite the high numbers of extinctions, the total number of species in the Caribbean reef coral fauna dropped only slightly over the time interval, due to similar numbers of originations and extinctions in the fauna. With one possible exception, new species arose in surviving genera, and no new genera formed.

Although similar numbers of species became extinct within early Pliocene, late Pliocene, and early Pleistocene time units, shallow water communities experienced higher numbers of extinctions during the late Miocene and early Pliocene. Deeper water communities experienced higher numbers of extinctions during the late Pliocene and early Pleistocene. Species surviving the turnover episode occur in deeper water communities and belong predominantly to the family Agariciidae. Nearshore grass flat communities contain the highest number of early extinctions. No difference in extinction patterns could be detected between taxa which reproduce primarily by fragmentation and those that reproduce primarily by larval recruitment. Although originations appear evenly distributed among community types, a large number occur in Florida along the northern margin of faunal distribution.

The increased extinctions in shallow water communities and increased originations in the north suggest that turnover occurred primarily in response to change in abiotic factors such as temperature and siltation, and not in response to species-area effects associated with sea level change.