One can argue that the critical factors in evolution are competitive interaction, dispersal, and survival in that they determine the life and death of individuals and thus govern gene flow and the waxing and waning of populations; the byproduct of this cascade happens to be the origination and extinction of species and phylogenetic lineages. Perhaps evolutionary “truth” can be found only in petri dish experiments of lichens competing for space, through documentation of the wildly successful ecological invasion of purple loosestrife in ditches of northeastern North America, or by molecular phylogeographic analyses of the distribution of fruit fly lineages across the Hawaiian Islands. Nonetheless, there is something fundamentally intriguing in the fact that there are some 300,000 species of angiosperms currently distributed around the planet; an order of magnitude greater than other, far more ancient clades such as cycads, ferns, and horsetails and a discrepancy that has spurred centuries of evolutionary theorizing on the causes of their high relative diversity—Darwin's “abominable mystery.” These sorts of macroevolutionary questions necessitate research agendas that target global distributions of taxa over long intervals of geological time. Did mammals stay low to the ground until the large-bodied herbivore niches were opened up when an asteroid knocked off the last of the non-avian dinosaurids at the end of the Cretaceous? Was the transition from the dazzling variety of trilobites that dominated Cambrian and Ordovician marine ecosystems to the diverse ammonoid fauna of the later Paleozoic associated with differing intrinsic taxonomic turnover rates? Are species in tightly integrated communities such as reefs more vulnerable to extinction during intervals of climate change than species with lower levels of ecological connectivity?

A major goal of paleobiological research since the early 1960s has been the reconstruction in quantitative terms of the history of biological diversity. Spearheaded by Valentine (1969), Raup (1972, 1976a, b), and Sepkoski (1979, 1981, 1984, 1990, 1993), this effort has yielded estimates of global diversity through time, as well as calculations of global rates and magnitudes of extinction and diversification. A consensus emerging in the early 1980s (Sepkoski et al. 1981) indicated that global marine invertebrate diversity rose through the Cambrian and Ordovician periods to a plateau, which with brief extinction-related interruptions was maintained from the mid-Paleozoic to the mid-Mesozoic. Beginning in the Cretaceous, diversity rose again, reaching a peak in the late Neogene. The five mass extinctions of the Phanerozoic, and more or less distinct episodes of diversification, were identified and distinguished from many lesser events (Raup and Sepkoski 1982). Comparable studies, with varying results, were conducted on land vertebrates (Benton 1985, 1989), land plants (Knoll et al. 1979; Niklas et al. 1980, 1983; Tiffney 1981; Knoll 1984), early protistans (Knoll 1994), insects (Labandeira and Sepkoski 1993), and life as a whole (Van Valen 1984, 1985; Van Valen and Maiorana 1985; Signor 1990; Valentine et al. 1991; Benton 1995; Courtillot and Gaudemer 1996; Miller and Foote 1996).

When ambitious large-scale projects are proposed, like the Paleobiology Database (Alroy et al. 2001) and Panama Paleontology Projects (Jackson and Johnson 2001), there is inevitably a negative reaction from various quarters, which is quickly forgotten when the projects start to yield results. Given that, it may be useful to sing the praises of “big picture” science more generally and I will do so after briefly addressing this discussion starter in the context of my own research.

The claim that measures of global biodiversity dynamics are meaningless is based upon several methodological problems, including underrepresentation of tropical regions in “global” Phanerozoic data sets, inaccuracies in taxonomic data, non-equivalence of higher taxa among groups of organisms, and uneven sampling intensity across groups, environments, and time intervals. Some of these problems are inherent in the fossil record, whereas others lie in documentation and interpretation of the subject. But the subject of global biodiversity is perfectly legitimate, even if problems persist in evaluating its full history. Moreover, recognition of the methodological problems has resulted in notable improvements in the Phanerozoic diversity database (e.g., Adrain and Westrop 2000; Alroy et al. 2001).

All measurements and estimates have meaning, if consistent with peer-reviewed data and gifted with heuristic value. In pure science, we judge measures and estimation techniques by their importance to theory. We devise them for maximum relevance, and advance their reliability and precision by successive approximations. If better measures and estimation techniques come along, either by shifts in theoretical context or advances in technology, we discard the old and use the new.

Regardless of the macroevolutionary issues at stake, most students of biodiversity would agree that there is value in calibrating global biodiversity trends through critical intervals. To cite one obvious example, given the overwhelming interest in mass extinctions, we would certainly like to know the extent to which diversity declined during these events. Just as significantly, if we are to argue that any mass extinction was truly a global phenomenon, we must demonstrate definitively that its biotic effects reached around the world. Clearly, “standard” global compendia (e.g., Sepkoski 1992, 2002) are insufficient for the latter objective, because they contain no geographic or environmental information. At the least, a database that compares biodiversity transitions among different regions or paleoenvironments is required. Such analyses have the added benefit of providing opportunities to evaluate geographic and environmental selectivity in extinctions, an important facet of any attempt to understand what caused them (e.g., Raup and Jablonski 1993; Jablonski and Raup 1995).

Global biodiversity dynamics result in large-scale patterns of change in the variety of life on earth. One deceptively simple measure of global biodiversity is the total count of species or supraspecific taxa that have been described from each subinterval of the Phanerozoic record. These tallies usually are obtained from data compilations based on extensive literature searches supplemented with examination of collections in museums (Sepkoski 1993; Alroy et al. 2001). Such measures of global biodiversity dynamics are probably not meaningless, but it is difficult to understand what they mean. The number of taxa alive on Earth at any one time is a function of innumerable ecological factors acting at the full range of temporal and spatial scales (Willis and Whittaker 2002). Changes in global richness might result from increasing local richness as local communities become more complex (Valentine 1969; Bambach 1977). At the regional scale, changing oceanographic conditions, climate, and the relative positions of continents and shallow seas might alter global taxonomic diversity by changing the size and arrangement of biogeographic units (Valentine 1970). Therefore, the best hope for understanding global diversity patterns is to collect information on local assemblages. These hierarchically organized data can then be integrated to test alternate hypothetical mechanisms of change. Data compiled as the endpoints of stratigraphic or geographic ranges are useless for this purpose. This has been known at least since Bambach (1977) explored patterns of change in alpha diversity of level-bottom marine communities.

Very different questions are involved when we attempt to assess modern versus ancient global biodiversity. Because of the megabiases of taphonomy, eustasy, and tectonics, our estimates of paleobiodiversity can never be absolute; whether or not we can accurately estimate total diversity in the modern world is an open question, but we certainly cannot in the fossil record. The issues are whether we have any way of studying relative change in biodiversity through time, and how best this might be accomplished. That is, can we meaningfully estimate the shape of a global temporal diversity curve?

For decades, paleobiologists have treated global diversity estimation as a straightforward problem (Miller 2000): count up the known higher taxa in each geological time interval, make a diversity curve, and go straight ahead to analyzing and interpreting the trends. However, global diversity curves recently have come under attack from all sides. Some researchers argue that although traditional curves are strongly affected by sampling biases (e.g., Smith 2001; Peters and Foote 2002), these biases can be corrected by assembling large, locality-level databases with detailed contextual information (Alroy et al. 2001). Others point to the large gap between true total global richness and the meager head counts the fossil record has to offer, and conclude that workers should focus exclusively on local and regional diversity (Jackson and Johnson 2001). Here I argue that although further fieldwork surely is needed, understanding global diversity in the short term remains a tractable goal—as long as we move quickly to build a discipline-wide, globally extensive paleontological database.

The negative consequences of anthropogenic activities such as agriculture and urbanization (e.g., deforestation, greenhouse gas emissions, and pollution) have become exacerbated by rapid rates of human population increase (see Pimm et al. 2001). Subsequent habitat loss and modification has accelerated rates of extinction, creating a biodiversity crises which arguably is one of the most pressing problems of the twenty-first century. Although causative agents are unclear, the fossil record suggests that biotas undergo periods of massive extinction as well as considerable diversification (Alroy et al. 2001; Jackson and Johnson 2001) at the global scale, even in the absence of human activities. As such, quantifying the spatial and temporal dynamics of biodiversity in past and contemporary times, and understanding their mechanistic bases represent disciplinary emphases of evolutionary and environmental biology. Equally important, such understanding is a critical step in informing regional as well as global management strategies and conservation efforts. Nonetheless, considerable controversy or uncertainty exists surrounding the patterns, underlying mechanisms, and strategies of conservation (Willig 2000; Andelman and Willig 2002). The past may provide important insights into a number of relevant issues regarding contemporary biodiversity (and vice versa), but only recently has the dialogue between neontologists and paleontologists charted productive areas of collaboration. Indeed, a growing body of work has questioned the meaning of global measures of biodiversity (past or present) and has suggested that only detailed studies at local sites provide resolution to important issues about biodiversity. This is due, in part, to considerable sampling problems associated with broad-scale estimation, including the averaging of local and regional patterns.

Paleontological data have for long been paramount in providing a long-term perspective on global biodiversity. But all is not as simple and secure as it once seemed. Apparently rapid diversification events recorded in the fossil record have been challenged by new molecular data (Bromham et al. 1999; Wray 2001; reviewed in Smith and Peterson 2002), certain mass extinctions are not as well founded as was previously supposed (Smith et al. 2001; Peters and Foote 2002b), and even such a deeply cherished belief as the long-term trend of increasing diversity through the Phanerozoic is once again under question (Alroy et al. 2001; Peters and Foote 2002a). Why is the fossil record not currently providing us with reliable, clear-cut data, and what can be done to correct the situation?

The recognition that past catastrophic events may have caused the simultaneous extinction of many taxa has prompted the development of statistical tests to determine the compatibility of the fossil record with such scenarios. Statistical tests necessitate simplifying assumptions, the most significant of which are continuous (as opposed to discrete) data in the sampling of the fossil record and random distribution of fossil occurrences because constant preservation potential and collecting intensity of fossils are assumed. The assumption of random distribution of fossil occurrences has been addressed quantitatively, but the continuity of data has not. The assumption of continuous data is not trivial, for although collecting may appear continuous, the resulting data are never strictly continuous because the stratigraphic positions of fossils are known with limited precision. For one test of simultaneous extinction, simulations demonstrate that the data behave in a less continuous manner as the occurrence rate increases, decreasing the reliability of the test at higher occurrence rates. Out of mathematical simplicity, nearly all tests use simultaneous extinction as the null hypothesis. However, even under ideal sampling circumstances, gradual extinctions that occurred over a sufficiently short stratigraphic interval are likely to be statistically indistinguishable from extinction occurring at a single horizon. Therefore, a range of gradual extinction scenarios will also be compatible with the fossil record even if the null hypothesis is not rejected. Because direct tests of gradual extinction scenarios have not yet been developed, simulations were used to determine the probability that an extinction occurring over a given stratigraphic distance with a given number of taxa will be statistically indistinguishable from extinction at a single horizon. The simulation results allow the test results to be used to define a range of extinction scenarios compatible with the fossil record. Finally, the simulation results were applied to two Late Cretaceous ammonite data sets. Although both data sets sufficiently approximate continuous sampling for the use of statistical tests, the method shows that the data are not always sufficient to rule out either stratigraphically simultaneous extinction or a literal reading of extinction rate as representing gradual or episodic extinction.

Avian skeletal remains occur in many fossil assemblages, and in spite of small sample sizes and incomplete preservation, they may be a source of valuable paleoecological information. In this paper, we examine the taphonomy of a modern avian bone assemblage and test the relationship between ecological data based on avifaunal skeletal remains and known ecological attributes of a living bird community. A total of 54 modern skeletal occurrences and a sample of 126 identifiable bones from Amboseli Park, Kenya, were analyzed for weathering features and skeletal part preservation in order to characterize preservation features and taphonomic biases. Avian remains, with the exception of ostrich, decay more rapidly than adult mammal bones and rarely reach advanced stages of weathering. Breakage and the percentage of anterior limb elements serve as indicators of taphonomic overprinting that may affect paleoecological signals. Using ecomorphic categories including body weight, diet, and habitat, we compared species in the bone assemblage with the living Amboseli avifauna. The documented bone sample is biased toward large body size, representation of open grassland habitats, and grazing or scavenging diets. In spite of this, multidimensional scaling analysis shows that the small faunal sample (16 out of 364 species) in the pre-fossil bone assemblage accurately represents general features of avian ecospace in Amboseli. This provides a measure of the potential fidelity of paleoecological reconstructions based on small samples of avian remains. In the Cenozoic, the utility of avian fossils is enhanced because bird ecomorphology is relatively well known and conservative through time, allowing back-extrapolations of habitat preferences, diet, etc. based on modern taxa.

One of the central goals in paleoecology is to understand the nature and consequences of biotic interactions. In marine systems, it has been argued that one of the major steps in the escalation of biotic interactions was marked by the origins of grazing fishes in the Cenozoic. Here I investigate the origins of herbivory and grazing in marine fishes using analyses of functional morphospace. Closing and opening lever ratios and relative length of the lower jaw are used to construct a plot of functional morphospace, a quantitative description of the potential feeding modes of fishes. Four fish faunas were examined, spanning the Mesozoic and Cenozoic (Triassic, Jurassic, Eocene and Recent). All three fossil faunas are from conservation Lagerstätten in the central Tethys, in the vicinity of coral reefs or coral-bearing hardgrounds. Changes in functional morphospace occupation reveal a marked shift in the Cenozoic, with the appearance of fishes with relatively small forceful jaws. In Recent faunas, this functional morphospace is occupied almost exclusively by grazing herbivores. This taxon-independent morphological signal of herbivory was lacking in the Mesozoic faunas, was first recorded in the Eocene, and persisted throughout the Cenozoic. This suggests that the Cenozoic did indeed witness the appearance and proliferation of herbivory and grazing by marine fishes. The arrival of these piscine herbivores had the potential to fundamentally alter the dynamics of benthic marine communities.

The living species Ginkgo biloba is phylogenetically isolated, has a relictual distribution, and is morphologically very similar to Mesozoic and Cenozoic congenerics. To investigate what adaptations may have allowed this lineage to persist with little or no morphological change for over 100 Myr, we analyzed both sedimentological and floral data from 51 latest Cretaceous to middle Miocene Ginkgo-bearing fossil plant sites in North America and northern Europe. The resulting data indicate that throughout the late Cretaceous and Cenozoic Ginkgo was largely confined to disturbed streamside and levee environments, where it occurred with a consistent set of other plants. These inferred habitats are surprising because the life-history traits of Ginkgo (e.g., slow growth rate, late reproductive maturity, extended reproductive cycle, large and complex seeds, large and slowly developing embryos) are counter to those considered advantageous in modern disturbed habitats. Many flowering plant lineages first appeared or became common in disturbed riparian habitats, and are inferred to have had reproductive and growth traits (e.g., rapid reproduction, small easily dispersed seeds, rapid growth) suited to such habitats. Paleoecological inferences based on both morphology and sedimentary environments thus support the idea that Ginkgo was displaced in riparian habitats by angiosperms with better adaptations to frequent disturbance.

Despite numerous studies, the thermal physiology of dinosaurs remains unresolved. Thus, perhaps the commonly asked question whether dinosaurs were ectotherms or endotherms is inappropriate, and it is more constructive to ask which dinosaurs were likely to have been endothermic and which ones ectothermic. Field data from crocodiles over a large size range show that body temperature fluctuations decrease with increasing body mass, and that average daily body temperatures increase with increasing mass. A biophysical model, the biological relevance of which was tested against field data, was used to predict body temperatures of dinosaurs. However, rather than predicting thermal relations of a hypothetical dinosaur, the model considered correct paleogeographical distribution and climate to predict the thermal relations of a large number of dinosaurs known from the fossil record (>700). Many dinosaurs could have had “high” (>30°) and stable (daily amplitude >2°) body temperatures without metabolic heat production even in winter, so it is unlikely that selection pressure would have favored the evolution of elevated resting metabolic rates in those species. Recent evidence of ontogenetic growth rates indicates that even the juveniles of large species (3000–4000 kg) could have had biologically functional body temperature ranges during early development. Smaller dinosaurs (<100 kg) at mid to high latitudes (>45°) could not have had high and stable body temperatures without metabolic heat production. However, elevated metabolic rates were unlikely to have provided selective advantage in the absence of some form of insulation, so probably insulation was present before endothermy evolved, or else it coevolved with elevated metabolic rates. Superimposing these findings onto a phylogeny of the Dinosauria suggests that endothermy most likely evolved among the Coelurosauria and, to a lesser extent, among the Hypsilophodontidae, but not among the Stegosauridae, Nodosauridae, Ankylosauridae, Hadrosauridae, Ceratopsidae, Prosauropoda, and Sauropoda.

The euphractine Macroeuphractus outesi, from the late Pliocene Chapadmalalan SALMA of Buenos Aires Province, Argentina, is one of the largest dasypodids known. Its skull preserves features remarkable for an armadillo. Its complete dental arcade and large caniniform teeth have received attention in the literature as indicative of scavenging behavior. This report considers the degree of carnivory within the context of the generally omnivorous feeding behavior of euphractine armadillos through morphological and biomechanical analyses. Morphological analyses reveal that the main differences between M. outesi and other euphractines are the enlargement of the cranium, particularly of the temporal fossa; more prominent muscular scars for origin of the temporalis muscle; a more expanded rostrum, particularly in dorsoventral height; a more powerful anterior dentition, especially in the great enlargement and caniniform modification of M2; and a deeper and more robust zygomatic arch. Biomechanical analyses indicate that the moment arm of the temporalis musculature is greater than that recorded for other armadillos. These analyses indicate that the temporalis was probably larger and played a more important role in Macroeuphractus than in other euphractines, a pattern that is more usual for carnivorous mammals. Combined with the second upper molariform, which is caniniform, the features suggest that Macroeuphractus occupied an extreme position in the carnivorous-omnivorous feeding behavior of euphractines. Its large size indicates that it could have easily preyed on hare-sized vertebrates.

Disparity appears to decrease or remain stable over geological time in numerous groups. This pattern is sometimes explained in terms of developmental constraints, but labile developmental systems might produce the same pattern should novelties interact, counterbalancing their individual effects. We test the hypothesis that counterbalancing can reduce disparity by comparing ontogenies of shape among nine species of piranhas to identify the developmental novelties. All three parameters examined change multiple times, sometimes dramatically. By comparing levels of disparity between species at two developmental phases, at the transition from larval to juvenile phases, and at maximum adult body size, we find that disparity decreases significantly and substantially over ontogeny. That reduction occurs because of, rather than despite, novelties of postlarval morphogenesis. Some interacting novelties are historically independent and affect different developmental phases, others are historically independent and affect the same developmental phase, and still others are historically correlated and affect either the same or different developmental phases. By modeling hypothetical ontogenies, constraining developmental parameters mathematically to one of the observed values, we find that variation in each parameter, taken by itself, and combinations of them taken two at a time, tend to increase disparity. It is the interactions among all three that reduce disparity. In this group divergent ontogenies transform disparate larvae into similar adults.