Temporal patterns in species occupancy and geographic range size are a major topic in evolutionary ecology research. Here we investigate these patterns in Pliocene to Recent large mammal species and genera in Western Eurasia. By using an extensively sampled fossil record including some 700 fossil localities, we found occupancy and range size trajectories over time to be predominantly peaked among both species and genera, meaning that occupancy and range size reached their maxima midway along taxon existence. These metrics are strongly correlated with each other and to body size, after phylogeny is accounted for by using two different phylogenetic topologies for both species and genera. Phylogenetic signal is strong in body size, and weaker but significant in both occupancy and range size mean values among genera, indicating that these variables are heritable. The intensity of phylogenetic signal is much weaker and often not significant at the species level. This suggests that within genera, occupancy and range size are somewhat variable. However, sister taxa inherit geographic position (the center of their geographic distribution). Taken together, the latter two results indicate that sister species occupy similar positions on the earth's surface, and that the expansion of the geographic range during the existence of a given genus is driven by range expansion of one or more of the species it includes, rather than simply being the summation of these species ranges.

Applications of the species-area equation to studies of fluctuations in Phanerozoic diversity have great promise but can involve questionable assumptions. Sepkoski's (1976) analysis of marine diversity throughout the Phanerozoic record assumes that total rock volume is a sufficient measure of sampling efficiency and that an isomorphous equation is appropriate for all of Phanerozoic time. The area of marine sedimentary rock and the area of continental seas are not independent variables. Residual variation in diversity (that which remains after subtracting the effects of rock volume) might be explained by either the species-area relationship or by another component of sampling efficiency. A species-area equation in which the slope (z) and intercept (k) are assumed constant receives mixed support from arguments based on Recent terrestrial and aquatic organisms. Observed z-values cluster near a value of 0.30 despite a wide taxonomic range, but are generally below those found for the Phanerozoic record. Temporal fluctuations in k values, in response to changes in the area of continental seas, may produce elevated estimates of z.

Application of computed tomography to the most recently recognized specimen of Archaeopteryx demonstrates the potential of this technique for paleontological issues. Contrary to earlier interpretations of these specimens, the results of computed tomography appear to show the presence of an avian-like doubled-headed quadrate bone in this earliest true bird.

Problems of stratigraphic completeness and poor temporal resolution make analysis of faunal change in terrestrial sequences difficult. The fluvial Neogene Siwalik formations of India and Pakistan are an exception. They contain a long vertebrate record and have good chronostratigraphic control, making it possible to assess the influence of biotic interchange on Siwalik fossil communities. In Pakistan, the interval between 18 and 7 Ma has been most intensively studied and changes in diversity and relative abundance of ruminant artiodactyls and muroid rodents are documented with temporal resolution of 200,000 years. Within this interval, diversity varies considerably, including an abrupt rise in species number between 15 and 13 Ma, followed by a decline in ruminant diversity after 12 Ma and a decline in muroid diversity in two steps at 13 and 10 Ma. Significant changes in relative abundance of taxa include an increase in bovids between 16.5 and 15 Ma, a decrease in tragulids after 9 Ma, and a very abrupt increase in murids at 12 Ma. Megacricetodontine rodents also decrease significantly at 12 Ma, and smaller declines are recorded among myocricetodontine and copemyine rodents after 16 Ma. An increase of dendromurine rodents at 15.5 Ma is also observed. There is also a trend of progressive size increase among giraffoids and bovids throughout the sequence.

We have also investigated relationships between biotic interchange and diversity, body size, and relative abundance, concluding that (1) the rapid increase in ruminant and muroid diversity was largely due to immigration, whereas in situ speciation had only a secondary role; (2) during intervals of increasing diversity, resident lineages did not have higher than average rates of in situ speciation; (3) during intervals with rising diversity, greater extinction did not accompany increased immigration; (4) during intervals with falling diversity, there may have been greater extinction in recently invading lineages; and (5) change in diversity was independent of changes in relative abundance and body size.

Fossil data suggest that the great majority of metazoan classes that existed in the Early Cambrian arose after about 700 my ago. The rectangular model of evolution, which views most evolutionary change as being concentrated in speciation events, can easily accommodate the implied rate of divergence.

If, as some authors believe, the eukaryotic cell arose long before the start of the Cambrian, an explanation is required for the delay of large-scale metazoan divergence. The advent of sexuality may have triggered diversification, not by accelerating phyletic evolution, as traditionally believed, but by making possible speciation and, hence, adaptive radiation. Another important delaying factor may have been the near-saturation of Precambrian algal systems in the absence of cropping by herbivores. Uncropped Precambrian systems should have been self-limiting in terms of diversification. When advanced heterotrophy finally arose, self-propagating feedback systems of diversification should have been set in motion. Even if the eukaryotic cell arose later than commonly envisioned and triggered the radiation of the Metazoa about 700 my ago, the earlier absence of sexuality and cropping may have delayed the transition from the prokaryotic condition to the eukaryotic condition.

The origin of ammonite sutures is one of the most interesting open problems in paleontology. Present theories of suture formation deal with function rather than morphogenesis. Here we present a study showing that sutures are scale-invariant. In each of ten different ammonite genera, the ontogenetic sequence of the suture can be characterized by the same fractal dimension. We propose a morphogenetic theory for ammonite sutures that is based on the similarity between sutures and the Saffman-Taylor instability in both fractal characters and physical mechanism.

Throughout the late Quaternary, the Sahul (Pleistocene Australia–New Guinea) vertebrate fauna was dominated by a diversity of large mammals, birds, and reptiles, commonly referred to as megafauna. Since ca. 450–400Ka, approximately 88 species disappeared in Sahul, including kangaroos exceeding 200kg in size, wombat-like animals the size of hippopotamuses, flightless birds, and giant monitor lizards that were likely venomous. Ongoing debates over the primary cause of these extinctions have typically favored climate change or human activities. Improving our understanding of the population biology of extinct megafauna as more refined paleoenvironmental data sets become available will assist in identifying their potential vulnerabilities. Here, we apply a multiproxy approach to analyze fossil teeth from deposits dated to the middle and late Pleistocene at Cuddie Springs in southeastern Australia, assessing relative aridity via oxygen isotopes as well as vegetation and megafaunal diets using both carbon isotopes and dental microwear texture analyses. We report that the Cuddie Springs middle Pleistocene fauna was largely dominated by browsers, including consumers of C4 shrubs, but that by late Pleistocene times the C4 dietary component was markedly reduced. Our results suggest dietary restriction in more arid conditions. These dietary shifts are consistent with other independently derived isotopic data from eggshells and wombat teeth that also suggest a reduction in C4 vegetation after ~45 Ka in southeastern Australia, coincident with increasing aridification through the middle to late Pleistocene. Understanding the ecology of extinct species is important in clarifying the primary drivers of faunal extinction in Sahul. The results presented here highlight the potential impacts of aridification on marsupial megafauna. The trend to increasingly arid conditions through the middle to late Pleistocene (as identified in other paleoenvironmental records and now also observed, in part, in the Cuddie Springs sequence) may have stressed the most vulnerable animals, perhaps accelerating the decline of late Pleistocene megafauna in Australia.

The proposition is presented that the large thecae of many Paleozoic crinoids housed gonads, unlike modern crinoids that have the gonads on the arms or pinnules. Early in their history, inadunate crinoid gonads migrated into a voluminous anal sac, effectively separating them from other vital organs. Excision of the sac by predatory fishes and cephalopods would have been less traumatic than an attack on the theca, and the sac could be more readily regenerated. The pores and slits between plates on inadunate sacs are interpreted as gonopores. Some anal sacs may also have served as brood chambers. The traditional explanation of the sac as a special respiratory structure is discounted.

Few would argue with the assertion that within the practice of comparative morphology, the comparison of shapes is fundamental to any line of synthesis in paleontology. Yet the common act of such a comparison involves a great range of judgments concerning the homology, correspondence and divergence of form of various parts of any two related shapes. Considerations of similarity must include the scalar effects of size and material, the conversion of proportions as descriptive geometric dimensions to those useful numerical values that will be represented as ratios of measured distance (relative or compared against a standard), and, by no means insignificant, the judgment about the design or functional geometry implicit in the static as well as dynamic systems being measured. This review is concerned with these considerations and with quantitative comparisons of biological shape wherein some parts of specimens obviously have changed and others parts have not.

Paleoecologists studying Paleozoic reef-builders have interpreted their growth forms as responses to conditions of depth and turbulence in reef complexes. Comparison of the shapes of Paleozoic stromatoporoids and corals with the growth forms of modern scleractinians has been used to reconstruct Paleozoic conditions. A review of shape zonation on modern reefs indicates that no general pattern is applicable to all reefs and variations in shape are the result of the interaction of many environmental factors with the genetically dictated growth pattern of the coral. In most zones of a reef a wide range of shapes co-exist. The growth forms of corals on modern reefs are not a simple vegetative response to the many environmental parameters that have been shown to influence form, but are constrained by phylogenetic and developmental influences as well as functional ones.

Interpretations of the environments of western Canadian and other mid-Paleozoic reefs have been based on the growth forms of stromatoporoids. The environmental significance of the shapes has been deduced from comparison with the shapes of modern scleractinians, functional morphology, nature of the enclosing sediment, position of growth, position within the reef, and diversity gradients. The validity of these criteria is open to question and considerable doubt remains concerning the significance of the growth forms. The shapes of reef animals are not specific guides to environments of modern reefs and should not be expected to be guides for ancient ones.

Fossil marine lineages are generally expected to exhibit long-term trends of increasing body size because of inherent fitness advantages or secular changes in environmental conditions. Because empirical documentation of this trend during the Paleozoic has been lacking for most taxonomic groups, the magnitude, timing, and taxonomic breadth of the trend have remained elusive. This study uses the largest existing database of fossil invertebrate sizes from four faunally important phyla to document ecosystem-wide size trends in well-preserved biotas from deep-subtidal, soft-substrate assemblages during the Cambrian through Devonian. Size of type specimens was measured along standard body axes from monographic plates and converted to body volume by using a broadly applicable empirical regression. Results demonstrate that mean body size (herein volume) of individual genera doubles during this interval, especially from the Late Ordovician through Early Devonian. The timing is gradual in spite of major radiations and extinctions, and the increase is primarily attributable to a net increase in the three-dimensionality of genera. The overall increase is not caused by replacement among clades because increases are widespread among arthropods, brachiopods, and echinoderms, at the phylum and class levels; in contrast, mollusks do not display a net size change at either taxonomic level. The increase is also more pronounced in microbivores than in carnivores. Combined with known environmental changes during this interval, and especially records of carbon dioxide, these trends provide support for the claim that primary productivity increased during the early to mid Paleozoic.

Arcoid bivalves occupy an intermediate position, in terms both of morphology and of adaptive range between the Pterioida and the Veneroida. The range and limits of arcoid adaptations are related to the growth patterns of their shells. Both the arcoid hinge and ligament grow by the serial repetition of simple structures, in contrast with the development of more specialized, complex structures in other groups. These simple growth patterns place significant mechanical constraints on the range of possible shell forms. Most arcoids live in moderately unstable environments, where they are liable to be excavated or detached from their substrates. Many employ recovery strategies, being adapted to regain their life positions. However, a variety of specialized forms, convergent on other groups of bivalves, have become adapted to avoid being dislodged in the first place. Thus, intrinsic growth patterns and substrate relationships have been the major factors in the evolution of the Arcoida.

The same three subtypes of derived multiserial Hunter-Schreger bands are found in the incisor enamel of African phiomorph rodents from the late Eocene-early Oligocene and the oldest South American Caviomorpha from the Deseadan (late Oligocene). The synapomorphies contained therein, especially arrangement and orientation of interprismatic matrix, make an African origin of the Caviomorpha very probable. A North American origin of the Caviomorpha is thus rejected, as only primitive pauciserial Hunter-Schreger bands have been observed in possible ischyromyoid caviomorph ancestors. A multiserial Schmelzmuster apparently never evolved in the North American rodent fauna.

A new account of the mechanical action of the heterocercal tail in fishes is given, developed from study of the swimming of sharks. The heterocercal tail is capable of delivering a thrust that can be oriented in a wide range of angles in the vertical plane. The orientation results from a balance of forces acting in the tail. Normally the heterocercal tail delivers neither an epibatic nor a hypobatic thrust, but rather one directly through the center of gravity of the fish. On the basis of the new account, predictions concerning the shape and proportions of the heterocercal tail are made and tested.

The Westermann Morphospace method displays fundamental morphotypes and hypothesized life modes of measured ammonoid fossils in a ternary diagram. It quantitatively describes shell shape, without assumption of theoretical coiling laws, in a single, easy-to-read diagram. This allows direct comparison between data sets presented in Westermann Morphospace, making it an ideal tool to communicate morphology. By linking measured shells to hypothesized life modes, the diagram estimates ecospace occupation of the water column. Application of this new method is demonstrated with Mesozoic data sets from monographs. Temporal variation, intraspecies variation, and ontogenetic variation are considered. This method can address hypothetical ecospace occupation in collections with tight stratigraphic, lithologic, and abundance control, even when taxonomy is in dispute.

Ecotypic correlations between stable isotopic signals and skeletal size indicate that some Late Cretaceous serial planktic foraminifera were strongly photosymbiotic. In contrast, coeval trochospiral planktic foraminifera do not exhibit the isotope/size signatures that typify strongly photosymbiotic species. Comparison to Cenozoic taxa demonstrates that photosymbiosis has recurred throughout planktic foraminiferal history and has evolved independently in superfamilies characterized by very different gross skeletal morphologies. The historical contingency of that evolution is illustrated by the consequences of the Cretaceous/Paleogene mass extinction, which terminated the Cretaceous lineages of photosymbiotic planktic foraminifera but did not permanently extinguish photosymbiont reliance by planktic foraminifera.

Reconstructing the tree of life involves more than identifying relationships among lineages; it also entails accurately estimating when lineages diverged. Paleontologists typically scale cladograms to time a posteriori by direct reference to first appearances of taxa in the stratigraphic record. Some approaches use probabilistic models of branching, extinction, and sampling processes to date samples of trees, such as the recently developed cal3 method, which stochastically draws divergence dates given a set of rates for those processes. However, these models require estimates of the rates of those processes, which may be hard to obtain, particularly for sampling. Here, we contrast the use of cal3 and other a posteriori time-scaling approaches by examining a previous study that documented a decelerating rate of morphological evolution in pterocephaliid trilobites. Although aspects of the data set make estimation of branching, extinction, and sampling rates difficult, we use a multifaceted approach to calculate and evaluate the rate estimates needed for applying cal3. In agreement with previous simulation studies, we find that the choice of phylogenetic dating method impacts downstream macroevolutionary conclusions. We also find contradictory evolutionary inferences between analyses on ancestor–descendant contrasts (based on ancestor trait reconstruction methods) and maximum-likelihood parameter estimates. Ancestral taxon inference in cal3 corroborates previously hypothesized ancestor–descendant sequences, but cal3 suggests greater support for budding cladogenesis than anagenesis. This case study demonstrates the potential and wide applicability of the cal3 method and the benefits afforded by choosing cal3 over simpler a posteriori time-scaling approaches.

Deep-sea submersible observations made in the Bahamas revealed interactions between the stalked crinoid Endoxocrinus parrae and the cidaroid sea urchin Calocidaris micans. The in situ observations include occurrence of cidaroids within “meadows” of sea lilies, close proximity of cidaroids to several upended isocrinids, a cidaroid perched over the distal end of the stalk of an upended isocrinid, and disarticulated crinoid cirri and columnals directly underneath a specimen of C. micans. Guts of two C. micans collected from the crinoid meadow contain up to 70% crinoid material. Two of three large museum specimens of another cidaroid species, Histocidaris nuttingi, contain 14–99% crinoid material.

A comparison of cidaroid gut contents with local sediment revealed significant differences: sediment-derived material consists of single crinoid ossicles often abraded and lacking soft tissue, whereas crinoid columnals, cirrals, brachials, and pinnulars found in the cidaroids are often articulated, linked by soft tissue, and unabraded. Furthermore, articulated, multi-element fragments often show a mode of fracture characteristic of fresh crinoid material. Taken together, these data suggest that cidaroids prey on live isocrinids.

We argue that isocrinid stalk-shedding, whose purpose has remained a puzzle, and the recently documented rapid crawling of isocrinids are used in escaping benthic predators: isocrinids sacrifice and shed the distal stalk portion when attacked by cidaroids and crawl away, reducing the chance of a subsequent encounter. If such predation occurred throughout the Mesozoic and Cenozoic (possibly since the mid-Paleozoic), several evolutionary trends among crinoids might represent strategies to escape predation by slow-moving benthic predators.

Growth of the colony is a basic element of morphological evolution and life history in cheilostome bryozoans. Here we consider the occurrence of different modes of growth in encrusting cheilostomes through geologic time and in well-studied living associations. We assess patterns of zooid formation by direct examination of skeletal characters in species from nearly all diverse fossil assemblages reported from North America and quantify within-assemblage diversities and abundance rankings for fossil encrusting species with different modes of growth. These data document macroevolutionary trends showing a transition from dominance of an apparently primitive mode of budding in the Early Cretaceous to derived modes through the Tertiary. The trends are characterized by their long duration and apparent convergence among systematic subgroups within the Cheilostomata. We then consider the validity of our observations as adaptive trends. Patterns of ecological dominance among living and fossil species indicate that different patterns of zooid formation are important determinants of success of colonies as reflected by their abundance, competitive ability, survivorship, and recovery from injury or predation. The consistency of the long-term trends and evidence for the existence of ecological mechanisms in fossil assemblages suggest a major evolutionary role for biotic interactions.

Coiled cephalopods constitute a major part of the Paleozoic nekton. They emerged in the Early Ordovician but nearly vanished in the Silurian. The Emsian appearance of ammonoids started a story of evolutionary success of coiled cephalopods, which lasted until the end-Permian extinction event. This story is investigated by using a taxonomic database of 1346 species of 253 genera of coiled nautiloids and 1114 genera of ammonoids. The per capita sampling diversities, the Van Valen metrics of origination and extinction, and the probabilities of origination and extinction were calculated at stage intervals. The outcome of these estimations largely reflects the known biotic events of the Paleozoic. The polyphyletic, iterative appearance of coiled cephalopods within this time frame is interpreted to be a process of adaptation to shell-crushing predatory pressure. The evolution of the diversity of coiled nautiloids and ammonoids is strongly correlated within the time intervals. Once established, assemblages of coiled cephalopods are related to changes in sea level. The general trends of decreasing mean (or background) origination and extinction rates during the Paleozoic are interpreted to reflect a successive stabilization of the coiled cephalopod assemblages. Different reproduction strategies in ammonoids and nautiloids apparently resulted in different modes of competition and morphological trends. Significant morphological trends toward a stronger ornamentation and a centrally positioned siphuncle characterize the evolution of Paleozoic nautiloids.