We documented changes in the relative abundance of bivalve genera and functional groups in the southwest Caribbean over the past 11 Myr to determine their response to oceanographic changes associated with the closure of the Central American Seaway ca. 3.5 Ma. Quantitative bulk samples from 29 localities yielded 106,000 specimens in 145 genera. All genera were assigned to functional groups based on diet, relationship to the substrate, and mobility. Ordinations of assemblages based on quantitative data for functional groups demonstrated strong shifts in community structure, with a stark contrast between assemblages older than 5 Ma and those younger than 3.5 Ma. These changes are primarily due to an increase in the abundance of attached epifaunal bivalves (e.g., Chama, Arcopsis, and Barbatia) and a decrease in infaunal bivalves (e.g., Varicorbula and Caryocorbula). Taxa associated with seagrasses, including deposit-feeding and chemosymbiotic bivalves (e.g., Lucina), also increased in relative abundance compared to suspension feeders. The composition of bivalve assemblages is correlated with the carbonate content of sediments and the percentage of skeletal biomass that is coral. Our results strongly support the hypothesis that increases in the extent of coral reefs and Thalassia communities were important drivers of biologic turnover in Neogene Caribbean benthic communities.

Sabertooth members of the Felidae, Nimravidae, and Barbourofelidae are well-known for their elongated saber-shaped canines. However, within these groups, there is a wide range of independently derived tooth shapes and lengths, including dirk-tooth and scimitar-tooth morphs. In conjunction with the saberteeth, forelimbs were also used to subdue prey. Thus, there may be a functional link between canine shape and forelimb morphology. Because there are no living sabertooth forms for comparison, extant felids make a good proxy for examining the morphology of these extinct organisms. Here, I examine the forelimb morphology of different sabertooth groups from across North America; I address whether forelimb morphologies are associated with tooth morphologies, and whether these associated tooth and forelimb morphologies are convergent among different families. To answer these questions, I analyzed six functional indices of the forelimbs and two canine characters for 13 species of sabertooth predators and 15 extant felid species. Results indicate that sabertooth morphs with longer, thinner canines show more robust limb proportions. These patterns were convergent among sabertooth felids, nimravids, and barbourofelids, and indicate a positive functional relationship between saber elongation and increased forelimb robustness. This suggests that sabertooth carnivorans demonstrated niche partitioning of predation strategies according to canine shape and corresponding forelimb morphology.

Rates of phenotypic evolution are central to many issues in paleontology, but traditional rate metrics such as darwins or haldanes are seldom used because of their strong dependence on interval length. In this paper, I argue that rates are usefully thought of as model parameters that relate magnitudes of evolutionary divergence to elapsed time. Starting with models of directional evolution, random walks, and stasis, I derive for each a reasonable rate metric. These metrics can be linked to existing approaches in evolutionary biology, and simulations show that they can be estimated accurately at any temporal resolution via maximum likelihood, but only when that metric's underlying model is true.

The estimation of generational rates of a random walk under realistic paleontological conditions is compared with simulations to that of a prominent alternative approach, Gingerich's LRI (log-rate, log-interval) method. Generational rates are estimated poorly by LRI; they often reflect sampling error more than the actual pace of change. Further simulations show that under some realistic conditions, it is simply not possible to infer generational rates from coarsely sampled populations.

These modeling results indicate a complex dependence between evolutionary mode and the measurement of evolutionary rates, and that there is unlikely to be a rate metric that works well for all traits and time scales. Compilations of paleontological and phylogenetic data indicate that all of the three rate metrics derived here show some relationship with interval length. Although there is no perfect rate metric, at present the most practical choices derive from the parameters of the stasis and random walk models. The latter, called the step variance, is particularly promising as a rate metric in paleontology and comparative biology.

Identifying biological traits that promote evolutionary success is fundamental for understanding biodiversity dynamics and for assessing the evolutionary response of organisms to global change. We tested the hypothesis that image-forming eyes have contributed to the diversification of taxa in the geological past. Using fossil occurrences in the Paleobiology Database, we analyzed the diversity and evolutionary rates of more than 17,000 Phanerozoic genera of marine invertebrates living on or above the shallow-water seafloor according to their visual capabilities. Analysis of the complete data set shows a peak in the proportional diversity of sighted genera early in the Phanerozoic, and their continuance at a relatively low and stable level after the Ordovician. As an explanation of this pattern we suggest that selection pressure to develop eyes rose in the Cambrian, and that behavioral constraints had a balancing effect thereafter. In contrast to the pooled data, a clade-level study of those subgroups that contain both sighted and blind genera revealed that—in trilobites, all epifaunal bivalves, pectinoid bivalves, gastropods, and echinoderms—sighted genera diversified more strongly than blind genera. This difference is controlled by significantly raised extinction rates of blind genera. These more finely resolved patterns support the hypothesis that good vision is a key trait that promoted preferential diversification.

Analysis of a global elevation database to measure changes in shallow-marine habitat area as a function of sea level reveals an unexpectedly complicated relationship. In contrast to prevailing views, sea level rise does not consistently generate an increase in shelf area, nor does sea level fall consistently reduce shelf area. Different depth-defined habitats on the same margin will experience different changes in area for the same sea level change, and different margins will likewise experience different changes in area for the same sea level change. Simple forward models incorporating a species-area relationship suggest that the diversity response to sea level change will be largely idiosyncratic. The change in habitat area is highly dependent on the starting position of sea level, the amount and direction of sea level change, and the habitat and region in question. Such an idiosyncratic relationship between diversity and sea level reconciles the widespread evidence from the fossil record for a link between diversity and sea level change with the lack of quantitative support for such a relationship throughout the Phanerozoic.

The carbon stable isotope (δ13C) composition of the calcitic tests of planktonic foraminifera has an important role as a geochemical tracer of ocean carbon system changes associated with the Cretaceous/Paleogene (K/Pg) mass extinction event and its aftermath. Questions remain, however, about the extent of δ13C isotopic disequilibrium effects and the impact of depth habitat evolution on test calcite δ13C among rapidly evolving Paleocene species, and the influence this has on reconstructed surface-to-deep ocean dissolved inorganic carbon (DIC) gradients. A synthesis of new and existing multispecies data, on the relationship between δ13C and δ18O and test size, sheds light on these issues. Results suggest that early Paleocene species quickly radiated into a range of depths habitats in a thermally stratified water column. Negative δ18O gradients with increasing test size in some species of Praemurica suggest either ontogenetic or ecotypic dependence on calcification temperature that may reflect depth/light controlled variability in symbiont photosynthetic activity. The pattern of positive δ13C test-size correlations allows us to (1) identify metabolic disequilibrium δ13C effects in small foraminifera tests, as occur in the immediate aftermath of the K/Pg event, (2) constrain the timing of evolution of foraminiferal photosymbiosis to 63.5 Ma, ∼0.9 Myr earlier than previously suggested, and (3) identify the apparent loss of symbiosis in a late-ranging morphotype of Praemurica. These findings have implications for interpreting δ13C DIC gradients at a resolution appropriate for incoming highly resolved K/Pg core records.

The study of spatial patterns in biotic compositional variability in deep time is key to understanding the macroecological response of species assemblages to global change. Globally warm climatic phases are marked by the expansion of megathermal climates into currently extra-tropical areas. However, there is currently little information on whether vegetation in these “paratropical” regions resembled spatially modern tropical or extra-tropical biomes. In this paper we explore spatial heterogeneity in extra-tropical megathermal vegetation, using sporomorph (pollen and spore) data from the late Paleocene Calvert Bluff and Tuscahoma Formations of the formerly paratropical U.S. Gulf Coast (Texas, Mississippi, and Alabama). The data set comprises 139 sporomorph taxa recorded from 56 samples. Additive diversity partitioning, nonmetric multidimensional scaling, and cluster analysis show compositional heterogeneity both spatially and lithologically within the U.S. Gulf Coastal Plain (GCP) microflora. We then use sporomorph data from Holocene lake cores to compare spatial patterns in the late Paleocene GCP with modern tropical and extra-tropical biomes. Distance decay analysis of the Holocene data reveals a higher rate of spatial turnover in tropical versus extra-tropical vegetation types, consistent with a latitudinal gradient in floral compositional heterogeneity. The specific combination of rate and scale dependency of distance decay in the Holocene assemblages prevented us from associating the late Paleocene GCP with any particular modern biome. Our results demonstrate the importance of spatial scale, taphonomy, and lithology in determining patterns of spatial heterogeneity, and show the potential of the fossil sporomorph record for studying spatial patterns and processes in deep time.

The Permian/Triassic mass extinction marks a permanent phylogenetic shift in the composition of the sessile benthos, from one largely dominated by articulate brachiopods to one dominated by mollusks. Widespread evidence of oceanic hypoxia and anoxia at this time provides a possible selective kill mechanism that could help explain the large taxonomic losses in brachiopods compared to the morphologically and ecologically similar bivalve molluscs. Our study compared the oxygen consumption of an articulate brachiopod, Terebratalia transversa, with that of two pteriomorph bivalves, Glycymeris septentrionalis and Mytilus trossulus, under normoxia and hypoxia, as well as their tolerance to anoxia, to gain insight into the relative metabolic characteristics of each group. We found no significant difference in the oxygen consumption of the three species when normalized to the same dry-tissue mass. However, when calculated for animals of the same external linear dimensions, bivalve oxygen consumption was two to three times greater than that of brachiopods. Our results also showed no significant decrease in the oxygen consumption of the three species until measured at a partial pressure of oxygen ∼10% of normoxic values. Finally, T. transversa and M. trossulus showed no significant difference in their tolerance to complete anoxia, but both showed a much lower tolerance than another bivalve, Acila castrensis. Findings from this study suggest that oxygen limitation is unlikely to account for the observed selective extinction of brachiopods during the Permian/Triassic mass extinction. Results may provide valuable information for assessing hypotheses put forth to explain why articulate brachiopods continue to remain a relatively minor group in marine environments.

The role of antagonistic organismal interactions in the production of long-term macroevolutionary trends has been debated for decades. Some evidence seems to suggest that temporal trends in predation frequency share a common causative mechanism with genus-level diversity, whereas studies on the role of parasites in “shaping” the evolutionary process are rare indeed. Digenean trematodes (Phylum Platyhelminthes) infest molluscs in at least one stage of their complex life cycle. Trematodes leave characteristic oval-shaped pits with raised rims on the interior of their bivalve hosts, and these pits are preserved in the fossil record. Here we survey 11,785 valves from the Pleistocene–Holocene deposits of the Po Plain and from nearby modern coastal environments on the northeast Adriatic coast of Italy. Of these, 205 valves exhibited trematode-induced pits. Trematodes were selective parasites in terms of host taxonomy and host body size. Infestation was restricted to lower shoreface/transition-to-platform paleoenvironments. During the Holocene, individuals from the transgressive systems tract were significantly more likely to be infested than those from highstand systems tracts. Temporal trends in infestation frequency cannot be explained as an ecological/evolutionary phenomenon (e.g., the hypothesis of escalation); instead the trend seems controlled by environmental variation induced by glacio-eustatic sea-level changes and inadequate sampling. Because this interaction appears to be ephemeral, both temporally and spatially, it is not likely that any selective pressure would be continuous over geologic time in this region. Furthermore, these results support the hypothesis that antagonistic interactions are lower in the northern Adriatic Sea in comparison to other midlatitude shallow marine settings.

The late Mesozoic through early Cenozoic is an interval of significant biologic turnover and ecologic reorganization within marine assemblages, but the timing and causes of these changes remain poorly understood. Here, we quantify the pattern and timing of shifts in the diversity (richness and evenness) and ecology of local (i.e., sample level) mollusk-dominated assemblages during this critical interval using field-collected and published data sets from the U.S. Gulf Coastal Plain. We test whether the biologic and ecologic patterns observed primarily at the global level during this time are also expressed at the local level, and whether the end-Cretaceous (K/Pg) mass extinction and recovery moderated these trends. To explore whether environment had any effect on these patterns, we examine data from shallow subtidal and offshore settings.

Assemblages from both settings recovered to pre-extinction diversity levels rapidly, in less than 7 million years. Following initial recovery, diversity remained unchanged in both settings. The trajectory of ecological restructuring was distinct for each setting in the wake of the K/Pg extinction. In offshore assemblages, the abundance and number of predatory carnivorous taxa dramatically increased, and surficial sessile suspension feeders were replaced by more active suspension feeders. In contrast, shallow subtidal assemblages did not experience ecological reorganization following the K/Pg extinction. The distinct ecological patterns displayed in each environment follow onshore-offshore patterns of innovation, whereby evolutionary novelties first appear in onshore settings relative to offshore habitats. Increased predation pressure may explain the significant ecological restructuring of offshore assemblages, whereby the explosive radiation of predators drove changes in their prey. Habitat-specific ecological restructuring, and its occurrence solely during the recovery interval, implies that disturbance and incumbency were also key in mediating these ecological changes.

The silicoflagellates are a class of enigmatic chrysophytes characterized by netlike skeletons composed of opaline silica. Other major groups of siliceous plankton—the diatoms and radiolarians—exhibit evidence of decreasing size or silicification over the Cenozoic. We investigated trends in the silicoflagellate fossil record by constructing a species-level database of diversity and morphological metrics. This new database reveals a proliferation of silicoflagellate species with spined skeletons along with an increase in the mean number of spines per species over the Cenozoic. Although there is little change in skeleton size or silicification among species with spines, those without spines are larger than species with spines and exhibit a decrease in size toward the present. Increased grazing pressure combined with declining surface silicate availability may have shifted the costs and benefits of silicification, causing divergent responses in skeletal morphology between these different morphological lineages of silicoflagellates over time. We postulate that diminishing Cenozoic surface silicic acid availability may have predisposed large spineless silicoflagellate species to extinction, whereas increased grazing pressure may have contributed to the extinction of all remaining spineless species within the edible size range of grazers.

Interpretations of morphologic radiations and macroevolutionary patterns are dependent on a priori choices of taxonomic and geographic scales of study. The results of disparity analysis at varying taxonomic (species and genus) and geographic (regional, biofacies, and community) scales are examined in a study of Ordovician though Early Silurian crinoids. Using discrete morphologic characters, we examined the disparity of 421 crinoids from 65 Laurentian biofacies. Crinoid disparity differs when analyzed at the regional and biofacies levels. Regardless of fluctuations in regional crinoid disparity, average within-biofacies disparity was static throughout the Ordovician, deviating only during the Silurian because of the proliferation of the morphologically aberrant myelodactylid crinoids. The choice of taxonomic level does not have an effect at the biofacies level. However, at the regional level, the two taxonomic scales (genus and species) can produce different results because of variation in the number of species per genus through time and the amount of morphologic variation within individual genera. Weighting disparity by abundance provides a metric combining morphology and community structure. Average weighted disparity at the community level showed patterns similar to that of the biofacies-level disparity curve, but this metric has a greater degree of variation between biofacies. Biofacies with a low ratio of weighted to unweighted disparity display the distinctive community structure (based on aerosol filtration theory) that is often reported in crinoid assemblages.

We investigate potential microevolutionary mechanisms of phenotypic change in a lineage of brackish-water gastropods from Lake Pannon. The lineage exhibits a threefold increase in body size and a pronounced increase in shell shouldering over a roughly 2.5-Myr interval. We use the stable oxygen isotope profiles of 13 shells to address the question of whether large size is due to more rapid growth or to greater longevity.

Results indicate that larger individuals have significantly greater longevity. Growth rates in large snails are comparable to those of their smaller-bodied ancestors.

Potentially relevant selective advantages of large size include escape from predators, avoidance of resource competition, and increased fecundity. We argue that the first two advantages may have accrued to larger individuals but are not likely to have driven the trend because selection for them would favor more rapid growth rates. Fecundity selection, on the other hand, is readily envisioned in a stable, predictable environment in which the need for early reproduction is relaxed. The evolution of large body size in Lake Pannon molluscs may be comparable to evolution on many islands, where reduced pressure from competition and predation lead to characteristic changes in body size.

Fish scales accumulating in marine laminated sediments can provide a record of population variability of small pelagic fishes. Although some studies have noted signs of scale degradation that could affect estimates of population variability, there are presently no well-developed means to evaluate degradation. We developed several indices as indicators of fish scale preservation in two box-cores that we collected off Pisco (14°S), one at 301 m near the center of the oxygen minimum zone (OMZ), and the other at 201 m near the upper limit of the OMZ. These indices include (1) an index of fish scale integrity (estimate of scale wholeness relative to fragmentation), (2) the fungi-free area of fish scales and vertebrae, (3) the ratio of fish scales to vertebrae (as well as fish scales to vertebrae and bones), and (4) the ratio of whole scales to fragments. We address whether lower numbers of anchovy scales occurring in association with reduced total organic carbon fluxes and higher bottom-water oxygen concentrations are due entirely to lower abundances of anchovy or whether differential preservation of the fish scales in the sediments plays an important role in reduced scale abundances. Comparison of temporal sequences between the two cores provides the means to assess whether there are differences in the preservation of fish scales. The combined indices indicate that the lower numbers of fish scales in the earliest period have been affected by degradation, and to a greater degree in the box-core from 201 meters, which can be subject to higher oxygen concentrations. On the other hand, decadal-scale variations in fish scale abundance within the period of better preservation are unlikely to be caused by degradation. We discuss the utility and drawbacks of different indices of preservation for reconstructing past changes in fish population sizes with fluxes of fish debris and also briefly discuss the utility of these indices to other paleobiological systems.

Evolutionary rates and selection intensities in eight cladistically defined species-level evolutionary sequences of the Middle and Upper Ordovician bryozoan genus Peronopora were calculated for comparison with values published for fossil and living taxa. Calculations were restricted to statistically significant unidirectional segments of anagenetic series to minimize the mixing of different modes, directions, and rates of evolutionary change.

Rates and selection intensities ranged from 10−7 to 10−6 darwins and from 10−6 to 10−5 haldanes. Across characters, the weighted mean evolutionary rate equaled 5.86 × 10−7 darwins and the mean selection intensity was 6.44 × 10−7. Mean rates of 2.15 × 10−6, 4.31 × 10−6, and 8.61 × 10−6 haldanes, and corresponding mean selection intensities equaling 2.39 × 10−6, 4.78 × 10−6, and 9.56 × 10−6, were calculated for generation lengths of 0.5, 1, and 2 years, respectively.

The magnitudes of positive and negative evolutionary rates and selection intensities do not differ statistically, individual characters display no consistent pattern of positive or negative values, and no character complexes were detectable. A mosaic pattern of change occurs across characters in evolutionary sequences.

Eighty percent of analyzed evolutionary series were multispecies lineages. Both individual and mean values provide direct estimates of the rates of evolution within those lineages at the moment of speciation.

Rates of anagenetic evolution in Peronopora were low and similar to published rates for a variety of fossil protists, invertebrates, and vertebrates. However, earlier rate calculations did not isolate the effect of unidirectional anagenesis from that of stasis, random walks, trend reversals, or rate variations. Eight percent of characters in Peronopora produced anagenetic series that were statistically significant, a percentage similar to the 5% calculated in a study of 251 sequences of evolving traits in 53 fossil lineages (Hunt 2007). Stasis and mutation-drift are the most common patterns detectable in the fossil record, although anagenesis remains a potentially important force in shaping the course of both micro- and macroevolution.

High-resolution palynological data sets from shallow marine Triassic-Jurassic (Tr/J) boundary beds of two principal sections in Europe (Hochalplgraben in Austria and St. Audrie's Bay in the United Kingdom) were analyzed to reconstruct changes in vegetation, biodiversity, and climate. In Hochalplgraben, a hardwood gymnosperm forest with conifers and seed ferns is replaced by vegetation with dominant ferns, club mosses and liverworts, which concurs with an increased diversification of spore types during the latest Rhaetian. Multivariate statistical analysis reveals a trend to warmer and wetter conditions across the Tr/J boundary in Hochalplgraben. The vegetation changes in St. Audrie's Bay are markedly different. Here, a mixed gymnosperm forest is replaced by monotonous vegetation consisting mainly of Cheirolepidiaceae (80–100%). This change is caused by a transition to a warmer and more arid climate. The observed diversity decrease in St. Audrie's Bay affirms this interpretation. Although both sections show major vegetation changes, neither of them demonstrates a distinctive floral mass extinction. A compilation of Tr/J boundary sections across the world demonstrates the presence of Cheirolepidiaceae-dominated forests in the Pangaean interior and increases in abundance of spore-producing plants adjacent to the Tethys Ocean. We propose that the non-uniform vegetation changes reflected in the Tr/J palynological records are the result of environmental changes caused by Central Atlantic Magmatic Province volcanism. The increase in greenhouse gases caused a warmer climate and an enhanced thermal contrast between the continent and the seas. Consequently, the monsoon system got stronger and induced a drier continental interior and more intensive rainfall near the margins of the Tethys Ocean.

Mesozoic tooth marks on bone surfaces directly link consumers to fossil assemblage formation. Striated tooth marks are believed to form by theropod denticle contact, and attempts have been made to identify theropod consumers by comparing these striations with denticle widths of contemporaneous taxa. The purpose of this study is to test whether ziphodont theropod consumer characteristics can be accurately identified from striated tooth marks on fossil surfaces. We had three major objectives (1) to experimentally produce striated tooth marks and explain how they form; (2) to determine whether body size characteristics are reflected in denticle widths; and (3) to determine whether denticle characters are accurately transcribed onto bone surfaces in the form of striated tooth marks. We conducted controlled feeding trials with the dental analogue Varanus komodoensis (the Komodo monitor). Goat (Capra hircus) carcasses were introduced to captive, isolated individuals. Striated tooth marks were then identified, and striation width, number, and degree of convergence were recorded for each. Denticle widths and tooth/body size characters were taken from photographs and published accounts of both theropod and V. komodoensis skeletal material, and regressions were compared among and between the two groups. Striated marks tend to be regularly striated with a variable degree of branching, and may co-occur with scores. Striation morphology directly reflects contact between the mesial carina and bone surfaces during the rostral reorientation when defleshing. Denticle width is influenced primarily by tooth size, and correlates well with body size, displaying negative allometry in both groups regardless of taxon or position. When compared, striation widths fall within or below the range of denticle widths extrapolated for similar-sized V. komodoensis individuals. Striation width is directly influenced by the orientation of the carina during feeding, and may underestimate but cannot overestimate denticle width. Although body size can theoretically be estimated solely by a striated tooth mark under ideal circumstances, many caveats should be considered. These include the influence of negative allometry across taxa and throughout ontogeny, the existence of theropods with extreme denticle widths, and the potential for striations to underestimate denticle widths. This method may be useful under specific circumstances, especially for establishing a lower limit body size for potential consumers.

A key question in studies of mass extinctions is whether the extinction was a sudden or gradual event. This question may be addressed by examining the locations of fossil occurrences in a stratigraphic section. However, the fossil record can be consistent with both sudden and gradual extinctions. Rather than being limited to rejecting or not rejecting a particular scenario, ideally we should estimate the range of extinction scenarios that is consistent with the fossil record. In other words, rather than testing the simplified distinction of “sudden versus gradual,” we should be asking, “How gradual?”

In this paper we answer the question “How gradual could the extinction have been?” by developing a confidence interval for the duration of a mass extinction. We define the duration of the extinction as the time or stratigraphic thickness between the first and last taxon to go extinct, which we denote by Δ. For example, we would like to be able to say with 90% confidence that the extinction took place over a duration of 0.3 to 1.1 million years, or 24 to 57 meters of stratigraphic thickness. Our method does not deny the possibility of a truly simultaneous extinction; rather, in this framework, a simultaneous extinction is one whose value of Δ is equal to zero years or meters.

We present an algorithm to derive such estimates and show that it produces valid confidence intervals. We illustrate its use with data from Late Permian ostracodes from Meishan, China, and Late Cretaceous ammonites from Seymour Island, Antarctica.

Large-scale trends in planktonic foraminiferal diversity have so far been based on utilization of synoptic biostratigraphic range charts. Although this approach ensures the taxonomic consistency and quality of the data being used, it takes no formal account of any sampling biases that might exist in the fossil record. We demonstrate that the occurrence data of planktonic foraminifera, as recorded in the primary literature, are strongly biased by sampling. We do this by demonstrating that raw diversity curves derived from the land-based and deep-sea records are strikingly different, but that they each correlate with the intensity of sampling in their respective environments, and thus are ultimately controlled by the structure of the geological record in each setting. Because sampling of the Mesozoic record is best in our land record whereas sampling of the Cenozoic is best in our deep-sea record, we combine the two to generate the best-supported estimates of species and genus diversity over time from these data. We correct for sampling bias using shareholder quorum subsampling and a modeling approach. The data are then transformed to generate a range-through plot of species richness that is compared with two earlier estimates of the diversity history where comparable species-in-bin data can be recovered. No robust statistical correlation is found among the three estimates. Although differences in amplitude are to be expected, differences in the actual shape of the curve are surprising. We conclude that these differences stem from the nature of the data themselves, namely the taxonomic scheme adopted and the taxonomic coverage used.

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.