Conspicuous centers of biodiversity are frequently attributed to local conditions that promote speciation or resistance to extinction, but recent diversification studies indicate this mode of explanation might not be very general, so it may be fruitful to revisit the role of dispersal in concentrating biodiversity. Here we consider the processes underlying the marine diversity hotspot in the Indo-West Pacific among comatulid crinoids, suspension-feeding echinoderms conspicuous on modern tropical reefs. We used ancestral-range reconstruction on a phylogeny of extant crinoids, assembled a new occurrence database of fossil comatulids and interrogated it with probabilistic preservational models, and developed a morphological character matrix to estimate the relationships among living and fossil comatulids. Ancestral-range reconstruction on a phylogeny of extant comatulids recovers an origin outside the Indo-Pacific and elevated dispersal into it. A new occurrence database records the comatulid clade spreading out gradually from origin in the Early Jurassic of the West Tethys. Comatulids do not appear in their modern hotspot until the Oligocene, and taphonomic analyses show these results cannot be explained solely as a result of inadequate sampling in Asia and Oceania. Finally, phylogenetic analyses demonstrate that deeply nested crown-group comatulids had originated before the clade became well established in the East Tethys, implying many independent dispersals into the modern hotspot. These consilient results suggest a biodiversity hotspot that owes its existence to dispersals out of the ancient West Tethys rather than to elevated in situ diversification.

For paleobiologists interested in extinct carnivorous reptiles, publication of Walter Auffenberg's (1981) 13–month field study of the Komodo dragon (Varanus komodoensis), or ora, as he prefers to call it, provides a useful portrait of a reptile as the top predator of a terrestrial community. A great deal of information about the ora's habitat utilization, activity patterns, diet, social behavior, and reproduction is presented.

Recent studies have shown that modes of evolution, namely directional trend, random walk, and stasis, vary across morphologic traits and over the geographic range of a taxon. If so, is it possible that our interpretation of evolutionary modes is actually driven by our selection of traits in a study? In an attempt to answer this question, we have restudied the middle Miocene planktonic foraminifera Fohsella lineage, an iconic example of gradual morphologic evolution. In contrast to previous studies that have focused on the gross morphology as embodied by the edge view of tests, we analyze here multiple phenotypic traits chosen because their biologic and ecologic significance is well understood in living populations. We find that traits in the lineage did not evolve in concert. The timing and geographic pattern of changes in shape, coiling direction, size, and ecology were different. The evolution of this lineage is a mosaic combination of different evolutionary modes for different traits. We suggest that overemphasis on the evolution of some single trait, such as the edge-view outline, from narrow geographic ranges has significantly underestimated the dynamic evolutionary history of this group.

Certain taxa are noticeably common within collections, widely distributed, and frequently long-lived. We have examined these dominant genera as compared with rarer genera, with a focus on their temporal histories. Using occurrence data from the Paleobiology Database, we determined which genera belonging to six target groups ranked among the most common within each of 49 temporal bins based on occurrences. The turnover among these dominant taxa from bin to bin was then determined for each of these groups, and all six groups when pooled. Although dominant genera are only a small fraction of all genera, the patterns of turnover mimic those seen in much larger compilations of total biodiversity. We also found that differences in patterns of turnover at the top ranks among the higher taxa reflect previously documented comparison of overall turnover among these classes. Both dominant and nondominant genera exhibit, on average, symmetrical patterns of rise and fall between first and last appearances. Dominant genera rarely begin at high ranks, but nevertheless tend to be more common when they first appear than nondominant genera. Moreover, dominant genera rarely are in the top 20 when they last appear, but still typically occupy more localities than nondominant genera occupy in their last interval. The mechanism(s) that produce dominant genera remain unclear. Nearly half of dominant genera are the type genus of a family or subfamily. This is consistent with a simple model of morphological and phylogenetic diversification and sampling.

As the most recent time in Earth history when global temperatures were warmer than at present, the peak of the last interglacial (Marine Isotope Substage [MIS] 5e; ~120,000 years ago) can serve as a pre-anthropogenic baseline for a warmer near-future world. Here we use a new compilation of 22 fossil localities in California that have been reliably dated to MIS 5e to establish baseline expectations for contemporary bivalve species movements by identifying and analyzing bivalve species with “extralimital” ranges, that is, species that occupied the California region during MIS 5e but are now restricted to adjacent regions. We find that 15% of species (n = 142) found in MIS 5e localities have extralimital ranges and currently occupy warmer waters to the south of the California region. The majority of extralimital occurrences occur in paleo-embayments, suggesting that these sheltered habitats were more suitable habitats for warm-water species than exposed coasts during the MIS 5e. We further find that extralimital species now tend to occur in cooler, more seasonally productive coastal waters and to occupy more offshore islands when compared with the broader species pool immediately south of California. These findings suggest that high dispersal potential and preexisting tolerances to environmental conditions similar to California's comparatively cool and seasonally productive environments may have enabled extralimital bivalves to colonize the California region during MIS 5e.

Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

Few methods exist that put a posterior probability on the hypothesis that a thing is gone forever given its sighting history. A recently proposed Bayesian method is highly accurate but aggressive, generating many near-zero or near-one probabilities of extinction. Here I explore a Bayesian method called the agnostic equation that makes radically different assumptions and is much more conservative. The method assumes that the overall prior probability of extinction is 50% and that slices of the prior are exponentially distributed across the time series. The conditional probability of the data given survival is based on a simple, long-known combinatorial expression that captures the chance all presences would fall at random before or within the last sighting’s interval (L) given that they could fall anywhere. The same equation is used to compute the conditional probability given extinction at the start of each interval i, that is, the chance that all sightings would fall before or within L given that none could equal or postdate i. The conditional probability is zero for all hypothesized extinction intervals through L. Bayes’s theorem is then used to compute the posterior extinction probability. It is noted that recycling the mean posterior for a population as a prior improves the method’s accuracy. The agnostic equation differs from an earlier, related one, because it explicitly includes a term to represent the hypothesis of survival, and it therefore does not assume that the species has necessarily gone extinct within the sampling window. Simulations demonstrate that the posterior extinction probabilities are highly accurate when considered as a suite but individually indecisive, rarely approaching one. This property is advantageous whenever inferring extinction would have dangerous consequences. The agnostic method is therefore advocated in cases where conservative estimates are desired.

Corallite sizes reflect a continuum in the efficacy of photosymbiosis in colonial reef corals, with smaller corallite sizes generally associated with higher autotrophy. Using a large compilation of reef-coral traits and corallite diameters as a proxy, we test here the hypothesis that photosymbiotic efficacy has increased over the evolutionary history of scleractinian corals. To gain a more comprehensive understanding of the evolutionary versus ecological patterns of corallite sizes of reef corals, we used three analytical methods: (1) occurrences-weighted within-bin analyses as a proxy for abundance or ecological dominance to depict ecological patterns; (2) unweighted range-through analyses; and (3) unweighted sampled-in-bin analyses to represent diversity in terms of taxonomic richness, enabling us to trace evolutionary patterns. By-genus, range-through analysis indicates a slightly positive trend of corallite sizes toward the Recent. However, the occurrences-weighted assessment shows a pronounced negative trend of corallite sizes in colonial corals since the Mesozoic. Random walk and directional evolution are both statistically supported to explain this long-term decrease. A driven trend is evolutionarily plausible, giving reef corals a selective advantage in the oligotrophic environments they largely occupy today.

Rates of speciation and extinction are often linked to many ecological factors, traits (emergent and nonemergent) such as environmental tolerance, body size, feeding type, and geographic range. Marine gastropods in particular have been used to examine the role of larval dispersal in speciation. However, relatively few studies have been conducted placing larval modes in species-level phylogenetic context. Those that have, have not incorporated fossil data, while landmark macroevolutionary studies on fossil clades have not considered both phylogenetic context and net speciation (speciation–extinction) rates. This study utilizes Eocene volutid Volutospina species from the U.S. Gulf Coastal Plain and the Hampshire Basin, U.K., to explore the relationships among larval mode, geographic range, and duration. Based on the phylogeny of these Volutospina, we calculated speciation and extinction rates in order to compare the macroevolutionary effects of larval mode. Species with planktotrophic larvae had a median duration of 9.7 Myr, which compared significantly to 4.7 Myr for those with non-planktotrophic larvae. Larval mode did not significantly factor into geographic-range size, but U.S. and U.K. species do differ, indicating a locality-specific component to maximum geographic-range size. Non-planktotrophs (NPTs)were absent among the Volutospina species during the Paleocene–early Eocene. The relative proportions of NPTs increased in the early middle Eocene, and the late Eocene was characterized by disappearance of planktotrophs (PTs). The pattern of observed lineage diversity shows an increasing preponderance of NPTs; however, this is clearly driven by a dramatic extinction of PTs, rather than higher NPT speciation rates during the late Eocene. This study adds nuance to paleontology's understanding of the macroevolutionary consequences of larval mode.

The Late Triassic conodont species Mockina ex gr. carinata and Mockina ex gr. englandi were exceptionally prevalent among the marine fauna of the Panthalassan realm from the middle Norian through to the Rhaetian. Leading into the complete extinction of conodonts near the Triassic/Jurassic boundary, a significant turnover event occurred in conodont fauna across the Norian/Rhaetian boundary (NRB), with the pectiniform elements of common Rhaetian genera from Tethys exhibiting minimal or absent platforms. This intergeneric trend of platform reduction is not as evident in Panthalassa, where these genera are very rare, but morphometric analyses of M. ex gr. carinata and M. ex gr. englandi specimens from across the Canadian Cordillera demonstrate that comparable shifts in morphology occurred intraspecifically in Panthalassa across the NRB, confirming the global extent of these trends. Pectiniform elements of M. ex gr. carinata display a sequential reduction of platform width from the middle Norian to late Norian to Rhaetian, whereas pectiniform elements of M. ex gr. englandi display a reduction of platform width only from the late Norian to Rhaetian. Specimens of both species that have a mid-platform length to breadth ratio greater than 3:1 are restricted to the Rhaetian. Specimens from the Kennecott Point section on Haida Gwaii, British Columbia, demonstrate that this morphological shift occurred somewhat later than other biostratigraphic proxies for the NRB. The global trend of platform width reduction in many conodont pectiniform elements may reflect a change in primary diet away from hard food sources, perhaps suggesting some degree of carbonate biomineralization suppression beginning around the NRB. This interpretation would support CO2 outgassing as the causal mechanism of the environmental disturbance at the NRB and identify the NRB as a significant turning point for Late Triassic ecosystems, marking the beginning of a protracted, multiphase end-Triassic mass extinction.

The frequency of biotic invasions in modern ecosystems is increasing due to global trade moving taxa outside their native ranges and climate change facilitating establishment of taxa in previously inhospitable regions. Thus, developing a holistic understanding of biotic invasions and how they impact ecosystems over different timescales—from annual to geologic timescales—is vital. Herein we examine a geologically brief invasion event, the Clarksville Phase of the Richmondian Invasion. Prior analyses have established general ecological and evolutionary patterns across the entire Richmondian Invasion, but recent sequence stratigraphic refinement makes analysis of individual invasion pulses possible for the first time. We examine biotic change across the Clarksville Phase and identify invasion impacts on diversity, paleocommunity composition, and niche stability. Invader arrival and success was strongly linked to increased propagule pressure facilitated by sea-level changes. Invaders initially colonized deep subtidal environments and then moved offshore facilitated by rapid niche evolution during the invasion interval. Invasive taxa that attained the largest population sizes belonged to previously underutilized ecological guilds. Overall, the introduction of the invasive taxa resulted in increased diversity that was maintained into the postinvasion interval accompanied by a change in community composition in which the invaders became dominant paleocommunity members. Combined, these analyses document a biotic invasion facilitated by climate change that increased local diversity through invaders occupying underutilized ecospace and competition-related niche contraction on millennial timescales. Developing a long-term perspective to accompany shorter-term studies facilitates predicting the long-term impacts of modern invasions and creating better-informed policies and practices.

With Jack Sepkoski's sudden death from heart failure on May 1, 1999, paleontology lost one of its most important figures. In his 25–year career, Jack published more than 70 research articles, 15 of them in this journal, and an equal number of reviews, commentaries, and abstracts. He co-edited Paleobiology (1983–86), received the Schuchert Award (1983), and served as President of the Paleontological Society (1995–96). In 1997, he was elected to the Polish Academy of Sciences and in the same year received the Medal of the University of Helsinki. Further recognition would surely have followed but for his untimely death.

Ecophenotypic variation in populations is driven by differences in environmental variables. In marine environments, ecophenotypic variation may be caused by differences in hydrodynamic conditions, substrate type, water depth, temperature, salinity, oxygen concentration, and habitat heterogeneity, among others. Instances of ecophenotypic variation in modern and fossil settings are common, but little is known about the influences of time averaging and spatial averaging on their preservation. Here we examine the shell morphology of two adjacent populations, both live collected and death assemblages, of the infaunal, suspension-feeding, intertidal bivalve Leukoma staminea from the well-studied Argyle Creek and Argyle Lagoon locations on San Juan Island, Washington. Individuals in the low-energy lagoon are free to burrow in the fine-grained substrate, while clams in the high-energy creek are precluded from burrowing in the rocky channel. Our results demonstrate variation in size and shape between the adjacent habitats. Lagoon clams are larger, more disk-shaped, and have relatively larger siphons than their creek counterparts, which are smaller, more spherical in shape, and have a relatively shallower pallial sinus. This ecophenotypy is preserved among death assemblages, although with generally greater variation due to time averaging and shell transport. Our interpretation is that ecophenotypic variation, in this case, is induced by differing hydrodynamic regimes and substrate types, cumulatively resulting in physiological trade-offs diverting resources from feeding and respiration to stability and shell strength, all of which have the potential to be preserved in the fossil record.

Trace fossils record foraging behaviors, the search for resources in patchy environments, of animals in the rock record. Quantification of the strength, density, and nature of foraging behaviors enables the investigation of how these may have changed through time. Here, we present a novel approach to explore such patterns using spatial point process analyses to quantify the scale and strength of ichnofossil spatial distributions on horizontal bedding planes. To demonstrate the utility of this approach, we use two samples from the terminal Ediacaran Shibantan Member in South China (between 551 and 543 Ma) and the early Cambrian Nagaur Sandstone in northwestern India (between 539 and 509 Ma). We find that ichnotaxa on both surfaces exhibited significant nonhomogeneous lateral patterns, with distinct levels of heterogeneity exhibited by different types of trace fossils. In the Shibantan, two ichnotaxa show evidence for mutual positive aggregation over a shared resource, suggesting the ability to focus on optimal resource areas. Trace fossils from the Nagaur Sandstone exhibit more sophisticated foraging behavior, with greater niche differentiation. Critically, mark correlation functions highlight significant spatial autocorrelation of trace fossil orientations, demonstrating the greater ability of these Cambrian tracemakers to focus on optimal patches. Despite potential limitations, these analyses hint at changes in the development and optimization of foraging at the Ediacaran/Cambrian transition and highlight the potential of spatial point process analysis to tease apart subtle differences in behavior in the trace fossil record.

With 14 species recorded, the Miocene La Venta bat fauna is the most diverse bat paleocommunity in South America. It includes the oldest plant-visiting bat in the New World and some of the earliest representatives of the extant families Phyllostomidae, Thyropteridae, and Noctilionidae. La Venta's Notonycteris magdalenensis is an extinct member of the subfamily Phyllostominae, a group of modern Neotropical animalivorous bats, and is commonly included in studies of the evolution of Neotropical bats, but aspects of its biology remain unclear. In this study, we used multivariate dental topography analysis (DTA) to reconstruct the diet of N. magdalenensis by quantitatively comparing measures of molar complexity with those of 25 modern noctilionoid species representing all major dietary habits in bats. We found clear differences in molar complexity between dietary guilds, indicating that DTA is potentially an informative tool to study bat ecomorphology. Our results suggest N. magdalenensis was probably an omnivore or insectivore, rather than a carnivore like its modern relatives Chrotopterus auritus and Vampyrum spectrum. Also, we reconstructed the body mass of N. magdalenensis to be ~95 g, larger than most insectivorous bats, but smaller than the largest carnivorous bat (V. spectrum). Our results confirm that N. magdalenensis was not a specialized carnivore. It remains to be demonstrated that the specialized carnivory ecological niche was occupied by the same lineage of phyllostomines from at least the middle Miocene. Combining our diet and body-mass reconstructions, we suggest that N. magdalenensis exhibits morphological pre-adaptations crucial for the evolution of specialized carnivory.

Conodont elements have high rates of morphological evolution, but the drivers of this disparity are debated. Positive allometric relationships between dimensions of food-processing surfaces and entire P1 elements have been used to argue that these elements performed mechanical digestion. If involved in food processing, the surface of the element should grow at a rate proportional to the increase in energy requirements of the animal. This inference of function relies on the assumption that the energy requirements of the animal grew faster (≅ mass0.75) than the tooth area (≅ mass0.67). We reevaluate this assumption based on metabolic rates across animals and calculate the allometry in platform-bearing P1 elements of Late Triassic co-occurring taxa, Metapolygnathus communisti and Epigondolella rigoi, using 3D models of ontogenetic series. Positive allometry is found in platform and element dimensions in both species, supporting a grasping-tooth hypothesis, based on the assumption that metabolic rate in conodonts scaled with body mass similarly to that in fish and ectotherms. We also calculate the curvature of the P1 platform surface using the Dirichlet normal energy (DNE) as a proxy for diet. DNE values increase with body mass, supporting the assumption that conodont metabolic rates increased faster than mass0.67. We finally find that adults in both taxa differ in their food bases, which supports trophic diversification as an important driver of the remarkable disparity of conodont elements.