The species-characteristic combination of morphological characters that depend on an environmental gradient can be used to determine the frequency distribution of the species along the gradient. All functional characters of a phylogenetically closely related species group demonstrate overlapping intervals along an environmental gradient. The gradual change in character composition along the gradient is called a morphocoenocline. Based on transfer functions, a morphocoenocline can be used for gradient values estimation (proxies) in the historical or geological past, similar to a coenocline based on species (democoenocline).

Transforming the empirical frequency distributions of characters and character states along the gradient to probability distributions enables calculating a probability density function of any subset of characters of the morphocoenocline. Because a species is distinguished by a specific combination of characters that are functionally related to the gradient, the distribution of this species along the gradient can be estimated using the probability density functions of combined characters. Assuming “functional uniformitarianism” this estimation can be extended into the geologic past for all fossil species, as long as their functional characters are homologous or analogous to those found among Recent forms. When a morphocoenocline is based on a compound environmental gradient, such as depth, which represents a combination of single environmental factors, the gradient estimation reflects only a specific combination of single factors.

A morphocoenocline for test characters of symbiont-bearing benthic foraminifera from the West Pacific was established for water depth. This compound environmental gradient represents tropical open sea conditions at a slope where the water is highly transparent (low inorganic nutrients and sediment input). Depth distributions based on probability density functions were compared with empirical distributions to prove the accuracy of this method, and were used to estimate the depth distribution of other living species that had not been included in the determination of the morphocoenocline because they live in other regions. The method was also applied to fossil species that are closely related to Recent forms (Nummulites, Assilina from the Eocene) and to fossil species that are more distantly related to the living species (Orbitoides from the Upper Cretaceous).

Cowen and Stockton (1978) seem to agree with one of our main conclusions (Mark and Flessa 1977, p. 21): “Problems of ecological classification, taxonomic consistency and temporal and geographic scale need resolution before evolutionary equilibrium models can be more than heuristic.” Their discussion points out other difficulties with hypotheses of evolutionary equilibrium and with tests for their validity.

Vertebrates and cephalochordates generate significant quantities of lactic acid during intense exercise. This is associated with heavy reliance on anaerobic metabolism for intramuscular ATP formation. We report here exercise-related generation of lactate in the appendicularian Oiko-pleura longicauda (Tunicata: Appendicularia) and in the brittle star Ophioderma panamensis (Echinodermata: Ophiuroidea). The chordate-wide distribution of this pattern of activity metabolism suggests its presence in Early Paleozoic prochordates. The presence of the chordate pattern of activity physiology in Ophioderma suggests that very early (Ediacarian?) deuterostomes may also have generated lactate during intense exercise. Further investigation of activity physiology in other echinoderms is warranted.

Stratigraphic paleobiology uses a modern understanding of the construction of the stratigraphic record—from beds to depositional sequences to sedimentary basins—to interpret patterns and guide sampling strategies in the fossil record. Over the past 25 years, its principles have been established primarily through forward numerical modeling, originally in shallow-marine systems and more recently in nonmarine systems. Predictions of these models have been tested through outcrop-scale and basin-scale field studies, which have also revealed new insights. At multi-basin and global scales, understanding the joint development of the biotic and sedimentary records has come largely from macrostratigraphy, the analysis of gap-bound packages of sedimentary rock. Here, we present recent advances in six major areas of stratigraphic paleobiology, including critical tests in the Po Plain of Italy, mass extinctions and recoveries, contrasts of shallow-marine and nonmarine systems, the interrelationships of habitats and stratigraphic architecture, large-scale stratigraphic architecture, and the assembly of regional ecosystems. We highlight the potential for future research that applies stratigraphic paleobiological concepts to studies of climate change, geochemistry, phylogenetics, and the large-scale structure of the fossil record. We conclude with the need for more stratigraphic thinking in paleobiology.

Understanding current and future biodiversity responses to changing climate is pivotal as anthropogenic climate change continues. This understanding is complicated by the multitude of available metrics to quantify dynamics and by biased sampling protocols. Here, we investigate the impact of sampling protocol strategies using a data-rich fossil record to calculate effective diversity using Hill numbers for the first time on Paleogene planktonic foraminifera. We sample 22,830 individual tests, in two different size classes, across a 7 Myr time slice of the middle Eocene featuring a major transient warming event, the middle Eocene climatic optimum (MECO; ~40 Ma), at study sites in the midlatitude North Atlantic. Using generalized additive models, we investigate community responses to climatic fluctuations. After correcting for any effects of fossil fragmentation, we show a peak in generic diversity in the early and middle stages of the MECO as well as divergent trajectories between the typical size-selected community (>180 μm) and a broader assemblage, including smaller genera (>63 μm). Assemblages featuring smaller genera are more resilient to the climatic fluctuations of the MECO than those assemblages that feature only larger genera, maintaining their community structure at the reference Hill numbers for Shannon's and Simpson's indices. These results raise fundamental questions about how communities respond to climate excursions. In addition, our results emphasize the need to design studies with the aim of collecting the most inclusive data possible to allow detection of community changes and determine which species are likely to dominate future environments.

Drilling predation is a common reason for mortality of benthic mollusks but did not become common until the late Mesozoic. The scarcity of drill holes in the early Mesozoic fossil record limits our understanding of the evolution of drilling behavior and its role on shaping early Mesozoic marine communities. Here, we use drilling traces on several bivalve taxa from the Lower Jurassic (Pliensbachian) marine soft-bottom deposits in northern Germany to explore behavioral patterns of the predator (e.g., site selectivity, change in site-selective behavior with age). Although none of the known drilling gastropod groups existed in the Pliensbachian, including the studied localities, the drill-hole morphology suggests that the predator was probably a gastropod. The ecology and identity of the target prey changes from a diverse array of epifaunal to infaunal taxa in older deposits to focus on a single, large, deep infaunal taxon, Gresslya intermedia, in younger deposits, suggesting a potential trend in prey selectivity over time. Spatial point pattern analysis of traces (SPPAT) reveals an aggregated pattern of drill holes on Gresslya, suggesting strong selectivity in drill-hole location. Drilling on a single large infaunal taxon and site selectivity are common patterns also inferred previously from the drilled deep infaunal Eothyasira from the Pliensbachian of southern Germany. In addition to the scarcity of predators, the highly specialized behavior of the early drilling predators, including strong prey selectivity in terms of prey identity and life habit, can partly explain the rarity of the early Mesozoic drill holes.

Two simple plate parameters, P, the height of the plate measured normal to the plate base, and α, the angle formed between the plate base and the adjacent edge of that plate, serve to model crinoid aboral cup morphology. With few exceptions, the resulting theoretical geometries replicate the range of calyx morphology observed in the natural world. A theoretical morphospace, derived from these parameters, encompasses both the realized and unrealized possibilities of crinoid calyx construction. The model and the associated morphospace demonstrate that the occupation of crinoid cup space varies non-uniformly in time and space and suggest that functional constraints and/or ecological habit are important components of the distribution of cup morphology in time.

A traditional typological approach to taxonomy often does not adequately account for intraspecific variation and can result in taxonomic oversplitting. For many groups, including ammonoids of the Placenticeras genus, intraspecific variation documented in recent studies (e.g., ontogenetic changes, sexual dimorphism, polymorphism) challenges the historic proliferation of species names. Here, we used a population approach to taxonomy and quantitatively evaluated morphometric variation in a sample of Late Cretaceous (Santonian–Campanian) Placenticeras from Alabama and adjacent counties.

We used linear mixed models (LMMs) to characterize how morphological variables scale with conch size across the sample, exploiting mixed longitudinal data to evaluate individual variation in growth and inform interpretations of multivariate analyses. Extended LMMs incorporating geological formation evaluated morphological changes through time. Principal component analysis and clustering analysis were then used to evaluate the number of distinct clusters that emerged in multivariate morphospace independent of previous taxon name assignments.

Discontinuous scaling relationships and distinct clusters in multivariate space suggest sexual dimorphism characterized by differences in adult size and, secondarily, shape. Previous Stantonoceras and Placenticeras assignments broadly overlap in our morphospace, failing to justify this historic distinction (as sexual dimorphs or as genera or subgenera). Placenticeras conch morphology and ornament placement changed through time, suggesting a potential utility for coarse (stage-level) biostratigraphy. However, temporal changes were not associated with distinct clusters in morphospace, and our data fail to support the plethora of reported species names. As few as one or two (successive) species may be present in our sample (representing 130 years of collection effort). In addition to highlighting the need for a significant taxonomic revision of the Placenticeras genus, this study demonstrates the utility of LMMs for distinguishing between different sources of morphological variation, improving interpretations of morphospace under a population approach to taxonomy, and maximizing the amount of ontogenetic information that can be obtained nondestructively.

A dramatic shift from carbonate-rich to chert-rich marine strata occurred during the Permian and is frequently attributed to the increased activity of siliceous sponges and their biosiliceous sedimentation. The first-order ecologic consequences of this transition, if any, remain opaque. We analyze fossil occurrence data from the Phosphoria Basin (western North America) to test whether the presence of siliceous sponges, which are correlated with basin-wide chert strata, influenced the recruitment of benthic fauna. Using published lithologic descriptions, we categorized fossil collections by formation, facies, and lithology and used these data to code detrended correspondence analysis and nonmetric multidimensional scaling ordinations. We also analyzed the clustering of taxa into faunal units termed biofacies.

Results from these analyses indicate that fossil collections occurring in chert and carbonate are closely associated in faunal composition and community structure. These collections preferentially occur in the inner- to mid-ramp facies, in agreement with previous studies. Although largely similar in composition, collections of chert and carbonate lithology exhibit differences in the frequency and abundance of accessory brachiopod taxa (e.g., Composita and Hustedia), possibly a result of greater biosiliceous sedimentary input.

I. Many believe that sooner or later molecular biology will mechanistically provide the precise genotypic basis for phenotypic change. This in turn will provide the basis for attacking several major evolutionary problems posed by paleontology, including the following:

1. — There are approximately 30 phylum-level taxa in the animal kingdom, and yet in the “fast” version of evolutionary history, many of then arose 600 Myr ago in a very short period of time (of order <30 Myr). In terms of basic body plan and inferred ecology, these sponges, clams, arthropods, etc. were seemingly as different then as they are now. It is as though the rate of morphologic change was much more rapid during that interval than during the nearly 600 Myr since then. Even the “slow” version of evolutionary history (which allows for an additional unfossilized record of about 500 Myr) demands an answer to what has controlled the development of major evolutionary Bauplans.

2. — Some morphologic traits (though probably not individual species) persist for immense periods of geologic time—the general shape of the horseshoe crab, for example, or the bristle patterns of taxa of meiofaunal “worms” living among sand grains. What is the developmental rationale for these persistent traits? In short, what is the molecular basis for genetic and morphologic canalization?

3. — The general pattern of species specialization proceeds unabated overtime, but every once in a while the developmental clock is reset. Organisms which are sexually mature but with simplified or “primitive” morphology arise de novo, and these lineages then form the stock of unspecialized forms from which future specializations evolve. What is the molecular basis for resetting the developmental clock?

4. — Reproductive isolation may arise “accidentally” through genomic changes unrelated to changes in the local environment. To the extent this is true, speciation has a largely accidental component. Knowledge of the rate and type of genomic change is critical for an evaluation of this idea.

Integration between phylogenetic systematics and paleontological data has proved to be an effective method for identifying periods that lack fossil evidence in the evolutionary history of clades. In this study we aim to analyze whether there is any correlation between various ecomorphological variables and the duration of these underrepresented portions of lineages, which we call ghost lineages for simplicity, in ruminants. Analyses within phylogenetic (Generalized Estimating Equations) and non-phylogenetic (ANOVAs and Pearson correlations) frameworks were performed on the whole phylogeny of this suborder of Cetartiodactyla (Mammalia). This is the first time ghost lineages are focused in this way. To test the robustness of our data, we compared the magnitude of ghost lineages among different continents and among phylogenies pruned at different ages (4, 8, 12, 16, and 20 Ma). Differences in mean ghost lineage were not significantly related to either geographic or temporal factors. Our results indicate that the proportion of the known fossil record in ruminants appears to be influenced by the preservation potential of the bone remains in different environments. Furthermore, large geographical ranges of species increase the likelihood of preservation.