A new fault-associated paleokarst and cave fill has been discovered in north-central Illinois, emplaced in Ordovician limestones. The paleokarst preserves many original solution features, such as oriented grooves, pendants, and half tubes. Many of the ancient cave passages have rounded bottoms and flat roofs. Together these suggest that the original elliptical, phreatic cave passages grew upward by paragenesis, in which the floor of the cave is protected from dissolution by the presence of sediment, while the ceiling of the cave grows upward by dissolution. The fill is dated as Moscovian (Middle Pennsylvanian) based on palynological data and can be correlated with the Tradewater Formation. The fills are composed of a fining-upward sequence of relatively unindurated clastic sediments that contain well-preserved plant fossils, most notably voltzialean conifer and cordaite remains, representative of vegetation living in well-drained areas. Many of the macrofossils are fragmentary but charcoalified and, along with the megaspores, are uncompressed and preserve exceptional morphological and anatomical data. The presence of abundant charcoal in the fills, as well as diagnostic polycyclic aromatic hydrocarbons, indicates significant wildfire activity in this area during this interval.

The hypothesis of coordinated stasis (CS) holds that taxa within ecological communities show a pattern of persistence over geologic time (faunal stability). This hypothesis has been examined by looking for evidence of stasis and change in paleocommunity structure based on patterns of taxon abundances obtained from bulk samples of fossil assemblages. Community structure based on taxon counts is often investigated using distance-based clustering methods, employing Analysis of Similarity (ANOSIM) or other multivariate statistical tools. We propose a new method for analyzing trends in community structure by viewing taxon counts from bulk samples as a time series and assess stasis and change based on a probabilistic assessment of the continuity of the species distribution patterns. In this flexible approach, taxon counts from samples ordered in time or space (or grouped by a geologically informed hypothesis) are modeled as a sequence of multinomial or Bernoulli outcomes drawn from an underlying ecological distribution. The optimal model of community structure may then be chosen from a set of hypotheses about those distributions, based on Akaike's Information Criterion, an information-theoretic measure of fit that penalizes likelihood of fitting the data with the number of parameters needed to attain the fit. CS is the model in which the underlying probabilities for each sample are constant across different samples. In other words, the most likely scenario is that all samples are drawn from the same underlying taxon abundance distribution. We propose that this approach is a powerful and flexible method to statistically assess CS, as well as other hypotheses about community structure, and we demonstrate this method using paleoecological data from the literature.

We present pollen and stable isotope (δ¹³C, δ¹⁸O, δ¹⁵N) data from a ∼4 m core (TNF-1) of primarily mangrove peat taken from Turneffe Atoll, Belize. Radiocarbon (accelerator mass spectrometry) dates show that the record represents ca. 5000 years of sediment accumulation. Vegetation composition varied between dominant mangroves (primarily Rhizophora mangle) and Chenopodiaceae-Amaranthaceae, most likely Salicornia bigelovii. The pollen data, along with inferences from stable isotope analyses of bulk peat and fossil leaf fragments, indicate that marked environmental changes occurred at this location over the past ca. 5000 years. There was a transition between ca. 4100 and 2900 cal yr BP, from vegetation dominated by relatively tall mangroves (R. mangle) to one dominated by Chenopodiaceae-Amaranthaceae and then Myrica, most likely wax myrtle (M. cerifera). These changes bracket a period centered at ca. 3500 calibrated years before present, where there is a peak in the δ¹⁸O of mangrove leaf fragments. This timing corresponds with other paleoenvironmental records of climate drying in Central America and increases the geographic and habitat scope (i.e., mangrove habitat) of records documenting these changes. Interpretations of shifts in mangrove habitat, however, require consideration of additional environmental influences, including changes in groundwater hydrology and relative inputs of seawater and freshwater (i.e., precipitation) during the Holocene.

The oldest known Jurassic coral reef is exposed in the Ardèche region of southern France. This reef site, consisting of at least three reefal bodies, is of early Hettangian age and thus immediately postdates the end-Triassic mass extinction, which is well known for its catastrophic effect on reef building. Bulk carbonate carbon isotopes of the limestones below the reef are likely to record environmental perturbations subsequent to the mass extinction. The main reef is surprisingly well developed (20 m in thickness, 200 m in lateral extent) and composed of at least four genera and six species of corals—not only holdover genera from the Triassic, but also one newly evolved genus (Phacelophyllia), contributed to reef construction. Just like their latest Triassic counterparts, the reef is dominated by phaceloid corals with a considerable contribution of microbialite. The reef predates similarly well developed structures by almost ten million years. The shelf setting of the reef renders it unlikely that refuges around oceanic islands are needed to explain survival of corals across the end-Triassic mass extinction.

An Early Jurassic tetrapod tracksite in the upper Elliot Formation at Moyeni, southern Lesotho, displays a variety of trackways attributed to large- and medium-sized theropod (Neotrisauropus-type) and ornithischian (Moyenisauropus-type) dinosaurs, basal crurotarsal archosaurs (chirotheroid-type), and a short-legged basal tetrapod (Episcopopus-type). The tracks are on a low-angle pointbar and are buried with loessic floodplain fine-grained sediment. Calcic paleosols indicate a warm semiarid climate. Many of the footprints were imprinted through an algal mat in a water-margin setting. Convergence of several trackways toward a single point suggests repeated visits to drink or cross the river. One of the two large Moyenisauropus-type trackways has a narrow gauge that suggests an upright, parasagittal gait, whereas the other shows changes in gauge width, stance, and posture as it proceeded up the pointbar slope. At least three resting traces with manus, metatarsal, and tail impressions attributable to the Moyenisauropus-type ornithischian are also preserved. Discovery of two manus-pes pairs of chirotheroid-type footprints in the Moyeni section highlights a mismatch between the body-fossil and trace-fossil records. Chirotheroid tracks are generally thought to be restricted to the Triassic, and their discovery at the Moyeni tracksite compounds the problem of where to place the Triassic-Jurassic boundary in this succession. Three possible scenarios could explain the occurrence of chirotheroid-type tracks at Moyeni: (1) the tracksite is Late Triassic in age; (2) the chirotheroid tracks were made by archosaurs other than basal crurotarsans; (3) the tracks are correctly identified and the age of the Moyeni section is correctly assigned, but the inferred range of chirotheroid-type tracks is incorrect. We suggest that the latter two are the most likely explanations.

Cyanobacterial calcification is promoted by CO₂-concentrating mechanisms (CCMs) developed in response to photosynthetic carbon limitation. Changes in atmospheric composition (CO₂ fall, O₂ rise) near the Devonian–Mississippian transition (ca. 360 Ma) were sufficiently large to induce CCMs in cyanobacteria. Cyanobacterial sheath calcification significantly increased during the Mississippian, ca. 325–355 Ma. It is proposed that these atmospheric changes triggered cyanobacteria to induce CCMs—previously developed during a large CO₂ decline in the Proterozoic—and that this promoted their calcification. CCMs in phytoplankton stimulate primary productivity by increasing photosynthetic efficiency and ameliorating carbon limitation. Phytoplankton community restructuring in favor of groups that possessed effective CCMs but had poor body-fossil records, such as picoplanktic cyanobacteria, could account for Late Devonian acritarch decline and the subsequent apparent scarcity of phytoplankton in the late Paleozoic (the so-called phytoplankton blackout). This is supported by biomarkers indicating an increase in cyanobacteria at the Devonian–Mississippian transition and by carbon isotope values and black shale deposition that, despite acritarch decline, reflect increased primary productivity. The Mississippian episode of cyanobacterial calcification was relatively short lived. Calcification declined ca. 325 Ma, before the end of the Mississippian, as a continued decline in CO₂ lowered seawater carbonate saturation. The induction of cyanobacterial CCMs, triggered by Late Devonian change to a relatively low CO₂ and high O₂ atmosphere, has probably persisted to the present day, but well-developed calcification in marine cyanobacteria has been restricted to intervals of elevated carbonate saturation state.

A bathymetric transect ranging from coral habitats down to a 1500-m-deep basin in the Red Sea and Gulf of Aden allows us to test the sensitivity of taphofacies to depth and sediment grain size in a tropical to subtropical carbonate basin, to partition variation in brachiopod preservation into extrinsic (environmental) and intrinsic (shell-specific) components, and to quantify residual variation that remains unexplained by such components. Factoring out environmental effects, thin-shelled, organic-poor rhynchonellids are more affected by fragmentation and fine-scale surface alteration and degrade rapidly compared to the more frequently bioeroded, organic-rich terebratulids. The negative role of shell organic content is overridden by shell thickness, and preservation rates of organic-rich brachiopods are enhanced by syndepositional cement precipitation. Environmental trends in preservation are confounded by shell-specific factors that account for 16% of variation in preservation: the amounts of multivariate variation explained by environment increase from 29% using combined brachiopod preservation to 46% using terebratulid preservation. Environmental sensitivity of taphofacies is driven by present-day variation in environment but also by past Pleistocene conditions. First, reduction in fragmentation, encrustation, and bioerosion is consistent with a decrease in light penetration and primary productivity. Second, brachiopods are coated with aragonite cement in basinal sites with lithified oozes and microbial carbonates that originated during the last glacial maximum when syndepositional aragonite cementation was favored by high temperature and salinity, and thus can be affected by millennial-scale time averaging. Skeletal preservation rates are thus not in steady state over the duration of time averaging, and the bathymetric reduction in alteration is partly related to past conditions amenable to cement precipitation.

The Middle–Upper Ordovician represents a significant period in the early evolution of fishes. During this time, many of the major lineages, including jawless and putative jawed taxa, made their first appearance in the fossil record, marking a series of diversification events. As a number of studies have focused on the habitat of Laurentian fish during this interval, work has been undertaken at a number of known Gondwanan vertebrate localities in order to provide new perspectives on the ecological preferences of early fish from the Southern Hemisphere. Ichnological and sedimentological data collated from these localities enable reconstructions of the habitats of a number of Ordovician fish, most notably those of the arandaspid-bearing successions of the Anzaldo Formation of Bolivia, the Stairway Sandstone of central Australia, and the Amdeh Formation of Oman, from which articulated or macroscopic fragmentary fossil remains are recorded. These data indicate that the arandaspids were constrained to very shallow marine habitats and prone to seasonal influxes of freshwater and terrigenous sediment. It is proposed that this narrow paleoecological range may be used as a prospecting tool to search for other Ordovician vertebrate-bearing horizons.