The composition and ecology of Late Carboniferous tropical, dryland plant communities are described for the first time. The study focuses on a 700-m-thick succession through the Langsettian Joggins Formation. Red bed units (5–110 m thick) bearing isolated pedogenic carbonate nodules occur at fourteen intervals and are interpreted as originating in a seasonally dry, well-drained, alluvial-plain setting characterized, in places, by an anastomosing fluvial geometry. A quantitative quadrat analysis of red bed floral assemblages preserved as compressions, impressions, calcareous permineralizations, and charcoal was undertaken. Cordaites, represented by woody trunks, branches, pith casts, leaves, and seeds, comprise 74% of the red bed floral thanatomass, together with minor pteridosperms and sphenopsids, and rare sigillarian lycopsids. Taphonomic data demonstrate that while fire-prone cordaite-pteridosperm vegetation dominated nearly all seasonally dry floodplain niches, hydrophilic lycopsids and sphenopsids were restricted to riparian settings where water availability was greatest. Calculation of standard diversity indices indicates that growing conditions were generally stressful, consistent with a seasonal environment. The composition of these dryland communities differs markedly from lycopsid-dominated wetland communities known from gray, coal-bearing successions at other intervals in the Joggins Formation. Sequence stratigraphic analysis of the Joggins Formation suggests that dryland communities represent the vegetation of seasonal continental-interior environments in contrast to wetland communities that grew in humid coastal settings. Repeated alternations between continental and coastal settings were caused by tectonically and/or eustatically driven base-level fluctuations that resulted in marine transgressive-regressive rhythms minimally hundreds of kilometers long.

The taphonomy, sedimentology, and paleoecology of a rare peritidal hardground in the Lower Devonian (Lochkovian) Thacher Limestone Member of the Manlius Formation in east-central New York State provides insights into sediment dynamics and modes of life of ancient hard substrate-inhabiting organisms. The hardground occurs near the top of a shallowing-upward carbonate cycle, slightly below desiccation-cracked micritic ribbon limestones. The hard surface developed on a partially exhumed tentaculitid pavement and overlying pelletal calcisiltite; the hardground has a relief of about 2–3 cm and is overlain by a thin siliciclastic mud layer. Tentative correlation of the hardground across a lateral distance of about 35 km perpendicular to depositional strike suggests a very subdued topographic profile for this region and development of an extensive peritidal hardground pavement. Tentaculites gyracanthus occurs in a dense pavement of strongly bimodally aligned shells with an ENE to WSW orientation, parallel to the inferred paleoshoreline. Some specimens also occur vertically embedded, suggesting possible life orientations within firm substrates. The presence of pits around the apertures of these shells suggests scouring effects around the shells burrowed into the substrate. Upper portions of the irregular hardground surface were preferentially colonized by an undescribed small postibulinid edrioasteroid, which may have lived somewhat like acorn barnacles on wave-swept rock platforms. The latter shows a population structure with few juveniles. Although fauna within the Thacher limestone includes leperditian ostracodes, ramose and encrusting bryozoans, Howellella vanuxemi brachiopods, and rare pterioid bivalves, the hardground community is rather limited. This low-diversity assemblage represents an unusual edrioasteroid-dominated hardground community type that persisted from at least Early Ordovician to Late Devonian in peritidal hardgrounds and rockgrounds.

Microbial boundstones from Alaska and Russia yield new insights into the paleoecology of Silurian biotas that inhabited stromatolite reefs. These high-energy reefs were built along the Uralian Seaway in the Late Silurian by a diverse suite of microorganisms in association with accessory metazoans, predominantly sphinctozoan sponges. Within the stromatolite framework, three species of small, solitary, sphinctozoans (aphrosalpingids) encrusted a variety of hard substrates, mostly skeletal remains but also microbial laminae and cavity surfaces. Fossils encrusted by the sponges include the problematic hydroid Fistulella, possible stromatoporoids (recrystallized), crinoids, the possible cyanobacterium Ludlovia, corals, and unidentifiable shelly debris. In addition to the ubiquitous microbial laminae, the sponges, Fistulella, and ?stromatoporoids were less commonly encrusted by Ludlovia, Renalcis, or crinoids.

Well-developed attachment surfaces, including enlarged holdfasts, allowed the sponges to achieve stability on the seafloor after larvae settled randomly on available hard surfaces. A greater incidence of sponge encrustations on Fistulella than on other organisms indicates that some of the sponges may have enjoyed a commensalistic relationship while attached as juveniles to a living substrate. The sponges’ orientation on Fistulella in the sediment suggests that the relationship between the two taxa may have become parasitic, whereby the weight of the sponges caused Fistulella to collapse into the muddy substrate. Recognition of the intimate growth relationships shared by Silurian sphinctozoans, Fistulella, and other organisms expands the fossil record of encrusting sponges, identifies a novel sponge-?hydroid association, and reveals organismal responses to competition for space in mid-Paleozoic microbial reefs.

Tests of benthic foraminifera were analyzed quantitatively in 43 surface sediment samples collected along E–W traverses across the modern isolated carbonate platforms of Glovers Reef (N=14), Lighthouse Reef (N=14), and Turneffe Islands (N=15), offshore Belize, Central America. Water depths of sample stations range from 0 m (beach) to 40 m (fore reef). Each sample was sieved in the size classes 2–1, 1–0.5, 0.5–0.25, and 0.25–0.125 mm (ϕ=1–0, 0–1, 1–2, and 2–3, respectively) and 300 foraminiferal identifications were attempted for each sieve fraction (i.e., 1,200 individuals per sample, totaling 46,003 specimens). Cluster analyses of samples characterized platform environments and distinguished four benthic foraminifera associations. Fore reef samples were characterized by abundant Amphistegina gibbosa and the occurrence of Asterigerina carinata, both rotaliids. In high-energy, marginal-reef areas the encrusting rotaliid Homotrema rubrum predominated. Platform-interior environments were marked by a variety of common taxa, the most common of which include Miliolina such as Archaias angulatus, Quinqueloculina sp., and Triloculina sp., as well as the rotaliid Cribroelphidium poeyanum, the latter indicating low-energy or deep-lagoonal regimes. Diversity, expressed as numbers of identified taxa, appears to be a function of relative degree of circulation. The highest number (147) of taxa was found in the shallow, high-energy platform of Lighthouse Reef, followed by Glovers Reef (78), both of which are open to the Caribbean Sea. The lowest number of taxa (66) occurred in Turneffe Islands where large parts of the platform are characterized by the restricted circulation imposed by dense mangrove growth behind platform margins. The occurrence of tests of common foraminiferal species outside their original habitats, coupled with trends towards smaller grain-sizes and better sorting of tests away from original habitats along parts of the sample traverses, indicates sediment transport across platform margins. In the great majority of samples, however, sediment redeposition did not significantly alter characteristic taxonomic compositions. This result has important implications for the use of benthic foraminifera as facies indicators in fossil carbonate platforms.

Cockroaches are the dominant insects in Carboniferous terrestrial biotas, however, approximately 90% of specimens consist only of isolated wings or wing fragments. This bias has been attributed variously to decay and selective preservation, transport, predation, or collection. The state of preservation of Carboniferous cockroaches was documented in extensive collections from the Westphalian at Writhlington, U.K., where collection bias was minimal. The wings may be intact, or more usually fracture across the veins. Laboratory experiments were conducted on the genera Periplaneta and Blaberus to determine the effects of decay and transport following drowning. The decay experiments revealed a series of disarticulation stages that were reached more rapidly in specimens transported in a circular flume, particularly where some decay had occurred first. The wings detached from the body at a late stage, and separated to varying degrees along the veins, whether or not transport was involved. Experiments on isolated wings showed that breakage occurs across the veins. This pattern is more similar to that observed in the fossils than is the pattern induced by decay in water. The results were compared with observations on predation on these cockroaches and other insects by reptiles and arachnids. Vertebrates such as lizards are indiscriminate feeders and commonly bite through the wings. Arachnids with cheliceral teeth fragment the cuticle but may leave the wings intact. Predation by arachnids followed by breakage provides a more likely explanation than decay and selective preservation for the predominance of isolated wings in the fossil biota.

Leaf size and shape are selected by climate and are strongly correlated with climatic variables. Accordingly, fossil dicotyledonous leaves are considered to be among the most reliable indicators of terrestrial paleoclimates. However, the methods used have much potential for improvement. All currently rely on discrete, usually binary characters, but leaf morphology is better evaluated and more reproducibly measured using continuous variables. Digital leaf measurement offers the possibility of continuous, reproducible variables, with the potential to improve paleoclimate estimates as well as the ecological and evolutionary understanding of leaf form. Results are reported for five variables measured on 238 leaves representing the woody species from three living test floras—two temperate and one humid tropical. The variables are: shape factor (an area:perimeter ratio standardized to a circle); the ratio of feret diameter (diameter if leaf’s area is contained in a circle) to major axis length; the ratio of tooth area to leaf area; tooth count; and tooth count standardized to leaf perimeter. It is well known that increased mean annual temperature is correlated with a high percentage of untoothed species. By extension, increasing temperature is expected to be associated with relatively undissected, more circular leaves (i.e., with high shape factor, low tooth-area:leaf-area ratio, and low tooth count). These trends were observed in the test floras, both between the tropical and the temperate sites and between the two temperate sites. Shape factor was the variable that resolved the three sites most significantly. The five variables show promise for testing on an expanded set of floras sufficient to develop statistical models for paleoclimatic studies.

The Chesapeake Bay impact structure, formed by a comet or meteorite that struck the Virginia continental shelf about 35.5 million years ago, is the focus of an extensive coring project by the U.S. Geological Survey and its cooperators. Organic-walled dinocysts recovered from impact-generated deposits in a deep core inside the 85–90 km-wide crater include welded organic clumps and fused, partially melted and bubbled dinocysts unlike any previously observed. Other observed damage to dinocysts consists of breakage, pitting, and folding in various combinations. The entire marine Cretaceous, Paleocene, and Eocene section that was once present at the site has been excavated and redeposited under extreme conditions that include shock, heat, collapse, tsunamis, and airfall. The preserved dinocysts reflect these conditions and, as products of a known impact, may serve as guides for recognizing impact-related deposits elsewhere. Features that are not unique to impacts, such as breakage and folding, may offer new insights into crater-history studies in general, and to the history of the Chesapeake Bay impact structure in particular. Impact-damaged dinocysts also are found sporadically in post-impact deposits and add to the story of continuing erosion and faulting of crater material.

Exceptionally detailed soft tissues have been identified within the fossilized feces of a large Cretaceous tyrannosaurid. Microscopic cord-like structures in the coprolitic ground mass are visible in thin section and with scanning electron microscopy. The morphology, organization, and context of these structures indicate that they are the fossilized remains of undigested muscle tissue. This unusual discovery indicates specific digestive and taphonomic conditions, including a relatively short gut-residence time, rapid lithification, and minimal diagenetic recrystallization. Rapid burial of the feces probably was facilitated by a flood event on the ancient coastal lowland plain on which the fecal mass was deposited.