The brachiopod genus Sowerbyella is an abundant component of many Ordovician paleocommunities of the eastern United States. Five successive populations from a limited geographic region in central Kentucky were tested for the response of brachial valve size and shape to alterations in paleoenvironmental conditions. The populations span the interval from Chatfieldian to Maysvillian (M5-C3), including the majority of an Ecological-Evolutionary (EE) subunit previously described for brachiopods in this area. A marked diminution in size occurs subsequent to maximum deepening in the M5 sequence, and is persistent for the remainder of the interval sampled. Shape follows a different pattern, with similar changes occurring each time deep-water facies occur in the area. Discriminant analysis shows a clear separation between populations sampled from nearshore and offshore facies along discriminant function 1. End member populations in both nearshore and offshore populations diverge significantly on discriminant function 2 over periods of 6.5 and 3.5 my, respectively, the longer period spanning the majority of the EE subunit. This contrasts with stasis in valve shape in Devonian brachiopods over an EE subunit of similar duration, but is in accordance with previous findings of less community-level stability in Ordovician EE subunits when compared with their Devonian counterparts.

The recent discovery of abundant trace fossils in the Lower Devonian Muth Formation (Pin Valley, Spiti, northern India) contributes to our understanding of the diversity and distribution of Early Devonian arthropod activities in a marginal marine environment. The ichnoassemblage consists of abundant Palmichnium antarcticum and Diplichnites gouldi with rarer Diplopodichnus biformis, Taenidium barretti, Didymaulichnus cf. lyelli, Didymaulyponomos cf. rowei, Selenichnites isp., and vertical burrows of unclear affinity. The abundance of trackways enables the documentation of size- and gait-variations among producers of single trackway ichnotaxa. The paleoenvironment of the Muth Formation is interpreted as a barrier island system. Four different facies associations are recognized; arthropod trackways occur only in beach to coastal dune environments (facies association 2). Most of the Palmichnium and Diplichnites trackways are interpreted as subaerial. The abundance and frequently sub-parallel orientation of the Palmichnium antarcticum trackways, predominantly perpendicular to the paleocoastline, suggest that stylonurid eurypterids, which are interpreted as their producer, were migrating across the shoreline and climbing up slip faces of barrier island dunes. The similarity of this ichnofauna to others in marginal marine environments of similar age in Antarctica and Australia allows the identification of a recurrent Lower Devonian ichnocoenosis around the margins of eastern Gondwana.

A scratch-marked burrow complex with multiple branching tunnels and terminal chambers was excavated from the Lower Triassic Driekoppen Formation, northeastern Free State, South Africa. The burrow complex is attributed to the therapsid Trirachodon, based on disarticulated but fairly complete skulls and skeletons of at least 20 individuals recovered from a nearby, less well-preserved system.

The entrance shaft slopes gently downward and is characterized by a bilobate floor and vaulted roof. The bilobate floor has a central flat-topped scratch-marked ridge flanked by two smooth grooves, each approximately the width of the occupant. At deeper levels, tunnels display tighter lateral curvatures, progressively decreasing burrow diameters, variable orientations, and some right angle branches. Burrow floors at these levels are vaguely bilobate. Distally, burrows flatten dorso-ventrally, becoming wedge-shaped before they terminate.

These complexes are interpreted as colonial dwelling structures. Numerous branching tunnels and terminal chambers, as well as an enlarged entrance, constitute an unrealistically high expenditure of energy for a single occupant. Furthermore, the bilobate floor is atypical of a single occupant system. Absence of scratch marks in the depressions reflects the regular locomotory activity of Trirachodon. In single-occupant burrows, the center of the structure is worn. The bilobate floor with preferential wear along the flanks suggests routine travel on one side of the tunnel or the other, as multiple occupants moved past one another during daily activity.

The presence of numerous fossilized Trirachodon individuals in terminal chambers at the second locality supports multiple cohabitation. There, the uniform sedimentary fill and vertebrate taphonomy suggest that the occupants were drowned in a flash flood. Vertebrate remains are absent at the first locality, where sediment influx was incremental, permitting the escape of burrow occupants.

This constitutes the earliest record of multiple cohabitation of a burrow complex by tetrapods. The Trirachodon (Cynodontia) of the Early Triassic Cynognathus Zone probably displayed complex social behaviors previously regarded to be restricted to the mammals of the Cenozoic. This fossorial behavior may have been for thermoregulation, protection from predators, sites of reproduction, and the rearing of young.

Shells were broken experimentally by compressive and compactional loading to determine the best predictors of shell strength among a number of morphologic (length, width, height, weight, thickness) and taphonomic (presence of a drillhole, exposure to seawater, point contacts of shells) features. Compressive strength of fresh (Mercenaria mercenaria, Mytilus edulis) and beach-collected (Anadara ovalis) shells was measured by placing a single valve flat on a surface and compressing it. Compactional strength of beach-collected Mulinia lateralis shells was measured by placing isolated valves and shell layers in fine sand and compacting the sand and shell mixture.

The most effective predictor of compressive shell strength of fresh shells was thickness; it was significant for all three species and it easily can be interpreted as an obvious defense against a shell-crushing predator. Size was comparatively less important. The presence of a drillhole reduced shell strength significantly, and strong correlations of weight and shell strength among beach collected Anadara shells may reflect different states of degradation of the original amounts of organic matrix. Supporting this conclusion is the observation that immersion in seawater for seven weeks significantly decreased shell strength of organic-rich shells (Mytilus), but did not affect shell strength of organic-poor shells (Mercenaria). Fracture patterns varied considerably between and within taxa. The breakage pattern of Anadara and Mercenaria shells generally consisted of a set of fractures radiating from the point of loading to the shell margin, including even the thick dorsal margin. The breakage pattern in Mytilus usually consisted of one fracture only, which did not extend from the point of loading but whose path was highly unpredictable. In compaction experiments with beach-collected Mulinia lateralis, the most important factor determining whether or how a shell would break was the contact between shells. Isolated shells, both drilled and undrilled, did not break. Among drilled valves in simulated shell beds, only 26 percent of the fragments > 2 mm fractured through the drillhole.

The oldest known fossil charcoal, to date, is herein reported from a Late Devonian (Famennian 2c) fluvial deposit in the Catskill Formation of north-central Pennsylvania. The charcoal was found in an abandoned channel setting in association with abundant well-preserved macrofossil plant remains of Archaeopteris, Rhacophyton, cormose lycopsids, Gillespiea, and cupulate and acupulate gymnosperms. Detailed anatomical preservation of the charcoal combined with its paleoecological setting suggests that in this landscape, mostly Rhacophyton burned, perhaps in association with an interpreted annual dry season. Alternating wet and dry seasons are indicated by the presence of paleovertisols. The fossil site where the charcoal was found also has yielded terrestrial arthropods, numerous fishes, and two early tetrapods.

A unique aquatic arthropod Konservat Lagerstätte occurs in lacustrine-derived carbonate concretions within the Miocene Barstow Formation of southern California. Faunal elements are primarily aquatic, salinity-tolerant, autochthonous predaceous diving beetle larvae, fly larvae and pupae, mosquito and thrip larvae, and fairy shrimp. Three-dimensional preservation of soft tissues is via replacement by silica-based minerals as well as calcite, celestite, apatite, and gypsum.

The fauna occurs in three beds (each 1–3 m thick) within an approximately 100 m sequence of predominantly microlaminated mudstone deposited in a saline-alkaline lacustrine environment. Faunal composition is consistent between sites and concretion beds, but faunal composition and diversity changed significantly during lake history, corresponding to differences in brine chemistry as well as preservational facies, resulting from the shift toward a more nearshore regime. The changes in lake chemistry and subsequent changes in fauna indicate lake shallowing as well as regional and global climate change towards greater aridity during the Miocene that also is coincident with regional uplift.

Infaunal bivalve shells were extracted from sediment cores taken in shallow seas off Phuket, South Thailand, and were scored for four types of taphonomic degradation to assess the effect that different types of bioturbation have on the preservation of such bioclasts. This gravel-sized fraction of off-reef biogenic (bivalve) sediments showed variation in the extent of degradation, depending on whether it was found in an area bioturbated by callianassid or alpheid shrimps. Cores taken in the alpheid area have a higher proportion of grains with poorly defined shape and ornamentation, a loss of surface luster and high levels of microbioerosion. In contrast, those from the callianassid area have a higher proportion of shiny, sharply defined fragments and a lower level of microbioerosion than those from the alpheid area. It is concluded that the different nature of bioturbation in the two areas accounts for the difference in preservation. In working the sediment, callianassids bury the gravel fraction, while alpheids repeatedly bring it to the sediment surface, thus exposing it to higher levels of physical and microbiological erosion. The shrimps' activities result in a difference in preservation potential of fine and coarse sediments, and this taphonomic bias will affect taphofacies interpretation. Rapid burial of gravel by callianassids also has implications for time-averaging, as a shell fragment's condition is more indicative of its residence time at the surface-water interface than its age.