While all modern crinoids are benthic filter feeders, some fossil species found in low-oxygen Konservat-Lagerstätten probably were pelagic. Pseudoplanktonic forms were mostly attached to driftwood (Seirocrinus, Traumatocrinus, Melocrinus); they had long, rope-like stems and enlarged, permanently splayed filter fans, as required for a passive tow-net function. However, the short and heavily cirrated stem of another driftwood-dweller (Pentacrinites) suggests active filter feeding. If the buoyant lobolith of Scyphocrinites acted as a swim bladder, this crinoid, by the same tow-net principle, could have made use of velocity gradients near a boundary layer. Paradigms are different for stemless forms, whether they floated passively over the bottom (Uintacrinus) or filtrated actively in the water column (Roveacrinids and Saccocoma). Some of the proposed models could not function with the muscular and ligamentary system of modern forms. Nevertheless, they represent distinctive peaks in the adaptive landscape that can be tested using taphonomic, morphological, and evolutionary evidence.

Morphological and environmental taphonomic gradient analysis provides insights into morphological, behavioral, and environmental influences on the preservation of fossil organisms. This paper explores morphological and environmental taphonomic gradients in six crinoid morphotypes (diplobathrids, monobathrids, dichocrinids, platycrinitids, cladids, and flexibles) from three stratigraphic units (the Maynes Creek Formation and the Starrs Cave and “Ollie” Members of the Wassonville Formation) representing distinct depositional environments along an onshore–offshore transect within the Early Mississippian (Kinderhookian) Wassonville Cycle of southeast Iowa. Taphonomic differences in stalk, calyx, and arm disarticulation, calyx compression, and arm orientation were categorized independently and subjected to a non-parametric ranking test with bootstrapping (rather than a parametric approach, due to the non-additive nature of the data analyzed herein) to explore taphonomic patterns. The results suggest that the disarticulation of the stalk, calyx, and arms behave independently, although patterns of arm disarticulation may be influenced by the disarticulation of the calyx. In general, preservational integrity in fossil crinoids appears to be a function of the relative proportion of articular to non-articular surface area, skeletal innovations, tissue type and properties, survival response behavior, and thickness and rapidity of burial. Furthermore, these results demonstrate a general decrease in preservational integrity from onshore to offshore environments in the Wassonville Cycle and that sedimentation dynamics associated with episodic events are more influential than background deposition in determining preservation in fossil Lagerstätten. The methodology employed herein also could be used effectively to identify morphological, behavioral, and environmental taphonomic influences on other fossil organisms.

A mathematical/computer model was constructed to explore the effects of changes in rates of taphonomic loss, sediment reworking, and burial on time-averaging in fossil deposits. Using a Monte Carlo algorithm, the main controlling variables were thickness of the taphonomically active zone (TAZ; the interval where shells are likely to be destroyed), depth of final burial (DFB; below which shells can no longer be reworked into the TAZ), and burial rate. Output included both the decay trajectory of shells above the DFB as well as the frequency distribution of post-mortem shell ages at final burial (entry into the fossil record). Output was justified ergodically as equivalent to time-averaging in a deposit. The model helps to illuminate several important concepts for time-averaging. For example, it clarifies that DFB and TAZ need not be coincident. In fact, the mechanism of shell sequestering (allowing shells to remain in a safe zone between the TAZ and DFB) as a means of shell survival for 100s or 1000s of years after death requires that DFB be below TAZ. In addition, the model demonstrates the use of a shell's expected residence times above TAZ and DFB as a means of comparing time-averaging from different settings. Lastly, the model focuses attention on the potential variability in time-averaging among fossil deposits created under identical conditions due to stochastic variation. These results indicate the useful role of models in developing a process-based understanding of the nature and controls of time-averaging in fossil accumulations.

Following extensive Late Triassic coral-constructed reefs and the aftermath of the Triassic–Jurassic mass extinction, Early Jurassic buildups are rare and constructed primarily by bivalves. The Pliensbachian exhibits a radiation of aberrant pterioid bivalves, the “Lithiotis” bivalves, which include: Lithiotis problematica, Cochlearites loppianus, Gervilleioperna sp., Mytiloperna sp., and Lithioperna scutata. These large bivalves are ubiquitous in shallow, nearshore tropical waters and restricted to the Early Jurassic recovery interval. Field and thin-section observations indicate a strong zonation of “Lithiotis” bivalves in shallow nearshore environments. Gervilleioperna and Mytiloperna are restricted to tidal-flat and inner-platform facies. Lithioperna scutata is found throughout the lagoonal subtidal facies and even in some low-oxygen environments. Lithiotis and Cochlearites construct buildups in subtidal facies, and both taxa exhibit discordant valves—one valve is converted into a pedestal, the other is an opercular valve. The largest buildups attain lengths over 60 m and thicknesses of 3–5 m. It is proposed that the reef-building bivalves Lithiotis problematica and Cochlearites loppianus filled the relatively empty ecological niche of reef-building during the Early Jurassic (Lias), only to be replaced by their predecessors, the scleractinian corals, by the Middle Jurassic. The other “Lithiotis” bivalves (Lithioperna scutata, Mytiloperna, and Gervilleioperna sp.) lived in restricted lagoonal environments with possible fluctuating salinity on Early Jurassic (Liassic) carbonate shelves. Lithiotis and Cochlearites, in contrast to many oysters, do not orient their commissure planes in a single direction. Instead, these two buildup-constructing genera radiate out from a central bouquet, possibly maximizing exposure to light rather than current. Due to their growth habit, extensive calcification, presumed oligotrophic environment, and pseudocoloniality, these two genera may have harbored photosymbionts. Severe environmental changes and associated unusual seawater chemistry of the protracted Early Jurassic recovery may have led to suppressed coral-reef growth and the rapid radiation of reef-building bivalves.

Sandstone pillars in the Lower Jurassic eolian strata of the Clarens Formation are concentrated in clusters, with up to four pillars within 25 m² in two localities in the Tuli Basin of northern South Africa and southern Zimbabwe. The pillars are generally vertical, have a preserved height of up to 3.3 m, and are elliptical in plan view. Pillars are grouped into two styles of architecture: those with oriented elliptical shapes and side buttresses, and those less well oriented with a smooth outer wall, internal open spaces, and vertical shafts cutting the pillar. The long axes of the elliptical pillars are generally oriented to the north. Northwards-oriented side buttresses also are associated with some of the pillars. The internal architecture of the pillars is characterized by intense bioturbation with two different burrowing styles. Type 1 burrows are composed of a network of randomly oriented, anastomosing sandstone-filled tubes, 0.3 to 0.8 cm in diameter. Type 2 burrows are rare, north-south oriented, and have a smaller diameter. Other associated features are back-filled tubes, open, vertical shafts, and open spaces between the interior and exterior of the pillars.

The pillars are interpreted as fossilized termite nests. Type 1 burrows are interpreted as termite passageways within the nest. Type 2 burrows may be related to invading ants. Back-filled burrows may be a result of either beetle predation on resident termites or backfilling by termites themselves. The strong north-south orientations are comparable with modern-day nest architecture of magnetic termites in northern Australia, where nest-orientation is related to cooling. The orientations and features reported here are interpreted to be modified for the high latitudes proposed for the Lower Jurassic Clarens desert. Complex nest architecture preserved in the Clarens Formation suggests that advanced eusocial behavior and ability to construct large nests had appeared in African termites by the Early Jurassic.

This study details occurrences of Teredolites ichnocoenoses from modern bay-margin settings in Willapa Bay, Washington. In particular, the paper scrutinizes in situ log-grounds from two intertidal zones situated immediately seaward of low-lying, supratidal, forested marshlands that are fed by small streams. Vestiges of remnant marshes and streams are preserved on intertidal flats as in-situ roots, broken stumps, strewn logs, abundant organic detritus, and organic sandy mud. Xylic material and organic sediment were deposited in the supratidal marshes: tide and wave processes truncated the swamps, exposing in situ tree-root networks and the lowermost supratidal sediments. Stream and swamp deposits overlie and incise older Pleistocene strata. Both units are overlain by discontinuous, modern intertidal deposits.

The intertidally exposed stumps and logs support a diverse community of animal and plant life. Boring organisms, encrusters, and refugium seekers are found on and within the xylic substrates. Some encrusting animals and all of the boring fauna produce traces that are comparable to ichnofossils reported by palichnologists. Wood-boring traces reported in this study are similar morphologically to the ichnogenera Caulostrepsis, Entobia, Meandropolydora, Psilonichnus, Rogerella, Teredolites, Thalassinoides, and Trypanites. Most of these ichnogenera have not been reported from rock-record examples of the Teredolites ichnofacies.

The stratigraphic and environmental significance of the reported (modern) locales is consistent with previous studies that associate Teredolites ichnofacies with base-level rise in marginal-marine environments. At Willapa Bay, bored xylic media form a coeval surface with adjacent, burrowed firmgrounds as well as softgrounds.

Six egg-filled depressions discovered in the Upper Cretaceous Anacleto Formation (Campanian) of Patagonia, Argentina, and interpreted as dinosaur nests, provide the only known evidence of titanosaurid sauropod nest construction. These nest trace fossils show truncation of sedimentary structures as well as differences in texture between the host substrate and in-filling sediment. Titanosaurid sauropods excavated and laid eggs in open nests rather than burying clutches in sediment. In addition, this paper establishes criteria for definitive recognition of excavated nests in the stratigraphic record.

A remarkable encounter between two Cretaceous mosasaurs of the same species and a sick or recently dead nautiloid (Argonautilus catarinae Sundberg) is recorded. It is possible that the mosasaur was training its young to attack shelled cephalopods. This is the first recorded attack by two mosasaurs on a nautiloid in the eastern Pacific Ocean, although ammonites preyed upon by mosasaurs are known from the west coast of North America.