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Selective feeding behavior of birds on burrowing irregular spatangoid sea urchins, normally out of reach for such predators, is described. Behavioral observations were made on Carrion Crows (Corvus corone) feeding on spatangoid sea urchins (Echinocardium cordatum) during low tide on two different beaches in Brittany, France. The on-site searching behavior of individuals and flocks of crows on the surf line was observed together with characteristic feeding traces on the sediment. Wound morphologies on collected tests were documented with respect to possible preservation potential and recognition in the fossil record. Documented traces on feeding sites allow for clear identification of predator species and can be linked to observed bird behavior.
The two sites differ in sea urchin size and the resulting predation traces on the echinoid tests. Predation on smaller specimens fragments the test, whereas predation on larger specimens leaves a characteristic wound morphology that is mainly restricted to the aboral side of the test. The wound morphology resulting from test puncturing involves both extensive inter- and intraplate fragmentation but does not completely destroy the tests. These predation traces are compared to other observed records of bird predation on echinoids. The potential for recognition and preservation in the rock record is then discussed.
Cryptic ecosystems of modern and ancient reefs contain substantial amounts of biodiversity. It remains uncertain, however, when and how metazoans adapted to such space. Early Cambrian reef systems witnessed the rise and fall of the earliest known cryptic sessile metazoans. Subsequent Middle Cambrian to Early Ordovician microbial-dominated reefs were generally devoid of true frame-building metazoans, as well as cryptic sessile fauna. The Early Ordovician microbial–siliceous sponge patch reefs of the Dumugol Formation, Korea represent one of the oldest in situ spiculate sponge-bearing cryptic communities exploiting intraskeletal cryptic environments. Less than half of these small millimeter- to centimeter-scale crypts contain low-diversity sessile cryptic assemblages of spiculate sponges and microbialites. The cryptic sponges that attach to the walls of the cavities or on top of internal sediments do not show any skeletal distortion at their contacts with host organisms. The spiculate sponges occur both in open spaces as well as in crypts, and are interpreted to be pioneers of intraskeletal crypts after the death of the cavity-providing organisms. The behavior of occupying transient cryptic habitats is interpreted as an incipient stage of sessile metazoan adaptation to a cryptic space by an opportunistic member of the epibenthic community. This resulted in the extension of the open surface community into crypts which occurred far in advance of the eventual establishment of obligate cryptic forms. The present study provides a critical link for establishing the origin and evolutionary history of early cryptic sessile metazoan adaptation.
Despite many advances in the study of the paleoecology of nautiloids and amonoids, there is still much ground to cover. Study of their encrusters provides information on their paleoecology and taphonomy. In this work the encrusting fauna of abundant material of the nautilid Cymatoceras perstriatum (Steuer) is statistically and taxonomically analyzed in order to infer paleoecological and taphonomic features of the fossil organism. The available material of C. perstriatum consists mainly of phragmocone fragments, with rare cases in which the body chamber was preserved. Nine encrusting taxa, evenly distributed across the nautilid shell (cementing bivalves, serpulids, sabellids, cyclostome bryozoans, and agglutinated foraminifers), were observed in and on C. perstriatum. Of these taxa, oysters are dominant. Encrusters are abundant, with a mean of 12 encrusters per shell. Internal encrustation is common, especially inside the body chamber. The orientation of encrusters is variable. Intensity of encrustation varies, with some shells heavily colonized while others remained clean. The encrusting fauna is interpreted as mainly postmortem. Encrusters are distributed across the shell in a uniform way, lack particular orientation, and are common on the inside of the body chamber, suggesting that encrustation occurred both during necroplanktonic drift and as the shell rested on the sea bottom. A few encrusters were trapped between shell whorls, indicating that less extensive in vivo encrustation took place. Some differences in encrustation parameters were found among localities, corresponding to minor paleoenvironmental differences. Variable encrustation intensity suggests moderate to prolonged duration of exposure of the shells. However, those collected from an exceptional concentration at the El Salado locality were probably buried shortly after death.
Although there is an emerging consensus about global climate patterns during the Cretaceous, details about the climate in Australia at this time are poorly resolved, and estimates for terrestrial climate are scarce. Using Climate Leaf Analysis Multivariate Program (CLAMP) and Bioclimatic Analysis (BA) on plant fossils from the mid- to Upper Cretaceous Winton Formation, central-western Queensland, and working within the context of global paleoclimatic reconstructions and the vertebrate fauna from this unit, we have improved the temporal and geographic resolution of Australia's Cretaceous climate. During the time that the Cenomanian–Turonian portion of the Winton Formation was deposited, the climate in central-western Queensland was warm, wet, and relatively equable. Frost would have been extremely uncommon, if it occurred at all, and much of the year would have been favorable for plant growth. These results are consistent with both previous isotope records for northern Australia, and the fauna of the Winton Formation, and are in keeping with current reconstructions of global Cretaceous climates.
The Ediacaran Lantian and Miaohe biotas (South China) are among the earliest-known fossil assemblages with macroscopic and morphologically complex life forms. Preservation of these macrofossils has been described as carbonaceous compressions in black shales. However, detailed study of their mode of preservation is lacking. We investigated the preservation of unweathered and weathered macrofossils from the Lantian and Miaohe biotas. Our results show that although some Miaohe and Lantian macrofossils are preserved as carbonaceous compressions lacking any enrichment of aluminosilicate clays, many Lantian and Miaohe macrofossils are preserved as carbonaceous compressions associated with densely packed framboidal pyrite, the loss of which leaves clustered cavities in weathered specimens. Pyritization probably did not happen until after extensive degradation of organisms and loss of three-dimensional morphology. Pyrite framboids in Lantian fossils are significantly larger than those in the adjacent matrix, implying different redox conditions.