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Integrative research including facies characterization, ichnological composition and foraminifer analysis has been conducted on cores from Site U1385 of the IODP Expedition 339 to evaluate the incidence of Marine Isotope Stage (MIS) 12 and MIS 11 on deep-sea environmental changes. Four color facies groups have been differentiated, showing variable transitions between them (bioturbated, gradual and sharp contacts). Trace fossil assemblage, assigned to the Zoophycos ichnofacies, consists of light and dark filled structures, with Alcyonidiopsis, Chondrites, Nereites, Planolites, Spirophyton, Thalassinoides, Thalassinoides-like structures, and Zoophycos. A deep-sea multi-tiered trace fossil community is interpreted, revealing predominance of well-oxygenated bottom and pore-waters, as well as abundance of food in the sediment for macrobenthic tracemaker community. Changes in environmental parameters are interpreted to be associated with significant variations in trace fossil distribution according to the differentiated intervals (A to M). Benthic foraminifer concentration in the sediments and variations of the planktonic foraminifer assemblages suggest significant changes in surface productivity and food supply to the sea floor since the ending of MIS 13 to the end of MIS 11 that could be correlated with the registered changes in facies and trace fossil assemblages. At the end of MIS 13 values of annual export productivity were very low, that together with the presence of light-color sediments and the continuous presence of light Planolites and Thalassinoides, reveal lower organic carbon flux to the bottom and high oxygen conditions (interval A). Afterwards the organic matter supply increased rapidly and remained very high until Termination V, determining an eutrophic environment, expressed by high benthic foraminifer accumulation rates, and reduced availability of oxygen, that correlate with the record of Spirophyton and Zoophycos, and the presence of Chondrites, observed in intervals B and D. Lower benthic foraminifer accumulation rates during MIS 11 suggest an oligotrophic environment at the bottom consistent with lower inputs of organic carbon, associated with high oxygen content of bottom waters that agrees with the lighter color of the sediments as well as by the continuous presence of light Planolites and Thalassinoides in the differentiated interval M. The evolution of the macrobenthic tracemaker community during MIS 12 and MIS 11 responds to major changes in bottom water ventilation probably linked to variations in deep water (North Atlantic) thermohaline circulation, determining variations in oxygen and food availability.

At least four styles of complex behavior are recorded in trace fossils: (1) Intricate, programmed behavior that is recorded in complex trace fossils, such as Spirophyton and Zoophycos. (2) Behavior that is complex in consisting of multiple simple behaviors performed by a single organism, as indicated by one trace fossil merging into another (compound trace fossils). (3) Behavior in which an animal constructs both complex and simple structures, as demonstrated by direct connection between the two structures. (4) Two scales of complex behavior reflected in multiple specimens of one trace fossil arranged in a pattern to produce a distinctive, larger-scale structure. Until recently complex trace fossils (e.g. Zoophycos) alone have served as proxies for complex behavior. Recognition and reconstruction of diverse modes of behavioral complexity allow more biological information to be gleaned from the trace fossil record.

Leperditiid and beyrichiid ostracodes in marine margin deposits of the Devonian Catskill magnafacies of New York State document brackish conditions in what were previously considered freshwater floodplain deposits. The very low diversity ostracode fauna (two species) includes an abundance of anomalously thin-shelled individuals that belong to the genera Leperditia ? and Welleria . This ostracode fauna is one of the oldest reported from brackish water in the stratigraphic record, and it documents the early ecological radiation of ostracodes into waters of reduced salinity. Associated fossils, including the bivalve Archanodon and the conchostracan Euestheria , have been considered to be freshwater forms, partly because of their occurrence in these rocks that were assumed to be fluvial in origin. Nearly everywhere, however, the ostracodes are associated with cosmine-bearing fish fragments, lingulid brachiopods, and the feeding trace Spirophyton , which have a marine or brackish-water affiliation. The presence of open carapaces on bedding planes as well as adults and several instar stages of each ostracode species indicate lack of postmortem transport. At least one ostracode-bearing mudstone contains the mineral amesite; associated calcareous mudrocks interbedded with these units contain symmetrical ripple marks, mudcracks, and locally intense manganese-oxide staining. Collectively, these features indicate extreme environmental conditions and suggest highly variable salinities in shallow pools or embayments along the paleoshoreline. The presence of brackish-water faunas, perhaps estuarine in origin, indicates an aspect of the diversity of Devonian paleoenvironments along this portion of the Catskill deltaic complex not previously recognized. The deposits are widespread, although not ubiquitous, within thick sequences of fine-grained flood-basin deposits. Because most previous paleoecological studies of fossils from these rocks assumed the sediments to be of freshwater origin, the new interpretation of brackish-water communities presented here could have important implications for understanding the evolution of early terrestrial organisms. For example, some animals may have evolved in brackish estuarine environments rather than in freshwater rivers as assumed in previous studies. Recognition of this brackish facies elsewhere in the Catskill succession will not only aid future identification of paleoshoreline position but may also help clarify whether early terrestrial organisms made the transition to land via brackish or freshwater environments.

The aim of this work is to describe and interpret well preserved Lower Carboniferous Zoophycos from Belgium. They are compared to other similar Zoophycos studied by the same authors from Jurassic and Lower Cretaceous from France. Finally, some general conclusions are proposed which are also supported by data from the literature. Lower Carboniferous deposits in the Tournai area (Belgium) are characterized by the abundance of well preserved Zoophycos previously described as Spirophyton. The upper unit of the Tournai Limestones, the Antoing Formation (Ivorian), was studied here. It is usually made of fine-grained carbonate mudstones or wackestones, occasionally passing to packstones. The paleoenvironmental setting is typical of the deep part of a carbonate ramp, with occasional storm deposition. The general organization of Tournaisian Zoophycos is the same as that seen in Jurassic and Lower Cretaceous specimens of southeastern France: a single open tube and a lamina with an upward helicoidal growth. This similar organization suggests a similar ethology for the corresponding tracemaker considered as a deep sediment feeder with an efficient mining program. The more simple morphology of the Tournaisian burrow system suggests that this program is less complex than for the Mesozoic equivalents. Zoophycos is best developed in fine-grained sediments. In opposition to the Jurassic examples of southeastern France, this sediment must have still been soft, never slightly firm, when colonized. In addition, the abundance of Zoophycos at the top of locally frequent storm deposits could indicate a fairly opportunistic behavior. Considering the above mentioned assumption, the increasing complexity of the morphology and the modification of the related ethology, a possible evolution from an r-strategy to a K-strategy is suggested for the Zoophycos-creating organism during geologic time.