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The mammalian fauna of the so-called chalicothere pit, lower Eocene basal Arshanto Formation, Erlian Basin, Inner Mongolia, comprises at least eight species, of which Litolophus gobiensis is the most abundant large mammal, represented by at least 24 individuals and 1252 specimens of skulls, mandibles, and postcranial elements. The Litolophus assemblage is dominated by young adult individuals, while juveniles are under-represented, an age profile that conforms to the theoretical model of a catastrophic assemblage. The assemblage is characterized by skeletal elements with limited weathering and moderate disarticulation, and a paucity of isolated teeth, suggesting that the carcasses were probably exposed to the environment after death for only a brief period. Fluvial activity was prominent and had sufficient energy to align most long bones of Litolophus (∼153.1 kg in mean value) in a NNE-SSW direction. Most elements in the assemblage belong to Voorhies Groups II and/or III, while elements of Group I are rare. In addition, the Litolophus carcasses were evidently disturbed by predators and/or scavengers before burial. Damage to the ends of long bones is unevenly distributed, probably reflecting both preferential feeding behavior by predators or scavengers and the timing of epiphyseal fusion in Litolophus. The scarcity of juvenile individuals can also partially be attributed to predation or scavenging; however, it seems unlikely that the chalicothere pit was a scavenger den.
Herein we report an analysis of an Oxfordian (Upper Jurassic) paleoreef located in the Swiss Jura Mountains. The paleoreef is located in a Middle Oxfordian transitional interval in which sedimentation switched from marl-dominated to carbonate-dominated deposits. The paleoecosystem is composed of four successive fossil communities characterized by microsolenid corals and organisms that specialized in suspension feeding. Carbon isotopes measured from echinoid spine carbonates exhibit a positive trend from ∼1.0‰ to 2.5‰ in δ13C values from the base to the top of the paleoreef. Comparison of δ13C curves with organic matter and belemnites shows different patterns not compatible with a global variation of the carbon cycle. Similar fossil assemblages and stratigraphic sequences identical in age are found along the continental margin of the Tethys–Atlantic Ocean. This biolithostratigraphic succession corresponds to increasing δ13C values of marine and biogenic carbonates, to the transition from marl-dominated to carbonate-dominated deposits, and to the development of carbonate platforms, which together suggest a change in the carbon cycling regime within the Tethys–Atlantic Ocean system.
Ophiomorpha group trace fossils occur abundantly in a range of Eocene-aged deep-marine environments of deposition in the Basque basin, northern Spain. The morphology and dimensions of these trace fossils, observed in off-axis submarine lobe deposits, are discussed. The reported specimens display a highly organized and systematic burrowing behavior preserved on turbidite bed bases that display interconnecting Y-shaped (hexagonal-polygonal) morphologies. This observation, together with the cross-cutting relationship with tool marks, suggests construction of postdepositional agrichnial burrow networks. The networks probably harvested microbes that broke down cellulose-based organic matter providing an exploitable nutrient source for crustacean trace makers of Ophiomorpha. Therefore, the Ophiomorpha group–related traces discussed herein are postulated to represent an ethological response to changes in deep marine environmental conditions driven by global climate change during the early Paleogene, including the early Eocene hyperthermal events.
The Furongian Orsten-type fossil Lagerstätte in the Alum Shale Formation of Sweden is an extraordinary deposit known for its detailed, three-dimensional preservation of the soft parts of small animal carcasses which have been replaced by calcium phosphate and occur in organic-rich nodular limestone. The exact cause and mechanism of this unusual fossil preservation, however, particularly the source of phosphorus, which plays a key role, remains unknown. Detailed observation in the Agnostus pisiformis Zone in the Backeborg section (Kinnekulle district) reveals that the phosphatocopine crustaceans showing soft-part preservation occur only in a few thin (<3 cm) layers containing abundant fecal pellets (pellet beds). Development of cross lamination suggests that the pellet beds were formed by low density sediment-gravity flow. Orsten-type preservation has been attributed to high phosphate levels in global marine waters during the Cambrian period; however, wavelength-dispersive X-ray and X-ray diffractometry analyses reveal that the Orsten limestones and surrounding shale were generally poor in phosphorus, which was mostly concentrated in the fecal pellets. The small animal carcasses preserved in such deposits were phosphatized during early diagenesis owing to the high local phosphorus levels of the accumulated fecal pellets. Searches for such cesspool-type preservation may yield further discoveries of Orsten-type fossil Lagerstätten in other strata of various ages.
Macroids provide a stable and three-dimensional habitat to which seaweeds, coralline red algae and invertebrates can attach. Some of these organisms act as borers and leave traces which are preservable in the fossil material and are potentially paleoenvironmental indicators in palaeoenvironmental analysis. Although most investigations of ichnocoenoses have focused on shallow-water settings, boring organisms such as sponges, suspension-feeding bivalves, polychaetes and annelid worms may also act in deeper fore-reef settings. We describe for the first time the ichnocoenosis of Entobia, Gastrochaenolites, Trypanites and Maeandropolydora from deep water reef settings. This ichnocoenosis, commonly so far identified only in shallow-marine rockgrounds and hardgrounds and in firm, compacted, but unlithified substrates, occurs in living macroid assemblages ranging in water depth from 61 to 105 m, southwest of Kikai-jima, northern Ryukyu Islands (southern Japan). Importantly, this discovery strengthens the hypothesis that this ichnocoenosis can be utilized as a palaeoenvironmental indicator of low sedimentation rate and high turbulence rather than as a palaeobathymetric proxy.
The mode of preservation dictates the preparation technique that will yield the most information about a specific fossil. Such considerations also include the time needed for preparation and degree of specimen destruction. Nowhere is this more clearly demonstrated than in the history of Carboniferous coal ball and chert research where the standard technique shifted from thin section to acetate peel preparations many years ago. Despite the ease and efficiency of acetate peels and the exponential increase in information they have provided about Carboniferous plants and ecosystems, we argue that there has been a concomitant decrease in attention directed at the microbial life also preserved in many cherts and coal balls. With this paper we endorse the use of thin sections, rather than peels, in order to study accurately the morphology and diversity of late Paleozoic microbial life.
In the Wadden Sea, shell repair frequency in the small gastropod Hydrobia ulvae varied from 2.8% to 11.2%. On tidal flats of the Mok, a small bay on the island of Texel, The Netherlands, in the Wadden Sea, higher repair frequencies varying from 11.8% to 41.8% were measured. The shelduck, Tadorna tadorna, a predator of Hydrobia, occurs here in densities far above average densities for the Wadden Sea. Shelducks ingest their prey whole and crush the shells of H. ulvae internally. Live specimens of H. ulvae were collected from shelduck feces. Those with intact operculum and only a damaged outer aperture rim of the shell were kept in aquaria and repaired their shell rapidly. This indicates that predators that ingest shelled prey can also leave repair scars on shells. Such scars, however, are indistinguishable from those resulting from failed predation by predators using such pre-ingestive shell breakage as decapod crustaceans.