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A three-dimensional reconstruction is provided of the composition, spatial distribution, and structure of a single-aged, Middle Pennsylvanian (Moscovian) peat-forming forest of a high-ash, planar (rheotrophic) mire, buried in situ by volcanic ash and preserved in the Lower Radnice Coal of the Radnice Basin (Czech Republic). The reconstruction is based on a detailed taxonomic and taphonomic analysis of fossils in a ∼0.5-m-thick tuff bed at the base of the Whetstone Horizon excavated over an area of 93.5 m2. In all, 24 whole-plant taxa of various growth forms were identified. This assemblage represents a lepidodendrid- and Cordaites borassifolius-dominated forest, with a well-developed understory of subarborescent lycopsids, tree ferns, medullosan pteridosperms, and calamites, as well as herbaceous ground cover. Lycopsids were dominated by Lepidodendron simile bearing Flemingites-type cones and L. lycopodioides; Lepidophloios cf. acerosus was subdominant. Lianas, mostly lyginopterid pteridosperms and some ferns, were usually found close to upright stems. The ground cover, mostly ferns and sphenophyllaleans, was taxonomically the most diverse stratum, although only a minor contributor to the peat. Based on samples from the coal roof, the palynological record is in agreement with the tuff bed assemblage except for the quantity of certain taxa. To reduce this bias, compression R-values were calculated from the percent cover of aerial plant parts in the excavation and in the dispersed palynoflora. These R-values suggest that in the palynological record, arborescent lycopsids and sphenophylls are greatly overrepresented, ferns and cordaites strongly underrepresented, and calamites are almost the same in both records.
Located at the interface between land and sea, marl prairies are sensitive to changes in water balance and useful recorders of climate and sea-level changes. Palustrine carbonate in marl prairies precipitates in temporary, barely flooded grasslands within microbial mats. Despite the special mode of carbonate production, descriptions of the sedimentary facies are exceptional and cursory because marl prairies are so far reported only from the recent of the Everglades (Florida, USA), where they produce an unspectacular calcite mud. We present a Pleistocene Everglades-type marl prairie from coastal Tanzania as the first fossil example. The unique preservation and high productivity (two times higher than in the Everglades) of the periphyton community in this marl prairie is due to increased calcification of coccoid and filamentous cyanobacteria. The excellent preservation allows us to characterize a marl prairie facies in great detail for the first time. Facies analyses of the sediments reveal a transition from tidal to terrestrial settings that started at ca. 44 14C ka in response to eustatic sea-level fall and coastal tectonic uplift. The resultant drop of the groundwater table triggered the development of the marl prairie. The decline of the marl prairie was initiated at ca. 33 14C ka due to the onset of the Last Glacial Aridity Maximum in equatorial East Africa.
Quantitative analysis of rare skeletal Lagerstätten of Paleozoic–early Mesozoic ages indicates that early dissolution of aragonite has seriously skewed community structures. The consequences of this widespread diagenetic process effectively preclude accurate interpretation and reconstruction of many fossil faunas in shelf settings. Trophic and ecologic loss focuses on the shallow infaunal tier of burrowing bivalves and the epifaunal vagrant detritus-feeding tier represented by gastropods. Case studies of the Ordovician–Carboniferous suggest that sequences with apparently typical Sepkoski Paleozoic faunas dominated by brachiopods were originally molluscan-dominated and included significant infaunal components. Early Mesozoic faunas dominated by epifaunal and semi-infaunal bivalves are similarly severely skewed by loss of ecologic diversity. Molluscan biodiversity appears more strongly affected in Paleozoic times. Such lower-energy environments as lagoons and mid-to-outer carbonate ramp settings are especially prone to dissolution loss. It is perhaps important to question for such faunas whether trophic tiers are reduced or missing.
Marine Pliocene mollusks are abundant in sand deposits at Langenboom, the Netherlands. Three samples, totaling nearly 15,000 mollusks, were identified and assessed for drill-hole predation marks. An approach commonly used by researchers was performed to calculate a drill-hole predation intensity based on bivalves with complete margins only. This method, however, introduced a significant taphonomic bias: an assemblage of bivalve drill-hole predation intensity of ∼30% was found for complete valves only, compared to an assemblage of bivalve drill-hole predation intensity of ∼20% based on complete and fragmented valves with more than 50% of the hinge preserved. This bias was caused by a significant change in the faunal composition when fragmented valves, primarily broken by compaction, were taken into account. For assemblages with many broken valves, this bias should be estimated to be comparable to drill-hole predation intensities based on pristine collections. This bias becomes especially important in studies on evolutionary escalation through time. Naticids appeared to be the predominant drill-hole-producing predator (only one definite drill hole was found) based on drill-hole morphology and the gastropod composition. Muricid predators were absent, probably because most bivalve prey is infaunal.
The juvenile tyrannosaurid specimen BMR P2002.4.1 possesses a series of four partially healed, oblong lesions along the left maxilla and nasal bones. The morphology of the lesions and their positioning and orientation are compatible with the jaws of the specimen, suggesting that the lesions may have been the result of a bite from an attacker of similar size and species as the bite victim. Bone remodeling of the lesions indicates partial healing and demonstrates that the injury was not fatal. The injury appears to have affected the growth of the skull, causing a slight warping of the left maxilla and a slight leftward curvature of the nasal. Previous examples of intraspecific behavior in theropods have noted various injuries on skulls; the majority of documented injuries are in adults. The presence and nature of these wounds suggests that juvenile tyrannosaurid behavior included intraspecific aggression among similar-sized individuals, as has been observed in modern crocodilians. Although it is not possible to unequivocally infer behavior from a fossil specimen, as a juvenile animal it is unlikely that the behavior directly reflects sexual competition or conflict, although it may represent learning behavior for later conflict as competing adults or territoriality over food or spatial resources.
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