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Seed dispersal spectra of woody taxa and seed size distribution of zoochorous woody taxa were studied in different forest types in Japan (Shirakami Sanchi, Mount Fuji, Nara, Shiroyama, and Yakushima Island) and China (Mount Emei, Longqi Mountain, Meili Snow Mountains, Xishuangbanna, and Jianfengling) to trace shifts in these fruit traits along the latitudinal and altitudinal gradients. The forest types studied are broad-leaved evergreen, mixed mesophytic, broad-leaved deciduous, subhumid sclerophyllous, and different tropical forests. Clear relationships are evident between dispersal mode, seed size class distributions, and the various forest types. The distribution of dispersal modes and of seed size classes differs significantly between the vegetation types. Animal dispersal is more important in broad-leaved evergreen and tropical moist forests, whereas wind dispersal is more common in subhumid sclerophyllous, tropical monsoon, and deciduous forest types. Large seeds (>15 mm) of fleshy-fruited taxa are predominant in tropical moist forests but almost absent in the other forest types. Large seeds of nonfleshy animal-dispersed taxa, however, are found across all forest types. Abiotic dispersal mechanisms are consistently low across the forest types. This study is designed as a source for the future evaluation of the Paleogene–Neogene plant record and will contribute to a more comprehensive understanding of ecosystem evolution and dynamics.
Skeletal remains of woolly mammoths have been studied using polarizing microscopy, SEM, XRD, and FTIR to characterize their diagenetic history. Formation of different secondary minerals in the bones is related to changing conditions of chemical diagenesis, both in the sediment and in the bone itself. Bone voids are commonly infilled with calcite and/or carbonate sediment, and dentinal tubules are coated or infilled with secondary apatite. The latter may have formed during the life of the organism. Some osteocyte lacunae were observed to be coated with Fe-Mn (hydroxy)oxides. The average hydroxylapatite Ca/P ratios are higher (1.78–2.10) than in stoichiometric hydroxylapatite. Hydroxylapatite crystallinity indices are generally low at 0.06–0.12, as expected for the young bones. Some of the bones are partly altered by microbial attack. Different postdepositional events affecting the bones (recrystallization of apatite, bacterial alterations, mineral and sediment infillings and cracking) were distinguished and their succession proposed.
Intriguing fossils encrusting oncoids and exhumed carbonate concretions are described from the Middle Jurassic (Bathonian) of Poland. The fossils, up to a few millimeters in diameter and preserved in a form of calcium carbonate, are characterized by a tubular, elongate shape with the external surface covered with distinctive semicircular to oval concavities. These tubes do not match any known fossils and do not represent trace fossils sensu stricto. They are similar to serpulid and/or sabellid polychaetes with which they are associated. The latter, however, have calcitic tubes and none are known to possess the concave structures that characterize the tubular fossils. The shape of the concavities and the presence of a carbonate lining within them suggest that the tubular fossils were originally covered with ooids, a few of which are still preserved in the concavities. These Middle Jurassic fossils may represent the fossilized remnants of agglutinated tubes formed by polychaete worms. Their greatest abundances are noted on media bearing thick microbial crusts (oncoidal in nature) on which they often form dense aggregations. This may indicate that the tube-building worms selected such media not only because they provided a suitable hard surface for settlement, but also because they were a rich source of food in the form of both microbes (Cyanophyta) and other organic matter present in the microbial mats. The selectivity of only ooids for tube building makes them dissimilar to any known recent tube-building polychaetes and, thus, the Middle Jurassic representatives are nonactualistic with respect to particle selection for the tube formation.
Two unusual, well-preserved, tridactyl trackways associated with sinuous grooves from the Lower Cretaceous Yanguoxia tracksite (Yongjing County, Gansu Province, China) are described and the behavior they present is discussed. The sinuous grooves are protracted and simple, with high percent interruption metric values and a low sinuosity. They are located between left and right pes tracks that have three separated, rounded distal digit impressions but lack plantar impressions. The presence of fine details such as delicate, double-sided, branching mud wrinkles in the grooves, coupled with backward drag marks at the rear of the tracks, indicate that the tracks and grooves are true tracks. We interpret the sinuous grooves as tail traces, and suggest that the tracks were made by a tridactyl dinosaur, probably by an ornithopod. It is hypothesized that the trackmakers made these trackways while partially submerged, propelled by toe-only steps, and leaving a subaqueously emplaced trail.
We examine the linkage between the sediment geochemical milieu and the process of carbonate degradation over a wide range of continental shelf and slope sediments using molluscan shells deployed for 13 years by the Shelf and Slope Experimental Taphonomy Initiative (SSETI). Geochemical characterization of the environment of preservation included the breadth of the pore-water carbonate undersaturation window, a depth-integrated carbonate dissolution index, the depth of minimum pore-water saturation, diffusive fluxes of oxygen and calcium, average sulfate and chloride concentration in the upper 5 cm, and the carbonate and organic carbon fractions in the same sedimentary horizon. Taphonomic indices included the maximum degree of dissolution; average dissolution; the incidences of chalkiness, pitting, deep dissolution, and a soft shell surface; the maximum degree of discoloration; the incidences of fading, gray-to-black discoloration, brown discoloration, and orange discoloration; the presence of pyrite; and edge rounding. Geochemical variables characterize the extent of most taphonomic processes with high three-variable multiple regression coefficients (R2 > 0.85). Dissolution was most intense at petroleum seeps where enhanced sediment respiration fueled by petroleum carbon and oxidation of reduced species (e.g., H2S) resulted in acute pore-water carbonate undersaturation near the sediment-water interface and high diffusive oxygen flux. In contrast, discoloration occurred as often or more commonly in shelf and slope sediments that were not subject to seep influence. The tendency for correlations between many taphonomic metrics, including those relating to dissolution, pyritization, and discoloration, and the breadths of the calcite/aragonite undersaturation windows, Ωcalcite, and oxygen flux emphasize the importance of near-surface geochemical conditions relating to organic carbon decomposition in determining the degree and type of carbonate degradation occuring at SSETI sites.
The recently expanded Norian stage now encompasses nearly half of the entire Triassic period, making it the longest single stage of the Phanerozoic. Very little is known about the paleoecological dynamics of shallow marine level-bottom benthos within the stage, however. Successive bulk samples from the Lombardian Alps, Italy, reveal gradual changes in dominant taxa throughout the Norian, and paleoecological transitions consistent with the Mesozoic Marine Revolution (MMR) hypothesis. At the expense of stationary epifauna, mobile infauna diversified and became dominant by the end of the Norian. In addition to increases in stationary semi-infauna, abundant mobile epifauna were perhaps early alternatives to increasing both mobility and infaunality during the middle Norian. The particular suite of trends observed suggests that an adaptive response to epifaunal and demersal predators was operating in this system, and is coincident with the known taxonomic radiations of shell-crushing predators from this interval (lobsters, fish). Thus, the MMR was gradually intensifying as early as 25 myr before the Triassic-Jurassic boundary.
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