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1.
DAVID D. BERMÚDEZ‐ROCHAS GRACIELA DELVENE J. IGNACIO RUIZ‐OMEÑACA 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2013,46(1):57-70
Here, we present evidence of possible vertebrate predation on freshwater bivalves from the Lower Cretaceous strata of the Cameros Basin (Spain). The described collection contains the largest number of vertebrate‐inflicted shell injuries in freshwater bivalve shells yet reported in the Mesozoic continental record. Several types of shell damage on fossil shells of Protopleurobema numantina (Bivalvia: Unionoida) are described and their respective modes of formation interpreted in the context of morphological attributes of the shell injuries and the inferred tooth morphology of predators that could have inflicted such injuries. Detailed study of these bite marks shows similarities with the well‐documented injuries in the shells of marine molluscs, namely ammonoids, that have likewise been attributed to reptilian predators. The most parsimonious interpretation suggests crocodiles as the vertebrates interacting with the bivalves in the Cameros Basin. □Barremian–Aptian; bite marks; freshwater bivalves; predation; reptile; Unionoida. 相似文献
2.
ROGER A. HEWITT JOHN M. HURST 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1977,10(4):287-301
Over 50 species of liparoceratid ammonites have previously been recognized from the Ibex and Davoei Zones (Lower Pliensbachian, Lower Jurassic) of England alone. Such a high specific diversity is an artifact caused by their stratigraphical importance and the complex nature of their shells. Simple bivariate analysis indicates that Aegoceras species are arbitrary subdivisions of an allometric growth trend. Principal component multivariate analysis shows that Liparoceras and Androgynoceras (sensu Callomon) are quite distinct from Aegoceras , and they display a more random pattern of variation. The existence of stratigraphically useful size changes in liparoceratids mirrors precisely size increases in benthic molluscan taxa, such as the bivalve 'Astarte' platymorpha and the archaeogastropod Eucyclus subimbricata. The ammonite size changes, at least, probably result from phenotypic variation analogous to that observed in the living cephalopod Sepia officinalis. This evidence taken in conjunction with the fact that kosmoceratid ammonite size changes correspond somewhat with benthic faunal changes suggests that ammonites maybe less useful for stratigraphy than is believed. 相似文献
3.
The oxygen and carbon isotopic compositions of 108 modern shells of various bivalve species collected from cold seeps and hydrothermal vents were investigated in order to evaluate whether these parameters can provide information on environmental geochemical variability as well as on bivalve species and on the type of symbiotic bacteria present in their gills. The results show that the carbonate of bivalve shells from hydrothermal vents is characterized by abnormal positive δ13C values due to kinetic isotope effects, whereas the carbonate of bivalve shells from cold seeps exhibits positive as well as negative δ13C values suggesting that oxidized methane emitted by the seeping fluids may be incorporated in the shell. Comparison of the δ18O and δ13C values of bivalve shells hosting different chemosymbiotic bacteria suggests that each type of symbiosis is associated with a specific environment and bivalve species, indicating that there is a strong physiological/metabolic control on the incorporation of stable isotopes during the biomineralization process. 相似文献
4.
Summary This report presents the results of taphofacies analyses of shelly cheniers (mollusk-dominated lag-concentrations) from the
tidal flats of northeastern Baja California, Mexico. The three generations of moderm (formed during last 70 years), submodem
(younger than 1,500 BP), and subfossil (5,000–2,000 BP) cheniers can be distinguished by their position relative to the shoreline,
their topography, and the radiocarbon-age of their shells. The generations differ in the duration and complexity of their
taphonomic history. Sixty-one samples from nine localities were collected to test the utility of the taphofacies approach
for studying chenier-type shell deposits. The three chenier generations, although all dominated by the bivalve molluskMulinia coloradoensis, differ significantly in their taxonomic composition due to taphonomic and/or biologic factors. The taphofacies analysis
included 4,334 specimens ofM. coloradoensis described by nine taphonomic variables. Univariate analysis of those variables indicated that the shells that accumulated
in the cheniers are little-affected by biological processes (bioerosion, encrustation), and moderately affected by physical
processes (fragmetation, cracking, peeling, edge preservation). Only the luster features of shells (external luster, internal
luster, and internal features) vary substantially and consistently with chenier age —a result of subaerial weathering. Multivariate
taphofacies analysis discriminates the three generations of cheniers even when the poorly preservable luster variables are
excluded from the analysis. This suggests that taphofacies discrimination is possible for fossil cheniers. The shells collected
from the chenier surface have substantially poorer preservation than shells from the subsurface, indicating that taphonomic
degradation in the chenier plain environment is a surface phenomenon. Chenier plain shelly assemblages are taphonomically
distinct from assemblages formed in other marine environments: they have a very low frequency of macroscopically recognizable
bioerosion and encrustation. The existence of preservable taphonomic differences between the cheniers that differ in their
age (i.e., duration of preburial history), suggests that fossil lag concentrations may be useful in detecting incompleteness
gradients along stratigraphic boundaries. A ‘taphonomic clock’—a correlation between a ‘time-sincedeath’ and shell preservation—was
found only for luster features, taphonomic attributes that are unlikely to be preserved in the fossil record. 相似文献
5.
The insoluble matrix of larval shells of the marine bivalve mollusk Mytilus galloprovincialis is investigated by confocal laser scanning microscopy using a GFP fusion protein with a chitin-binding domain for labeling of chitinous structures. We show that chitinous material is present in the larval shell, presumably as a chitin-protein complex. We further show that the structure of the chitinous material changes with the development of the larvae. We conclude from the presence of characteristic chitinous structures in certain shell regions that chitin fulfills an important function in the formation and functionality of larval bivalve shells. 相似文献
6.
LOUIS LILJEDAHL 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1985,18(1):53-66
The silicified Wenlockian (Silurian) bivalve fauna from MÖllbos, Gotland, is part of a life assemblage. The vast number of shells show unusual phenomena, e.g. shell repair, pearl and tumour formation, etc. A number of shells contain epibionts and bored, round holes. Presumptive predators of the bivalve community are discussed. Size-frequency distribution of the two most abundant species possibly reflects age classes. The fauna, comprising eleven species, is dominated by deposit-feeders (90 %). They exhibit niche diversification, including at least three different feeding levels within the sediment. 相似文献
7.
FrankSTILLER 《古生物学报》2005,44(3):396-411
论文描述的双壳类壳体内的钻孔遗迹组合发现于湖南省东南部宜章县下坪附近的心田门组上部(早侏罗世,早辛涅缪尔期)浅海沉积地层中。这个遗迹化石群中,帚虫类动物制造的钻孔Talpinahunanensisichnosp.nov.(新遗迹化石种)明显地占据了大部分,偶尔共生的其它钻孔包括:Rogerellaichnosp.(蔓足亚纲尖胸类的遗迹)、Calcideletrixichnosp.(可能是藻类的遗迹)、藻或菌造的遗迹(暂定为"Mycelites"ichnosp.)、以及一种可能被海绵动物制造的未定钻孔。生物侵蚀者侵害了海底上较大的双壳类壳体。钻孔保存为天然印模(石核),它们是文石质壳体溶解后留下的空间中的充填物。此外,文中还讨论了遗迹化石属TalpinaHagenow,1840,尤其讨论了有关遗迹种颇为复杂的鉴别问题,同时校正了该遗迹属的属征。 相似文献
8.
Viewed under UV light the diverse and exceptionally well-preserved molluscs from the Late Jurassic Cordebugle Konservat Lagerstätte (Calvados, Normandy, France) reveal fluorescent fossil shell colour patterns predating the oldest previously known instance of such patterns by 100 Myr. Evidently, residual colour patterns are observable in Mesozoic molluscs by application of this non-destructive method, provided the shells are not decalcified or recrystallized. Among 46 species which are assigned to twelve gastropod families and eight bivalve families, no less than 25 species yielded positive results. Out of nine colour pattern morphologies that have been distinguished six occur in gastropods and three in bivalves. The presence of these variant morphologies clearly indicates a significant pre-Cenozoic diversification of colour patterns, especially in gastropods. In addition, the occurrence of two distinct types of fluorescence highlights a major difference in the chemical composition of the pigments involved in colour pattern formation in gastropods. This discovery enables us to discriminate members of higher clades, i.e. the Vetigastropoda emitting red fluorescence from the Caenogastropoda and Heterobranchia emitting whitish-beige to yellow fluorescence. Consequently, fluorescent colour patterns may help to allocate part of the numerous enigmatic Mesozoic gastropod taxa to their correct systematic position. 相似文献
9.
The current model for the ultrastructure of the interlamellar membranes of molluscan nacre imply that they consist of a core of aligned chitin fibers surrounded on both sides by acidic proteins. This model was based on observations taken on previously demineralized shells, where the original structure had disappeared. Despite other earlier claims, no direct observations exist in which the different components can be unequivocally discriminated. We have applied different labeling protocols on non-demineralized nacreous shells of the bivalve Pteria. With this method, we have revealed the disposition and nature of the different fibers of the interlamellar membranes that can be observed on the surface of the nacreous shell of the bivalve Pteria hirundo by high resolution scanning electron microscopy (SEM). The minor chitin component consists of very thin fibers with a high aspect ratio and which are seemingly disoriented. Each fiber has a protein coat, which probably forms a complex with the chitin. The chitin-protein-complex fibers are embedded in an additional proteinaceous matrix. This is the first time in which the sizes, positions and distribution of the chitin fibers have been observed in situ. 相似文献
10.
SHMUEL RAZ JOHN H. GRAHAM HAGIT HEL‐OR TOMÁŠ PAVLÍČEK EVIATAR NEVO 《Biological journal of the Linnean Society. Linnean Society of London》2011,102(4):786-797
Rocellaria dubia bores into subtidal rocks of karsted limestone in the Adriatic Sea and elsewhere. It also bores into the shells of various bivalve species. The mechanism of boring has hitherto been debated, but examination of occupied shells suggest that this is achieved by mechanical (the shell) abrasion and chemical etching using secretions produced from glands in the anterior mantle. Fast‐growing bivalves such as Ostrea edulis and Pinna nobilis carry heavy R. dubia burdens, and encapsulate the borer in secreted calluses. Slow‐growing bivalves such as the burrowing Venus verrucosa and Glycymeris violacescens carry low R. dubia burdens, are less able to encapsulate the borers, and probably incur enhanced mortalities as a result. Individuals of R. dubia removed from their limestone boreholes re‐secreted adventitious tubes around their siphons, probably from glands in the posterior mantle. The lifestyle of R. dubia is now better understood, and its ability to bore bivalve shells in particular suggests how the more advanced tropical gastrochaenids Cucurbitula and Eufistulana have evolved from initial (as juveniles) bivalve shell borers into occupants of adventitious crypts and tubes, respectively. It is further argued that the Gastrochaenidae show convergent similarities with the similar crypt‐ and tube‐building representatives of the Clavagelloidea. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 786–804. 相似文献
11.
12.
In the cold-temperate setting of the Swedish Kosterfjord, a 2-year experiment was launched in order to assess bioerosion rates and to investigate the endolithic borer communities in relation to light availability (relative bathymetry), hydrography and exposure time. The inventory of microendolithic traces, studied by SEM analysis of epoxy resin casts of planted bivalve shells, yields diverse ichnocoenoses comprising a total of 21 traces produced by boring cyanobacteria (7), chlorophytes (4), fungi (6) and traces of uncertain affinity (4). The link between the endoliths (biotaxa) and the traces they leave (ichnotaxa) is evaluated by the study of the boring organisms in situ by transmission light microscopy of planted Iceland spar and bivalve shells. Additionally, the activity of various macroborers (foraminiferans, polychaetes, echinoids, gastropods and sponges) is documented, adding to a distinct diversity maximum at 7 m water depth. A highly condensed photic zonation, due to the high latitude (59°) and eutrophic conditions, is recorded by the measurement of the Photosynthetically Active Radiation (PAR) and is confirmed by the bathymetric range of the photic related ichnocoenoses. At 1 m water depth, a mature shallow euphotic ichnocoenosis dominated by cyanobacteria and at 7 m, a deep euphotic ichnocoenosis dominated by chlorophytes, respectively, is developed after as little as 12 months exposure. With the vanishing light availability from 15 m downwards, the ichnocoenoses development is significantly slowed and only immature dysphotic and aphotic borer communities (dominated by fungi) are encountered. Strong fluctuations of salinity (down to 8%) and temperature (0–20°C) in the euphotic zone indicate most phototrophs present to be considerably euryhaline and eurytherm, while most endolithic fungi appear preferentially in the deeper, more stable marine waters. 相似文献
13.
Clara L. Mackenzie Graham A. Ormondroyd Simon F. Curling Richard J. Ball Nia M. Whiteley Shelagh K. Malham 《PloS one》2014,9(1)
Ocean surface pH levels are predicted to fall by 0.3–0.4 pH units by the end of the century and are likely to coincide with an increase in sea surface temperature of 2–4°C. The combined effect of ocean acidification and warming on the functional properties of bivalve shells is largely unknown and of growing concern as the shell provides protection from mechanical and environmental challenges. We examined the effects of near-future pH (ambient pH –0.4 pH units) and warming (ambient temperature +4°C) on the shells of the commercially important bivalve, Mytilus edulis when fed for a limited period (4–6 h day−1). After six months exposure, warming, but not acidification, significantly reduced shell strength determined as reductions in the maximum load endured by the shells. However, acidification resulted in a reduction in shell flex before failure. Reductions in shell strength with warming could not be explained by alterations in morphology, or shell composition but were accompanied by reductions in shell surface area, and by a fall in whole-body condition index. It appears that warming has an indirect effect on shell strength by re-allocating energy from shell formation to support temperature-related increases in maintenance costs, especially as food supply was limited and the mussels were probably relying on internal energy reserves. The maintenance of shell strength despite seawater acidification suggests that biomineralisation processes are unaffected by the associated changes in CaCO3 saturation levels. We conclude that under near-future climate change conditions, ocean warming will pose a greater risk to shell integrity in M. edulis than ocean acidification when food availability is limited. 相似文献
14.
Synthesis and Assembly of Simian Virus 40 I. Differential Synthesis of Intact Virions and Empty Shells 总被引:22,自引:22,他引:0
Harvey L. Ozer 《Journal of virology》1972,9(1):41-51
Intact virions and empty shells of simian virus 40 may be rapidly separated from each other and from cell contaminants by a procedure employing a CsCl cushion. This approach permits quantitation of their respective syntheses in infected cells labeled with radioactive amino acids. As much as 5 to 10% of the total acid-precipitable radioactive lysine in infected cell extracts was incorporated into viral particles in a two-hour pulse late in infection. Evidence for multiple origins of empty shells is presented. Some of the empty shells result from breakdown of intact virions. However, empty shells can also form independently of intact virions. First, labeling for periods of 15 min to 2 hr late in the course of infection results in preferential incorporation of (3)H-lysine into empty shells. Secondly, treatment with the deoxyribonucleic acid inhibitor cytosine-beta-d-arabinofuranoside late in infection results in a 50% inhibition in the rate of formation of intact virions with minimal reduction in the rate of appearance of empty shells. 相似文献
15.
In shells of the oysters Exogyra cancellata and Pycnodonte mutabilis from the Mount Laurel and Marshalltown Formations (Campanian‐Maestrichtian), three‐quarters of all valves bear sponge borings (Entobia isp.) borings and 30% have borings of a lithophagid bivalve (Gastrochaenolites isp.). Non‐random distributions of these euendoliths, documented in this paper, may in part be accounted for by differential survival of sponge and lithophagid larvae and spat in varying circumstances. In addition, exterior shell architectures and post‐mortem orientations of shells are inferred to have prompted active geophobic (antigravity), rugophilic (groove‐seeking), and rheophilic (current‐seeking) behavior that enhanced survivorship of the settling larvae. 相似文献
16.
Dr. R. Pamela Reid Dr. Ian G. Macintyre Dr. Kathleen M. Browne Dr. Robert S. Steneck Dr. Timothy Miller 《Facies》1995,33(1):1-17
Summary Modern stromatolites in open marine environments, unknown until recently, are common throughout the Exuma Cays, Bahamas. They
occur in three distinct settings: subtidal tidal passes, subtidal sandy embayments and intertidal beaches. These stromatolites
have a relief of up to 2.5 m and occur in water depths ranging from intertidal to 10 m. Surfaces near the sediment-water interface
are typically colonized by cyanobacterial mats, whereas high relief surfaces are commonly colonized by algal turf and other
macroalgae such asBatophora, Acetabularia, andSargassum. The internal structure of the stromatolites is characterized by millimeter-scale lamination defined by differential lithification
of agglutinated sediment. In thin section, the lithified laminae appear as micritic horizons with distinct microstructures:
they consist of thin micritic crusts (20–40 μm thick) overlying layers of micritized sediment grains (200–1000 μm thick);
the micritized grains are cemented at point-contacts and are trucated along a surface of intense microboring. The Exuma stromatolites
are built by cyanobacterial-dominated communities. These laminated prokaryotic structures grade to unlayered thrombolites
built by eukaryotic algae. The variety of sites, settings and shapes of stromatolites in the Exuma Cays present excellent
opportunities for future studies of stromatolite morphogenesis. 相似文献
17.
C. Poulain A. Lorrain J. Flye-Sainte-Marie E. Amice E. Morize Y-M. Paulet 《Journal of experimental marine biology and ecology》2011,397(1):58-64
The periodicity of increment formation in the shell of the Manila clam Ruditapes philippinarum was investigated in the subtidal zone of the Auray River estuary (South Brittany, France). Calcein markings were performed at different periods between May and October 2007 using in situ benthic chambers tented by scuba divers. This study shows that shell microgrowth increments were well-defined and deposited with a tidal periodicity in the subtidal zone, providing the calendar base for high-resolution ecological studies and environmental reconstruction from these R. philippinarum shells. Endogenous rhythmicity in shell microgrowth increment formation and oxygen consumption was previously documented in this species from intertidal flats. Our study suggests that, in the subtidal zone, Manila clams' rhythmic activity may be controlled by such an endogenous process, synchronized by tidal cues. As in other bivalves, R. philippinarum is an osmoconformer euryhaline bivalve. The tidal rhythmicity of shell microgrowth increments in subtidal specimens of this species could be explained by a behavioral adaptation of valve closure at low tide to protect the clam from low salinities and/or to synchronize with food availability. Finally, large inter-individual variability in tidally associated growth rates and asynchronous growth breaks were observed, and could be due to genetic variability between individuals, asynchronous partial spawning events or predation. 相似文献
18.
Jörn Thiede 《Palaeogeography, Palaeoclimatology, Palaeoecology》1974,15(4):267-290
Larval shells of benthic marine bivalves occur frequently in plankton samples from temperate to tropical eastern North Atlantic waters. At many sites their abundance is higher than fifty specimens per cubic meter of surface water, thus outnumbering the other planktonic components with calcareous shells. Generally they are more frequent in nearshore water masses than far from land, but it could be shown that not only faunas on continental shelves, but also on oceanic inlands and on submarine elevations, produce larvae, which can be found far out in the ocean.Although it cannot be excluded that long-transported bivalve larvae have also been found in these samples, two arguments seem to assure that the bulk of these shells has been produced in the neighbouring shallow-water areas: decreasing abundance as well as increasing size of shells with increasing distance from the shallow-water area (this applies both to island and continental shelves).The bulk of bivalve shells is concentrated in surface waters. However, shells have also been found with decreasing abundance in water depths down to 600 m. The size distribution in the water column is qualitatively similar for water masses close to the coast and far from land; large shells occur in the upper 50 m, but average diameter decreases below this depth. However, far from land in water depths of 500–600 m they can reach sizes up to about 0.5 mm in diameter (according to one specimen). Generally, shell sizes are larger in corresponding water depth levels far from than in those close to land.The occurrence of larval shells of bivalves throughout the eastern North Atlantic also has wide paleogeographic implications. Since no specific determinations of these bivalves have been tried, it is unknown in which water depths their parental generations occur. However, it can be assumed that eastern North Atlantic island shelves and peaks of submarine guyots and other subsurface elevations which reach to within a few hundred. meters of the surface, can be populated by faunas from eastern Atlantic continental margins being transported by off-shore currents far into the ocean. Since the islands and presumably guyots, etc. as well, produce pelagic larval assemblages from their own benthic molluscan faunas, it can easily be assumed that larval shells can be transported across the ocean by surface and subsurface currents. 相似文献
19.
Shells of Calliostoma zizyphinum taken from Strangford Lough,N. Ireland are divisible into three distinct colour forms: white(=var lyonsi) intermediate (a pale variegated form) and purple(a dark variegated form). The predominance of white and paleshelled individuals within and the absence of white Calliostomaoutside the lough was confirmed. The proportions of animalswith white and variegated shells at selected sites were almostidentical with those previously documented, suggesting a temporalstability of colour form ratios. No differences in shell thicknessand pedal adhesion were demonstrated between these forms. Snails with white shells reflect radiant heat better, have lightercoloured feet, move more rapidly, show a greater incidence ofshell repair and are more frequently exposed on weed at lowtide, than those with either intermediate or purple shells.Increased proportions of white individuals may be associatedwith high population densities. Under such circumstances, itis suggested that increased mobility may, by increasing dispersion,reduce intraspecific competition. In the event of exposure atlow tide a white shell would help minimize thermal stress. (Received 9 February 1987; 相似文献
20.
The genus Maminka Barrande, 1881 (Lunulacardiidae) from the Wenlock and Ludlow (Silurian, Lower Paleozoic) of Europe is the oldest known bivalve with enantiomorphous dimorphism which is common among the Silurian and Devonian Lunulacardiidae and Antipleuridae. It represents the result of a special adaptation to the reclining mode of life combined with byssal attachment when early in ontogeny either the left or right valve became the lower valve; later, the bivalve develops as two enantiomorphous sets of shells. Distribution, ontogeny and evolution of this interesting feature in the genera Maminka Barrande, 1881, Stolidotus Hede, 1915, Mila Barrande, 1881, Dualina Barrande, 1881, Antipleura Barrande, 1881, Silurina Barrande, 1881 and Hercynella Kayser, 1878 are discussed. 相似文献