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Wyszukujesz frazę "ammonoidea" wg kryterium: Temat


Wyświetlanie 1-7 z 7
Tytuł:
Terminal Maastrichtian ammonites from Turkmenistan, Central Asia
Autorzy:
Machalski, M.
Jagt, J.W.M.
Alekseev, A.S.
Jagt-Yazykova, E.A.
Powiązania:
https://bibliotekanauki.pl/articles/20971.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
Maastrichtian
ammonite
Turkmenistan
Central Asia
Ammonoidea
extinction
paleobiogeography
Cretaceous
Paleogene
Opis:
A complete uppermost Maastrichtian–Danian succession in the Sumbar River section, western Kopet Dagh (southwest Turkmenistan, Central Asia), constitutes one of the few instances in the world where the fossil record of the last ammonites can be directly positioned with respect to the iridium−rich, impact−related clay layer, which defines the Cretaceous–Paleogene (K–Pg) boundary. Two ammonite taxa, Baculites cf. vertebralis and Hoploscaphites constrictus johnjagti, range up to a level directly beneath the K–Pg boundary clay in the Sumbar River section. Thus, these two forms probably survived until the very end of the Maastrichtian in the western Kopet Dagh area. The terminal Maastrichtian ammonite records from the Sumbar River area represent the southeasternmost occurrences of these essentially Boreal taxa.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The last Cretaceous ammonites in Latin America
Autorzy:
Stinnesbeck, W.
Ifrim, C.
Salazar, C.
Powiązania:
https://bibliotekanauki.pl/articles/20513.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
Cretaceous
ammonite
Latin America
Ammonoidea
Paleogene
Maastrichtian
Chile
Argentina
South America
Opis:
Sections yielding late Maastrichtian ammonite assemblages are rare in Latin America and precise biostratigraphic correlation with European type sections remains difficult. In all, the extinction pattern of ammonites appears to differ between sites in southern high latitudes and those in the tropics to subtropics. In austral sections of Chile, and possibly also in southern Argentina, diverse assemblages range throughout most of the substage and then show a gradual decline prior to the Cretaceous–Paleogene (K–Pg) boundary. Further north, in northeast Brazil, only two genera (Diplomoceras, Pachydiscus) range into the uppermost Maastrichtian, but disappear within the last 0.3 Ma of the Cretaceous. In tropical sections of Columbia and Mexico, the decline of ammonites started earlier and Sphenodiscus is the last ammonite known to occur in the late Maastrichtian. In all sections revised here the disappearance of ammonites was completed prior to the end of the Maastrichtian and was thus independent of the asteroid impact at, or near, the end of the Cretaceous.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ammonite faunal dynamics across bio-events during the mid- and Late Cretaceous along the Russian Pacific coast
Autorzy:
Jagt-Yazykova, E.A.
Powiązania:
https://bibliotekanauki.pl/articles/22657.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
ammonite
fauna dynamics
Late Cretaceous
Cretaceous
Russian coast
Pacific coast
Ammonoidea
evolution
Opis:
The present paper focuses on the evolutionary dynamics of ammonites from sections along the Russian Pacific coast during the midand Late Cretaceous. Changes in ammonite diversity (i.e., disappearance [extinction or emigration], appearance [origination or immigration], and total number of species present) constitute the basis for the identification of the main bio−events. The regional diversity curve reflects all global mass extinctions, faunal turnovers, and radiations. In the case of the Pacific coastal regions, such bio−events (which are comparatively easily recognised and have been described in detail), rather than first or last appearance datums of index species, should be used for global correlation. This is because of the high degree of endemism and provinciality of Cretaceous macrofaunas from the Pacific region in general and of ammonites in particular.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Size-shape relationships in the Mesozoic planispiral ammonites
Autorzy:
Parent, H.
Greco, A.F.
Bejas, M.
Powiązania:
https://bibliotekanauki.pl/articles/19942.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
size-shape relationship
Mesozoic
planispiral ammonite
ammonite
Ammonoidea
shell
Cephalopoda
paleontology
marine fossil
Opis:
Ammonites are of outstanding importance in dating events of the Mesozoic and in the study of mechanisms, modes and timing of evolutionary processes. These applications rely on a detailed understanding of their morphology and the modes of variation. It has been known for a long time that their shape is composed of a number of highly correlated features. A new model, called the ADA−model, is introduced for the study of shell morphology (size and shape). The new model is based on classic dimensions which are stable parameters throughout ontogeny, giving very close agreement between pre− dictions and actual observations. It was applied in the exploration of the morphospace occupied by the planispirally coiled and the regularly uncoiled Mesozoic Ammonoidea, based on two new reduced morphospaces introduced for the analysis. Results obtained expose close relationships between size and shape, and general patterns in the ammonite shell morphol− ogy and morphogenesis. (i) The relative apertural height of the whorl section relative to the diameter of the shell (H₂/D) is involved in definition of size and shape. (ii) This same dimension shows a strong tendency to be H₂/D = 0.3. (iii) There are some geometrically possible shell shapes (or morphotypes) which seem to have not been developed since they are not known in the current record. Assuming the known ranges of protoconch size and whorl number as constraints, the ADA−model strongly suggests that these morphotypes have not been developed for the too large or too small sizes the shells would have attained, well outside of the actual size range of the planispirally coiled Ammonoidea. (iv) The law of covariation is shown to be a general pattern within the planispiral ammonites which describes structured variation of the shell shape. (v) A large fraction of the non−structured variation seems originate in the lack of correlation between the rela− tive umbilical diameter and width of the whorl section.
Źródło:
Acta Palaeontologica Polonica; 2010, 55, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Short-term survival of ammonites in New Jersey after the end-Cretaceous bolide impact
Autorzy:
Landman, N.H.
Garb, M.P.
Rovelli, R.
Ebel, D.S.
Edwards, L.E.
Powiązania:
https://bibliotekanauki.pl/articles/22198.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
short-term survival
ammonite
New Jersey
Cretaceous
bolide impact
Ammonoidea
biostratigraphy
extinction
Paleogene
boundary
Opis:
A section containing the Cretaceous/Paleogene (= Cretaceous/Tertiary) boundary in Monmouth County, New Jersey, preserves a record of ammonites extending from the end of the Cretaceous into possibly the beginning of the Danian. The section includes the upper part of the Tinton Formation and lower part of the Hornerstown Formation. The top of the Tinton Formation is represented by a richly fossiliferous unit (the Pinna Layer) that contains many bivalves in life position as well as ammonite jaws preserved inside body chambers. Ammonites include Pachydiscus (Neodesmoceras) mokotibensis, Sphenodiscus lobatus, Eubaculites carinatus, E. latecarinatus, Discoscaphites iris, D. sphaeroidalis, D. minardi, and D. jerseyensis. The Pinna Layer probably represents a relatively short interval of time lasting tens to hundreds of years; it is conformably overlain by the Burrowed Unit, which contains a single fragment of Discoscaphites sp. and several fragments of E. latecarinatus, as well as several isolated specimens of ammonite jaws including two of Eubaculites. Examination of the mode of preservation of the ammonites and jaws suggests that they were fossilized during deposition of the Burrowed Unit and were not reworked from older deposits. Based on the ammonites and dinoflagellates in the Pinna Layer and the Burrowed Unit, these strata traditionally would be assigned to the uppermost Maastrichtian, corresponding to calcareous nannofossil Subzone CC26b. However, a weak iridium anomaly (500–600 pg/g) is present at the base of the Pinna Layer, which presumably represents the record of the bolide impact. Correlation with the iridium layer at the Global Stratotype Section and Point at El Kef, Tunisia, would, therefore, imply that these assemblages are actually Danian, provided that the iridium anomaly is in place and the ammonites and dinoflagellates are not reworked. If the iridium anomaly is in place, or even if it has migrated downward from the top of the Pinna Layer, the ammonites would have survived the impact at this site for a brief interval of time lasting from a few days to hundreds of years.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New Lower Kimmeridgian ataxioceratin ammonite from the eastern Iberian Chain, Spain: Systematic, biogeographic, and biostratigraphic relevance
Autorzy:
Moliner, L.
Oloriz, F.
Powiązania:
https://bibliotekanauki.pl/articles/20591.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Lower Kimmeridgian
ataxioceratin ammonite
ammonite
Spain
systematics
biogeography
biostratigraphy
paleontology
Ammonoidea
Ataxioceratinae
Geyericeras
Jurassic
Late Jurassic
Opis:
New ammonites collected bed−by−bed from the upper part of Ataxioceras hypselocyclum Chronozone deposits in the eastern Iberian Chain are described as Geyericeras gen. nov. The new genus includes microand macroconchiate Ataxioceratinae of small size, with moderate to loose coiling and subpolyplocoid ribs, a character crucial for its identification. Key points for the comparative identification of Geyericeras gen. nov. are: (i) microconchiate Geyericerasshow morphological convergence with evolute specimens of the stratigraphically older genus Schneidia [m]; (ii) contemporary Ataxioceratinae genera such as Ardescia [m, M] and Lithacosphinctes [m, M] did not develop subpolyplocoid ribbing; (iii) smoothing of sculpture combined with short primary ribs are not realized in Geyericeras gen. nov. [M] and can be therefore used to separate the new genus from Ataxioceras[M]; and (iv) smaller shells, and weaker and less dense ribbing with no parabolic structures differentiate Geyericeras gen. nov. [m, M] from Parataxioceras[m, M], as well as the type of subpolyplocoid ribs seen among microconchiate specimens of these two genera. The new species Geyericeras aragoniense sp. nov. is the index and guide fossil for identification of a biohorizon occurring below the first occurrence of the genus Crussoliceras in the eastern Iberian Chain.
Źródło:
Acta Palaeontologica Polonica; 2010, 55, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The soft-tissue attachment scars in Late Jurassic ammonites from Central Russia
Autorzy:
Mironenko, A.A.
Powiązania:
https://bibliotekanauki.pl/articles/22288.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Ammonoidea
Craspeditidae
Kachpurites
Garniericeras
soft tissue attachment
attachment scar
Late Jurassic
Jurassic
ammonite
paleobiology
Central Russia
Russia
Opis:
Soft-tissue attachment scars of two genera and four species of Late Jurassic craspeditid ammonites from the Russian Platform are described. A previously suggested relationship between lateral attachment scars and ammonoid hyponome is confirmed, however, a new interpretation is proposed for dorsal attachment scars: they could have been areas not only for attachment of the dorsal (nuchal) retractors, but also of the cephalic retractors. The new type of the soft-tissue attachment—anterior lateral sinuses, located between the lateral attachment scars and the aperture of the ammonite body chamber is described. Enclosed elliptical or subtriangular areas in apertural parts of the anterior lateral sinuses were found for the first time. Their presence and location suggest that this structure could have been used for attaching the funnel-locking apparatus, similar to those of coleoids. A transformation of shape and position of lateral attachment scars through the evolution of the Late Jurassic craspeditid lineage starting from platycones (Kachpurites fulgens) to keeled oxycones (Garniericeras catenulatum) is recognized.
Źródło:
Acta Palaeontologica Polonica; 2015, 60, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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