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Wyszukujesz frazę "darriwilian" wg kryterium: Temat


Wyświetlanie 1-4 z 4
Tytuł:
A crustoid graptolite lithoimmured inside a Middle Ordovician nautiloid conch from northern Estonia
Autorzy:
Vinn, Olev
Wilson, Mark A.
Toom, Ursula
Powiązania:
https://bibliotekanauki.pl/articles/191686.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
Encrustation
graptolites
nautiloids
cryptic fauna
Darriwilian
Baltica
Opis:
A light grey nautiloid conch has a dark brown colony attached to its internal surface. This colonial fossil resembles hederellids and bryozoans, but is in fact a crustoid graptolite (Hormograptus? sp.). The colony has been lithoimmured inside this nautiloid conch by early cementation. Crustoid graptolites were a part of the encrusting communities in the Middle Ordovician of Baltica, but their abundance among encrusters of biogenic substrates reached a peak in the middle Sandbian. The cryptic mode of life appeared very early in the evolution of the crus- toids. The discovery of this crustoid graptolite in a nautiloid conch indicates that the Baltic Middle Ordovician cryptic communities were taxonomically more diverse than was known previously. The nautiloid conch studied is sparsely encrusted with an encrustation density that is similar to those of other Middle Ordovician cryptic surfaces described from Estonia.
Źródło:
Annales Societatis Geologorum Poloniae; 2019, 89, 3; 285-290
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Early ontogenetic growth stages of Middle Ordovician orthoceratoid cephalopods from Bohemia
Autorzy:
Aubrechtova, M.
Turek, V.
Zicha, O.
Powiązania:
https://bibliotekanauki.pl/articles/2082221.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cephalopoda
Orthoceratida
early ontogeny
embryonic shell
Paleozoic
Darriwilian
Bohemia
Czech
Republic
Opis:
This study describes 18 specimens representing the earliest growth parts of orthoceratoid cephalopods, most of which have been recently obtained from the Middle Ordovician strata of the Prague Basin, central Bohemia. Only about 20 specimens of Ordovician orthoceratoids displaying embryonic shell are known globally and the Bohemian material thus significantly expands their current record. The studied collection includes twelve specimens assigned to the species Bactroceras sandbergeri and shows that the morphological variability in early ontogenetic growth stages of this species was rather low. The absence of a cicatrix was definitely confirmed in this phylogenetically important cephalopod. Six other specimens investigated herein are indeterminate orthoceratids. Initial chambers, where preserved, are generally large compared to known, stratigraphically younger specimens. This is interpreted here as supporting the previously postulated trend of decreasing the egg- and hatchling sizes in orthoceratoid cephalopods from mid-Ordovician times onwards. Alternatively, the large sizes of these Bohemian orthoceratids may be explained by the position of the Prague Basin in relatively cool-water high palaeolatitudes during the Middle Ordovician.
Źródło:
Acta Palaeontologica Polonica; 2020, 65, 3; 575-588
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Review of the Ordovician stratigraphy and fauna of the Anarak Region in Central Iran
Autorzy:
Popov, L. E.
Hairapetian, V.
Evans, D. H.
Ghobadi Pour, M.
Holmer, L. E.
Baars, C.
Powiązania:
https://bibliotekanauki.pl/articles/138968.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
darriwilian
katian
brachiopods
cephalopods
trilobites
biogeography
darriwil
kat
ramienionogi
głowonogi
trylobity
biogeografia
Opis:
The Ordovician sedimentary succession of the Pol-e Khavand area, situated on the northern margin of the Yazd block, has important differences from those in other parts of Central Iran. It has been established that the presumably terminal Cambrian to Lower Ordovician volcano-sedimentary Polekhavand Formation, exposed in the Pol-e Khavand area, has non-conformable contact with greenschists of the Doshakh Metamorphic Complex. The succeeding, mainly siliciclastic Chahgonbad Formation contains low to moderately diverse faunal assemblages, including brachiopods, cephalopods, trilobites and tentaculitids. The Darriwilian age of the lower part of the formation is well established by the co-occurrence of brachiopod genera Camerella, Phragmorthis, Tritoechia and Yangtzeella. The associated rich cephalopod fauna is different from the Darriwilian cephalopod associations of the Alborz terrane and may show some affinity with warm water faunas of North China and South Korea. It is likely that the Mid Ordovician fauna recovered from the lower part of the Chahgonbad Formation settled in the area sometime during a warming episode in the late Darriwilian. By contrast the low diversity mid Katian brachiopod association includes only three taxa, which occur together with the trilobite Vietnamia cf. teichmulleri and abundant, but poorly preserved tentaculitids questionably assigned to the genus Costatulites. This faunal association bears clear signatures linking it to the contemporaneous cold water faunas of the Arabian, Mediterranean and North African segments of Gondwana. Four brachiopod species recovered from the Chahgonbad Formation, including Hibernodonta lakhensis, Hindella prima, Lomatorthis? multilamellosa and Yangtzeella chupananica are new to science.
Źródło:
Acta Geologica Polonica; 2015, 65, 4; 403-435
0001-5709
Pojawia się w:
Acta Geologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Brachiopods from the Middle Ordovician Shihtzupu Formation of Yunnan Province, China
Autorzy:
Zhan, R
Jin, J.
Powiązania:
https://bibliotekanauki.pl/articles/20755.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
brachiopod
Darriwilian
Middle Ordovician
China
Shihtzupu Formation
Ordovician
taxonomy
Brachiopoda
paleobiogeography
paleontology
Yunnan Province
Opis:
The brachiopod fauna of the Middle Ordovician (upper Darriwilian) Shihtzupu Formation in the Weixin area, northeastern Yunnan Province, southwestern China, comprises 16 genera and 18 species, including one new genus (Halirhachis) and five new species (Glyptorthis sarcina, Protoskenidioides weixinensis, Halirhachis leonina, Leptellina spatiosa, and Leptestiina veturna). Cluster and principal component analyses of the latest Arenigian–mid−Caradocian faunas of the Upper Yangtze Platform with selected faunas of similar age from other palaeoplates or terranes indicate that the Weixin brachiopods have closest faunal affinities to those of the typical Shihtzupu Formation in Guizhou Province and the Naungkangyi Group of Burma (Myanmar). During latest Arenigian–mid−Caradocian times, the brachiopods of the Upper Yangtze Platform, Sibumasu, and Chu−Ili palaeogeographical regions constituted a distinct faunal province, characterized by a large number of endemic taxa as well as regionally widespread genera such as Saucrorthis, Martellia, and Yangtzeella. This brachiopod faunal province has very low similarity coefficients with the coeval brachiopod faunas of Laurentia and Avalonia.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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