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Wyświetlanie 1-4 z 4
Tytuł:
Revision of Middle Ordovician orthoceratacean nautiloids from Baltoscandia
Autorzy:
Kroger, B
Powiązania:
https://bibliotekanauki.pl/articles/20263.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
fauna
Cephalopoda
Orthoceratacea
Archigeisonoceras folkeslundense
Archigeisonoceras repplingense
Plagiostomoceras fragile
Nautiloidea
nautiloid
Nilssonoceras latisiphonatum
Archigeisonoceras picus
Kinnekulloceras kinnekullense
orthoceratacean nautiloid
Middle Ordovician
Ordovician
Baltoscandic Orthoceratite Limestone
paleontology
Opis:
The fauna of the Baltoscandic Orthocerataceae is important because it fills a documentary gap between the Lower Ordovician fauna of North America and the upper Middle Ordovician fauna of China and North America. A revision of the Orthoceratidae, Geisonoceratidae, and Arionoceratidae is given on a material of more than 450 specimens. Intraspecific and ontogenetic variations were observed. The following new taxa are erected: Plagiostomoceras fragile sp. nov., Archigeisonoceras repplingense sp. nov., Archigeisonoceras picus sp. nov. Archigeisonoceras folkeslundense sp. nov., Nilssonoceras latisiphonatum gen. et sp. nov., Kinnekulloceras kinnekullense gen. et sp. nov., and Arionoceras lotskirkense sp. nov. The genus Archigeisonoceras is described for the first time in the Baltoscandic area and the oldest occurrence of the genus Arionoceras is documented from the Middle Ordovician of Baltoscandia. It is shown that the endosiphuncular deposits of the Middle Ordovician orthoceratacaceans are highly variable and widespread in the apical parts of the phragmocone.
Źródło:
Acta Palaeontologica Polonica; 2004, 49, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new genus of middle Tremadocian orthoceratoids and the Early Ordovician origin of orthoceratoid cephalopods
Autorzy:
Kroger, B.
Powiązania:
https://bibliotekanauki.pl/articles/22312.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
new genus
Middle Tremadocian
orthoceratoid
Early Ordovician
Orthoceratoidea
cephalopod
remains
Orthocerida
Orthoceratoidae
Opis:
The cephalopods of the subclass Orthoceratoidea, which are termed “orthoceratoids” herein, are a group that remains “the last unexplored wilderness in the Cephalopoda” (Flower 1962: 23). After 45 years this statement still holds true because phylogeny reconstructions are hindered by their morphological simplicity, numerous homeomorphies and iterative evolution. The Orthocerida, straight cephalopods that are characterised by a wide chamber spacing, a thin tubular siphuncle and a small spherical initial chamber, lacking a cicatrix (Kröger 2006) were the ancestors of bactritoids, ammonoids, and coleoids (Engeser 1996). The origin of the Orthocerida is poorly understood. The earliest unequivocal Orthocerida are known from the Floian (Early Ordovician). A number of poorly known possible Orthocerida and/or stem group Orthocerida are known from the Tremadocian. Here, I reassign the long known middle Tremadocian “Orthoceras attavus” to the new genus Slemmestadoceras belonging to a group of worldwide distributed orthoceratoids. The presence of Slemmestadoceras with a thin, probable tubular siphuncle and small initial chambers in the middle Tremadocian suggests that the Orthocerida may have originated already at that time. The comparison of Slemmestadoceras with following late Tremadocian and Floian orthoceratoids demonstrates that a higher level taxon comprising these forms, such as the subclass Orthoceratoidea may constitute a paraphylum.
Źródło:
Acta Palaeontologica Polonica; 2008, 53, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Concentration of juvenile and small cephalopods in the Hirnantian cherts [Late Ordovician] of Porkuni, Estonia
Autorzy:
Kroger, B
Powiązania:
https://bibliotekanauki.pl/articles/20351.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
juvenile cephalopod
Cephalopoda
Nautiloidea
small adult cephalopod
cephalopod
Late Ordovician
Ordovician
life mode
Porkuni village
paleontology
Estonia
Opis:
The quarry in the north Estonian village of Porkuni provides a succession of shallow−water limestones and cherts spanning the Ashgillian Normalograptus? extraordinarius graptolite Biozone. This interval comprises the initial pulse of the end−Ordovician extinction. The succession of Porkuni contains abundant and extraordinarily well−preserved fossils. 71 cephalopod specimens were extracted from these strata at Porkuni. Many of these specimens are fragments of juvenile shells or small adults. The embryonic shells of the cephalopods are usually preserved and provide insight into their early ontogeny. The faunal composition is considered as autochthonous and reflects a “palaeo−nursery” in a Hirnantian reef environment. The collected specimens represent twelve genera and four orders. Small oncoceridans and orthoceridans dominate the association. The rate of endemism is very high, since only two genera found in Porkuni, are known from outside Baltoscandia. The new genera Parvihebetoceras, Pomerantsoceras, Porkunioceras, and the new species Parvihebetoceras wahli, Pomerantsoceras tibia, Porkunioceras tuba, and Strandoceras orvikui are erected.
Źródło:
Acta Palaeontologica Polonica; 2007, 52, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Soft-tissue attachments in orthocerid and bactritid cephalopods from the Early and Middle Devonian of Germany and Morocco
Autorzy:
Kroger, B
Klug, C.
Mapes, R.
Powiązania:
https://bibliotekanauki.pl/articles/20326.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cephalopoda
Germany
Orthocerida
Emsian
Morocco
Middle Devonian
soft tissue attachment
Early Devonian
Bactritida
muscle scar
Eifelian
Devonian
cephalopod
paleontology
Opis:
In the Early to Middle Devonian shale sequences of Germany and Morocco, pyritised and secondarily limonitised cephalopod remains are common. Details of the soft−tissue attachment structures are sometimes preserved on the internal moulds of the body chamber and phragmocone of these cephalopods. Some of the studied Orthocerida show a very faint annular elevation and a dorsal furrow. A few Bactritida show a distinctive annular elevation with two circular bands. The bands form a paired or threefold lobe at the dorsum of the shell. Morphological differences between Orthocerida and Bactritida suggest different soft part morphologies. A comparison of the attachment scars shows that the Bactritida are intermediate between the Orthocerida and ammonoids with regard to their muscle attachment scars. The shape of the muscle scars are interpreted as indication for a planktonic lifestyle in Orthocerida and a comparatively active, nektonic lifestyle in Bactritida and ammonoids. The new genus Acanthomichelinoceras is erected. Acanthomichelinoceras commutatum, Cycloceras sp., Bactrites gracile, Bactrites sp. A, Bactrites sp. B, and Bactrites sp. C are described.
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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