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Wyszukujesz frazę "Chaetognatha" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
Cambrian chaetognaths recognized in Burgess Shale fossils
Autorzy:
Szaniawski, H
Powiązania:
https://bibliotekanauki.pl/articles/20273.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Oesia disjuncta
fossil
Burgess Shale
paleobiology
protoconodont
Canada
Cambrian
Chaetognatha
chaetognath
Opis:
Oesia disjuncta, one of the species of the soft−bodied fauna collected and described by Walcott (1911) from the Middle Cambrian Phyllopod Bed (Burgess Shale, British Columbia, Canada) is recognized as a chaetognath. For anatomical comparisons many specimens of Recent chaetognaths were specially compressed and dried to obtain forms similar to the fossils preserved in shales. The most characteristic features shared by the fossil and Recent specimens include: strongly elongated, transversely striated and very flexible body, large size, and characteristically diversified shape of head, pronounced intestine and horizontally oriented caudal fin. Possible traces of other chaetognath structures—grasping apparatus, lateral fins, seminal vesicles, ventral ganglion, ovaries and anus—are also present but preserved in one specimen only. Among extant genera, those showing the closest similarity to Oesia Walcott, 1911 are the hyperbenthic Archeterokrohnia Casanova, 1986¹, and Heterokrohnia Ritter−Záhony, 1911, which are considered by some authors as evolutionarily most primitive.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New evidence for the protoconodont origin of chaetognaths
Autorzy:
Szaniawski, H
Powiązania:
https://bibliotekanauki.pl/articles/20936.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
phylogenesis
paleobiology
fossil
Conodonta
marine animal
protoconodont
Metazoan
Cambrian
chaetognath
Chaetognatha
body fossil
Opis:
An earlier hypothesis concerning the origin of chaetognaths from protoconodonts found additional support in new discoveries and in recent structural, chemical and molecular investigations. The new findings show that the head armature of protoconodonts was composed not only of grasping spines but also of much smaller spicules corresponding in size and shape to the chaetognath teeth. Grasping spines of protoconodonts were originally built mainly of an organic substance. Their original composition was changed by secondary phosphatisation. The thickest layer of the protoconodont spines was originally constructed of organic fibrils, similar to those in the corresponding layer of chaetognaths. Recent molecular investigations show that the chaetognath lineage separated in the early stage of metazoan radiation, which fits the presented hypothesis. Described are some previously unknown structural details of chaetognath grasping spines, including composition of the outer layer and the origin of their distinctive tips.
Źródło:
Acta Palaeontologica Polonica; 2002, 47, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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