- Tytuł:
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Porosphaera z górnej kredy okolic Krakowa
Porosphaera from the upper cretacreous in the vicinity of Krakow
Porosphaera iz verkhnego mela okrestnostejj Krakova - Autorzy:
- Hurcewicz, H.
- Powiązania:
- https://bibliotekanauki.pl/articles/21145.pdf
- Data publikacji:
- 1960
- Wydawca:
- Polska Akademia Nauk. Instytut Paleobiologii PAN
- Opis:
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W niniejszej pracy autorka dokonała analizy struktury gąbki wapiennej Porosphaera globularis (Phillips), która przez autorów XIX w. zaliczana była przeważnie do Hydrozoa. Stwierdzono spikularną budowę szkieletu głównego i dermalnego. Przeanalizowano również znaczenie taksonomiczne poszczególnych cech morfologicznych. Porosphaera występuje w Polsce szczególnie często w kampanie dolnym.
A report is here made on the results of investigation of Porosphaera globularis (Phillips), based on copious material (409 specimens) collected from grey marls and "opoka" beds in the Actinocamax quadratus and Belemnitella mucronata horizon in the neighbourhood of Kraków, Miechów and Lelów. Outside of Poland, the here considered genus has been reported from France, Germany, Denmark, Czechoslovakia and England, where it is known from the beginning of the Middle Turonian. The systematic position of the here studied fossil has been much discussed. Phillips was the first to describe it in 1829 as Millepora globularis. Later, under different names, it was referred either to the hydrozoans or to the Porifera, even to the bryozoans or the foraminifers. The generic name of Porosphaera was introduced by Steinmann (1878) who assigned it to the Hydrozoa-Milleporidae on the fibrous skeletal structure and resemblances with the Cylindrohyphasma. Other authors believed Porosphaera to be a sponge, To support this opinion they attempted to explain its rather peculiar skeletal structure by postulating that its originally spicular character had been altered into the present structure owing to re-crystallization of calcium carbonate. It ought to be stressed that Hinde (1904) had ascertained in Porosphaera globularis the spicular charaeter of the dermal and the main skeleton, the latter consistlng of cemented tetraclads. This author distinguished several species within this genus on such charactors as shape, grooving of exterior surface and arrangement of canals. The examination of variously oriented thin slides, and an analysis of the outer morphology suggest that the Polish specimens are all conspecific and referable to the species Porosphaera globularis (Phillips). This species is distinguished by strong variability of shape, size, morphology of outer surface, mode of attachment, arrangement of water canals and structure of the skeletal mesh. All these features have been affected either by manner of growth under varying ecological conditions, or by aga of the given individual. A calcareous skeleton of spicular character constitutes the index feature on which the here considered specimens have been referred to the Calcispongea. In two specimens fragmentary spicules have persisted of the type described by Hinde (1904) in specimens from England, These are tetraclads consisting of one longer sharp-pointed apical ray and three shorter, tripod-shaped facial rays. In the main skeleton the spicules are arranged according to three different patterns. In the centre (core) the tetraclads are irregularly placed. This part varies in size. Sometimes it is considerable with distinct numerous skeletal meshes, elsewhere small, with but a few meshes. The second pattern occurs in the skeletal mesh delimiting the water canals. Here the arrangement of spicules is regular, the apical rays being directed outwards. The average number of spicules along the canal is 5-6. The tetraclads change their position at the ends of canals. Their apical rays converge and the skeleton meshes grow narrower. This part of the skeleton indicates a check in the growth of the individual. Skeleton growth in Porosphaera occurred by zones, but not uniformly throughout the surface, hence its uneven bulgy appearance. The whole exterior surface is covered by the skeletal mesh consisting of the facial rays of three tetraclads rimming the minute apertures of straight simple canals. The meshes of the network are oval or polygonal. The surface of some specimens is marked by grooves of various length, breadth and depth. Hinde regarded them as surficial water canals and believed them to have some systematic significance. These grooves, however, discernible on some specimens from Bonarka and Miechów, do not display regularity and sometimes seem to be accidental and correspond to traces of alien organisms living attached on the surface of the sponge. The skeleton of Porosphaera is pierced throughout by canals showing a radially concentric arrangement. The system of canals and of the skeletal mesh permits a distinction between young and mature specimens. During the juvenile stage the central portion is large and the canals irregularly arranged, The mature stage, on the contrary, is characterized by the regularity of the radial system with the central portion or core notably small and the canals long. All the examined specimens, in spite of size- and shape differences, display essentially the same pattern of the skeletal mesh and the water canals, Their shape may be globose, discoidal, pyriform or rhomboidal, with size ranging from 4 to 27 mm. - Źródło:
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Acta Palaeontologica Polonica; 1960, 05, 4
0567-7920 - Pojawia się w:
- Acta Palaeontologica Polonica
- Dostawca treści:
- Biblioteka Nauki
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