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An ultrastructural study of the haptor of the microbothriid monogenean Leptocotyle minor from the skin of the dogfish Scyliorhinus canicula [Scyliorhinidae]

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Kearn G. C., Evans-Gowing R., Rees J.

Acta Parasitologica

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2001

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tom 46

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nr 4

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Catshark egg capsules from a Late Eocene deep-water methane-seep deposit in western Washington State, USA

80%

Kiel S., Peckmann J., Simon K.

Acta Palaeontologica Polonica

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2013

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tom 58

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nr 1

Fossil catshark egg capsules, Scyliorhinotheca goederti gen. et sp. nov., are reported from a Late Eocene deep−water methane−seep calcareous deposit in western Washington State, USA. The capsules are preserved three−dimensionally and some show mineralized remnants of the ribbed capsule wall consisting of small globular crystals that are embedded in a microsparitic matrix. The globules are calcitic, but a strontium content of 2400–3000 ppm suggests that they were origi− nally aragonitic. The carbonate enclosing the egg capsules, and the capsule wall itself, show 13C values as low as −36.5‰, suggesting that formation was induced by the anaerobic oxidation of methane and hence in an anoxic environ− ment. We put forward the following scenario for the mineralization of the capsule wall: (i) the collagenous capsules expe− rienced a sudden change from oxic to anoxic conditions favouring an increase of alkalinity; (ii) this led to the precipitation of aragonitic globules within the collagenous capsule wall; (iii) subsequently the remaining capsule wall was mineralized by calcite or aragonite; (iv) finally the aragonitic parts of the wall recrystallized to calcite. The unusual globular habit of the early carbonate precipitates apparently represents a taphonomic feature, resulting from mineralization mediated by an organic matrix. Taphonomic processes, however, are at best contributed to an increase of alkalinity, which was mostly driven by methane oxidation at the ancient seep site.

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Late Eocene scyliorhinid sharks from the Trans-Urals, Russia

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Malyshkina T.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 3

Priabonian deposits from two localities, Kurgan and Derney, in the Trans−Urals (Western Siberia) have yielded numerous selachian teeth. The carcharhiniform family Scyliorhinidae is represented by three species, including two new: Premontreia uralica sp. nov., Foumtizia zhelezkoi sp. nov., and F. pattersoni (Cappetta, 1976). Both genera are recorded from the West−Siberian Basin for the first time. Presumably all three species (including the one morphologically mimicking F. pattersoni, a species recorded from Ypresian of England) are endemic for the Trans−Urals region (contrary to the cosmopolitan lamniforms recorded previously from the area. The known distribution pattern of extant scyliorhinids supports the probability of endemism of the cat sharks from the West−Siberian Basin, which has also been isolated geographically from the Peri−Tethys during the Late Eocene marine regression. The peculiar local environmental conditions due to the Priabonian climatic cooling in the Boreal realm might have also facilitated the speciation.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Acta Parasitologica

1 Evans-Gowing R.

1 Kearn G. C.

1 Kiel S.

1 Malyshkina T.

1 Peckmann J.

1 Rees J.

1 Simon K.

1 2013

1 2006

1 2001

An ultrastructural study of the haptor of the microbothriid monogenean Leptocotyle minor from the skin of the dogfish Scyliorhinus canicula [Scyliorhinidae]

Catshark egg capsules from a Late Eocene deep-water methane-seep deposit in western Washington State, USA

Late Eocene scyliorhinid sharks from the Trans-Urals, Russia