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The Late Devonian trematid lingulate brachiopod Schizobolus from Poland

100%

Balinski A., Holmer L. E.

Acta Palaeontologica Polonica

1999

tom 44

nr 3

335-346

A new species of the poorly known lingulate brachiopod Schizobolus is described from the Famennian (Upper Devonian) of Poland. S. polonicus sp. n. has a triangular pedicle notch and a small listrium, indicating that it belongs to the Trematidae within the superfamily Discinoidea. S. polonicus retains some linguloid features, such as a linguloid-like 'pedicle groove' and a V-shaped imprint of the pedicle nerve. The disturbance band, which occurs in the apical part of the larval shell, probably delimits two stages of growth, namely pre-larval (embryonic?) and larval, or, early-larval and late-larval. S. polonicus is the youngest member of the genus, and of the family Trematidae. Five incompletely preserved discinids from the Famennian of Łagów are described as Trematidae gen. et sp. indet.

Development and calcification of the ammonitella shell

100%

Kulicki C., Doguzhaeva L. A.

Acta Palaeontologica Polonica

1994

tom 39

nr 1

17-44

Aconeceras trautscholdi ammonitellae mass occurring in the Aptian of Symbirsk, central Russia represent consecutive calcification stages of the primary organic shell wall. Already after the formation of the organic shell with proseptum, the first whorl and umbilical walls of the initial chamber were calcified, then the remaining part of the initial chamber, and finally the nacreous primary constriction was formed and the proseptum was calcified. The original mineral participating in calcification was aragonite, which formed primary prismatic layers. The ammonite embryonic shell was thus formed similarly to the archaeogastropod larval shell. This explains the microstructural distinction of the ammonitella and proseptum walls with respect to the rest of the ammonite shell.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Balinski A.

1 Doguzhaeva L. A.

1 Holmer L. E.

1 Kulicki C.

1 1999

1 1994

Wyniki wyszukiwania

The Late Devonian trematid lingulate brachiopod Schizobolus from Poland

Development and calcification of the ammonitella shell