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Early astogeny and relationships of the Ordovician rhabdomesine bryozoans

100%

Dzik J.

Acta Palaeontologica Polonica

1992

tom 37

nr 1

37-54

A diverse Ordovician assemblage of juvenile bryozoan colonies, with external phosphatic coatings allowing chemical extraction from the rock, shows a morphologic series probably corresponding to evolutionary step-by-step suppression in the formation of the external colony wall. Its formation was initially delayed leading to formation of the common bud (advanced corynotrypids). Then the permanent double-walled colony organization developed along the colony margin (Flabellotrypa-like). In the following evolutionary stage, the external wall was secreted only at the conical creeping stage immediately following ancestrula (typical rhabdomesines). With subsequent evolution the external wall completely disappeared, and the double-walled ancestrula grew vertically (advanced rhabdomesines and phylloporinids). This kind of the early astogeny characterizes also the oldest phyllodictyid cryptostome Prophyllodictya, studied in serial peels. Flabellotrypidae fam. n., Mojczatrypa halysitoides gen. et sp. n., Kielceporidae fam. n., Kielcepora ornata gen. et sp. n., Ojlepora gen. n., and Kielanopora gracilis gen. et sp. n. are proposed.

A segmented Paleocene cheilostomatous bryozoan and its possible relationships with pseudarcellids

80%

Szczechura J.

Acta Palaeontologica Polonica

1994

tom 39

nr 2

223-231

Paired, cup-like calcitic structures from the Paleocene of Pomerania, Poland, are interpreted as complete zoaria or zoarial segments of an unknown group of cheilostomatous Bryozoa. Each of the cups in the twinned unit resembles the alleged Eocene tintinnid Pseudarcella. These fossil organisms may thus represent a connecting link between the more complex segmented bryozoan of bicorniferids and the extremely simplified pseudarcellids. Geminella polonica gen. et sp. n. is proposed.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Dzik J.

1 Szczechura J.

1 1994

1 1992

Wyniki wyszukiwania

Early astogeny and relationships of the Ordovician rhabdomesine bryozoans

A segmented Paleocene cheilostomatous bryozoan and its possible relationships with pseudarcellids