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The tube‐like structures on the juvenile shells of earliest strophomenides and billingsellides as evidence of their life cyclesстатья
Статья опубликована в высокорейтинговом журнале
Статья опубликована в журнале из списка Web of Science и/или Scopus- Авторы: Madison A.A., Kuzmina T.V.
- Журнал: Lethaia
- Год издания: 2019
- Издательство: Taylor & Francis
- Местоположение издательства: United Kingdom
- DOI: 10.1111/let.12342
- Аннотация: Possible life cycle of some ancient plectambonitoids (order Strophomenida) from the Middle Ordovician of Russia is reconstructed based on the well‐preserved specimens composing the ontogenetic series. Four regions may be distinguished on their shell surface: protegulum, brephic shell, neanic shell and adult shell. The posterior margin of ventral protegulum bears pedicle sheath, which is a tubular outgrowth with a 40‐μm‐wide aperture at the distal end. The protegulum and brephic shell have common type of microstructure that possibly is spherular; the neanic and adult shells are fibrous. The strophomenide ontogeny possibly was similar to that of recent discinides. The strophomenide life cycle possibly included the planktotrophic juvenile stage; the protegulum and brephic shell were formed in the water column. The aperture of the pedicle sheath was possibly used as an anal opening of the floating juvenile and as an attachment organ during the settlement; at early adult stages, the sheath erased, the anus closed, and the animal started to lie on the ventral valve. The origin of the order Strophomenida and its relative groups is possibly connected with the loss of the pedicle lobe; judging by some strophomenide morphological features, true pedicle was present in the strophomenide ancestors. The tubes on the ventral umbones of strophomenides and billingsellides are not homologous as pedicle sheaths of strophomenides are formed at the planktotrophic swimming stage, and the tubes surrounding the pedicles of billingsellides were formed by deltidial plates of almost adult shell after settling.
- Добавил в систему: Кузьмина Татьяна Валерьевна