An asymmetric segmented organism from the Vendian of Russia and the status of the dipleurozoa
Titel:
An asymmetric segmented organism from the Vendian of Russia and the status of the dipleurozoa
Auteur:
Dzik, Jerzy Ivantsov, Andrey Yu.
Verschenen in:
Historical biology
Paginering:
Jaargang 13 (1999) nr. 4 pagina's 255-268
Jaar:
1999
Inhoud:
A large animal, formally described as Yorgia waggoneri (Ivantsov, in press) has been discovered at a Vendian locality on the shore of the White Sea, in northern Russia. It is anatomically transitional between the Ediacaran “segmented worms”; Dickinsonia and Spriggina. Like Dickinsonia, it had a metameric dorsal quilt, composed of a series of muscular chambers, and presumed intestinal caeca. Yorgia was unlike Dickinsonia, but similar to Spriggina, Marywadea, and Praecambridium, in that the anterior part of the dorsal quilt did not overhang the caeca. Rather, it was displaced posteriorly, with the medial chamber arched to the left. In effect, a lunate anterior region with ramified caeca was exposed dorsally. The left and right series of chambers were asymmetric, alternating along the mid-line. These organisms are not related to either annelids or arthropods, but possible homologies between characters of these animals and those of present day nemerteans and some deuterostomian phyla are proposed here.
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