Portal of Graptolites and Pterobranchs sponsored by "M.M. PLUS M." SZTANDARY
The stolon system in Rhabdopleura compacta (Hemichordata)
and its phylogenetic implications
Adam Urbanek and P. Noel Dilly
Abstract of the paper (p. 201):

"Studies made with the light microscope on the stolon system of extant pterobranch hemichordate
Rhabdopleura compacta Hincks, 1880 have revealed the presence of characteristic structures called herein
diaphragm complexes. Each complex consists of the stonal diaphragm proper and a thin-walled conical
encasement, produced by a rapid inflation of the stolonal sheath around the diaphragm. Such structures
have never been observed before either in the Recent of fossil
Rhabdopleurida. However, both in their origin
and in their relations to the stolon and to the zooidal tube, diaphragm complexes strongly resemble the
internal portions of thecae as recognized in the sessile orders of the Graptolithina. The significance of the
presence of these homologues of the enclosed initial portions of thecae in
Rhabdopleura compacta for the
understanding of the phylogenetic relationships between pterobranchs and graptolites is discussed."

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