| - Graptolite stolons described as hydroid remnants - |
Fossil remnants of pterobranch and graptolite stolon system are moderately
common organic microfossils to be found in some marine deposits,
especially of Ordovician and Silurian age. However, they were repeatedly
misinterpreted for decades as remains of the "chitinous hydroids" or
incertae sedis forms. According to Mierzejewski (1986), such alleged
"hydroid" genera as Calyxhydra Kozłowski, 1959, Cylindrotheca
Eisenack, 1934, Kystodendron KozĹ‚owski, 1959, Lagenohydra KozĹ
‚owski, 1959, Palaeotuba Eisenack, 1934, and fossils described by KozĹ
‚owski (1959) as parataxonomic units Gonothecae Formae A, B, and C are
simply rhabdopleurid stolons and dormant bud capsules. Moreover, the
enigmatic Xenocyathus stolonifer Eisenack, 1982, was recognized as a
fragment of the stolonal system of crustoid graptolites (Mierzejewski 1984).
Recently, another "hydroid" genus, Diplohydra Kozłowski, 1959, was
also reinterpreted as an aberrant member of the Order Rhabdopleuroidea
(Mierzejewski & Kulicki 2002).
To the right is the holotype of Trimerohydra glabra Kozłowski, 1959,
the type species of the genus Trimerohydra Kozłowski, 1959. This form
was described from Ordovician glacial boulders of Baltic origin collected in
Poland, similarly as the second species of this genus, T. annulata KozĹ
‚owski, 1959.The alleged hydroid nature of Trimerohydra was questioned
by Bulman (1970) in Treatise on Invertebrate Paleontology and regarded
as a possible synonym of the graptolite genus Koremagraptus Bulman,
1927.
Beneath is a fragment of a dendroid graptolite stipe showing details of a
stolon trifurcation. The presented stolon are strikingly similar to the holotype
of T. glabra.
common organic microfossils to be found in some marine deposits,
especially of Ordovician and Silurian age. However, they were repeatedly
misinterpreted for decades as remains of the "chitinous hydroids" or
incertae sedis forms. According to Mierzejewski (1986), such alleged
"hydroid" genera as Calyxhydra Kozłowski, 1959, Cylindrotheca
Eisenack, 1934, Kystodendron KozĹ‚owski, 1959, Lagenohydra KozĹ
‚owski, 1959, Palaeotuba Eisenack, 1934, and fossils described by KozĹ
‚owski (1959) as parataxonomic units Gonothecae Formae A, B, and C are
simply rhabdopleurid stolons and dormant bud capsules. Moreover, the
enigmatic Xenocyathus stolonifer Eisenack, 1982, was recognized as a
fragment of the stolonal system of crustoid graptolites (Mierzejewski 1984).
Recently, another "hydroid" genus, Diplohydra Kozłowski, 1959, was
also reinterpreted as an aberrant member of the Order Rhabdopleuroidea
(Mierzejewski & Kulicki 2002).
To the right is the holotype of Trimerohydra glabra Kozłowski, 1959,
the type species of the genus Trimerohydra Kozłowski, 1959. This form
was described from Ordovician glacial boulders of Baltic origin collected in
Poland, similarly as the second species of this genus, T. annulata KozĹ
‚owski, 1959.The alleged hydroid nature of Trimerohydra was questioned
by Bulman (1970) in Treatise on Invertebrate Paleontology and regarded
as a possible synonym of the graptolite genus Koremagraptus Bulman,
1927.
Beneath is a fragment of a dendroid graptolite stipe showing details of a
stolon trifurcation. The presented stolon are strikingly similar to the holotype
of T. glabra.
R e l a t e d p a g e s:
Graptolite stolons resembling tracheids of vascular plants.
Maenniligraptus ursulae - an Ordovician graptolite with a strange stolon system.
Graptolite stolons resembling tracheids of vascular plants.
Maenniligraptus ursulae - an Ordovician graptolite with a strange stolon system.
| _______________________________________ Graptolite Net Edited by Piotr Mierzejewski,The Count of Calmont and Countess Maja Anna Korwin-Kossakowska |
| Some fragments of stolons of Trimerohydra glabra (= ? Koremagraptus sp.) were studied with a transmission electron microscope (Mierzejewski 1986). Ultrathin sections through the stolon reveal that their walls are made of a homogenous substance with rather uniform electron density, resembling the crassal fabric of Dictyonema and other sessile graptolites. |
Photo: Cyprian Kulicki
Photo: Cyprian Kulicki
| From R. Kozłowski |
