|Graptolite Net | Graptolites & Graptoliters | Scolecodonts | Rhabdopleuroidea | Cephalodiscoidea
|- 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 KozĹ‚owski, 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 KozĹ‚owski, 1959, was
also reinterpreted as an aberrant member of the Order Rhabdopleuroidea
(Mierzejewski & Kulicki 2002).
To the right is the holotype of Trimerohydra glabra KozĹ‚owski,
1959, the type species of the genus Trimerohydra KozĹ‚owski, 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.
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.
|From R. KozĹ‚owski