- 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
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
(Mierzejewski & Kulicki

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
Bulman (1970) in Treatise on Invertebrate Paleontology and regarded
as a possible synonym of the graptolite genus
Koremagraptus Bulman,

Beneath is a fragment of a dendroid graptolite stipe showing  details of a
stolon trifurcation. The presented stolon are strikingly similar to the holotype
T. glabra.

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