Cambrian   -   Ordovician   -   THE WORLD OF ORGANIC MICROFOSSILS    -   Silurian   -   Devonian
 
Class Scyphozoa, Subclass Scyphomedusae, Order: ?Coronata, Incertae familiae, Genus: Byronia Matthew, 1899
 
Byronia robusta (Kozłowski) Mierzejewski, 1986
synonym:    Ascosyrinx robustus Kozłowski, 1967
 


Diagnosis by Mierzejewski (1986, p. 146):
"Scyphothecae varying in height, distally widening, circular in cross-
section, unculpured. Scyphorhiza strongly developed, usually in the
form of flat-convex disc. Stolons present in colonial forms."

Ultrastructure: The SEM studies showed lamellar structure of
periderm but they failed to give more detailed data on the structure.
Details of ultrastructure appeared easier to trace in the TEM
studies on ultrathin sections. Lamellae found in periderm fragments
range from 30 to 35 in numbbbber in periderm the total thickness of
which euals 10-15 micrometers. Individual lamellae are built of
electron-dense, acuatly bent fibres embedded in a matrix of low
electron density. The fibre pattern forms a specific image known in
the literature as "parabolic pattern" or "Bouligand pattern".
Depending on the angle whichperiderm is cut, the ultrastructural
image varies. Fibres vary in thickness from 250 to 370 A, and
lamellae from. 0.15 to 1.10 micrometers.
---------Some fragments display fibres slightly denser that the basic
matter. A sudden pulse with a strong beam of electrons of such
prepararions usually results in a markedincrese of contrast. This may
be explained by breakage of the basic matter and, possibly, shrinkage
of fibres.
-----"The ultrastructure recorded appears identical with some
images of chitin-protein complexes. (...)the results of electron
microscope studies suggest chitin character of B. robusta
periderm."

---------Byronia robusta was originally described under the generic
name Ascosyrinx Kozłowski, 1967 and tretaed as an organims with
enigmatic systematic position. This was connected with the fact that
the type series of this species was comprising incomplete specimens
with missing distal parts of scyphothecae which made them somewhat
similar to Ascosyrinx tenuis Kozłowski, 1967.
---------Byronia robusta differs from Byronia naumovi Kozłowski. It is
not clear wether or not the differences in ultrastructure of the
scyphothecae of the two species are of primary nature and what
istheir eventual taxonomic value.

---------Byronia robusta is known from the erratic boulders of
Ordovician (?Silurian) age in the area of Poland.
                                
                                          References:

Kozłowski, R. 1967. Sur certains fossiles a test organique. - Acta Palaeontologica
Polonica 12, 2, 99-137.

Mierzejewska, G. & Mierzejewski, P. 1979. Chitin-protein complex in the
Ordovician organic microfossil. - Acta Medica Polona 20, 1, 33-34.

Mierzejewski, P. 1986. Ultrastructure, taxonomy and affinities of some
Ordovician and Silurian organic microfossils. - Palaeontologia Polonica 47, 129-220.
Byronia robusta (Kozłowski) Mierzejewski
from an erratic boulder no. MZ/39, Ustka (Baltic coast),
Ordovician or Silurian.
Isolated scyphothecae and their fragments.
From Piotr Mierzejewski.
Byronia robusta (Kozłowski) Mierzejewski
TEM micrograph showing "parabolic pattern" of
a chitin-protein complex.
From Mierzejewska & Mierzejewski.