Epoch Lower
Cambrian
to Upper
Ordovician.
Cephalon
Among the already upper- mentioned characteristics,
the PTYCHOPARIIDA are featuring a broad cephalon, with genal spines at
many species. A furrowed glabella with 3 pairs of furrows is typical.
The
sutures
are normally running
ophistoparian (Gr.- cheek). Between the PTYCHOPARIIDA there are
blins species, too. The representatives
of this Order are featuring a
natant
hypostome.
Thorax
In the
majority of cases the great
thorax has 8 up to 17 segments. At the Olenoina up to 24 segments are to
be found.
Pygidium
Regarding
size and structures the pygidium varied species-specific. Whereas the
early species featuring little pygidia with fringe, the species of
later periods featuring big pygidia without fringe. Some representatives
of Olenina have spines.
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