| AN ABERRANT ENCRUSTING GRAPTOLITE FROM THE ORDOVICIAN OF ESTONIA PIOTR MIERZEJEWSKI |
An organic microfossil, Erecticamara maennili gen. et sp. n., superficially similar to some imprefectly preserved
chitinozoans, is described as an aberrant camaroid graptolite from the Lower Ordovician Kunda Stage, Aluoja
Substage, of the Tallinn area, North Estonia. Its elongated, bottle-shaped or subconical thecae, interpreted as
autothecae, are differentiated into a broader proximal part (camara), provided with a convex, rarely flat, bottom,
and a narrower distal one (collum), devoid of any kind of apertural processes. The wall of the fossil is made of the
chitinozoans, is described as an aberrant camaroid graptolite from the Lower Ordovician Kunda Stage, Aluoja
Substage, of the Tallinn area, North Estonia. Its elongated, bottle-shaped or subconical thecae, interpreted as
autothecae, are differentiated into a broader proximal part (camara), provided with a convex, rarely flat, bottom,
and a narrower distal one (collum), devoid of any kind of apertural processes. The wall of the fossil is made of the
| Acta Palaeontologica Polonica 2000, 45, 3, 239-250 |
fusellar tissue; irregularly distributed oblique sutures of fuselli are not arranged in a zigzag line. A sudden change of
fuselli width leading to an appearence of the microfusellar tissue is sometimes observed in the distal part of the
tube. The presence of primitive cortex (paracortex? pseudocortex?) is suggested. Robust, elongated vesicles are
found inside two autothecae and interpreted as a dormant structure, tentatively compared with cysts of crustoid
graptolites or a blastocrypt of graptoblasts. Its upper wall is situated between the camara and collum and looks like a
sclerotized diaphragm described in other camaroids. The fossil unites certain characters of the Cephalodiscoidea
and the Camaroidea but is not interpreted as truly transient link between these two hemichordate groups.
fuselli width leading to an appearence of the microfusellar tissue is sometimes observed in the distal part of the
tube. The presence of primitive cortex (paracortex? pseudocortex?) is suggested. Robust, elongated vesicles are
found inside two autothecae and interpreted as a dormant structure, tentatively compared with cysts of crustoid
graptolites or a blastocrypt of graptoblasts. Its upper wall is situated between the camara and collum and looks like a
sclerotized diaphragm described in other camaroids. The fossil unites certain characters of the Cephalodiscoidea
and the Camaroidea but is not interpreted as truly transient link between these two hemichordate groups.
| GRAPTOLITE NET edited by Piotr Mierzejewski, the Count of Calmont and Countess Maja A. Korwin-Kossakowska since 2002 |
