An aberrant encrusting graptolite from the Ordovician of Estonia

An organic microfossil, Erecticamara maennili gen. et sp. n., superficially similar to some imperfectly preserved chitinozoans, is described as an abe rrant camaroid graptolite from the Lower Ordovician Kunda Stage, Aluoja Sub stage, of the Tallinn area, North Estonia. Its elongated, bottle-shaped or subconical thecae, interpreted as autothecae, are differentiated into a bro ader proximal part (camara), provided with a convex, rarely flat, bottom, a nd a narrower distal one (collum), devoid of any kind of apertural processe s. The wall, of the fossil is made of the fusellar tissue; irregularly dist ributed oblique sutures of fuselli are not arranged in a zigzag line. A sud den change of fuselli width leading to an appearence of the microfusellar t issue is sometimes observed in the distal part of the tube. The presence of primitive cortex (paracortex? pseudocortex?) is suggested. Robust, elongat ed vesicles are found inside two autothecae and interpreted as a dormant st ructure, tentatively compared with cysts of crustoid graptolites or a blast ocrypt of graptoblasts. Its upper wall is situated between the camara and c ollum and looks like a sclerotized diaphragm described in other camaroids. The fossil unites certain characters of cephalodiscid pterobranchs and cama roid graptolites but is not interpreted as truly transient link between the se two hemichordate groups.