|Genus Rakvereprion Mierzejewski, 1978
|Type species: Staurocephalites? balticus Eisenack, 1975
Diagnosis: " Jaw apparatus of placognath type with symmetric posterior part
consisting of right and left MI, basal and laeobasal plates. Anterior part of the
apparatus unknown. MIr almost straight, slightly bent outwards in its anterior
part, elongate. Basal plate elongate, compressed laterally, equal in length to
MIr, adhering to its outer margin. MIl and laeobasal plate forming mirror
images of MIr and basal plate." (Mierzejewski 1978, p. 279).
Remarks. -The type species of the genus has been tentatively assigned by
Eisenack (1975) to the genus Staurocephalites Hinde, 1879. Actually,
however, the latter name is nomen dubium.
Kielan-Jaworowska (1966) mentioned an undescribed apparatus with its MI
resembling MI and MII of Xanioprion Kielan-Jaworowska, attached one to the
other; the apparatus was assigned to Xanioprion sp. One may claim that
Rakvereprion is closely related to Xanioprion, the main differences being in
the wholeness of the apparatus elements in the former genus, while they are
split transversally in the latter one. In fact, Rakvereprion appears
intermediate between the Mochtyellidae and Xanioprionidae.
Eisenack, A. 1975. BeitrĂ¤ge zur Anneliden-Forschung. - Neues Jahrbuch fĂĽr Geologie und PalĂ¤ontologie Abhandlunge,
Monatshefte, 150 (2), 227-252.
Kielan-Jaworowska, Z. 1966. Polychaete jaw apparatuses from the Ordovician and Silurian of Poland and a comparison with
modern forms. - Palaeontologia Polonica 16, 1-152.