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Mochtyella angelini Mierzejewski, 1978
Diagnosis.- "Both right and left MI strongly compressed laterally. Basal ridge distinctly denticulated, 0.17-0.30 total jaw long. Second ridge straight, smooth, very narrow, 0.19-0.31 total-jaw long. Laeobasal ridge prominent, denticulated, half total-jaw long. Anterior teeth (not less than 5 in number) decreasing in size anteriorly; the last one provided with 3 tips. Lateral teeth subtriangular, relatively short" (Mierzejewski 1978, p. 275).
Occurence. Upper Silurian erratic boulders of Poland; Wenlock of Gotland, Sweden.
Remarks. Named in honour of N.P. Angelin who was the first student of isolated jaws of the fossil Polychaeta.
    Isolated right MI from erratic boulders of Silurian age attributed by Kielan-Jaworowska (1966) to two distinct species (Mochtyella sp. c and M. sp. d) appear to fall within the range of intrapopulation variability of Mochtyella angelini.
     M. angelini
resembles most closely the Silurian species M. trapezoidea Kielan-Jaworowska; the most important difference is in the absence of second ridge in the latter species. M. angelini resembles also M. kielanae Szaniawski & Wrona, the differences are in the distinctness of both outer and inner margins due to the masiveness of the jaws, the smoothness of the second ridge, and the more distincly denticulated basal ridge of M. angelini. Furthermore, both the species differ also in the outline of left and right anterior margins of MI. According to Kielan-Jaworowska (1966), M. kielane (= M. sp. b Kielan-Jaworowska, 1966) and M. angelini represent distinct phyletic lineages; namely, cristata-group and trapezoidea-group, respectively. Then, one may claim that the morphological similarity of both the species is due to a parallel evolution.
References:
Mierzejewski, P. 1978. New placognath Eunicida (Polychaeta) from the Ordovician and Silurian of Poland. - Acta Geologica Polonica 28, 2, 271-281.
Class Polychaeta, Ordo Eunicida, Family Mochtyellidae
(= Mochtyella sp. c Kielan-Jaworowska 1966; = Mochyella sp. d Kielan-Jaworowska, 1966)
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.
Edited by

Countess Maja Anna Korwin-Kossakowska and Piotr Mierzejewski, the Count of Calmont

2002-2004