On the Placodermi of the Upper Devonian of East Greenland. II. Antiarchi: subfamily Bothriolepinae

General part

Abstract

Part I of this monograph "On the Placodermi of the Upper Devonian of East Greenland", treating the Phyllolepida and Euarthrodira, appeared in the spring of 1934 (Stensiö 1934b). Two supplements to part I were published later on, the first one in 1936, the second one in 1939 (Stensiö 1936, 1939a).

Part II herewith brought out deals with all the Bothriolepis-material collected by the Danish East Greenland expeditions undertaken under Dr. Lauge Koch's leadership in the summers of 1929- 34 and 1936 (cf. Stensiö 1934b, pp. 5-6; 1936, pp. 5-7; 1939a, p. 3; 1939b). In addition it contains also a general account of the organization of the Bothriolepinae, a fairly complete systematic description of Bothriolepis canadensis, and a first attempt at a revision of the other species of the subfamily Bothriolepinae.

According to the original plan for the publishing of this monograph drawn up in 1933 (Stensiö 1934b, p. 5) part II would have treated the whole Upper Devonian Antiarchi-material from East Greenland, i. e. both the Bothriolepis-material and the Remigolepis-material. This plan had to be abandoned, however, since in 1939 it appeared that a description of all that material would be much too large to be printed in one volume. Part II of the monograph had, therefore, to be devoted only to the Bothriolepis-material, whereas the description of the Remigolepis-material, that is now under preparation, will be published later on, as a third and last part of the monograph.

During my work on it I perceived pretty soon, that, because of its state of preservation and wide range of variation, the Bothriolepis-material from the Upper Devonian of East Greenland was difficult to determine, and that a satisfactory description of it could be worked out only after a thorough reexamination of, at least, the majority of the previously known Bothriolepis species.

Such a reexamination, above all of the Canadian and British species, was, therefore, begun in 1938. Though, owing to the present political conditions in Europe, this reexamination could not nearly be carried through to the extent originally planned the results gained from it are nevertheless of much importance. These results help considerably in throwing new light not only upon the characters of the various species representing the Bothriolepinae and the range of variation of these characters, but also upon the organization of the Bothriolepinae and the Antiarchi in general. It is therefore appropriate that they are published here together with the description of the Greenland material.