FIELDIANA · GEOLOGY
CHICAGO NATURAL HISTORY MUSEUM
A Revision of the Families and Genera of the Stylonuracea (Eurypterida)
Erik N. Kjellesvig-Waering
Research Associate, Department of Geology
The genus Stylonurus was first made known by Page in 1855 in a report to the British Association. In the first edition of his famed Advanced Text-Book of Geology (1856, p. 135, fig, 2), he figured and named the single specimen as Stylonurus powriensis, a name which he altered to Stylonurus powriei in the second edition of his Text-Book (1859, p. 181, fig. 3). If the genus Stylonurus is to date from 1856 when Page first proposed it with S. powriensis as obvious type species by monotypy, then the original name of the species must be used, since the genus could not have been proposed without a type species. The nearly whole specimen came from the Lower Devonian Old Red Sandstone of Scotland, and revealed long, slender legs without the characteristic paddles which characterized the hitherto known eurypterids. In the later publication, Page described another Stylonurus as S. spinipes (1859, p. 181, fig. 1) from the Silurian of Scotland. It is curious, and not entirely understandable, that the specific name Stylonurus powriensis Page (S. powriei) became established in the literature, but Stylonurus spinipes Page did not, although it was redescribed on the basis of the same specimen by Woodward (1866–78 , pp. 129–131, pl. XXIV, fig. 1) as Stylonurus logani Woodward. There is no question that Page's Stylonurus spinipes 1859 has clear priority over Stylonurus logani Woodward, 1872. It would be inconsistent to accept the name Stylonurus powriensis Page (S. powriei) and not Stylonurus spinipes Page when both were equally well figured and "described." The type of the latter is an important specimen and the species became in fact better known than the genotype. Since Stylonurus spinipes Page will be referred to repeatedly below, I wish to emphasize its validity.
Library of Congress Catalog Card Number: 66–17467