Page:A Revision of the Families and Genera of the Stylonuracea (Eurypterida).djvu/11

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Type species.—Dolichopterus stylonuroides Clarke and Ruedemann, 1912.

Derivation of name.—Named in honor of Rudolf Ruedemann whose many contributions to our knowledge of the Chelicerata are basic and well known to all who work in this group.

Distribution.—Eastern New York.

Stratigraphic range.—Ordovician.

Remarks.—Ruedemannipterus seems to be an interesting connecting genus between the Dolichopteridae and Stylonuridae. The distinctly elongated carapace and narrow mesosoma, as well as the narrow sixth leg, resemble features of some of the Stylonuridae. However, the development of a paddle, although narrow, with numerous supplementary lobes, probably should designate this genus as one of the Dolichopteridae. As it is obviously a connecting genus, good arguments for it being a stylonurid can also be advanced. Brachyopterus Størmer, 1951, has a carapace which in general shape resembles Ruedemannipterus, although the position of the eyes and the stylonurid type of legs make further comparison unnecessary.

A number of other eurypterids which have aroused uncertainty as to their generic affinities can now be referred to the genus Ruedemannipterus. These include Dolichopterus latifrons Clarke and Ruedemann, 1912, from the Ordovician Schenectady shales of Schenectady, New York, and Dolichopterus breviceps Clarke and Ruedemann, 1912, from the Ordovician Normanskill shale of Catskill, New York.

Genus Tarsopterella Størmer, 1951

Diagnosis.—Medium-to-large dolichopterids, outer surface with strongly developed knobs and scales; prosoma broadly subrectangular, slightly concave in front; lateral eyes small; opisthosoma with pronounced epimers; prosomal legs unknown, except fragments of last leg which indicate presence of a wide paddle, possibly dolichopteroid (diagnosis modified from Størmer, 1955, pp. 38–39).

Type species.—Stylonurus scoticus Woodward, 1864.

Distribution.—Scotland and Germany.

Stratigraphic range.—Devonian.

Remarks.—The two podomeres preserved on the left side of the holotype are flat structures indicating the presence of a paddle. On the other hand, Størmer (1955, p. 39) believes that the legs were probably stylonuroid. The overall aspect of the eurypterid could in-