The pelvic fin is seen in only two specimens (K. U. nos. 786F, 788). That on no. 788 is lobate and has 25 lepidotrichia, jointed for approximately the distal half, and 2.5 to 13.0 mm. in length. Total length of the fin is 25.0 mm. There is no trace of the internal skeletal structure or of the articulation to the basal plate in either specimen. For a description of the fin on no. 786F, see Hibbard (1933:281).
A few isolated bones on K. U. no. 788 (fig. 7) are interpreted as basal plates of the unpaired fins. For additional description of the unpaired fins on the type, K. U. no. 786F, see Hibbard (1933).
Two of these bones are flat, smooth and oblong, bearing a diagonal ridge that extends in the form of a projection. Orientation is completely unknown. These may be basal plates of the anterior dorsal fin. The fin on no. 786F that Hibbard (1933:281) interpreted as the posterior dorsal fin is now thought to be the anterior dorsal fin.
[Illustration: FIG. 7. _Synaptotylus newelli_ (Hibbard). Basal plates of unpaired fins. A, anterior dorsal fin, based on K. U. no. 788, × 10. B, posterior dorsal fin, based on K. U. no. 788, × 12. C, anal fin, based on K. U. no. 11450, × 5. Anterior is toward the left.]
One distinctive bone may represent the basal plate of the posterior dorsal fin. This incomplete specimen shows two projecting curved processes, bearing low but distinct ridges, which diverge, probably anteriorly. The central portion is narrow. The two ridges continue onto the posterior portion. This has been broken off, but shows that the ridges diverge again. The surface is smooth, except for the ridges. As before, orientation is uncertain. On no. 786F this fin was interpreted by Hibbard (1933:281) as the anal fin.
Only part of one basal plate of the anal fin was preserved on K. U. no. 11450. That plate is oblong and has an expanded anterior end. The narrow, constricted part bears two oblique ridges and a few tubercles. The posterior part has nearly straight margins (represented by impressions) and the posterior margin is oblique, sloping anteroventrally. The flared anterior part has a smooth surface. This basal plate is more nearly like those of _Coelacanthus_, according to the descriptions given by Moy-Thomas (1937:399). The basal plate is associated with seven apparently unjointed, incomplete lepidotrichia. The anal fin on no. 786F is interpreted as the anterior dorsal fin (Hibbard, 1933:281).