Subclass Amphigastropoda Simroth, 1906
Order Bellerophontida McCoy, 1852
Superfamily Bellerophontoidea McCoy, 1852
Family Bellerophontidae McCoy, 1852
Genus Cymatospira Knight 1942

Cymatospira and Pharkidonotus are similar at a distance, but the differences are easy to see once observed closer. Cymatospira has collabral undulations and aperture flares during growth, which appear as thickened growth lines following the aperture shape. There is a delicate spiral ornament over the shell, which crosses these flare lines unbroken. This shell detail supports the observation that the spiral ornament occurs well after aperture growth when the older part of the shell surface plunges into the aperture. Additionally, occasional transverse plicae (thickened folds) appear on either side of the selenizone. The selenizone is slightly depressed, which differs from the prominent raised ridge of Pharkidonotus.

Last, specimens of Cymatospira are smaller on average compared to Pharkidonotus.

Fig. 1—Cymatospira from the Pine Creek limestone at SL 6445. A–B, a specimen with preserved lateral aperture piece, CG-0767; C–D, a specimen with preserved anterior end, CG-0768; E, Single specimen, CG-0574. Scale bar = 5 mm

References