. Bulletins of American paleontology. Jurassic Ammonites of British Columbia: Smith and Tipper 37. QpAO , Text-figure 32. —Whorl shape cross-sections for species of the Po- lymorphitidae. Figures are natural size. a. Tropidoceras n. sp. (GSC 98648); b. Tropidoceras aciaeon (D'Orbigny, 1844) (GSC 98645); c. Polymorphites confusus (Quenstedt. 1856) (GSC 98626); d,f Acan- thopleuroceras thomsoni. (d. Holotype GSC 98638, f Paratype GSC 98637); e. Tropidoceras masseanum rotunda (Futterer, 1893) (Holotype GSC 95573); g-h. Acanthopleuroceras whiteavesi Smith and Tipper. 1988 (g. GSC 98653.
. Bulletins of American paleontology. Jurassic Ammonites of British Columbia: Smith and Tipper 37. QpAO , Text-figure 32. —Whorl shape cross-sections for species of the Po- lymorphitidae. Figures are natural size. a. Tropidoceras n. sp. (GSC 98648); b. Tropidoceras aciaeon (D'Orbigny, 1844) (GSC 98645); c. Polymorphites confusus (Quenstedt. 1856) (GSC 98626); d,f Acan- thopleuroceras thomsoni. (d. Holotype GSC 98638, f Paratype GSC 98637); e. Tropidoceras masseanum rotunda (Futterer, 1893) (Holotype GSC 95573); g-h. Acanthopleuroceras whiteavesi Smith and Tipper. 1988 (g. GSC 98653. h. Holotype GSC 87790). 1988, pi. 2, figs. 1, 2; refigured herein, PI. 7, fig. 7). Paratype: GSC 87791 (Smith et ai, pi. 2, figs. 3, 4; refigured herein, PI. 7, fig. 6). Material. —Forty-three specimens preserved in limestone, sandstone, and, rarely, in siltstone of the Sandilands and Ghost Creek formations and the Ren- nell Junction Member. Occurrence. —This species is the zonal index for the Whiteavesi Zone to which it is restricted. Apart from the Queen Charlotte Islands, the species is also known from the Hurwal and Keller Creek formations of Or- egon, information inadvertently omitted from the orig- inal species description by Smith and Tipper (;>; Smith et ai, 1988, p. 1521). ^0\.. A02, A06, B03. C02, D02, D07, Dl 1, ETl, E27, E34. E35, G04, 116. rlge.—Whiteavesi Zone (Early Pliensbachian). Genus TROPIDOCERAS Hyatt, 1867 Type species.—Aninwnites masseanum d'Orbigny, 1844, pi. 58, by subsequent designation (Haug, 1885, p. 606). Reinarks.—Fairly evolute forms with a compressed whorl section bearing a sharp keel. Ribbing is often weak and sometimes divided into primaries and sec- ondaries. Species are non-tuberculate or weakly bitu- berculate. The suture line is complex with a bifid lateral lobe. Most workers have concluded that Tropidoceras and .Acanthopleuroceras are closely related (, Dom- mergues and Mouterde, 1978, but see Wiedenmayer, 197
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