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Problems of Ammonite Nomenclature

Published online by Cambridge University Press:  01 May 2009

L. F. Spath
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AMMONITES VARIANS J. Sowerby2 is a composite species, based on five syntypes, which are preserved in the British Museum (Natural History),3 and have long been accessible to any reviser who wished to select a lectotype from among these syntypes. Nobody, however, has yet done so. In the days of the early revisers, of course, from Mantell and Brongniart (1822) to Sharpe (1853), nomenclatorial restrictions were unknown; and even when Semenow (1899)4 dealt with Sowerby's species, he accepted the customary interpretation of Schloenbachia varians without going back to Sowerby's original description and figures. Semenow took d'Orbigny's5 excellent figure as typical, and his restriction seemed to me convenient to adopt,6 if not actually binding. But on going more fully into the matter I discovered not only that Semenow's selection (if it be selection) is not valid but also that none of the forms which authors nowadays identify with Schloenbachia varians agrees either with Sowerby's description or with any of the syntypes in the British Museum. It is thus highly desirable to discuss this common zonal ammonite species and place its interpretation on a sound footing.

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Type
Original Articles
Information
Geological Magazine , Volume 75 , Issue 12 , December 1938, pp. 543 - 547
Copyright
Copyright © Cambridge University Press 1938

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References

page 543 note 1 Bulman, O. M. B., 1938, Handbuch der Paläozoologie, Borntraeger, Berlin, Bd. 2D, Lief. 2, p. 58, table ii.Google Scholar

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page 544 note 1 Fossils of the South Downs, 1822, pp. 115–17, pl. xxi, figa. 2, 5, 7.Google Scholar

page 544 note 2 The larger specimen (fig. 7) is lost, so that the smaller example (fig. 5) in the British Museum (No. 33547) is chosen as lectotype of S. intermedia. It differs from the Amm. varians figured by Schliiter (“Cephalopoden der oberen deutschen Kreide,” Palaeontographica, xxi, 1871, pl. iv, figs. 11–12 only) chiefly in being smaller and less strongly ornamented on the earlier half of the last whorl.Google Scholar

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page 545 note 3 loc. cit., Proc. Geol. Assoc., 1926, p. 430. I then interpreted S. coupei in Semenow's sense. S. trituberculata is connected with the typical S. varians and S. tetrammata by forms like Sharpe's fig. 2 (pl. viii) or Sowerby's largest syntype (fig. 2).Google Scholar

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page 546 note 5 loc. cit., Geol. Mag., 1926, p. 81, and Proc. Geol. Assoc., 1926, p. 430 (with vara, aperta and densicostata).Google Scholar

page 546 note 6 Based on Amm. varians (non Sowerby) in Bronn, Lethaea geognostica, Stuttgart, 1851–2, pl. xxxiii, fig. 2, which is difficult to interpret by those who have not examined specimens, such as Stieler's types at Lille. Schlüter's small form (loc. cit., Palaeontographica, 1871, pl. iv, figs. 3–4 only), though apparently different, well shows the peculiar hoplitid ornamentation of S. nodulosa.Google Scholar