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Species / Maussenetia Dimorphospira

Maussenetia Dimorphospira


Original Description of Chenopus (Maussenetia) dimorphospira Cossmann & Pissarro, 1909

  • “Size moderate: shape ventricose, biconical without the wing; spire moderately elongate, conoidal, with dimorphous ornamentation; the spire consists of seven or eight whorls, the earliest of which are convex and smooth, the next ones spirally striate, the later ones angular towards their lower (posterior) third; the height of each whorl equals nearly half its width; sutures linear. The later whorls are ornamented with seven coarse spiral threads, of feeble relief, equally spaced, somewhat wider than the intervals between them. Body-whorl large, globose, gibbous on the side opposite to that of the wing, slightly excavated beneath (behind) the prominent keel which correspondents with the third spiral thread counted from the suture; base oval, declivous, ornamented with spiral threads which are thicker and more crowded than those of the spire, and which persist on to the canal. Aperture very narrow, closely following the curve of the columella, bearing the remains of a winged expansion which was probably keeled like the body-whorl, and which is prolonged up to the apex of the spire; columellar callus broadly spread out over the base, and bounded by a keel along the neck; rostrum and digitations unknown.”

Locus typicus: India. “Jhirak: zone 3, zone 4. According to Mr. Vredenburg, this species, or one very closely related, occurs also abundantly, as casts, in the Laki limestone overlying the Ranikot group.”

Stratum typicum: lower Eocene. “upper Ranikot.”

“Comparision with other species. - The fragments originally sent to us (Pl. IV, figs. 26-28) recalled Sulcogladius on account of their ornamentation and keel, both of which closely resembles the same features in Rostellaria goniophora Bellardi, the type of the subgenus Sulcogladius. But this impression was dispelled by our examination of a much more complete specimen subsequently forwarded to us by Mr. Vredenburg, showing the columellar callus, and the remnants of a wing extending up to the apex of the spire (Pl. VIII, figs 4, 4a): the shell must evidently be classified with the subgenus Maussentia, Cossm. (Essays Pal. Comp., 1904, fasc. VI, p. 118), the type of which is M. staadti, Cossm., characterised by the same ornamentation, with the same keel and gibbosity on the body-whorl. Nevertheless, Chenopus dimorphospira is much more ventricose than the European species, and its threads are more regular. No comparison can be established in the case of the wing which has disappeared in the Indian specimens. It is very interesting to find in the Eocene of India, a representative of this paleocenic form from the Paris basin; perhaps it will ultimately be shown that the species of Sulcogladius from the nummulitics of the Mediterranean (none of which have yet been found with the wing preserved), will have to be united with Maussenetia, indicating stages in the migration of this form.”


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