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Glyptoxoceras tenuisulcatum Forbes 1846 from: Kennedy, W.J..Henderson, R.A.. (1992): Heteromorph ammonites from the Upper Maastrichtian of Pondicherry, south India . Palaeontology Vol. 35 p. 693-731
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Species Glyptoxoceras tenuisulcatum Forbes 1846



Diagnosis / Definition:
Kennedy & Henderson (1992):
DESCRIPTION.- The earliest stages are in the form of a low loose helix, with a low translation rate (Pl. 2, figs. 2, 6, 8) and a slightly compressed, subcircular whorl section. Ornament is of very fine, delicate ribs, with a rib index of 14. The ribs are weak on the inner whorl face, but strengthen over the juncture of inner and upper whorl faces, are concave on the upper, markedly prorsiradiate on the outer, sweeping back and markedly concave across the lower whorl face. These helices can be linked, via BMNH C4105, to the lectotype (Pl. 2, fig. 30) which is a shaft and part of a helicoid whorl, in all 94 mm long. The whorl breadth to height ratio is 0.9 at the greatest whorl height preserved, and the rib index 15 or 16. The ribs are very fine, sharp and narrower than the interspaces. They are transverse to feebly concave on the dorsum, sweeping forwards and markedly prorsiradiate on the flanks, and markedly oblique on the venter, rather than transverse. Suture florid, with deeply incised bifid elements (Text-fig. 28).
Discussion / Comments:
Kennedy & Henderson (1992):
TYPES.- The lectotype, by the subsequent designation of Matsumoto (1959a, p. 168), is BMNH C51104, the original of Forbes (1846, pl. 10, fig. 8), GSC R10493. Paralectotypes are BMNH C51107, the original of Forbes (1846, pl. 11, fig. 3a-b); BMNH C51105, the original of Forbes (1846, pl. 11, fig. 3c-e); GSC R10495; BMNH C51106, the original of Kossmat (1895, pl. 19 (5), fig. 5a-b); GSC R10494; BMNH C51108 (4 specimens), and C51135, all from the Valudavur Formation of Pondicherry, south India (ex Kaye and Cunliffe Collection), BMNH C82504 is a topotype (ex Marsham Collection). DISCUSSION.- Matsumoto (1959a) thought tenuisulcatus might be a Diplomoceras, but the helicoid whorls indicate, rather, that it is a Glyptoxoceras; Diplomoceras have ptychoceratid early growth stages (Matsumoto 1984, p. 31, pl. 8, fig. 3); Matsumoto and Miyauchi 1984, p. 68, pl. 27, fig. 2; text-fig. 11a). Glyptoxoceras tenuisulcatum differs from all other described Glyptoxoceras in the very fine ornament, markedly prorsiradiate on the flanks, and oblique, rather than transverse on the venter, as well as its retention of helicoid coiling to a much larger size than D. indicum, the other species in which helices are known. OCCURRENCE.- Maastrichtian of south India and Denmark.
Synonym list:
Kennedy & Henderson (1992):
1846 Hamites tenuisulcatus Forbes. - Forbes : p.116 pl. 10, fig. 8; pl. 11, fig. 3
1850 Ancycloceras tenuisulcatus Forbes. - d'Orbigny : p.214
1865 Anisoceras sp. tenuisulcatum Forbes. - Stoliczka : p.177 pl. 85; fig. 14-16
1895 Hamites (Anisoceras) tenuisulcatus Forbes. - Kossmat : 147(51) pl. 19 (5), fig. 5-6
1959 "Hamites" tenuisulcatus Forbes. - Matsumoto : p.168
1977 Diplomoceras tenuisulcatum Forbes. - Phillips : p.49
1979 Glyptoxoceras cf. indicum Forbes. - BIRKELUND : p.55
1992 Glyptoxoceras tenuisulcatum Forbes. - Kennedy & Henderson : p. 701, 703 pl. 2, fig. 2, 6, 8, 30; text-fig. 2B
Stratigraphy - relative ages:
Maastrichtian: Kennedy & Henderson (1992)
References:

Forbes,E.. (1846):
Report on the Cretaceous fossil invertebrates from southern India, collected by Mr. Kaye and Mr. Cunliffe . Transactions of the Geological Society of London Vol. 2(7) p. 97–174

d'Orbigny,A. (1850):
Prodrome de Paléontologie. Stratigraphique universelle des animaux mollusques & rayonnés faisant suitre au cours élémentaire de paléontologie et de géologie stratigraphique. , Cours Élémentaire de Paléontologie et de Géologie Stratigraphiques Vol. 2

Stoliczka,F.. (1865):
The fossil Cephalopoda of the Cretaceous rocks of southern India. Ammonitidae with revision of the Nautilidae etc. . Memoirs of the Geological Survey of India, (1), Palaeontologica Indica6-9 p. 107-154

Kossmat,F.. (1895):
Untersuchungen über die Südindische Kreideformation. Erster Theil . Beiträge zur Paläontologie Österreich-Ungarns und des Orient Vol. 9 p. 97-203

Matsumoto,T.. (1959):
Upper Cretaceous ammonites of California, Part I: Introduction and Baculitidae . Memoirs of the Faculty of Science, Kyushu University, Series D, Geology Vol. 8 p. 91-171

Phillips,D.. (1977):
Catalogue of the type andjigured specimens of Mesozoic Ammonoidea in the British Museum (Natural History). , Trustees of the British Museum (Natural History) p. 220 pp.

BIRKELUND,T.. (1979):
The last Maastrichian ammonites.
In: Cretaceous-Tertiary Boundary, The Maastrichtian and Danian of Denmark Eds: Events Symposium, 1.. p. 210 pp.

Kennedy,W.J.. and Henderson,R.A.. (1992):
Heteromorph ammonites from the Upper Maastrichtian of Pondicherry, south India . Palaeontology Vol. 35 p. 693-731

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