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Species Zelandites varuna Forbes 1846

[1] text-fig. 3o Ifrim et al. (2004) [2] text-fig. 3p Ifrim et al. (2004) [3] text-fig. 6f-g, j Ifrim et al. (2004)

Diagnosis / Definition:
Ifrim et al. (2004):
Description. The specimens show two stages of growth that differ considerably. The early juvenile specimens (Textfig. 6F-G) show a low whorl section in which whorl breadth is double whorl height (WB/WH is 2·1). The conch is evolute with a moderate expansion rate. The venter is very widely rounded and bends narrowly into funnel-shaped flanks that converge slightly towards the venter. Flanks bend into a very short umbilical wall shortly before touching the previous whorl. Ventrolateral shoulders are ornamented by faint bullae which disappear towards the venter and dorsum. Fine prorsiradiate lirae are visible in the wide umbilicus. The internal moulds show three constrictions per whorl that are each accompanied by a rib. Constrictions cross the venter in a wide concave arch and are slightly prorsiradiate on the flanks. During the fourth or fifth whorl (D is then 4-5 mm), a rapid change is notable into a more involute growth stage (compare Text-fig. 6F-G). Whorl section becomes compressed and discoidal. The flanks are high and slightly convergent, and the venter narrowly rounded. Maximum whorl breadth is now in a dorsolateral position immediately above the umbilical wall, which is short and steep. At this stage a whorl covers c. 60 per cent of the former whorl so that small juvenile growth stages are not visible any more (Text-fig. 61). Faint broad ribs of the early juvenile conch continue on the ventrolateral shoulders, but become increasingly faint. Instead, faint striae cross the flanks. They present convex wide bows on the umbilical and ventrolateral shoulders, but are otherwise straight. They are not visible across the venter on any specimen. The suture line of the early juvenile stage is already complex; the median saddle is extended to a septum, EIL is biphylloid, L is bifid. The umbilical lobes are retracted parallel to the ornament. With increasing diameter the suture line becomes gradually more incised, and L exceeds E in depth. With the change to a high-whorled cross section more umbilicallobes evolve.
SUPPLEMENTARY DESCRIPTION.- Shell small (Table 2), very involute, with narrow and impressed umbilicus. Whorl section compressed, lanceolate, with flanks converging towards an acute venter. Maximum width near the umbilicus. Young stages totally smooth, two or three constrictions per whorl developing after a diameter of 2.5 cm. Constrictions moderately incised in the middle of the flank, disappearing towards the venter, with gaudryceratid pattern (prorsiradiate in the inner portion of the flank, with a sharp bend in the center of the flank and then rectiradiate in the outer portion of the venter). Shell almost smooth, with only weak lirae following the shape of the constrictions. Suture line with a gaudryceratid pattern. L and U, lobes slender, with L deeper than E. Lobes usually symmetric with the exception of L which is slightly asymmetric (Figure 12).
Discussion / Comments:
Ifrim et al. (2004):
Remarks: Early juvenile growth stages of Z. varuna with a trapezoidal whorl section have never been shown. Only Stinnesbeck (1986) described juvenile forms of Z. varuna at different diameters. A comparison of the WBIWH ratio with WD reveals strang changes during early ontogeny (see Textfig. 7). Measurements of our specimens fit so well with those documented from Chile that we assign our juvenile specimens directly to Z. varuna. Occurrence: Maastrichtian of southern India (Kennedy and Henderson 1992b), Japan (Matsumoto 1938), and Madagascar (Collignon 1956); Upper Maastrichtian of Chile (Stinnesbeck 1986), Antarctica (Macellari 1986; Zinsmeister et al. 1989) and Sakhalin Island, the Russian Far East (Yazikova 1994).
MATERIAL.- Three well preserved specimens. REMARKS.- These specimens represent the first record of Zelandites in Antarctica. The subspecies Z. varuna japonica Matsumoto was established on the basis of specimens displaying a more involute coiling, a narrower umbilicus. and a more com~ressedw horl section than' the typical Z. varuna (Matsumote, 1938, p. 140). These differences, however, are evident when the figured syntype (Forbes, 1846, Pl. 18, figs. 5a, b, c; BM C.5 1059). The drawing of this specimen in Kossmat (1895, Pl. 16, fig. 4b) shows a more compressed shape than does the actual specimen. W/H values in the Japanese specimens range from 0.65 to 0.60 (excluding a deformed specimen) (Matsumoto, 1938, p. 142), whereas in the figured syntype the W/ H is 0.66. Seymour Island specimens are also within this range (0.60-0.64). The degree of involution is also very close between the Japanese specimens (U/D = 19-20) and the lectotype (19), whereas the Seymour Island material shows a slightly more involute coiling (U/D = 15-18). In conclusion, it does not seem justified to separate the Japanese specimens as a different subspecies. Zelandites varuna differs from Z. kaiparaensis Marshall from New Zealand by the greater degree of involution and by its smaller number of constrictions, which are slightly flexuous and not straight (cf. Henderson, 1970). Z. odiensis (Kossmat) from South Africa (i.e., Kennedy and Klinger, 1979, p. 163- 164, Pl. 14, fig. 4) has a more compressed whorl section, and the maximum whorl breadth is displaced more to the venter than in Z. varuna. STRATIGRAPHIC DISTRIBUTION.- Zelandites varuna is restricted on Seymour Island to the uppermost ammonite-bearing horizon of the Pachydiscus ultimus Zone (uppermost Maastrichtian), Stations 411 and St. 5. Zelandites varuna was originally described for the Maastrichtian (?) Valudayur Group of India. It is also present in the Maastrichtian of Quiriquina Island and in Japan, associated with Pachydiscus subcompressus obsoletus Matsumoto (Matsumoto and Yoshida, 1979, p. 67).
Synonym list:
Ifrim et al. (2004):
1846 Ammonites varuna Forbes. - Forbes : p.107 pl. 8, fig. 5
1895 Lytoceras (Gaudryceras) varuna Forbes. - Kossmat : p.161 pl. 16, fig. 4; pl. 17, fig. 8
1938 Zelandites varuna var. japonica Matsumoto. - Matsumoto : p.140 pl. 14, figs. 1-7; text-fig. 1
1956 Zelandites varuna Forbes. - COLLIGNON : p.67
1979 Zelandites varuna Forbes. - Kennedy & KLINGER : p.296 figs. 30-31
1986 Zelandites varuna Forbes. - MACELLARI : p.14 figs. 11.11-11.12, 12.
1986 Zelandites varuna Forbes. - Stinnesbeck : p.195 pl. 8, figs. 5-6; text-fig. 20
1992 Zelandites varuna Forbes. - Kennedy & Henderson : p.404 pl. 5, figs. 13-15; pl. 17, figs. 2-3
2004 Zelandites varuna Forbes. - Ifrim et al. : 7, 17 text-figs. 3o-p, 6f-g,j
1846 Ammonites varuna Forbes. - Forbes : p.107 pl. 8; fig. 5a, b, c
1895 Lytoceras (Gaudryceras) varuna Forbes. - Kossmat : p.161 pl. 16, fig. 4; pl. 17, fig. 8
1895 Lytoceras varuna Forbes. - STEINMANN : p.84 pl. 5, fig. 2a, b; text-fig. 7
1938 Zelandites varuna var. japonica Matsumoto. - Matsumoto : p.140 pl. 14, fig. 5a, b, 6a, b, 7a, b, c; text-fig. 1a-d
1986 Zelandites varuna Forbes. - MACELLARI : p. 15, 16 fig. 11.11-11.12, 12
Stratigraphy - relative ages:
Maastrichtian: Ifrim et al. (2004)
upper Maastrichtian: MACELLARI (1986)

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

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

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

STEINMANN,G.. (1895):
Die Cephalopoden der Quiriquina-Schichten.
In: Neues Jahrbuch für Mineralogie, Geologie undPaläontologie, 1895 p. 64-94

Kossmat,F.. (1895):
1895-1898. Untersuchungen Ober die Sudindische Kreideformation. . Beiträge zur Paleontologie Österreich-Ungarns und des Orients. p. 9 (1895):97-203

Matsumoto,T.. (1938):
Zelandites, a genus of Cretaceous ammonite . Japanese Journal of Geography and Geology Vol. 15 p. 137-148

Matsumoto,T.. (1938):
A chronostratigraphic study on the Cretaceous deposits of the Naibuti Valley, South Karahuto . Proceedings of the Imperial Academy, Tokyo Vol. 14 p. 190-194

COLLIGNON,M.. (1956):
Ammonites neocretacees du Menabe (Madagascar) IV. - Les Phylloceratides; V. - Les Gaudryceratides; VI. - Les Tetragonitidae. . Annales Geologiques du Service des Mines de Madagascar Vol. 23 p. 1-106

Kennedy,W.J.. and KLINGER,H.C.. (1979):
Cretaceous faunas from Zululand and Natal, South Africa. The ammonite family Gaudryceratidae. . Bulletin of the British Museum (Natural History ) Geology Vol. 31 p. 121-173

Stinnesbeck,W.. (1986):
Zu den faunistischen und palökologischen Verhältnissen in der Quriquina Formation (Maastrichtium)Zentral-Chiles . Palaeontographica A194((4-6)) p. 99-237

MACELLARI,C.E.. (1986):
Late Campanian-Maastrichtian ammonite fauna from Seymour Island (Antarctic Peninsula) . Memoirs of the Paleontological Society Vol. 18(2) p. 1-55

Kennedy,W.J.. and Henderson,R.A.. (1992):
Non-heteromorph ammonites from the Upper Maastrichtian of Pondicherry, south India . Palaeontology Vol. 35 p. 381-442

Ifrim,C..; Stinnesbeck,W.. and López-Oliva,J.G.. (2004):
Maastrichtian cephalopods from Cerralvo, north-eastern Mexico . Palaeontology Vol. 47(6) p. 1575–1627

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