Zelandites varuna Forbes 1846 from: Ifrim, C..Stinnesbeck, W..López-Oliva, J.G.. (2004): Maastrichtian cephalopods from Cerralvo, north-eastern Mexico . Palaeontology Vol. 47(6) p. 1575–1627
|Notice: This catalogue page may contain unedited data.
Species Zelandites varuna Forbes 1846
| text-fig. 3o Ifrim et al. (2004)  text-fig. 3p Ifrim et al. (2004)  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.
(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).
Three well preserved specimens.
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.
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.
|Ifrim et al. (2004):
1992 Zelandites varuna Forbes. - Kennedy & Henderson
: p.404 pl. 5, figs. 13-15; pl. 17, figs. 2-3
|Stratigraphy - relative ages:
| Maastrichtian: Ifrim et al. (2004)
upper Maastrichtian: MACELLARI (1986)
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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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