Phylloptychoceras sipho Forbes 1846 from: Ward, P.D..Kennedy, W.J.. (1993): Maastrichtian Ammonites from the Biscay Region (France, Spain) . Memoir (The Paleontological Society), Journal of Paleontology34 (Supplement to Vol. 67)(5) p. 1-58
|Notice: This catalogue page may contain unedited data.
Species Phylloptychoceras sipho Forbes 1846
|Diagnosis / Definition:
Kennedy & Henderson (1992):
The earliest development stages are shown by BMNH C51155 and 51160 (Pl. 5, figs. 18, 24), which consist of minute subparallel shafts in tight contact, linked by narrowly curved sections, where shafts are separated by tear-shaped opening; the shell is smooth, but for prorsiradiate growth lines, BMNH C51161 is a similar fragment (Pl. 5, fig. 19), but much larger, BMNH C51154 (Pl. 5, fig. 23) is the same size and shape as BMNH C51161, with a circular cross section and feeble ornament of low, broad, feebly prorsiradiate ribs, and a single constriction. If, as seems likely, these are correctly interpreted as successive growth stages of the same form (rather than of macro- and microconchs), then the shell consisted of four closely adpressed subparallel shafts, the first three and part of the fourth being septate. The lectotype (Pl. 5, fig. 31-32) is the best-preserved of the adult specimens, and is 107mm long. The whorl section is subcircular, slightly compressed at the adapical end, and consists of a slightly curved shaft and short recurved crozier. The whorl breadth to height ratio is 0.83 at the mid-point of the shaft, but becomes markedly depressed and reniform on the final curved sector. Ornament on the shaft is of low, broad, distant, round ribs; the rib index is two. Ribs are weak and transverse on the dorsum, straight and feebly prorsiradiate on the flanks, and strong and transverse across the venter. The ribs weaken, narrow and crowd on the final section of the shaft and the initial part of the hook, disappearing altogether on the final section of the hook, where they are replaced by crowded growth lines. The final, adult aperture appears to have been flared and trumpet-shaped, as suggested by BMNH C41503. Suture (Text-fig. 2D)greatly simplified with narrow-stemmed, bifid saddles with only minor identations; lobes have narrow necks, with splayed bifid lateral elements and a larger median element, entire in L and U.
Ward & Kennedy (1993):
Description and discussion. -
The Biscay examples are juveniles
consisting of two parallel shafts in close proximity, but not
in contact, linked by a narrow curved portion. The composite
mold is smooth, as in paralectotypes of comparable size (e.g.,
BMNH C5 1 155, the original of Forbes, 1846, P1. 1 1, fig. 5c, f,
C5 1 160; Figure 18.8). The holotype of Neocyrtochilus bryani Anderson, 1958 (p. 189, P1. 72, fig. 5) is of comparable size,
nearly smooth, and a possible synonym.
|Discussion / Comments:
Kennedy & Henderson (1992):
Lectotype, by the subsequent designation of Howarth (1965, p. 386) is BMNH C51153, the original of Forbes (1846, pl. 11, fig. 5a), GSC R10504; paralectotype BMNH C51154 is the original of Forbes (1846, pl. 11, figs. 5b, e), GSC R10506; paralectotype BMNH C51155 is the original of Forbes (1846, pl. 11, figs. 5c, f), GSC R10507; paralectotype BMNH C41502 is probably the original of Forbes (1846, pl. 11, fig. 5d); unfigured paralectotypes are BMNH C41503, C51156-51161, all from the Valudavur Formation of Pondicherry, south India (ex Kaye and Cunliffe Collection). Topotypes are BMNH C3521, and 24199. The holotype of Hamites constrictus d’Orbigny, 1847 (pl. 3, figs. 7-8), is MNHP R982 (Pl. 5, figs. 27-28), also a topotype of P. sipho.
Hamites constrictus d'Orbigny, 1847a (pl. 3, fig. 7-8) is based on a Pondicherry specimen of P. sipho (Pl. 5, figs. 27-28). The holotype of Neocyrtochilus bryani Anderson, 1958 (p. 189, pl. 72, fig. 5) is based on a small smooth form with ptychoceratid coiling like the early stages of the present species, and said, by Anderson, to be of Maastrichtian age; it is a possible synonym, as is the Phylloptychoceras sp. of Stinnisbeck (1986, p. 200, pl. 15, fig. 3; text-fig. 22), from the Maastrichtian of Chile.
Maastrichtian of south India and, possibly, Chile and California, and the Biscay region of France and Spain.
Ward & Kennedy (1993):
Lectotype is BMNH C5 1 153, the original of Forbes,
1846, P1. 1 1, fig. 5a, designated by Howarth, 1965, p. 386; from
the Valudavur Formation of Pondichemy, south India.
In the Biscay region this taxon is restricted to
Member 111 (upper Maastrichtian). The types are from the upper
Maastrichtian of south India, and if Neocyrtochilus bryani is a
synonym, the geographic range extends to California.
|Kennedy & Henderson (1992):
1989 Phylloptychoceras Spath. - Kennedy : text-fig. 18f
Ward & Kennedy (1993):
1992 Phylloptychoceras sipho Forbes. - Kennedy & Henderson
: p. 711, 715, 703 pl. 4, fig. 5;
pl. 5, fig. 18-32;
|Stratigraphy - relative ages:
|upper Maastrichtian: Ward & Kennedy (1993)
Maastrichtian: Kennedy & Henderson (1992)
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Ward,P.D.. and Kennedy,W.J.. (1993):
Maastrichtian Ammonites from the Biscay Region (France, Spain) . Memoir (The Paleontological Society), Journal of Paleontology34 (Supplement to Vol. 67)(5) p. 1-58
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