Phylloceras (Neophylloceras) ramosum Meek 1857 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 Phylloceras (Neophylloceras) ramosum Meek 1857
|Diagnosis / Definition:
Ward & Kennedy (1993):
Best specimen is composite mold 34 mm in
diameter. Fragments suggest species reached moderate diameters.
Coiling very involute, with umbilicus comprising less than
10 percent of diameter. Ornament of fine, dense lirae numbering
an estimated 300-350 per whorl. Lirae very weak, straight, and
prorsiradiate on inner half of flank, flex back and strengthen
over outer half of flank, where they increase by branching and
intercalation; strongest development on ventrolateral shoulders
and venter, which they cross in very shallow convexity. Faint
periodic narrow and shallow constrictions on inner flank, but
number cannot be determined.
|Discussion / Comments:
Ward & Kennedy (1993):
Matsumoto (1 959) and Henderson and Mc- Namara (1985) give full descriptions of this species, based upon well-preserved, uncrushed material. The latter authors note the
difficulty in differentiating between Phylloceras (Neophylloceras) ramosum and P. (N.) hetonaiense Matsumoto, 1942 (p. 675, text-figs. la,, b,) (see revision in Jones, 1963, p. 23, P1. 6, figs. 9,lO, P1.7, figs. 1-5, text-fig. 12) and P. (N.) woodsi Van Hoepen, 1921 (p. 3, P1. 2, figs. 1-6, text-fig. 1; see revision in Kennedy and Klinger, 1977a (p. 366, P1. 13, figs. 3-5, text-figs. 4-6)),
suggesting that it may be more compressed when young and
have more flexuous lirae. Phylloceras (N.) ramosum has been
differentiated from P. (N.) nera (Forbes, 1846) (p. 106, Pl. 8, fig. 7) (holotype reillustrated here as Figure 18.2) by its more flexuous lirae that are not projected on the venter. All these ornamental differences are minor, and might be encompassed within the variation of a variable P. (N.) nera, but this cannot be demonstrated at this time. Specimens referred to P. (N.) ramosum are easily distinguished from other phylloceratids in
the present fauna. Thus, P. (N.) surya (Forbes, 1846) (p. 106, P1. 7, fig. 10; see Figures 17.13, 18.3, 18.4, 18.16, 18.17) has much coarserlirae on outer flank and venter, linked into bundles at broad, distant inner flank ribs. Phyllopachyceras forbesianum (d'Orbigny, 1850)(p. 213; see figs. 17.14-17.17, 18.5-18.7) has a much more inflated whorl section and is nearly smooth when
small, developing pronounced ventrolateral and ventral folds
in middle growth with very coarse ventral lirae that are utterly distinctive (Figure 17.15).
In the Biscay sections this taxon ranges from
low in Member I to the last meter of the Cretaceous(at Zumaya).
It is the highest ammonite yet found at Zumaya, with an upper
occurrence within 15 cm of the K-T boundary there. Elsewhere,
the species ranges from upper Campanian to upper Maastrichtian,
with records from Alaska, Vancouver Island, British Columbia,
California, southern Argentina, Chile, the Antarctic
Peninsula, western Australia, and New Zealand. It is said to
occur as low as the Turonian in California and Japan (Matsumoto,
1959, p. 4, 5).
Species Phylloceras (Neophylloceras) ramosum
Species Phyllopachyceras forbesianum
|Ward & Kennedy (1993):
1959 Neophylloceras ramosum Meek. - Matsumoto
: p.1 pl. 1, fig. 1;
pl. 2, fig. 2;
pl. 8, fig. 1 (with full synonymy)
|Stratigraphy - relative ages:
|upper Maastrichtian - lower Maastrichtian: Ward & Kennedy (1993)
|"Komooks, Vancouver Island", Inventory number: USNM 12415
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Ammonoidea from the Mata Series (Santonian - Maastrichtian) of New Zealand . Special Papers in Palaeontology Vol. 6 p. 1-82
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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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