Phylloceras (Neophylloceras) ramosum Meek 1857 (TaxonConcept

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Species Phylloceras (Neophylloceras) ramosum Meek 1857

Alternative name:

Phylloceras ramosum Meek 1857

Diagnosis / Definition:

Ward & Kennedy (1993):
Description.- 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):
Discussion.- 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). Occurrence.- 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).

Systematics:

38
Ordo Ammonoidea
  Subordo Phylloceratina
   Superfamilia Phyllocerataceae
    Familia Phylloceratidae
     Subfamilia Phylloceratinae
      Genus Phylloceras
       Genus Phyllopachyceras
        Subgenus Neophylloceras
         Species Phylloceras (Neophylloceras) ramosum
          Species Phyllopachyceras forbesianum

Synonym list:

Ward & Kennedy (1993):

1857 Ammonites? (Scaphites) ramosum Meek. - Meek : p.45

1959 Neophylloceras ramosum Meek. - Matsumoto : p.1 pl. 1, fig. 1; pl. 2, fig. 2; pl. 8, fig. 1 (with full synonymy)

1970 Neophylloceras ramosum Meek. - Henderson : p.5 pl. 1, fig. 3; text-fig. 2a

1971 Hypophylloceras (Neophylloceras) ramosum Meek. - Dundo : pl. 1; fig. 1

1980 Hypophylloceras ramosum Meek. - Blasco de Nullo et al. : p.477 pl. 2, fig. 1-4

1985 Phylloceras (Neophylloceras) ramosum Meek. - Henderson & McNamara : p.40 pl. 1, fig. 1-3; text-fig. 2c (with additional synonymy)

1986 Phylloceras (Hypophylloceras) ramosum Meek. - Stinnesbeck : p.189 pl. 7, fig. 1, 2; text-fig. 16a, 17b

1993 Phylloceras (Neophylloceras) ramosum Meek. - Ward & Kennedy : p.18 fig. 17.2, 17.5, 17.6

Stratigraphy - relative ages:

upper Maastrichtian - lower Maastrichtian: Ward & Kennedy (1993)

Specimen:

"Komooks, Vancouver Island", Inventory number: USNM 12415

References:

Meek,F.B.. (1857):
Descriptions of new organic remains from the Cretaceous rocks of Vancouver Island . Transactions of the Albany Institute Vol. 4 p. 37-49

Matsumoto,T.. (1959):
Upper Cretaceous ammonites of California, Part II. . Memoirs of the Faculty of Science, Kyushu University, Series D, Geology, Special Volume Vol. 1 p. 1-172

Henderson,R.A.. (1970):
Ammonoidea from the Mata Series (Santonian - Maastrichtian) of New Zealand . Special Papers in Palaeontology Vol. 6 p. 1-82

Dundo,O.P.. (1971):
Maastrichtian fossils from the northern chalk. p. 84-92 [in Russi

Blasco de Nullo,.; Nullo,G.F.. and Proserpio,C.. (1980):
Santo-niano- Campaniano: estratigrafia y contenido ammonitifero, Cuenca Austral . Revista de la Associacion Geologica Argentina Vol. 35 p. 467-493

Henderson,R.A.. and McNamara,K.J.. (1985):
Maastrichtian non-heteromorph ammonites from the Miria Formation, Western Australia . Palaeontology Vol. 28 p. 35-88

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

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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