Hoploscaphites Nowak, 1911

KENNEDY, W. J., LANDMAN, N. H., COBBAN, W. A. & JOHNSON, R. O., 2000, Additions to the Ammonite Fauna of the Upper Cretaceous Navesink Formation of New Jersey, American Museum Novitates 3306, pp. 1-31 : 18-20

Genus Hoploscaphites Nowak, 1911

TYPE SPECIES: Ammonites constrictus J. Sowerby, 1817, p. 189 , pl. A, fig. 1, by original designation .

Hoploscaphites pumilus (Stephenson, 1941)

Figure 9A–F

Scaphites pumilus Stephenson, 1941: 426 , pl. 90, figs. 10–12.

Discoscaphites erucoides Stephenson, 1941: 429 , pl. 91, figs 2–4.

Hoploscaphites pumilus Stephenson, Cobban, 1974a: 16 , pl. 11, figs. 9–12, text­fig. 13.

Hoploscaphites pumilis (sic) Stephenson, 1941, Kennedy, 1986c: 1018, pl. 5, figs. 18–20.

Hoploscaphites pumilis (sic) Stephenson, 1941, Kennedy and Cobban, 1993: 426, figs. 9.3, 9.6, 12.5, 16.1–16.26, 17.1–17.21.

Hoploscaphites pumilus (Stephenson, 1941) , Kennedy et al., 1995: pl. 6, figs. 1, 2.

TYPE: The holotype, by original designation, is USNM 21041 , the original of Stephenson, 1941: pl. 90, figs. 10–12, from the Nacatoch Sand in the vicinity of Chatfield , Navarro County, Texas .

DESCRIPTION: MAPS A2032a1 (fig. 9A, B) is the most complete specimen. It is a microconch 44.0 mm long. The phragmocone is fairly involute with a small, deep umbilicus. The whorl section at the ultimate septum is compressed (ratio of whorl breadth to whorl height is 0.74), with the greatest breadth at the umbilical shoulder. Primary ribs arise at the umbilical seam and strengthen across the umbilical wall. The ribs are straight and prorsiradiate on the inner flanks and increase by branching and intercalation on the outer flanks. All ribs are equally strong on the venter. Umbilicolateral and ventrolateral tubercles develop on the adoral part of the phragmocone. The body chamber is compressed (ratio of whorl breadth to whorl height at mid­shaft is 0.84) with a steep umbilical wall and nearly flattened flanks that converge to a broadly rounded venter. The flanks are covered with broad, poorly defined ribs. There are five umbilicolateral tubercles. The ventrolateral tubercles become stronger and more clavate on the adoral part of the shaft but weaken on the final hook.

DISCUSSION: These specimens supplement material described by Cobban (1974a). Tubercles are absent on the inner whorls of the phragmocone but develop on the outer whorls. This is a feature of the holotype, but is not visible on Stephenson’s figures. Small specimens differ in no significant respects from Discoscaphites erucoides Stephenson, 1941 (p. 429, pl. 91, figs. 2–4), which is here regarded as a synonym.

OCCURRENCE: Upper Campanian; lower phosphatic layer, basal part of Navesink Formation, Atlantic Highlands, New Jersey; Saratoga Chalk, Arkansas; Nacatoch Sand, Navarro County, Texas; Marnes de Plagne, Paillon, Haute Garonne, France; and Tercis, Landes, France.

Figures

Fig. 9. A–F. Hoploscaphites pumilus (Stephenson, 1941). A, B. MAPS 2032a1; C, D. MAPS 2032a2; E, F. MAPS 2032a3; G–I. Discoscaphites gulosus (Morton, 1834), NJSM 16121, Inversand Pit, Sewell, Gloucester County, New Jersey. J–P. Jeletzkytes cf. J. nodosus (Owen, 1852). J–L. MAPS A2020a3; M, N. MAPS A2020a5; O, P. MAPS A2020a4. All specimens are from the lower phosphatic layer, Navesink Formation, Atlantic Highlands, unless otherwise stated. All figures are X1.