Eubaculites sp.

Landman, Neil H., 2004, Cephalopods From The Cretaceous / Tertiary Boundary Interval On The Atlantic Coastal Plain, With A Description Of The Highest Ammonite Zones In North America. Part 2. Northeastern Monmouth County, New Jersey, Bulletin of the American Museum of Natural History 2004 (287), pp. 1-107 : 70-71

Eubaculites sp. Figure 33A–T

Compare: Eubaculites latecarinatus ( Brunnschweiler, 1966) . Kennedy et al., 1997: 20, figs. 15A–D, K, L, 16G, H, 19.

MATERIAL: There are four specimens ( MAPS A 2053c1, ­2, AMNH 47160, and 47161) from AMNH loc. 3346 from the upper part of the New Egypt Formation 1.5–2 m below the base of the Hornerstown Formation, Parkers Creek, near Eatontown, northeastern Monmouth County. All of the specimens are internal molds of parts of body chambers.

DESCRIPTION: MAPS A 2053c1 is a large piece of a body chamber 68.4 mm long (fig. 33A–E). The whorl heights at the adapical and adoral ends are 20.2 mm and 24.1 mm, respectively. The whorl section is better preserved at the adapical end and is compressed ovoid with a ratio of whorl width to height of 0.68. The angle of taper is 1.6°. The dorsum is nearly flat and the dorsolateral shoul­ der is fairly abruptly rounded. The inner flanks are broadly rounded and nearly parallel and the outer flanks converge toward the venter. There is a shallow longitudinal depression that borders the venter. The ventrolateral shoulder is fairly abruptly rounded and the venter is narrow and broadly round­ ed. The inner flanks are covered with weak, concave ribs with a rib index of 14. The venter is ornamented with broad, transverse ribs that show a moderately strong adoral projection; the rib index is approximately 11. The adoral end of this specimen shows two interesting features: (1) the left side shows a bulge, which may represent a healed injury; and (2) the dorsum is flared and projected forward and may represent a mature modification of the aperture.

AMNH 47160 is a fragment of a body chamber 42.4 mm long with whorl heights of 14.9 mm and 16.0 mm at the adoral and adapical ends, respectively (fig. 33F–J). The whorl section at the adoral end is compressed ovoid with a ratio of whorl width to height of 0.67. The venter is demarcated by a shallow, longitudinal depression and is narrow and broadly rounded. There are weak undulations on the dorsum. The flanks on the right side bear two asymmetrically crescentic ribs near the adoral end that are 6 mm apart, so that the rib index is approximately 5. Adapical of these ribs, there is a dent in the flanks, possibly due to an injury. The venter is covered with weak transverse ribs with a rib index of 13.

AMNH 47161 is a fragment of a body chamber 44.4 mm long with whorl heights of 11.6 mm and 14.4 mm at the adapical and adoral ends, respectively (fig. 33K–O). The ratio of whorl width to height at the adoral end is 0.74. The whorl section is ovoid with maximum width at midwhorl height. The dorsum is broadly rounded, the inner flanks are divergent and nearly flat, and the outer flanks gradually converge to the venter. The venter is narrow and broadly rounded and is covered with barely perceptible, closely spaced ribs. The flanks are smooth except for one thin crescentic rib.

MAPS A 2053c2 is a body chamber fragment 56.3 mm long with whorl heights of 15.8 mm and 19.5 mm at the adapical and adoral ends, respectively (fig. 33P–T). The whorl section at the adoral end is compressed ovoid with a ratio of whorl width to height of 0.70. Most of the flanks are smooth but weak ribs slant markedly forward on the out­ er flanks at an angle of 20°. The venter is narrow and broadly rounded and bears transverse ribs. They are irregularly spaced with a rib index of approximately 8.

DISCUSSION: These specimens resemble Eubaculites latecarinatus in their oval whorl section with narrow venter, and weak ornament, but differ in having a broadly rounded rather than tabulate venter. In this respect, these specimens are reminiscent of Eubaculites sp. illustrated by Kennedy et al. (2000: fig. 8I–T) from the lower part of the Navesink Formation in a tributary on the west side of Crosswicks Creek, south of Allentown, southwestern Monmouth County, New Jersey. However, our specimens are not as coarsely ornamented. The specimen of Baculites sp. illustrated by Kennedy et al. (2000: fig. 7A–C) from the top of the New Egypt Formation at the Inversand Pit, Gloucester County, New Jersey, also bears some resemblance to our material.

OCCURRENCE: AMNH loc. 3346 from the upper part of the New Egypt Formation, 1.5– 2 m below the base of the Hornerstown Formation, Parkers Creek, near Eatontown, northeastern Monmouth County, New Jersey.

SUPERFAMILY SCAPHITACEAE GILL, 1871

FAMILY SCAPHITIDAE GILL, 1871

SUBFAMILY SCAPHITINAE GILL, 1871

Figures

Fig. 33. A–T. Eubaculites sp. Upper New Egypt Formation, 1.5–2 m below the base of the Hornerstown Formation, AMNH loc. 3346, northwest of Eatontown, Monmouth County, New Jersey. A– E. MAPS A2053c1. A, Right lateral; B, dorsal; C, ventral; D, left lateral; E, whorl cross section at adapical end. F–J. AMNH 47160. F, Right lateral; G, dorsal; H, ventral; I, left lateral; J, whorl cross