Exiteloceras Hyatt, 1894

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 : 15-16

Genus Exiteloceras Hyatt, 1894

TYPE SPECIES: Ancyloceras jenneyi Whitfield, 1877 (p. 42, by the subsequent designation of Diener, 1925, p. 88).

Exiteloceras rude , new species

Figure 5F–H

HOLOTYPE: USNM 433778 , Navesink Formation, Big Brook , near Marlboro , Monmouth County, New Jersey.

ETYMOLOGY: Latin, rudis, rough.

DIAGNOSIS: An exceptionally coarse­ribbed species of Exiteloceras , with a rib index of 4.

DESCRIPTION: The holotype is a broadly, evenly curved septate fragment 37.5 mm long with a stout, oval whorl section 15.7 mm high and 13.1 mm wide; the greatest width is below mid­flank. The dorsum is broadly rounded and the flanks are very broadly rounded and converge to a slightly flattened, narrow venter. The ornament consists of strong, rounded, slightly rursiradiate, straight ribs with a rib index of 4. The ribs are weak on the dorsum, and strong on the flanks and venter. Each rib supports a strong, rounded tubercle at the margin of the venter. The suture is too poorly preserved for description.

DISCUSSION: This specimen is most unusual in its coarse ribbing and in its stratigraphic position. The rib index of 4 contrasts with 5 or more for comparable­sized specimens of Exiteloceras jenneyi (Whitfield, 1877) , an older species. Lewyites oronensis (Lewy, 1969) (p. 127, pl. 3, figs. 10, 11), a loosely coiled planispiral heteromorph that has been found in the basal Navesink at Atlantic Highlands, New Jersey, is much more densely ribbed and has tubercles on every other rib.

OCCURRENCE: This specimen was found as float in the bed of Big Brook near Marlboro, Monmouth County, New Jersey, but is presumed to be derived from the Navesink Formation.

FAMILY BACULITIDAE GILL, 1871

[= EUBACULITINAE BRUNNSCHWEILER, 1966, p. 24]

Genus Baculites Lamarck, 1799

[= Homaloceratites Hupsch, 1768, p. 110 (non binominal); Euhomaloceras Spath, 1926, p. 80 ]

TYPE SPECIES: Baculites vertebralis Lamarck, 1801 (p. 103) by subsequent designation by Meek, 1876: 391.

Figures

Fig. 5. A–E, K–O. Nostoceras (Nostoceras) approximans (Conrad, 1855). A, B. MAPS A2027a2, macroconch; C–E. holotype, ANSP 12861, microconch, White River, Arkansas; K–M. MAPS 2027a1, microconch; N, O. USNM 445246, pathological microconch. F–H. Exiteloceras rude, n. sp., holotype, USNM 433778, Big Brook, near Marlboro, Monmouth County. I, J. Didymoceras cf. D. draconis (Stephenson, 1941), MAPS A2040b1. All specimens are from the lower phosphatic layer, Navesink Formation, Atlantic Highlands, New Jersey, unless otherwise stated. All figures are X1.