Discoscaphites spp.

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 : 94-95

Discoscaphites spp. Figures 36I, J, R, a–k, q–v , 37m, n , 39U–

X, c–f, 40E–I, Q–S , 41F

MATERIAL: Approximately two dozen specimens, the majority of which are from the upper part of the New Egypt Formation and base of the Hornerstown Formation, AMNH loc. 3345, Parkers Creek, near Eatontown, northeastern Monmouth County, New Jersey. The other locality is AMNH loc. 3346, 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. Of the specimens described, AMNH 47340, 47371, 47391, and 51063 are from AMNH loc. 3345 and AMNH 47304 is from AMNH loc. 3346.

DESCRIPTION: This material is all fragmentary. Some specimens show enough morphological features to differentiate them from known species of discoscaphites but there are not enough of these specimens to justify describing a new species. The vast majority of this material is, however, simply too worn or fragmentary for species identification. We describe five of the more complete specimens.

AMNH 47371 is the adoral part of the phragmocone and adapical part of the body chamber of a compressed microconch (fig. 39U–X). A piece of the inner whorls of the phragmocone is also preserved. The flanks are covered by straight to slightly convex prorsiradiate ribs that bend forward to link the inner and outer ventrolateral tubercles. The umbilical tubercles are arcuate with steep adapical and more gently inclined adoral sides. The midflank tubercles are represented by weak bullae, which may have developed into tubercles on the adoral part of the body chamber.

AMNH 47340 is the adapical portion of a compressed body chamber with an extremely narrow venter (fig. 36t –v). There is a strong, arcuate prorsiradiate rib on the adoral end of the specimen. The umbilical and ventrolateral tubercles are present but the midflank tubercles are absent, although part of the shell in this area is covered by matrix. The two rows of ventrolateral tubercles are very closely spaced together, approximately 2.5 mm apart. The distance between ventrolateral tubercles on either side of the venter is also very small, approximately 2.5 mm.

AMNH 47391 is a piece of the middle of the shaft of a fairly compressed body chamber with nearly flat flanks (fig. 36k). Most of the right side is still attached to a phosphatic nodule, which bears the impressions of two other scaphites. The midflank and ventrolateral rows of tubercles are present but the umbilical row is absent, probably because too little of the specimen is preserved in this area. Several fine prorsiradiate ribs appear on the adoral end of the fragment. They swing backward on the umbilical shoulder and then forward on the inner flanks and cross the midflanks and outer flanks with a broad convexity.

AMNH 51063 is still attached to an indurated cluster of specimens that contains parts of three other specimens and impressions of three more (fig. 36R). It is an internal mold of the adapical one­half of a body chamber. The whorl section is compressed with nearly flat flanks and a flat, narrow venter. Two rows of ventrolateral tubercles are present, but the midflank and umbilical rows are not well developed, perhaps due to poor preservation. The distance between rows of inner and outer ventrolateral tubercles and between outer ventrolateral tubercles on ei­ ther side of the venter on the adoral end of the specimen is 2.5 mm in both instances.

AMNH 47304 is the adapical two­thirds of a body chamber (fig. 40Q–S). It is slightly distorted with adhering matrix on the dorsal side. Although crushed, the whorl section at midshaft was originally compressed with flat, nearly subparallel flanks and a very narrow venter. The specimen is distinguished by its broad prorsirdiate ribs, each of which bears an umbilicolateral tubercle or bulla. Ribs bifurcate and join the inner ventrolateral tubercles. Midflank tubercles are absent. The inner and outer rows of ventrolateral tubercles are very closely spaced together (2.5 mm apart at midshaft), so that adjacent tubercles occupy the same base. The distance between outer ventrolateral tubercles on either side of the venter is also small, approximately 4 mm. Tubercles are offset on either side of the venter on the adapical part of the specimen and paired on the adoral part.

OCCURRENCE: Upper part of the New Egypt Formation 1.5–2 m below the base of the Hornerstown Formation at AMNH loc. 3346 and in the uppermost 20 cm of the New Egypt Formation and base of the Hornerstown Formation at AMNH loc. 3345, Parkers Creek, near Eatontown, northeastern Monmouth County, New Jersey.

Figures

Fig. 36. A–H, K–Q, S–Z, l–p. Discoscaphites iris (Conrad, 1858), cluster 1, uppermost New Egypt Formation, AMNH loc. 3345, northwest of Eatontown, Monmouth County, New Jersey. A–D. AMNH 47355, macroconch with a repaired injury. A, Right lateral; B, apertural; C, ventral; D, left lateral. E– H. AMNH 47351, macroconch. E, Right lateral; F, apertural; G, ventral; H, left lateral. K–M. AMNH 47347, macroconch. K, Right lateral; L, apertural; M, ventral. N–Q. AMNH 47343, dimorph indeterminate. N, Right lateral; O, apertural; P, ventral; Q, left lateral. S–V. AMNH 47349, dimorph indeterminate. S, Right lateral; T, apertural; U, ventral; V, left lateral. W–Z. AMNH 47339, dimorph indeterminate. W, Right lateral; X, apertural; Y, ventral; Z, left lateral. l–n. AMNH 47336, dimorph indeterminate. l, Apertural; m, ventral; n, left lateral. o, p. AMNH 47332, dimorph indeterminate. o, Right lateral; p, ventral. I, J, R, a–k, q–v. Discoscaphites spp., same loc. as A–H. I, J. AMNH 47350. I, Right lateral; J, apertural; R. AMNH 51063, right lateral. a–d. AMNH 47328. a, Right lateral; b, apertural; c, ventral; d, left lateral. e, f. AMNH 47324. e, Right lateral; f, ventral. g–j. AMNH 47335. g, Right lateral; h, apertural; i, ventral; j, left lateral. k. AMNH 47391, left lateral. q–s. AMNH 47329. q, Right lateral; r, ventral; s, left lateral. t–v. AMNH 47340. t, Right lateral; u, ventral; v, left lateral. All figures are X1.

Fig. 37. A–l. Discoscaphites iris (Conrad, 1858), cluster 1, uppermost New Egypt Formation, AMNH loc. 3345, northwest of Eatontown, Monmouth County, New Jersey. A–D. AMNH 51057, compressed microconch. A, Right lateral; B, apertural; C, ventral; D, left lateral. E–H. AMNH 47354, microconch. E, Right lateral; F, apertural; G, ventral; H, left lateral. I–L. AMNH 51058, microconch. I, Right lateral; J, apertural; K, ventral; L, left lateral. M–P. AMNH 47342, microconch. M, Right lateral; N, apertural; O, ventral; P, left lateral. Q–T. AMNH 47356, microconch. Q, Right lateral; R, apertural; S, ventral; T, left lateral; U–X. AMNH 47352, dimorph indeterminate. U, Right lateral; V, apertural; W, ventral; X, left lateral. Y–b. AMNH 47346, microconch. Y, Right lateral; Z, apertural; a, ventral; b, left lateral. c–f. AMNH 47353, microconch. c, Right lateral; d, apertural; e, ventral; f, left lateral. g, h. AMNH 47345, microconch. g, Right lateral; h, ventral. i–l. AMNH 47337, microconch. i, Right lateral; j, apertural; k, ventral; l, left lateral. m, n. Discoscaphites sp., AMNH 47338, same locality as A–l. m, Right lateral; n, ventral. All figures are X1.

Fig. 39. A–P. Discoscaphites iris (Conrad, 1858), uppermost New Egypt Formation and basal Hornerstown Formation, AMNH loc. 3345, northwest of Eatontown, Monmouth County, New Jersey. A– D. AMNH 47105, microconch. A, Right lateral; B, apertural; C, ventral; D, left lateral. E–H. AMNH 51056, microconch. E, Right lateral; F, apertural; G, ventral; H, left lateral. I, J. AMNH 37359, dimorph indeterminate. I, Ventral; J, left lateral. K–M. AMNH 47368, dimorph indeterminate. K, Right lateral; L, ventral; M, left lateral. N–P. AMNH 47105, dimorph indeterminate. N, Right lateral; O, apertural; P, ventral. Q–T. Discoscaphites minardi Landman et al., 2004, AMNH 47369, microconch, same locality as A–P. Q, Right lateral; R, apertural; S, ventral; T, left lateral. U–X, c–f. Discoscaphites spp., same locality as A–P. U–X. AMNH 47371. U, Right lateral; V, apertural; W, ventral; X, left lateral. c– f. AMNH 47374. c, Right lateral; d, apertural; e, ventral; f, left lateral. Y–Z, a, b. Discoscaphites gulosus (Morton, 1834), AMNH 47106, same locality as A–P. Y, Right lateral; Z, apertural; a, ventral; b, left lateral. All figures are X1.

Fig. 40. A–D, J–P. Discoscaphites minardi Landman et al., 2004. A–D. MAPS A2059b2, macroconch, upper New Egypt Formation, 1.5–2 m below the base of the Hornerstown Formation, AMNH loc. 3347, northwest of Eatontown, Monmouth County, New Jersey. A, Left lateral; B, apertural; C, ventral; D, left lateral. J–M. AMNH 47307, macroconch, 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. J. Right lateral; K, apertural; L, ventral; M, left lateral. N–P. AMNH 47305, microconch, same locality as J–M. N, Right lateral; O, ventral, P, left lateral. E–I, Q–S. Discoscaphites spp., same locality as J–P. E–G. AMNH 47301. E, Right lateral; F, ventral; G, left lateral. H, I. AMNH 47300. H, Right lateral; I, left lateral. Q–S. AMNH 47304. Q, Right lateral; R, ventral; S, left lateral. All specimens are X1.

Fig. 41. A–D. Discoscaphites iris (Conrad, 1858), uppermost New Egypt Formation and basal Hornerstown Formation, AMNH loc. 3345, northwest of Eatontown, Monmouth County, New Jersey. A, B. AMNH 47365, a fragment of a macroconch, part of the last suture at a whorl height of approximately 18.2 mm and internal lobe of another suture on the inner whorls. C. AMNH 51060, a macroconch, part of the last suture at a whorl height of 19.7 mm. D. AMNH 51059, a macroconch, part of a composite of two sutures at a whorl height of 7.9 mm. E. Discoscaphites gulosus (Morton, 1834), AMNH 47106, same locality as A–D, part of a composite of two sutures at whorl heights of 17.3 mm and 17.6 mm. F. Discoscaphites sp., AMNH 47107, a fragment, same locality as A–D, part of a suture at a whorl height of approximately 10.3 mm.