Baculites Lamarck, 1799

LANDMAN, NEIL H., JOHNSON, RALPH O. & EDWARDS, LUCY E., 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 1. Maryland and North Carolina, American Museum Novitates 3454 (1), pp. 1-64 : 29-34

Genus Baculites Lamarck, 1799

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

Baculites vertebralis Lamarck, 1801

Figures 13A–Z, a–f , 14A

Baculites vertebralis Lamarck, 1801: 103 .

Baculites vertebralis Lamarck, 1801 . Kennedy, 1986: 57, pl. 11, figs. 6–11; pl. 12, figs. 1–6; text­figs. 3a–d, 7d–f, 8 (with synonymy).

Baculites vertebralis Lamarck, 1801 . Kennedy, in Kennedy et al., 1986: 1012, pl. 1, figs. 8, 9.

Baculites vertebralis Lamarck, 1801 . Kennedy, 1987: 187, pl. 19, figs. 1–4, 7–10; pl. 20, figs. 3–5; pl. 28, figs. 2, 7–10, 14–16; pl. 29, figs. 1–5; pl. 30, figs. 1–9; text­figs. 11a, b, 12 (with full synonymy).

Baculites vertebralis Lamarck, 1801 . Kennedy et al., 1997: 18, figs. 15E–J, M–O, 16A–F, I–K, 17, 18.

Baculites vertebralis Lamarck, 1801 . Klinger and Kennedy, 2001: 215, figs. 160, 161.

TYPE: Lectotype, by the subsequent designation of Kennedy (1986: 57), is the original of Faujas­Saint­Fond (1799: pl. 21, figs. 2, 3).

MATERIAL: There are 30 specimens, mostly fragments of body chambers, all of which are internal molds, from AMNH loc. 3252, the Severn Formation, Kent County, Maryland: MAPS A2035 c1–3, AMNH 47427 , 49400 , 49401 , 49403–49405 , 49408–49411 , 49427 , 49428 , 50543 , and 50683–50690, and USNM 522939–522944 .

DESCRIPTION: The collection consists of robust and slender specimens, which may represent macroconchs and microconchs, respectively. However, this is difficult to determine because the stage of ontogeny of each specimen is unknown (no evidence of septal approximation or apertural modification indicative of maturity). There are three robust specimens: MAPS A2035c1, 2, and AMNH 47428.

MAPS A2035c1 is a fragment of a body chamber 46.7 mm long with a taper angle of 5.0° (fig. 13Q–T). The whorl section is compressed ovoid with maximum whorl width at midwhorl height; the ratio of whorl width to height near the adoral end is 0.62. The dorsum is broadly rounded although it appears slightly angular due to crushing and wear on the dorsal half of the flanks on the left side. The flanks are broadly rounded and gently converge to an abruptly rounded ventrolateral shoulder and a narrow, broadly rounded venter. Ribs are absent on the dorsum but slant gently backward on the dorsal third of the flanks forming a broad concavity just dorsal of midflank. The rib index is approximately 5 based on the average distance between three consecutive ribs. Ribs break down into riblets on the ventral third of the flanks and slant strongly forward before disappearing on the ventrolateral shoulder.

MAPS A2035c2 is a fragment of a body chamber 35.3 mm long (fig. 13E–H). The whorl height is 22.8 and 19.8 mm at the adoral and adapical ends, respectively. The whorl section is compressed ovoid with maximum whorl width at midwhorl height; the ratio of whorl width to height at the adoral end is 0.60. The dorsum is very broadly rounded, and the dorsolateral shoulder is fairly abruptly rounded. The dorsal half of the flanks are flat and subparallel and the ventral half of the flanks are broadly rounded, and converge to an abruptly rounded ventrolateral shoulder and a narrow, broadly rounded venter. Ribs cross the dorsum with a weak convexity; the rib index is approximately 6 based on the distance between two consecutive ribs. The flanks are covered with broad crescentic ribs with a rib index of approximately 7 based on the average distance between three consecutive ribs. The ribs project strongly forward on the outer third of the flanks and intersect the line of the venter at an angle of 39°. Very faint ribs are visible on the venter on the adapical end of the specimen.

AMNH 47428 is a small fragment of a body chamber 37.0 mm long (fig. 13I–L). It is slightly crushed and worn on the venter. The whorl section is compressed ovoid with a ratio of whorl width to height of 0.63 at the adoral end. The dorsum is very broadly rounded with a fairly abruptly rounded dorsolateral shoulder. The flanks are nearly flat and gently converge to a narrow, broadly rounded venter. Ribs cross the dorsum with a weak convexity; the rib index is approximately 7 based on the distance between two consecutive ribs. Ribs slant gently backward on the dorsal third of the flanks and merge to form weak nodelike swellings on the midflanks. The rib index on the dorsal third of the flanks is approximately 7 based on the average distance between five consecutive ribs. Ribs project strongly forward on the outer third of the flanks but are not preserved on the venter.

There are five good examples of fairly slender variants. MAPS A2035c3 is a small fragment of a body chamer 29.2 mm long (fig. 13A–D). The shell is slightly crushed laterally and shows a shallow constriction along the flanks at midwhorl height on the left side, which may represent a growth deformity. The whorl height is 17.3 and 15.5 mm at the adoral and adapical ends, respectively. The whorl section is compressed ovoid with a ratio of whorl width to height of 0.67 at the adoral end. The dorsum is broadly rounded, and the dorsolateral shoul­ der is fairly abruptly rounded. The flanks are nearly parallel to just dorsal of midwhorl height and then converge more steeply toward the venter. The venter is narrow and sharply rounded although this may be due in part to lateral crushing. Faint ribs sweep strongly forward on the ventral two­thirds of the flanks; the rib index is 8 based on the average distance between three consecutive ribs.

AMNH 47427 consists of four pieces comprising the adapical part of the body chamber and last chamber of the phragmocone (fig. 13U–X). Altogether, it is 56.0 mm long with a taper angle of 5.7°. The whorl height is 18.2 and 13.5 mm at the adoral and adapical ends, respectively. The whorl section is compressed ovoid with maximum width at midwhorl height; the ratio of whorl width to height at the adoral end is 0.66. The dorsum is wide and broadly rounded and the dorsolateral shoulder is fairly abruptly round­ ed. The dorsal half of the flanks are broadly rounded and divergent and the ventral half of the flanks are broadly rounded and converge to a fairly abruptly rounded ventrolateral shoulder and a narrow, broadly rounded venter. No ornament is visible on the dorsum and dorsal third of the flanks because this part of the specimen is worn. Ribs slant strongly forward on the ventral two­thirds of the flanks and intersect the line of the venter at an angle of 34°. The rib index is approximately 6 based on the distance between two consecutive ribs. Ribs cross the venter with a weak convexity; the rib index is approximately 6.5 based on the average distance between three consecutive ribs.

AMNH 49427 is a small fragment of a body chamber 31.2 mm long (fig. 13M–P). The whorl height is 12.1 and 10.1 mm at the adoral and adapical ends, respectively. The ratio of whorl width to height at the adoral end is 0.70. The whorl section is compressed ovoid with maximum width at midwhorl height. The dorsum is more broadly rounded than the venter, and the flanks are very broadly rounded to flat. The specimen is nearly smooth with very faint ribs on the ventral half of the flanks and venter. Ribs cross the venter with a marked convexity; the rib index is approximately 5.5 based on the average distance between three consecutive ribs.

AMNH 49411 is a small, worn fragment of a body chamber 29.0 mm long with a taper angle of 3.8° (fig. 13Y, Z, a, b). The whorl height is 14.8 and 13.4 mm at the adoral and adapical ends, respectively. The ratio of whorl width to height at the adoral end is 0.77. The whorl section is ovoid but slightly more tear­shaped than in other specimens in the collection. The dorsum is very broadly rounded, and the dorsolateral shoulder is well rounded. The dorsal half of the flanks are nearly flat and the ventral half of the flanks are broadly rounded and converge to a narrowly rounded venter. The specimen is smooth except for weak ribs on the venter.

AMNH 49408 is a very small, smooth septate fragment 15.3 mm long with a whorl height of 11.2 mm at the adoral end (fig. 13c–f). The ratio of whorl width to height is 0.67. The whorl section is compressed ovoid with the dorsum more broadly rounded than the venter. The suture shows narrow, rectangular bifid lobes and saddles (fig. 14A).

USNM 522939–522944 (not illustrated) are fragments of body chambers 23.7–37.8 mm long, of which three are robust, one is intermediate, and two are slender.

OCCURRENCE: Severn Formation, Kent County, Maryland; Severn Formation, Prince Georges County, Maryland ( Kennedy et al., 1997). Elsewhere on the Atlantic Coastal Plain, this species has been reported from the end. M–P. AMNH 49427. M, Dorsal; N, ventral; O, left lateral; P, whorl cross section at adoral end. Q–T. MAPS A2035c1. Q, Right lateral; R, dorsal; S, ventral; T, whorl cross section at adoral end. U–X. AMNH 47427. U, Right lateral; V, dorsal; W, ventral; X, whorl cross­section at adoral end. Y, Z, a, b. AMNH 49411. Y, Dorsal; Z, ventral; a, left lateral; b, whorl cross section at adoral end. c–f. AMNH 49408. c, Dorsal; d, ventral; e, left lateral; f, whorl cross section at adoral end. g–j. Eubaculites latecarinatus ( Brunnschweiler, 1966) , AMNH 49402, same locality as A–Z, a–f. g, Right lateral; h, dorsal; i, ventral; j, whorl cross­section at adoral end. All figures ×1.

upper part of the Navesink Formation and the lower part of the New Egypt Formation in Monmouth County, New Jersey (Landman et al., in prep. c). According to Kennedy et al. (1997), this species occurs in western Europe in the upper Maastrichtian Belemnitella junior and Belemnella kasimiroviensis belemnite zones. It is reported from the Maastricht area of Limburg, The Netherlands; the Cotentin Peninsula, Manche, France; Petites Pyrénées, Haute Garonne, France; Belgium; Denmark; southern Sweden; northern Germany; Poland; southern Russia; Ukraine; Turkmenia; Kazakstan; and Tunisia (see Klinger and Kennedy, 2001, for references).

Genus Eubaculites Spath, 1926 (= Giralites Brunnschweiler, 1966 ; Cardabites Brunnschweiler, 1966 ; Eubaculiceras Brunnschweiler, 1966 ) TYPE SPECIES: Baculites vagina var. ootacodensis Stoliczka, 1866: 199 , pl. 90, fig. 14,

by original designation of Spath, 1926: 80; = Baculites labyrinthicus Morton, 1834: 44 , pl. 13, fig. 10.

Figures

Fig. 13. A–Z, a–f. Baculites vertebralis Lamarck, 1801, AMNH loc. 3252, Severn Formation, Kent County, Maryland. A–D. MAPS A2035c3. A, Dorsal; B, ventral; C, left lateral; D, whorl cross section at adoral end. E–H. MAPS A2035c2. E, Right lateral; F, dorsal; G, ventral; H, whorl cross­section at adoral end. I–L. AMNH 47428. I, Right lateral; J, dorsal; K, ventral; L, whorl cross­section at adapical

Fig. 14. A. Suture of Baculites vertebralis Lamarck, 1801, AMNH 49408, at a whorl height of 10.3 mm, AMNH loc. 3252, Severn Formation, Kent County, Maryland. B. Suture of Eubaculites latecarinatus (Brunnschweiler, 1966), AMNH 49402, at a whorl height of approximately 15 mm, same locality as A.