Eubaculites carinatus ( Morton, 1834 )

Witts, James D., Landman, Neil H., Garb, Matthew P., Irizarry, Kayla M., Larina, Ekaterina, Thibault, Nicolas, Razmjooei, Mohammad J., Yancey, Thomas E. & Myers, Corinne E., 2021, Cephalopods from the Cretaceous-Paleogene (K-Pg) boundary interval on the Brazos River, Texas, and extinction of the ammonites, American Museum Novitates 2021 (3964), pp. 1-52 : 25-27

Eubaculites carinatus ( Morton, 1834)

Figure 10A–J, N–S

Eubaculites carinatus ( Morton, 1834) figs. 29–35

Baculites carinatus Morton, 1834: 44 , pl. 13, fig. 1.

Baculites lyelli d’Orbigny, 1847 : pl. 1, figs. 3–7.

Baculites tippaensis Conrad, 1858: 334, pl. 3, fig. 27.

Baculites spillmani Conrad, 1858: 335, pl. 35, fig. 24.

Baculites sheromingensis Crick, 1924: 139, pl. 9, figs. 1–3 .

Eubaculites lyelli (d’Orbigny, 1847) . Kennedy, 1987: 195, pl. 27, figs. 5–8; pl. 32, figs. 13, 14 (with full synonymy).

Eubaculites carinatus ( Morton, 1834) . Klinger and Kennedy, 1993: 218, text-figs. 7a–e, 21–30, 31a–g, 32– 35, 36e, f, 37, 38, 42a, 52g, h.

Eubaculites carinatus ( Morton, 1834) . Kennedy and Cobban, 2000: 180, pl. 2, figs. 1–23, 27, 28; text figs. 3, 4 (with additional synonymy).

Eu baculites carinatus ( Morton, 1834) . Kennedy et al., 2001: 168, fig. 4a, e.

Eubaculites carinatus ( Morton, 1834) . Landman et al., 2004a: 35, fig. 15P, Q.

Eubaculites carinatus ( Morton, 1834) . Landman et al., 2004b: 55, figs. 27–29, 30A, B, 33U–Y.

Eubaculites carinatus ( Morton, 1834) . Landman et al., 2007a: 64, figs. 29–35.

TYPE: The holotype, by monotypy, is ANSP 72866 , the original of Morton (1834: pl. 13, fig. 1), from the Maastrichtian Prairie Bluff Chalk of Alabama .

MATERIAL: Approximately 40 specimens in the AMNH collections in the top 1 m of the Corsicana Formation at AMNH locs. 3620 and 3621, and as reworked material in the upper portion of the first unit (mudstone-clast-bearing unit) of the overlying K-Pg event deposit at the base of the Kincaid Formation, AMNH loc. 3620 .

DESCRIPTION: Nearly all the specimens are crushed but bear weak to strong, slightly crescentic nodate swellings on the flanks. The largest specimen is AMNH 108203, which retains part of the body chamber. The whorl height at the broken end of the body chamber is 30.5 mm, suggesting that it is a macroconch. The only fully three-dimensional specimen is AMNH 111960 from the K-Pg event deposit. It is a fragment 58.0 mm long with a whorl height of 30.0 mm at its adoral end. It is completely septate suggesting that it is probably a macroconch. The dorsum is very broadly rounded, and the dorsolateral margin is fairly sharply rounded. The inner flanks are broadly rounded with maximum width at one-third whorl height. The outer flanks converge to a tabulate venter bordered by a shallow longitudinal groove on each side. The flanks bear two prominent nodate swellings and the venter is covered with transverse ribs that project slightly forward, producing a serrated appearance.

REMARKS: Several specimens from the Corsicana Formation are associated with oysters and represent postmortem encrustations (fig. 5A, B). The whorl height of the largest specimen in our collection (30.5 mm) exceeds that of the largest specimen of this species at the ageequivalent Tinton Formation in Monmouth County, New Jersey (25.4 mm). However, the specimens in the Corsicana Formation do not approach the size of the largest specimens of this species from Argentina and Zululand, which are approximately 90 mm in whorl height (Klinger and Kennedy, 2001: 62). Our collection is too small to confirm the hypothesis of dimorphism in Eubaculites carinatus , as suggested by bimodal size distributions of specimens from South Africa and South American localities by Klinger and Kennedy (2001).

OCCURRENCE: Top 1 m of the Corsicana Formation at AMNH locs. 3620 and 3621, and basal Kincaid Formation at AMNH loc. 3620. We also found specimens of Eubaculites carinatus 17.68–18.29 mbs and 20.12–20.73 mbs in the Mullinax-1 core, correlated to planktonic foraminiferal zone CF3. The species has also been recorded throughout an approximately 11 m succession of the Corsicana Formation at Brazos by Kennedy et al. (2001). This species is widely distributed and, according to Henderson et al. (1992: 153), “is a useful indicator of middle to late Maastrichtian age and represents the last widely distributed heteromorph taxon to appear in the stratigraphic record.” On the eastern Gulf Coastal Plain, it is reported from the Owl Creek Formation in Mississippi, Missouri, and Tennessee ( Kennedy and Cobban, 2000) and the Prairie Bluff Chalk in Alabama and Mississippi ( Cobban and Kennedy, 1995). On the Atlantic Coastal Plain, it occurs in the Tinton and New Egypt formations, and as reworked material in the Hornerstown Formation in Monmouth and Gloucester counties, New Jersey ( Kennedy and Cobban, 1996; Landman et al., 2004b; 2007a) and in the Severn Formation in Prince Georges and Anne Arundel counties, Maryland ( Kennedy et al., 1997; Landman et al., 2004). It has also been reported from southeastern and southwestern France, northern Spain, Austria, the Netherlands, Zululand ( South Africa), Mozambique, Madagascar, South India, Western Australia, Chile, Argentina, and California ( Klinger and Kennedy, 1993; Klinger et al., 2001).

Figures

FIGURE 1. Locality map of the Brazos River area south of Texas Rt. 413 in southern Falls County, Texas, showing outcrops (AMNH locs. 3620, 3621, 3968, Brazos 1) and drill cores (Mullinax-1-3) mentioned in the text.

FIGURE 2.

FIGURE 3. Litho- and biostratigraphic sections. K-Pg boundary shown as dashed line connecting outcrops. Biostratigraphy is illustrated for each section based on (1) ammonites, (2) calcareous nannofossils, and (3) planktonic foraminifera. Cephalopod-occurrence color code: green = Cretaceous; white = incorporated into K-Pg event deposit; orange = Paleogene. Abbreviations: DSB, Dirty Sandstone Bed; LCH, Lower Concretion Horizon; MSB, Middle Sandstone Bed; va, volcanic ash horizon at AMNH loc. 3621; * single cephalopod occurrence from the MSB (Eutrephoceras sp.) collected at Darting Minnow Creek (AMNH loc. 3620), but illustrated on the stratigraphically continuous section at AMNH loc. 3698 from Hart et al. (2012) and Leighton et al. (2017). The DSB, LCH, and MSB concretionary marker beds can be found and correlated throughout the Brazos River area (e.g., Yancey, 1996; Hart et al., 2012).

FIGURE 10.