Gaudryceras, de Grossouvre, 1894

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 : 20

Gaudryceras sp.

Figure 8

MATERIAL: One small specimen AMNH 111956 from the Corsicana Formation 1 m below the K-Pg boundary at AMNH loc. 3620 (Darting Minnow Creek).

DESCRIPTION: Diameter of the specimen is 15.6 mm. It is entirely septate and mostly covered with shell ( fig. 2F ), with a tiny bit of suture exposed. It is serpenticonic with UD = 8.9 mm. The rate of whorl expansion is low. The ornament consists of thin lirae that are convex on the umbilical wall and shoulder and straight and prorsiradiate on the middle and outer flanks. They cross the venter with a slight adoral projection.

REMARKS: Because of the small size of this specimen, it is impossible to identify it to the species level (R. Hoffmann and Y. Shigeta, personal commun., 2019). However, it is the only specimen of Gaudryceras ever found at Brazos and one of only a handful of lytoceratid ammonite specimens described from the Maastrichtian of North America ( Cobban and Kennedy, 1995; Kennedy et al., 2000).

OCCURRENCE: Gaudryceras is worldwide in its distribution and is reported from the Maastrichtian of Tunisia, Zululand, and Pondoland, South Africa (Klinger and Kennedy, 1979), Madagascar, south India, Japan, western Australia, California, Chile, and the Antarctic Peninsula. The closest occurrences of this genus to the Brazos River locality are in the lower Campanian of Travis County, Texas ( Young, 1963), the lower upper Maastrichtian Corsicana Formation near San Antonio, Bexar County, Texas ( Woehr, 2013), the upper Campanian Saratoga Chalk of Arkansas ( Kennedy and Cobban, 1993b), and the Maastrichtian Méndez Formation of northeastern Mexico ( Ifrim et al., 2004).

Figures

FIGURE 2.

FIGURE 8. Gaudryceras sp., AMNH 111956, AMNH loc. 3620, Corsicana Formation, 1 m below the K-Pg boundary, Darting Minnow Creek, Falls County, Texas. A, B. Part and counterpart.