Discoscaphites Meek 1871
Creators: name: Witts, James D.
name: Landman, Neil H.
name: Garb, Matthew P.
name: Irizarry, Kayla M.
name: Larina, Ekaterina
name: Thibault, Nicolas
name: Razmjooei, Mohammad J.
name: Yancey, Thomas E.
name: Myers, Corinne E.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Cephalopoda
Ammonitida
Scaphitidae
Discoscaphites

description: Discoscaphites sp.
Figures 15, 16
MATERIAL: All sites we studied at the Brazos River localities yield many small juveniles of Discoscaphites (fig. 15). Because of their small size, it is impossible to identify them to a species level.
DESCRIPTION: Juvenile specimens range in LMAX from 1.7 to 10.4 mm and retain part or all of their body chamber (fig. 15; table 1) Although the specimens preserve traces of the outer
shell wall, the ornamentation is subdued or absent. Several specimens show exquisite details of the microornamentation of the embryonic shell (ammonitella; fig. 16).
REMARKS: The presence of complete to nearly complete juveniles suggests that the animals lived at the site in which they are buried. All the specimens appear as isolated occurrences except for AMNH 63319, which occurs in a concentration of shell hash along with other juveniles and fish debris.
OCCURRENCE: All specimens are from the upper portion of the Corsicana Formation just below the K-Pg boundary at AMNH locs. 3620 and 3621, Darting Minnow and Cottonmouth creeks, respectively.
Lower jaws of Discoscaphites
Figure 11E–J
MATERIAL: Four isolated specimens (AMNH 108284, 108179, 108282, 63317) and one preserved in situ (AMNH 63312) from the top 1.25 m of the Corsicana Formation at AMNH loc. 3620 and AMNH loc. 3621, Darting Minnow and Cottonmouth creeks, Falls County, Texas. The specimens consist of the outer calcareous valve (aptychus), although three of them also retain traces of the inner black layer
DESCRIPTION: Each valve is roughly triangular in outline. The ratio of valve length to valve width ranges from 1.4 to 1.9 in our sample. The symphysal edge is straight and forms a flange that increases in height posteriorly. The anterior margin is nearly straight, the lateral margin is broadly rounded, and the posterior margin is sharply rounded. The ventral surface of each valve is covered with small folds that parallel the posterior margin.
Most of the jaws are preserved with only one valve exposed. However, in AMNH 63317 the two valves are folded folio style. As a result, the ventral surface of one valve and part of the dorsal surface of the other valve are exposed. AMNH 66312 occurs inside a very poorly preserved specimen of Discoscaphites iris surrounded by small oysters. The specimen of D. iris is 32.1 mm in maximum length, so that the ratio of LMAX to the length of the jaw is 2.3.
REMARKS: These specimens are similar to the lower jaws of scaphites illustrated from Maastrichtian deposits of South Dakota (Landman and Waage, 1993: figs. 37–41, 167E–I) and northern Europe (Birkelund, 1982: pl. 2, figs. 6, 7; Birkelund, 1993: pl. 17, figs. 2–4; Machalski, 2005b: fig. 26).
description: Published as part of 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, pp. 1-52 in American Museum Novitates 2021 (3964) on pages 37-39, DOI: 10.1206/3964.1, http://zenodo.org/record/4566589