Menabites (Delawarella) uddeni ( Young, 1963 )

Ifrim, Christina & Stinnesbeck, Wolfgang, 2021, Ammonoids and their biozonation across the Santonian-Campanian boundary in north-eastern Coahuila, Mexico, Palaeontologia Electronica (a 34) 24 (3), pp. 1-62 : 23-25

Menabites (Delawarella) uddeni ( Young, 1963)

Figure 18 , Table 9

1963 Submortoniceras uddeni , n. sp.; Young,

p. 105, p1. 59, figures 1, 2, 4-9; pI. 60,

figures 2, 3, 7, 9, 10; text-figures 14d, e,

28c non 1993a Submortoniceras uddeni Young, 1963 ;

Kennedy and Cobban, p. 842, figures

10.1, 12.3, 12.4, 12.7, 12.8 [= possibly M.

(D.) vandaliense). Type. The holotype is USNM –130739, by original designation of Young (1963, p. 105, plate 59, figures 5, 7-9; text-figure 14e) from near the top of the Terlingua Formation near the east end of Maverick Mountain , Brewster County, Texas .

Material. Eight specimens, CPC –2396, –2399, – 2400, –2402, –2405, –2415, –2416, and –2574 .

Description. Involute shell, U/D is between 0.2 and 0.1 and decreases with growth. The whorl section is compressed, with WB/WH ranging between 0.58 and 0.29. Rounded umbilical tubercles give rise to moderately prorsiradiate ribs, which efface on the flanks. Fifty-eight ribs are present on the last whorl at D= 80 mm.

Dimensions. Table 9.

Remarks. This species is closely related to Menabites (Delawarella) mariscalense , but differs from the latter by a stronger and more prorsiradiate ventrolateral ornament and the absence of a rounded venter near the aperture. M. (D.) vandaliense is also closely related but differs by more delicate, more abundant, and more rounded and less prominent ventrolateral tubercles.

According to Young (1963), the species is restricted to the upper Menabites (Delawarella) tequesquitense zone , but at Tepeyac it occurs at higher levels of the lower Campanian.

Occurrence. Lower lower Campanian in Texas, upper lower Campanian at Tepeyac .

Figures

FIGURE 18. Compressed Menabites (Delawarella) from the Tepeyac section. A–B: Menabites (Delawarella) vandaliense (Young, 1963), CPC–2576 from bed TPY77. Menabites (Delawarella) uddeni (Young, 1963) C–D: CPC– 2399, E–H: CPC–2400, both from bed TPY74; I–J: CPC–2416, K–N: CPC– 2415, both from bed TPY77. Scale: 50 mm.