Hoploscaphites criptonodosus ( Riccardi, 1983 )

Landman, Neil H., Kennedy, W. James, Larson, Neal L., Grier, Joyce C., Grier, James W. & Linn, Tom, 2019, Description Of Two Species Of Hoploscaphites (Ammonoidea: Ancyloceratina) From The Upper Cretaceous (Lower Maastrichtian) Of The U. S. Western Interior, Bulletin of the American Museum of Natural History 2019 (427), pp. 1-72 : 44

Hoploscaphites criptonodosus ( Riccardi, 1983)

Figures 8C, D , 9 , 11A, B, 23D, E, 26–38

1983. Jeletzkytes criptonodosus . Riccardi, p. 28, pl. 6, fig. 10; pl. 7, figs. 1, 2; pl. 8, figs. 7–9; text-figs. 25–27.

1983. Jeletzkytes cf. criptonodosus . Riccardi, p. 30, pl. 11, figs. 1–11, 15–21; text-figs. 28, 29b, 30, 31.

non 1983. Jeletzkytes cf. criptonodosus . Riccardi, p. 30, pl. 11, figs. 12–14; text-fig. 29a (= Hoploscaphites sargklofak ).

1994. Jeletzkyites (Karlwaageites) criptonodosus Riccardi. Cooper , p. 181.

1995. Jeletzkytes criptonodosus Riccardi, 1983 . Cobban and Kennedy, p. 31, figs. 6.4, 6.5, 22.5–22.12, 23.1–23.5.

1997. Jeletzkytes criptonodosus Riccardi, 1983 . Larson et al., p. 81, fig. on bottom; p. 82. top (= Riccardi, 1983, pl. 6, fig. 10, pl. 7, fig. 1).

2000. Jeletzkytes criptonodosus Riccardi, 1983 . Kennedy et al., p. 26, fig. 12A, B.

2016. Jeletzkytes criptonodosus Riccardi, 1983 . Klein, p. 138.

EMENDED DIAGNOSIS: Macroconchs oval in lateral view; robust, with compressed subquadrate whorl section of shaft consisting of broadly rounded flanks and nearly flat venter; small umbilicus commonly with umbilical bulge; apertural angle averaging approximately 60°; ribbing coarse on the adapical end of the phragmocone, becoming finer on the body chamber; moderately closely spaced, medium sized ventrolateral tubercles; small umbilicolateral tubercles on phragmocone and body chamber; one or two rows of lateral tubercles on the outer flanks on the adapical end of the phragmocone; microconchs oval in lateral view; whorl section of shaft subquadrate with broadly rounded flanks converging toward ventrolateral shoulder; large umbilicus exposing earlier whorls; moderately closely spaced, medium sized ventrolateral tubercles; relatively prominent umbilicolateral tubercles on body chamber; one or two rows of lateral tubercles on the adapical end of the phragmocone; suture deeply incised, with a broad, asymmetrically bifid first lateral saddle and a narrow, symmetrically to asymmetrically bifid first lateral lobe (slightly modified from Riccardi, 1983).

TYPES: The holotype and paratype are GSC 67104 and 67105, respectively, illustrated in Riccardi (1983: pl. 6, fig. 10; pl. 7, figs. 1, 2; pl. 8, figs. 7–9). They are both from GSC loc. 10374 from the Baculites baculus Zone of the Belanger Member of the Bearpaw Shale, on the north side of Frenchman River, sec. 14, T. 6, R. 25, W3rd Mer., Saskatchewan, Canada .

MATERIAL: The collection consists of approximately 90 specimens of which 61 comprise the measured set (tables 3, 4) representing 43 macroconchs and 18 microconchs. The specimens in our collection are from the upper part of the Baculites baculus and B. grandis zones of the Pierre Shale in Wyoming, Colorado, Montana, and possibly South Dakota, and the Bearpaw Shale in Montana.

MACROCONCH DESCRIPTION: In the measured sample, LMAX averages 79.2 mm and ranges from 60.9 to 102.4 mm (table 3). The ratio of the size of the largest specimen to that of the smallest is 1.68. The specimens form a broad size distribution, with a primary peak at 65–70 mm and a secondary peak at 75–80 mm (fig. 26). Adults are stout with an oval outline in side view. LMAX /HS averages 2.09 and ranges from 1.86 to 2.32 (2.04 in the holotype). USNM 463215 (fig. 33) is an example of a specimen with an oval outline ( LMAX /HS = 2.27) and AMNH 108445 (fig. 30) is an example of a specimen with a more rounded outline ( LMAX /HS = 1.98).

The umbilicus is small and deep. The umbilical diameter averages 5.0 mm and ranges from 3.7 to 7.6 mm. UD/ LMAX averages 0.06 and ranges from 0.05 to 0.10. The umbilicus is unusually large (7.6 mm) in AMNH 108456 (fig. 31). In lateral view, the umbilical shoulder is straight and usually exhibits a pronounced umbilical bulge. Most specimens are tightly coiled with little or no gap between the phragmocone and hook. LMAX /HP 2 averages 2.83 and ranges from 2.59 to 3.04 (2.79 in the holotype). AMNH 95771 (fig. 32A–C) is an

Figures

FIGURE 8. A, B. Unpaired ventral muscle scar (arrow) just adoral of the last suture, Hoploscaphites macer, microconch, AMNH 69736, AMNH loc. 3921, upper Baculites baculus or lower B. grandis Zone, Pierre Shale, Cedar Creek Anticline, east-central Montana. C. Apertural view of dorsal projection (arrow), Hoploscaphites criptonodosus (Riccardi, 1983), AMNH 108459, AMNH loc. 3278, Baculites grandis Zone, Pierre Shale, Weston County, Wyoming. The hook of the body chamber has broken off exposing the dorsal projection, which is plastered against the venter of the phragmocone. D. Kidney-shaped apertural opening showing the dorsal projection, Hoploscaphites criptonodosus (Riccardi, 1983), macroconch, AMNH 71830, AMNH loc. 3921, upper Baculites baculus or lower B. grandis Zone, Pierre Shale, Cedar Creek Anticline, east-central Montana.

FIGURE 9. Cross section of the shell wall at the apertural margin of a mature macroconch of Hoploscaphites criptonodosus (Riccardi, 1983), AMNH 94676, AMNH loc. 3728, Baculites grandis Zone, Pierre Shale, Weston County, Wyoming. A. Overview of part of the apertural margin. The exterior direction is toward the right and the adoral direction is toward the top. The shell wall bends sharply inward at nearly a right angle forming a thick varix and then reflects outward terminating in a flared lip. During fossilization, sediments usually accumulate in the narrow gap behind the flared lip (for a rare example in which epizoans colonized this gap during the lifetime of the ammonite, see Landman et al., 2016). B, C. Close-ups of the shell wall showing the recurved layers of shell.