Type Species: Ammonites constrictus J. Sowerby (1817: 189, pl. A, fig. 1), by original designation.

Diagnosis: “Small to large scaphites, strongly dimorphic, with broad variation in degree of whorl compression ranging from slender to robust, with involute phragmocone, short to long shaft, and weakly recurved hook; apertural angle ranging from approximately 35° to 85°; aperture constricted with dorsal projection; ribs straight to flexuous, increasing by branching and intercalation, with weak to strong adoral projection on venter; adult shell with or without umbilicolateral, flank, and ventrolateral tubercles; suture fairly indented, with symmetrically to slightly asymmetrically bifid first lateral lobe” (Landman et al., 2010: 93).

Discussion: In their monograph on the scaphites of the “nodosus group,” Landman et al. (2010) treated Jeletzkytes Riccardi, 1983, as a junior subjective synonym of Hoploscaphites. They argued that the shape of the shell, the pattern of ornamentation, and the complexity of the suture are the same in both genera, the only differences being the degree of compression and, as a result, the flexuosity of the ribs and the size of the tubercles. They noted that such variation already exists within the genus Hoploscaphites, as previously defined, and exemplified by the type species H. constrictus. Wright (1996: 261–262) cited the same reason for synonymizing the two genera: “Separation of the large and inflated species of the nodosus group as Jeletzkytes seems unnecessary, given the great variation within most scaphitid species.” Later, Cooper (1994) erected the new subgenus Karlwaageites for derived members of Jeletzkytes from North America that bear lateral tubercles. However, the number and distribution of lateral tubercles can vary even within a single species, casting doubt on the utility of this character for subgeneric separation. Until a thorough phylogenetic revision of all scaphitid genera and subgenera is undertaken, we prefer to follow a more conservative approach and treat all these species in the genus Hoploscaphites.

Diagnosis: Macroconchs oval to nearly circular in lateral view; cross section of shaft compressed subovoid with high whorls consisting of broadly rounded flanks and nearly flat venter; maximum width at adoral part of shaft; small umbilicus commonly with umbilical bulge; ribs coarse on phragmocone at the point of exposure, subsequently becoming finer; small, moderately closely spaced ventrolateral tubercles; small umbilicolateral tubercles on body chamber; occasional lateral tubercles on adapical part of phragmocone; apertural angle averaging 56°; microconchs oval in lateral view; cross section of shaft subovoid with broadly rounded flanks converging toward ventrolateral shoulder; large umbilicus exposing earlier whorls; closely spaced ventrolateral tubercles; relatively prominent umbilicolateral tubercles on body chamber; suture with broad, asymmetrically bifid first lateral saddle and narrow, symmetrically to asymmetrically bifid first lateral lobe.

Etymology: The name is derived from the Latin word macer, “thin,” which is one's first impression of this species relative to other species in the same biostratigraphic zones. Upon inspection, however, the shell is slightly inflated. Nevertheless, this name has been used informally for the last 20 years, and for the sake of stability, we decided to retain the name for this species.

Types: The holotype is AMNH 71839 (figs. 19E–H, 23A), a macroconch, from the lower part of the B. grandis Zone of the Pierre Shale on the Cedar Creek Anticline, Montana. It is a steinkern with some attached shell 54.2 mm in diameter with a small umbilicus. The macroconch paratypes are AMNH 113323 (fig. 20D–F) and 113324 (fig. 20G–I), both from the upper part of the B. baculus Zone or the lower part of the B. grandis Zone of the Pierre Shale on the Cedar Creek Anticline, Montana, and USNM 713612 (fig. 17A–C) from the B. grandis Zone of the Bearpaw Shale in Roosevelt County, Montana. The microconch paratypes are AMNH 72634 (fig. 24M–P) and 108314 (fig. 24E–H) from the upper part of the B. baculus Zone or the lower part of the B. grandis Zone of the Pierre Shale on the Cedar Creek Anticline, Montana.

Material: The collection consists of approximately 100 specimens of which 75 comprise the measured set (40 macroconchs and 35 microconchs) (tables 1, 2). All the specimens in our collection are from the upper part of the Baculites baculus Zone or lower part of the B. grandis Zone of the Pierre Shale in Wyoming, Colorado, and Montana and the Bearpaw Shale in Montana.

Macroconch Description: In the measured sample, LMAX averages 61.4 mm and ranges from 45.2 to 76.0 mm (table 1). 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 peak at 50–55 mm (fig. 13). Adults are slender with an oval to circular outline in side view. LMAX/H_Saverages 2.05 and ranges from 1.86 to 2.25 (1.94 in the holotype). BHI 4346 (fig. 14A–D) is an example of a specimen with an oval outline (LMAX/H_S= 2.17) and AMNH 108487 (fig. 19A–D) is an example of a specimen with a more rounded, nearly perfectly circular outline (LMAX/H_S= 1.98).

The umbilicus is small and deep. The umbilical diameter averages 3.8 mm and ranges from 1.9 to 6.5 mm. UD/LMAX averages 0.06 and ranges from 0.04 to 0.12. In lateral view, the umbilical wall is straight and usually exhibits a pronounced umbilical bulge, so that part of the umbilicus of the phragmocone is concealed. All specimens are tightly coiled with little or no gap between the phragmocone and hook. LMAX/H_P2averages 2.78 and ranges from 2.55 to 2.98 (2.70 in the holotype). AMNH 76388 (fig. 18A–C) is an example of a tightly coiled specimen (LMAX/H_P2= 2.75) and BHI 4346 (fig. 14A–D) is an example of a more loosely coiled specimen (LMAX/H_P2= 2.89).

The exposed phragmocone occupies approximately one-half whorl and usually terminates just below the line of maximum length. AMNH 76367 (not figured) is an exception in which the phragmocone terminates just adapical of midshaft. An unpaired muscle scar appears on the venter just adoral of the end of the phragmocone (fig. 8A, B). The body chamber consists of a short shaft and recurved hook totaling slightly more than one-half whorl. The apertural lip is flexuous with a deep constriction, as in other scaphites (fig. 9). The apertural angle averages 55.9° and ranges from to 36.0° to 69.0° (44.5° in the holotype).

The whorl section of the phragmocone near the point of exposure is compressed subovoid with maximum whorl width at one-third whorl height. W_P1/H_P1averages 0.98 and ranges from 0.82 to 1.16 (0.99 in the holotype). The umbilical wall is steep and subvertical and the umbilical shoulder is sharply rounded. The flanks are broadly rounded and converge toward the venter starting at two-thirds whorl height. The ventrolateral shoulder is sharply rounded and the venter is broadly rounded. The whorl section of the phragmocone at the line of maximum length is more compressed than that at the point of exposure, reflecting a marked increase in whorl height. W_P2/H_P2averages 0.88 and ranges from 0.74 to 0.98 (0.84 in the holotype). In addition, the flanks are very broadly rounded and the venter is nearly flat.

As the shell passes from the phragmocone into the body chamber, the whorl width increases and reaches its maximum value on the adoral part of the shaft and, as a result, the shell forms a bulge in this area. Whorl height increases even more markedly during this transition and reaches its maximum value at midshaft. Thereafter, it diminishes to the point of recurvature and remains nearly the same up to the aperture. Because of these changes in whorl width and height, the whorl section at midshaft is only slightly more compressed than that along the line of maximum length (table 1). W_S/H_Saverages 0.81 and ranges from 0.67 to 0.95 (0.80 in the holotype). The whorl section is subovoid with maximum whorl width at one-quarter whorl height. The umbilical wall is steep and subvertical and the umbilical shoulder is sharply rounded. The whorls are very high and broadly rounded and gently converge to the venter. The ventrolateral shoulder is sharply rounded and the venter is nearly flat. V_S/H_Saverages 0.40 and ranges from 0.30 to 0.51 (0.38 in the holotype).

The whorl section at the point of recurvature is less compressed than that at midshaft, mainly due to a decrease in whorl height. W_H/H_Haverages 1.06 and ranges from 0.94 to 1.19 (1.11 in the holotype). The whorl section at the point of recurvature is subovoid with maximum whorl width at one-half whorl height. The umbilical wall is slightly concave and the umbilical shoulder is sharply rounded. The flanks are broadly rounded and gently converge toward the venter.

At the adapical end of the exposed phragmocone, ribs emerge at the umbilical seam and strengthen across the umbilical wall and shoulder. They attain their maximum strength at onethird whorl height and in some specimens, such as AMNH 113324 (fig. 20G–I) develop into small umbilicolateral tubercles at this point. Ribs are rectiradiate to slightly prorsiradiate and weakly flexuous, bending slightly backward on the inner flanks, slightly forward on the midflanks, and slightly backward again on the outer flanks. They are widely spaced, with intercalation and branching occurring at one-third and two-thirds whorl height, so that the outer flanks are more densely covered with ribs than the inner flanks. Ribs are uniformly strong on the venter, which they cross with a slight adoral projection. The rib density on the venter on the adapical end of the phragmocone ranges from 6 to 8 ribs/cm in our measured sample (7 ribs/cm in the holotype).

The same pattern of ribbing persists onto the adoral part of the phragmocone. However, because the whorl section is more compressed at this point than on the adapical part of the phragmocone due to an increase in whorl height and a flattening of the flanks, the ribs on the adoral part of the phragmocone are relatively longer and more closely spaced. The rib density on the venter on the adoral end of the phragmocone ranges from 6 to 9 ribs/cm in our measured sample (9 ribs/cm in the holotype).

On the body chamber, ribs arise at the umbilical seam and are rursiradiate on the umbilical wall and shoulder. They are adorally concave at one-third whorl height and in many specimens form small umbilicolateral tubercles at this point. The tubercles are evenly spaced and usually extend to the aperture. In the holotype, the distance between consecutive umbilicolateral tubercles at midshaft is 5 mm. Ribs are straight and prorsiradiate on the middle and outer flanks, with branching and intercalation occurring at two-thirds whorl height. As a result, the outer flanks are more densely covered with ribs than the inner flanks. Ribs cross the venter with a strong adoral projection. They become more closely spaced toward the aperture. In our measured sample, the rib density ranges from 7 to 10 ribs/cm on the midshaft versus 8 to 13 ribs/cm on the hook (10 versus 13 ribs/cm, respectively, in the holotype).

Ventrolateral tubercles develop early in ontogeny at a diameter of approximately 6 mm and persist onto the exposed phragmocone (fig. 22). Because the venter is broadly rounded, the tubercles occur slightly below the ventrolateral shoulder. The tubercles are widely and unevenly spaced on the adapical end of the exposed phragmocone, but become more closely and uniformly spaced toward the adoral end. In the holotype, the distance between consecutive tubercles on the exposed phragmocone, starting at the point of exposure, is 7, 6.5, 4.5, 3, 5, 3, 5, 3, 4, and 4 mm (fig. 19E–H). The total number of ventrolateral tubercles on the exposed phragmocone ranges from 6 to 13 in our measured sample (11 tubercles in the holotype). The tubercles are conical in shape and change from slightly radially elongate at the point of exposure to slightly clavate at the adoral end of the phragmocone.

Ventrolateral tubercles persist onto the body chamber. They gradually become more widely spaced, attaining their maximum spacing on the adoral end of the shaft, and become more closely spaced again on the hook. In the holotype, the distance between consecutive ventrolateral tubercles is 6 mm at midshaft, 7.5 mm on the adoral end of the shaft, and 4.5 mm on the hook (fig. 19E–H). Three or four ribs loop between tubercles on opposite sides of the venter at midshaft, with an equal number of ribs intercalating between them. Because the venter is broadly rounded to nearly flat, the tubercles appear at or just below the ventrolateral shoulder. The number of ventrolateral tubercles on the body chamber ranges from 10 to 25 in our measured sample (16 in the holotype). The tubercles are clavate on the adoral end of the shaft where they attain their maximum height. They become smaller on the hook and, in some instances, slightly radially elongate.

In a few specimens, small lateral tubercles occur on the adapical end of the exposed phragmocone. They form a single row at two-thirds whorl height and persist for as much as onequarter whorl. For example, in USNM 713623 (not figured), a single row of five lateral tubercles is present beginning at the point of exposure. They occur on every rib and are evenly spaced at intervals of 2.5 mm. Similarly, in AMNH 113323 (fig. 20D–F), a single row of five lateral tubercles appears on the adapical end of the phragmocone and persists for one-eighth whorl.

The suture is deeply incised, with a broad, asymmetrically bifid first lateral saddle (E/L) and a narrow, symmetrically to asymmetrically bifid first lateral lobe (L) (fig. 23A, B).

Microconch Description: In comparison with macroconchs, microconchs are characterized by a more openly coiled shell with a larger umbilicus. In addition, the umbilical shoulder is concave in lateral view and the umbilicolateral tubercles are more prominent. LMAX averages 45.1 mm and ranges from 35.4 to 56.6 mm (table 2). The ratio of the average size of microconchs to that of macroconchs is 0.73. The size distribution is unimodal with a peak at 35–40 mm (fig. 13).

Microconchs are oval in lateral view. The phragmocone usually terminates at or below the line of maximum length. Microconchs are less tightly coiled than macroconchs with a gap between the phragmocone and hook. LMAX/H_P2averages 2.90 and ranges from 2.56 to 3.22. AMNH 72624 (fig. 25E–G) is an example of an openly coiled specimen (LMAX/ H_P2= 3.19) and AMNH 76383 (fig. 24I–L) is an example of a more tightly coiled specimen (LMAX/H_P2= 2.90). The body chamber occupies slightly more than one-half whorl. The umbilicus is relatively large. UD/LMAX averages 0.08 and ranges from 0.06 to 0.11. The average value of UD/LMAX is significantly higher in microconchs than it is in macroconchs (UD/LMAX = 0.06).

The whorl section of the exposed phragmocone is compressed subquadrate. W_P1/H_P1averages 0.89 and ranges from 0.64 to 1.16; W_P2/H_P2averages 0.86 and ranges from 0.70 to 1.01. The umbilical wall is steep and nearly vertical, the umbilical shoulder is sharply rounded, and the flanks are broadly rounded and gently converge to the ventrolateral shoulder. The ventrolateral shoulder is sharply rounded and the venter is broadly rounded.

Whorl width gradually increases from the phragmocone into the body chamber, attaining its maximum value on the hook. Whorl height also increases gradually from the phragmocone into the body chamber, but reaches its maximum value at midshaft and remains nearly the same thereafter. The whorl section at midshaft is compressed subquadrate with maximum width at one-quarter whorl height. W_S/H_Saverages 0.86 and ranges from 0.75 to 0.99 (table 2). The umbilical wall is steep and slopes outward at an acute angle. The flanks are broadly rounded and converge gently toward the ventrolateral shoulder. The ventrolateral shoulder is sharply rounded and the venter is nearly flat. V_S/H_Saverages 0.41 and ranges from 0.31 to 0.54. The whorl section at the hook is more ovate than that at midshaft. W_H/H_Haverages 0.99 and ranges from 0.82 to 1.17. The venter is broadly rounded, which is accentuated by the disappearance of the ventrolateral tubercles.

On the exposed phragmocone, ribs emerge at the umbilical seam and are slightly rursiradiate on the umbilical wall. They are weakly flexuous on the flanks, swinging gently backward on the inner flanks, gently forward on the midflanks, and gently backward again on the outer flanks. Ribs are uniformly strong on the venter, which they cross with a weak adoral projection. They are relatively closely spaced with an average of 8 ribs/cm on both the adapical and adoral portions of the phragmocone.

Ribs are long and prorsiradiate on the shaft, swinging gently forward on the midflanks and backward again on the outer flanks. In general, ribs are much weaker on the shaft than on the phragmocone. Intercalation and branching occur at two-thirds whorl height. Ribs cross the venter with a strong adoral projection and become more closely spaced on the hook. For example, in AMNH 108314 (fig. 24E–H), the rib density increases from 9 to 11 ribs/cm in passing from the midshaft to the hook.

Umbilicolateral tubercles are absent on the adapical end of the phragmocone, and usually appear on the adoral end, and continue onto the body chamber up to the aperture. They are perched on the umbilical shoulder, which constitutes one of the distinctive features of microconchs. The tubercles are small, radially elongate, and evenly spaced. The distance between consecutive tubercles at midshaft is 4.6 mm in AMNH 108314 (fig. 24E–H) and 4.2 mm in AMNH 72634 (fig. 24M–P). The number of umbilicolateral tubercles on the body chamber ranges from 5 to 8 in our measured sample, e.g., 5 in AMNH 108314 (fig. 24E–H) and 7 in AMNH 72634 (fig. 24M–P).

Ventrolateral tubercles are usually present at the point of exposure. They are initially closely spaced but become more widely spaced toward the adoral end of the phragmocone. In AMNH 72634 (fig. 24M–P), the distance between consecutive tubercles is 4.1 mm at the adapical end of the phragmocone and 6.3 mm at the adoral end of the phragmocone. The tubercles are small and conical. The number of ventrolateral tubercles on the phragmocone ranges from 4 to 8 in our measured sample, e.g., 4 in AMNH 108314 (fig. 24E–H) and 7 in AMNH 72634 (fig. 24M–P). Two ribs loop between ventrolateral tubercles on opposite sides of the venter with as many as three ribs intercalating between them.

Ventrolateral tubercles persist onto the body chamber and become more widely spaced toward the adoral end of the shaft. The distance between ventrolateral tubercles at midshaft is 8.2 mm in AMNH 108314 (fig. 24E–H) and 7.2 mm in AMNH 72634 (fig. 24M–P). The number of ventrolateral tubercles on the body chamber ranges from 7 to 10 in our measured sample. The total number of ventrolateral tubercles on the adult shell ranges from 12 to 19, e.g., a total of 12 tubercles in AMNH 108314 (fig. 24E–H) and 15 tubercles in AMNH 72634 (fig. 24M–P). They are clavate on the midshaft, with steeply sloping adapical sides and more gently sloping adoral sides. In larger specimens, as many as four ribs loop between ventrolateral tubercles on opposites sides of the venter, with up to five ribs intercalating between them. In smaller specimens, as many as three ribs loop between tubercles on opposite sides of the venter, with up to five ribs intercalating between them. Tubercles disappear on the adoral end of the shaft.

Two specimens (AMNH 72589 and 74354) in our measured set exhibit a single row of lateral tubercles on the adapical end of the phragmocone (not figured). The tubercles are closely and evenly spaced and nearly the same size as the ventrolateral tubercles. However, the ventrolateral tubercles persist onto the body chamber whereas the lateral tubercles disappear on the adoral end of the phragmocone.

Occurrence: This species occurs in the upper part of the Baculites baculus Zone and lower part of the B. grandis Zone in the Pierre Shale in Montana, Colorado, and Wyoming. Nearly all the specimens that were collected with precise biostratigraphic information (down to zone) are from the lower part the B. grandis Zone.

Discussion: Among older species from the Western Interior of North America, small specimens of Hoploscaphites macer most closely resemble small specimens of H. brevis from the Baculites compressus–B. cuneatus zones. However, H. macer differs from H. brevis in its more tightly coiled shell, with more inflated flanks, its less flexuous ribs, and its smaller, more numerous, and more closely spaced ventrolateral tubercles. Among younger species from the Western Interior, H. macer most closely resembles H. criptonodosus and H. sargklofak. It differs from H. criptonodosus in its finer ribbing and, in general, the absence of lateral tubercles on the exposed phragmocone. However, as noted above, in some specimens of H. macer such as USNM 713623 from the B. grandis Zone, a few lateral tubercles appear on the adapical end of the exposed phragmocone. It differs from H. sargklofak in its more inflated shell, with more broadly rounded flanks, and its fewer and more widely spaced ventrolateral tubercles. However, in some specimens of H. macer, such as BHI 4346 (fig. 14) from the B. grandis Zone, the spacing of the ventrolateral tubercles begins to approach that of H. sargklofak.

Outside the Western Interior, Hoploscaphites macer most closely resembles H. youngi Larson, 2016, from the upper Campanian Coon Creek Member of the Ripley Formation, McNairy County, Tennessee (Larson, 2016: fig. 11F–I), and the Nacatoch Sand, Red River County, Texas (Stephenson, 1941: pl. 90, figs. 7, 8). However, it differs from this species in its more inflated whorl section with more broadly rounded flanks. Outside North America, H. macer most closely resembles H. constrictus from northern Europe (see Kennedy, 1986: pl. 13, figs. 1–3, 16–24; pl. 14, figs. 1–38; pl. 15, figs. 1–31; text-figs. 9, 11; Machalski, 2005: figs. 5–7, 10, 12), which ranges from the base of the Maastrichtian to the Cretaceous-Paleogene boundary and possibly into the lower Paleocene (Machalski and Heinberg, 2005). However, H. macer differs from H. constrictus in having more numerous ventrolateral tubercles on the exposed phragmocone. In addition, the distance between ventrolateral tubercles on opposite sides of the venter at midshaft is greater in H. macer than in H. constrictus.

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/H_Saverages 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/H_S= 2.27) and AMNH 108445 (fig. 30) is an example of a specimen with a more rounded outline (LMAX/H_S= 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/H_P2averages 2.83 and ranges from 2.59 to 3.04 (2.79 in the holotype). AMNH 95771 (fig. 32A–C) is an example of a tightly coiled specimen (LMAX/H_P2= 2.76) and USNM 463215 (fig. 33) is an example of a more loosely coiled specimen (LMAX/H_P2= 2.91). The exposed phragmocone occupies approximately one-half whorl and generally terminates just below the line of maximum length. The body chamber consists of a short shaft and recurved hook totaling slightly more than onehalf whorl. The apertural lip is flexuous with a dorsal projection (fig. 8C, D). The apertural angle averages 58.8° and ranges from 26.0 to 78.0° (47.5° in the holotype). AMNH 108456 (fig. 31) exhibits a very low apertural angle (26.0°) and is associated with a very large umbilicus (7.6 mm diameter).

The whorl section of the phragmocone near the point of exposure is depressed subquadrate with maximum whorl width at one-third whorl height. W_P1/H_P1averages 1.08 and ranges from 0.91 to 1.23 (1.06 in the holotype). The umbilical wall is steep and subvertical and the umbilical shoulder is sharply rounded. The flanks are broadly rounded and converge toward the ventrolateral shoulder starting at two-thirds whorl height. The ventrolateral shoulder is sharply rounded and the venter is broadly rounded. The whorl section of the phragmocone at the line of maximum length is slightly more compressed than that at the point of exposure, reflecting a steep increase in whorl height. W_P2/H_P2averages 0.96 and ranges from 0.84 to 1.11 (0.94 in the holotype). The flanks are very broadly rounded and the venter is nearly flat.

The whorl width increases as the shell passes from the phragmocone into the body chamber and reaches its maximum value on the adoral part of the shaft but does not produce a conspicuous bulge in this area. Whorl height increases much more markedly during this transition and reaches its maximum value at midshaft. Thereafter, it diminishes to the point of recurvature and remains nearly the same up to the aperture. These changes in whorl width and height result in a slightly more compressed whorl section at midshaft than at the adoral end of the phragmocone. W_S/H_Saverages 0.90 and ranges from 0.74 to 1.07 (0.88 in the holotype). The whorl section is subquadrate with maximum whorl width at one-quarter whorl height. The umbilical wall is steep and subvertical and the umbilical shoulder is sharply rounded. The whorls are very high and broadly rounded, and gently converge toward the venter. The ventrolateral shoulder is sharply rounded and the venter is broadly rounded. V_S/ H_Saverages 0.43 and ranges from 0.31 to 0.73 (0.44 in the holotype). In USNM 463215 (fig. 33), the value of V_S/H_Sis very high (0.73) because the ventrolateral tubercles occur slightly below the ventrolateral shoulder, so that the distance between ventrolateral tubercles on opposite sides of the venter is unusually high.

The whorl section at the point of recurvature is less compressed than that at midshaft, mainly due to a decrease in whorl height. W_H/ H_Haverages 1.14 and ranges from 0.93 to 1.33 (1.16 in the holotype). The whorl section at the point of recurvature is subovoid with maximum whorl width at one-third whorl height. The umbilical wall is slightly concave and the umbilical shoulder is sharply rounded. The flanks are broadly rounded and gently converge toward the venter.

At the adapical end of the exposed phragmocone, ribs emerge at the umbilical seam. They are strong and widely spaced on the flanks and bend slightly forward at two-thirds whorl height. They attain their maximum strength at one-third whorl height and develop into small umbilicolateral tubercles at this point. Ribs are equally spaced on the venter, which they cross with a slight adoral projection. In the holotype, the rib density on the adapical end of the phragmocone is 4.5 ribs/cm. The rib density is nearly the same on the adoral end of the phragmocone (e.g., 5 ribs/cm in the holotype).

On the body chamber, ribs arise at the umbilical seam and are rursiradiate on the umbilical wall and shoulder. They are long, broad, straight, and rectiradiate at midshaft, becoming more prorsiradiate toward the adoral end of the shaft. Umbilicolateral tubercles are usually present on the body chamber, but given the large size and robust cross section of the shell, they are surprisingly small. In the holotype, the distance between consecutive umbilicolateral tubercles at midshaft is 4.9 mm. Branching and intercalation occur at two-thirds whorl height, with the result that the outer flanks are more densely covered with ribs than the inner flanks. Ribs are usually not preserved on the venter of the shaft, but in AMNH 108313 (fig. 28) in which they are preserved, the rib density is 6 ribs/cm. Ribs are narrow and closely spaced on the venter of the hook, which they cross with a strong adoral projection. In AMNH 108313, the rib density on the hook is 9 ribs/cm (fig. 28).

Ventrolateral tubercles appear early in ontogeny at a diameter of approximately 6 mm and continue onto the exposed phragmocone (fig. 36). They are closely and evenly spaced, occurring on every rib or every other rib. In the holotype, the distance between consecutive tubercles is 4.3 mm on the adapical end and 6.3 mm on the adoral end of the exposed phragmocone, yielding a total of 17 tubercles. The tubercles are conical in shape and change from slightly radially elongate at the point of exposure to slightly clavate on the adoral end of the phragmocone.

Ventrolateral tubercles are closely and evenly spaced on the midshaft, becoming slightly more widely spaced on the adoral end of the shaft, and slightly more closely spaced again near the aperture. In the holotype, the distance between consecutive ventrolateral tubercles is 9.6 mm on the midshaft, 12.7 mm on the adoral end of the shaft, and 7.4 mm on the hook, yielding a total of 15 tubercles on the body chamber (32 tubercles on the whole exposed shell). In AMNH 108313 (fig. 28) in which the ribs are well preserved on the venter at midshaft, two or three ribs loop between ventrolateral tubercles on opposite sides of the venter with one or two ribs intercalating between them. The tubercles are slightly clavate on the adoral end of the shaft where they attain their maximum height.

A single row of outer lateral tubercles appears early in ontogeny at approximately 10 mm diameter (fig. 36). It is joined by another row of inner lateral tubercles, both of which continue onto the exposed phragmocone for an additional oneeighth to one-half whorl. The tubercles are closely spaced and occur on every rib or every other rib. The tubercles in the outermost row are only slightly smaller than those in the ventrolateral row.

The suture is deeply incised, with a broad, asymmetrically bifid first lateral saddle (E/L) and a narrow, symmetrically to asymmetrically bifid first lateral lobe (L) (fig. 23D, E).

Microconch Description: Microconchs are smaller than macroconchs. LMAX averages 51.0 mm and ranges from 43.2 to 68.2 mm (table 4). The size distribution is unimodal with a broad peak at 45–55 mm (fig. 26). The ratio of the average size of microconchs to that of macroconchs is 0.64. This is lower than that in most species of Hoploscaphites and may reflect the fact that the sample of microconchs is biased because of its small size.

Microconchs are oval in lateral view with a large gap between the phragmocone and hook. LMAX/H_P2averages 3.10 and ranges from 2.81 to 3.39. The average value of LMAX/H_P2in microconchs is significantly higher than that in macroconchs (2.83). The phragmocone occupies slightly more than one-half whorl and terminates just below the line of maximum length. The umbilical diameter is relatively larger in microconchs than in macroconchs. UD/LMAX averages 0.10 in microconchs whereas it averages 0.06 in macroconchs. In addition, the umbilical seam in microconchs is concave in side view. The body chamber occupies slightly more than onehalf whorl and terminates in a constriction and accompanying varix.

The whorl section at the adapical end of the phragmocone is robust and subquadrate with maximum whorl width at one-quarter whorl height. W_P1/H_P1averages 0.96 and ranges from 0.82 to 1.09. The umbilical wall is nearly vertical and the umbilical shoulder is sharply rounded. The flanks are broadly rounded and gently converge toward the ventrolateral shoulder. In costal cross section, the flanks flatten out between the inner lateral and ventrolateral tubercles. The venter is broadly rounded. The whorl section at the adoral end of the phragmocone is more quadrate than that at the adapical end of the phragmocone, with flatter flanks and more sharply rounded ventrolateral shoulder. However, the average value of W_P2/H_P2(0.95) is nearly the same as that of W_P1/H_P1(0.96).

In passing from the phragmocone to the body chamber, both whorl width and height gradually increase, but the increase in whorl height is much less dramatic than in macroconchs. Whorl height attains its maximum value at midshaft and remains nearly the same thereafter, but whorl width attains its maximum value on the hook and decreases slightly thereafter. The whorl section at midshaft is compressed subquadrate, with maximum width at one-quarter whorl height. W_S/H_Saverages 0.92 and ranges from 0.77 to 1.01. The umbilical wall is broad and slopes gently outward culminating in the umbilicolateral tubercles. The flanks are nearly flat and converge toward the ventrolateral shoulder. The ventrolateral shoulder is abruptly rounded and the venter is nearly flat. The whorl section at the point of recurvature is compressed subovate. W_H/H_Haverages 1.01 and ranges from 0.85 to 1.10. The flanks are broadly rounded with maximum width at one-quarter whorl height. The venter is broadly rounded, which is accentuated in specimens without ventrolateral tubercles.

On the adapical end of the phragmocone, ribs emerge at the umbilical seam and strengthen on the flanks. They are strong and widely spaced. In more finely ribbed specimens such as AMNH 74357 (fig. 38B–D), they bend slightly backward on the inner flanks, slightly forward on the midflanks, and slightly backward again on the outer flanks. However, in more coarsely ornamented specimens such as USNM 713635 (fig. 38E–H), the ribs are nearly straight and bend only slightly backward on the outer flanks. Ribs are uniformly strong on the venter, which they cross with a slight adoral projection. They are relatively closely spaced with an average of 7 ribs/cm. They are equally coarse on the adoral end of the phragmocone, with branching and interca lation occurring at one-third and two-thirds whorl height.

Ribs are strong and prorsiradiate on the shaft and cross the flanks with a broad adoral convexity. Branching and intercalation occur at onethird whorl height (at and between the umbilicolateral tubercles) and, again, at twothirds whorl height. Ribs are generally not preserved on the venter. However, in USNM 713635 (fig. 38E–H) in which they are preserved, they are closely spaced (9 ribs/cm), with a strong adoral projection. Ribs are prorsiradiate on the hook, with branching and intercalation occurring at one-quarter whorl height (at and between the umbilicolateral tubercles) and at one-half whorl height. The outer flanks and venter are covered with fine, closely spaced ribs. The rib density ranges from 8 to 10 ribs/cm in our measured sample.

Umbilicolateral tubercles appear on the adoral end of the phragmocone and continue uninterruptedly to the aperture. They become slightly more widely spaced adorally, attaining their maximum spacing on the adoral end of the shaft, e.g., 6 mm in USNM 713635 (fig. 38E–H), 7 mm in AMNH 74357 (fig. 38B–D), and 8 mm in USNM 713626 (fig. 38I–K). The tubercles are radially elongate on the adoral end of the phragmocone, conical on the midshaft, and clavate on the adoral end of the shaft and hook.

Ventrolateral tubercles are present at the point of exposure. They are initially closely and evenly spaced, becoming slightly more widely spaced on the adoral end of the phragmocone. For example, in USNM 713635 (fig. 38E–H), the distance between consecutive tubercles is 2.5 mm and 4.5 mm on the adapical and adoral ends of the phragmocone, respectively. In contrast, in AMNH 74346 (fig. 37E–H), the tubercles are uniformly spaced at distances of 3–4 mm, except for two gaps of 5–6 mm each on the adapical end of the phragmocone. One or two ribs loop between tubercles on opposite sides of the venter, with up to three ribs intercalating between them. The number of ventrolateral tubercles on the phragmocone ranges from 9 to 13 in our measured sample.

Ventrolateral tubercles continue onto the body chamber and gradually become more widely spaced until the adoral end of the shaft, after which they disappear. The distance between consecutive tubercles on the adoral end of the shaft is 7.5 mm in smaller specimens such as AMNH 74357 (fig. 38B–D) and 11.5 mm in larger specimens such as USNM 713626 (fig. 38I–K). The number of ventrolateral tubercles on the body chamber ranges from 6 to 10 in our measured sample, so that the total number of ventrolateral tubercles on the adult shell ranges from 17 to 24. In specimens in which the ribs are well preserved on the venter of the shaft such as USNM 713635 (fig. 38E–H), as many as four ribs loop between ventrolateral tubercles on opposite sides of the venter, with two or three nontuberculate ribs intercalating between them. The tubercles become progressively larger and more clavate toward the adoral end of the shaft. They are asymmetric in profile. with steeply sloping adapical faces and more gently sloping adoral faces.

One or two lateral rows of tubercles are usually present at the point of exposure. As a result, most of the surface of the shell in this area is covered with tubercles (umbilicolateral, lateral, and ventrolateral tubercles). The lateral tubercles persist to the middle of the phragmocone, but if two rows are present, the inner lateral row usually dies out first. The lateral and ventrolateral tubercles occur on the same rib, with the height of the rib dipping between tubercles. The lateral tubercles are more or less evenly spaced; for example, in USNM 713635 (fig. 38E–H), the distance between consecutive outer lateral tubercles is 5 mm.

Occurrence: This species occurs in the upper part of the Baculites baculus Zone and B. grandis Zone in the Pierre Shale of Montana, Colorado, and Wyoming and in the Bearpaw Shale of Montana. It is also possible that it occurs in the Pierre Shale of South Dakota but our only specimen from this area (BHI 4345) is from a gravel pit, and its provenance is unknown (fig. 37M, N). Riccardi (1983) also recorded it from the B. baculus Zone in the Bearpaw Shale of Saskatchewan, Canada. On the U.S. Gulf Coastal Plain, it occurs in the Coon Creek Member of the Ripley Formation of Mississippi, in the Prairie Bluff Chalk of Alabama (Cobban and Kennedy, 1995), and possibly in the Nacatoch Sand of Arkansas. On the U.S. Atlantic Coastal Plain, it occurs in the Navesink Formation of New Jersey (Kennedy et al., 2000).

Discussion: Most of the microconchs in our measured sample are small. The largest microconch is USNM 713626 (fig. 38I–K), which presumably corresponds to one of the larger macroconchs in our sample, for example, AMNH 108445 (fig. 30). All the microconchs illustrated by Riccardi (1983: pl. 11, figs. 1–21) are equally small and, in this context, it is worth noting that the illustrations of some of his specimens are magnified and, in reality, the specimens are much smaller than they appear (Riccardi, 1983: pl. 11, figs. 7–11). The absence of larger microconchs in both collections may be a preservational bias. We also illustrate a pathologic specimen (AMNH 108325), which is very openly coiled even for a microconch (fig. 37O, P).

The specimens illustrated by Riccardi (1983) are from the Baculites baculus Zone, but most of the specimens that we describe are from the B. grandis Zone. We also illustrate two specimens of this species from the U.S. Gulf Coastal Plain. FM 10689 (fig. 35A–C) is a macroconch erroneously labelled as coming from the Pierre Shale, Arkadelphia, Clark County, Arkansas, but probably from the Nacatoch Sand. MMNS-IP 7881.3 (fig. 35D–F) and 8825.1 (fig. 38A) are a macroconch and microconch, respectively, from the Coon Creek Member of the Ripley Formation, Union County, Mississippi. Cobban and Kennedy (1995: fig. 22.5–12) illustrated fragments of similar material from the Prairie Bluff Chalk, Wilcox County, Alabama.

Among older species in the Western Interior, Hoploscaphites criptonodosus is most closely similar to large specimens of H. brevis from the Baculites compressus–B. cuneatus Zones. It differs, however, in its more closely coiled shell and, notably, multituberculate phragmocone, the character from which its name is derived (Riccardi, 1983). As noted above, H. criptonodosus is also similar to H. sargklofak (fig. 10), which occurs in the same biostratigraphic zone. Indeed, lateral tubercles appear on the adapical end of the exposed phragmocone in both species. However, H. criptonodosus is larger and more coarsely ornamented than H. sargklofak, although it is possible that the two forms represent the coarsely and finely ornamented end members of a single species.