Volviceramus koeneni ( Müller, 1888 )

Landman, Neil H., Plint, A. Guy & Walaszczyk, Ireneusz, 2017, Allostratigraphy And Biostratigraphy Of The Upper Cretaceous (Coniacian-Santonian) Western Canada Foreland Basin, Bulletin of the American Museum of Natural History 2017 (414), pp. 1-173 : 73-89

Volviceramus koeneni ( Müller, 1888)

Figure 11

1888. Inoceramus (Volviceramus) Koeneni n.sp., Müller: 412, pl. 17, fig. 1.

1891. Inoceramus paradoxus v. Haenlein. Langenhan and Grundey: 12, pl. 5, figs. 3–4.

1891. Inoceramus varius v. Haenlein. Langenhan and Grundey: 12, pl. 5, figs. 1;?pl. 5, fig. 2.

1913. Inoceramus (Volviceramus) (aff.?) involutus Sowerby. Scupin : 213, pl. 12, fig. 3.

1928. Inoceramus koeneni Müller. Heinz : 37, pl. 3, fig. 2.

1929. Inoceramus koeneni Müller. Heine : 98, pl. 15, fig. 63; pl. 17, fig. 66; pl. 18, fig. 67.

1932. Rhadinoceramus regalis , sp. nov., Heinz: 21.

non 1933. Cymatoceramus (Cymatoceramus) cf. koeneni Müller. Heinz : 253; pl. 19, fig. 3 [= Tethyoceramus basseae Sornay ]

1934. Inoceramus koeneni Müller. Andert : 132, text-figs. 16a–c; pl. 8, figs. 2–3.

?1959. Inoceramus involutus Sowerby. Dobrov and Pavlova : 153; pl. 10, fig. 1.

?1968. Inoceramus koeneni Müller. Kotsubinsky : 135; pl. 23, figs. 4, 5

1969. Inoceramus koeneni G. Müller. Tröger : 68, pl. 1, figs. 1–6; pl. 2, figs. 1–5.

1974. Inoceramus koeneni G. Müller. Tröger , pl. 5, figs. X4302, X4303, X4305, X4306.

1991. Inoceramus (Volviceramus) koeneni Müller. Tröger and Christensen : 31, pl. 3, fig. 7;?pl. 2, figs. 2–3.

1994. Volviceramus koeneni (G. Müller, 1888) . Tröger and Summesberger: 169, pl. 2, figs. 1–3.

non 1994. Inoceramus (Volviceramus) cf. koeneni Müller. Malchus et al. : 116, text-fig. 4a, pl. 1, fig. 7 [= Cordiceramus cordiforis ]

? non 1996. Inoceramus (Volviceramus) koeneni Müller, 1888 . Noda: 566, fig. 10.

? non 1998. Inoceramus (Volviceramus) koeneni Müller, 1887 . Noda and Matsumoto: 459, pl. 13, fig. 3. [reillustrated specimen of Noda, 1996: fig. 10]

2006. Volviceramus koeneni ( Müller, 1888) . Walaszczyk and Cobban: 282; text-fig. 24, 25.2–25.4, 29.2.

TYPE: The lectotype, by subsequent designation of Tröger (1969), is the original of Müller (1888: pl. 17, fig. 1) from the middle Coniacian of Lehofsberg, near Quedlinburg, Germany.

MATERIAL: Nine specimens in total. Single specimen, TMP 2016.041.0076, from Sullivan Creek . Eight specimens from Chungo Creek: LV almost smooth, and with strong, typically complete, double-valve TMP 2016.041.0184 ; ornamented RV.

TMP 2016.041.0182, TMP 2016.041.0183 (2 REMARKS: V. koeneni is morphologically the specimens), and TMP 2016.041.0187, and TMP closest to V. involutus . The differences are (see 2016.041.0189 (2 specimens). Single specimen Tröger, 1969) that V. involutus exhibits: stronger (cf.) from Sheep River, TMP 2016.041.0333. inequivalvness, lack of undulation on the LV, and MEASUREMENTS: See table 1. distinctly stronger inflation and coiling of LV. DESCRIPTION: TMP 2016.041.084 (fig. 11) is a Transitional forms between both species occur. well-preserved double-valved specimen, almost The stronger inflation of the RV in V. koeneni complete (a small fragment of the anterior part of than in V. involutus , mentioned by Müller (1888), the LV is missing), slightly deformed; with much is difficult to evaluate; one would need two-valve of its shell intact. LV is 107 mm high; RV is 90 mm specimens, which are extremely rare. Volvicerahigh. Both valves are slender (with b/h ration 0.56 mus koeneni is the oldest member of the Volvice- and 063 in the RV and LV respectively), however, ramus clade.

this is partly due to secondary deformation per- Cymatoceramus (Cymatoceramus) cf. koeneni pendicular to the commissure. The LV is more Müller from Madagascar, illustrated by Heinz (p. inflated than the RV; its h/b ratio being 0.54. The 253; pl. 19, fig. 3), is Tethyoceramus basseae (Sor- LV juvenile growth is slightly oblique, with δ angle nay) as shown by Sornay (1980). To Tethyoceramus c. 75°. At h = 60 mm, δ angle increases to 90°. Its also belongs, most probably, the specimen of Inocbeak is pointed and curved dorsally. The LV bears eramus (Volviceramus) koeneni as reported from weak, poorly developed commarginal rugae. In Japan by Noda (1996: fig. 10; see also Noda and the ventral part it is almost smooth. The RV is Matsumoto, 1998: pl. 13, fig. 3). The Japanese specimoderately inflated; its b/h ratio is 0.42. Its obliq- men shows a regular pattern of concentric rugae, uity is almost constant, with δ approximating 90°. typical for Tethyoceramus / Cremnoceramus .

The anterior wall is steep, high, and slightly con- OCCURRENCE: Volviceramus koeneni spans the cave. The posterior auricle is well separated from middle Coniacian. At the base of the middle the disc, with a distinct sulcus in the dorsal part. Coniacian it forms a distinct interval zone, being The beak is pointed, projecting above the hinge followed by V. involutus (see also Müller, 1900; line. The disc is ornamented with well-developed Stille, 1909; Heinz, 1928; Tröger, 1969). It is known commarignal rugae, superimposed by radial sulci from the Euramerican biogeographic region; neiin the axial part of the midadult stage (fig. 11D). ther the Madagascan report ( Heinz, 1933) nor the TMP 2016.041.082, TMP 2016.041.087, and Japanese one ( Noda, 1996) can be confirmed.

TMP 2016.041.0333 are juvenile fragments of the

LVs, undeformed; TMP 2016.041.0333 is with Volviceramus involutus Sowerby, 1828 fragments of shell intact. They are referred to the

Figure 12

Müller’s species based on their ornamented valve.

The double valve specimen TMP 1828. Inoceramus involutus J. de C. Sowerby: vol. 2016.041.0189 is complete, moderately large vi: 160, pl. 583, figs. 1–3

specimen (hmax of RV = 104 mm), strongly 1846. Inoceramus involutus Sowerby. d’Orbigny , deformed. It is moderately inequivalve, with the vol. iii: 520, pl. 413, figs. 1–3.

1846. Inoceramus lamarcki d’Orbigny , vol. iii: 518, pl. 412.

1850. Inoceramus involutus . Dixon: pl. 28, fig. 32.[= Volviceramus anglo-germanicus of Heinz, 1932; = Inoceramus involutus belovodiensis of Glasunova, 1972]

1858. Inoceramus umbonatus Meek and Hayden : 50.

1871. Inoceramus (Volviceramus) involutus Sowerby. Stoliczka : 394, 401

1876. Inoceramus umbonatus Meek and Hayden. Meek : 44, pl. 3, fig. 1; pl. 4, fig. 1–2.

1888. Inoceramus (Volvicerasmus) involutus Sowerby. Müller : pl. 16, figs. 3, 4,

1901. Inoceramus involutus Sowerby. Sturm : pl. 9, fig. 4.

1902. Inoceramus involutus Sowerby. Wollemann : pl. 1, fig. 4; pl. 2, figs. 7, 8

1907. Inoceramus umbonatus Meek and Hayden. Veatch : pl. 10, fig. 2.

1912. Inoceramus involutus Sowerby. Woods : 327, text-figs. 88–94.

1932. Volviceramus anglo-germanicus Heinz : 22. [= Inoceramus involutus Sowerby ; Dixon, 1850, pl. 28, fig. 32]

?1959. Inoceramus involutus Sowerby. Dobrov and Pavlova : 153, pl. 10, fig. 1a, b.

1972. Inoceramus involutus Sowerby subsp. belovodiensis Glazunova , subsp. nov., Glazunova: 63; pl. 8, fig. 1; pl. 12, figs. 1, 2; pl. 13, fig. 5.

1974. Inoceramus involutus Sowerby. Kotsubinsky : 81, pl. 18.

2006. Volviceramus involutus (J. de C. Sowerby, 1829). Walaszczyk and Cobban, text-figs. 9.3, 25.1, 26.1–26.3, 27.3–27.4, 28.3, 30.2.

TYPE: By subsequent designation of Woods (1912: 334) the lectotype is BM 43268, being the original of J. de C. Sowerby (1929: pl. 583, fig. 1) from the Upper Chalk , England ; the locality is unknown.

DIAGNOSIS: Moderately large for genus, strongly inequivalve; LV coiled, growing moderately obliquely, almost smooth; RV weakly to moderately inflated, ornamented with well-developed rugae.

MATERIAL: Twelve specimens in total. Three specimens from Sheep River: TMP 2016.041.0321, TMP 2016.041.0329 and TMP 2016.041.0335, from 143 m. Two specimens from West Thistle Creek: TMP 2016.041.0243 from 72.5 m, and TMP 2016.041.0240 from 100.3 m. Single specimen from Bighorn River, TMP 2016.041.0362 from 51.8 m. Single specimen from Chungo Creek, TMP 2016.041.0188 from 75.7 m. Single specimen from James River, TMP 2016.041.0160 from 80.0 m. Single, unnumbered specimen from Cutpick Creek. Three specimens from Bighorn Dam: TMP 2016.041.0418 from 65.5 m, TMP 2016.041.0423 from 67.5 m, and TMP 2016.041.0431 from 67.5 m.

MEASUREMENTS: See table 1.

DESCRIPTION: The species is small to medium men was chosen as the type of the new subspesize for the genus; inequilateral, strongly inequi- cies Inoceramus involutus belovodiensis by valve. LV is strongly coiled, up to 1.5 whorls, Glazunova (1972: 63), with the same diagnosis tightly coiled, in the studied specimens (TMP and the same aim to separate the slender mor- 2016.041.0243; fig. 12). The LVs grow uniformly photype of Volviceramus involutus . Based on our at δ = 60°, with strong inflation. The anterior mar- material it is clear, however, that both morphotgin gives a more or less consequent plane, and ypes are extreme variants of the same type and forms a well-developed planispiral coiling. The are, consequently, regarded as infraspecific variwhorl in cross section is rounded in the lateral, ants (see also Walaszczyk and Cobban, 2006). anterior, and posterior parts; the “aperture” is oval. The American species Volviceramus umbo- The LV is almost smooth. Only in the juvenile natus (Meek and Hayden, 1858) is a typical reppart may irregular, low, rounded rugae occur. resentative of V. involutus , and consequently is a Irregular rugae also occur in some specimens in synonym of Sowerby’s species. Volviceramus exothe adult stage, usually at the anterior margin. The gyroides and I. undabundus , which have previ- RV, when isolated, does not have any characteris- ously been considered as synonyms of V. tic feature that allows it to be identified as belong- involutus , are well defined, separate species (see ing to a particular species of Volviceramus . discussion herein).

REMARKS: Volviceramus involutus is the only OCCURRENCE: Volviceramus involutus first Volviceramus species with almost perfect coiling appears in the middle part of the middle Coniaof the LV, as seen on the anterior wall of the valve, cian and ranges into the upper Coniacian. It is resembling Nautilus or some involute ammonites. well represented in the entire Western Interior The posterior, or lateral (which would be ventral Basin. The species is widely known from Europe in ammonoids), margin is certainly quite differ- and western Central Asia. It does not range ent. The species-level identification of the RV is at south into the Mediterranean Province, although the moment impossible. Based on species, of it was reported from Gosau in Austria (Tröger which double-valved specimens are available, the and Summesberger, 1994). The reports from variability of RVs is high, and more double-valved Madagascar ( Heinz, 1933) and from the western specimens of every species would be necessary to North Pacific Province ( Pergament, 1971) have make a reliable assessment. not been confirmed.

The infraspecific variability concerns mainly the l/h ratio, which results in more slender or Volviceramus exogyroides (Meek and Hayden, more robust forms. The type species (Sowerby, 1862) 1828: pl. 583, figs. 1–3; see also Woods, 1912:

Figures 13–15 text-fig. 88) is one of the robust forms, with high l/h ratio, well above 0.8. The slender form is best 1862. Inoceramus exogyroides Meek and Hayden : represented by Dixon’s specimen (1850: pl. 28, 26. fig. 32; see also Woods, 1912, text-fig. 89), with 1876. Inoceramus exogyroides Meek and Hayden. l/h ration about 0.75. The slender form, with Meek: 46, pl. 5, fig. 3. Dixon’s specimen as its type, was referred by 1893. Inoceramus exogyroides Meek and Hayden. Heinz (1932: 22) to a new species, Volviceramus Stanton : 83, pl. 17, figs. 1–2 [reillustration anglogermanicus. Subsequently, the same speci- of Meek, 1876: pl. 5, fig. 3, specimen] FIG. 14 . Volviceramus exogyroides (Meek and Hayden, 1862) , A, B, F, G, TMP 2016.041.0417, LV, Wapiabi Formation, Bighorn Dam, 65.5 m, A, dorsal view, B, lateral view, F, anterior view; G, apertural view. C–E, TMP 2016.041.0363, LV, Bighorn River, 51.8 m, C, anterior view, D, apertural view, E, dorsal view. All photographs are ×1.

1898. Inoceramus exogyroides Meek and Hayden. Logan : 454, pl. 88, figs. 1–2 [reillustration of Meek, 1876: pl. 5, fig. 3, specimen].

1907. Inoceramus exogyroides Meek and Hayden. Veatch : pl. 11, fig. 1.

pars 1929. Inoceramus undabundus Meek and Hayden. Heine : 100, pl. 11, fig. 51; pl. 19, fig. 71 [non pl. 11, fig. 50; pl. 13, fig. 57, which are Inoceramus undabundus Meek and Hayden ].

1972. Inoceramus obliquus , sp. nov., Glazunova: 63, pl. 8, figs. 2, 3.

2006. Volviceramus exogyroides (Meek and Hayden, 1862) . Walaszczyk and Cobban: 291; text-figs. 27.1, 28.1, 29.1, 30.1.

TYPE: The holotype, by monotypy, is the original of Meek (1876: pl. 5, fig. 3) from the Marias River Shale (Fort Benton Group), 20 miles below “Fort Benton,” on the upper Missouri River, in north-central Montana.

MATERIAL: Nineteen specimens. Ten specimens from Bighorn Dam: TMP 2016.041.0404 and TMP 2016.041.0405 from 47.5 m ; TMP 2016.041.0414, TMP 2016.041.0415 and TMP 2016.041.0416, from an interval 50–60 m; TMP 2016.041.0417 from 65.6 m; TMP 2016.041.0433 from 67.5 m; TMP 2016.041.0420 from 72.0 m; TMP 2016.041.0441 from 75.4 m; and TMP 2016.041.0438 from 81.0 m. Single specimen from Sheep River , TMP 2016.041.0332 from 110.5 m. Single specimen from West Thistle Creek, TMP 2016.041.0234 from 53.2 m. Four specimens from Chungo Creek: TMP 2016.041.0193, and TMP 2016.041.0194, from 65.8 m ; TMP 2016.041.0200 from 65.9 m; and one unnumbered specimen from 65.8 m. Three specimens from Bighorn River : TMP 2016.041.0363, TMP 2016.041.0364, from 51.8 m, and TMP 2016.041.0357, from 93.6 m .

MEASUREMENTS: See table 1.

DESCRIPTION: The following description refers only to the LV; RVs are not represented in the studied material.

The shell is of small to moderate size, inequilateral. Its outline changes during ontogeny following the change of growth direction; its juvenile outline is triangular, strongly oblique, elongated parallel to the ligament; its adult outline is trapezoidal, due to the change of growth, to distinctly less oblique. The specimens vary between well-geniculated ones (see fig. 13) to forms with a gradual change from the juvenile to adult stage (fig. 14A, B, F, G). The beak is pointed, anteriorly terminal. The umbo is variably coiled, prosogyrate. The change from the oblique juvenile stage to less oblique adult stage is sometimes quite abrupt, geniculated. The juvenile stage is oblique, with δ angle ranging between 30° and 40°; the adult stage growth at δ between 50° and 60°. The outline of the juvenile stage varies with variable inflation; the more inflated specimens have more coiled umbos and are more slender. Depending on the length of the juvenile stage, the adult stage is more or less subquadrate.

The valve is ornamented with regular to subregular commarginal rugae, with regular, ventralward increase of interspaces. The rugae are round topped, symmetrical to slightly asymmetrical. The ornament becomes less distinct in the adult stage, or it disappears completely.

DISCUSSION: Both the original material of Meek and Hayden (1862; also Meek, 1876) and the material recently described from the U.S. Western Interior by Walaszczyk and Cobban (2006) are represented exclusively by LVs. The only reports of the RV come from Europe. These are by Heine (1929) from northern Germany, who referred these forms to Inoceramus undabundus Meek and Hayden ; and by Glazunova (1972), who described this species under the new name Inoceramus obliquus (actually, the name is the homonym of v. Haenlein’s species). Describing the RV Glazunova (1972) states that the RV is distinctly smaller than the LV and its outline is L-elongated. The beak is pointed, not projecting above the ligament, the umbo is weakly inflated. The valve is more evenly inflated than the LV. The ligamental plate is concave, covered with shallow resilifers intercalated with relatively narrower interresilifers.

Volviceramus exogyroides resembles closely 50–60 m of the succession, TMP 2016.041.0413 Volviceramus cardinalensis , sp. nov. Both have a from 43.0 m, TMP 2016.041.0406 from 47.5 m, and distinctly oblique juvenile stage and change to TMP 2016.041.0421 from 105.0 m. 10 specimens lower obliquity in the adult stage. The juvenile from Sheep River, from 144 m: TMP 2016.041.0310, stage of V. cardinalensis , sp. nov., is, however, TMP 2016.041.0314, TMP 2016.041.0315, TMP almost subrectangular, poorly inflated, and 2016.041.0316, TMP 2016.041.0317 (holotype), almost smooth. TMP 2016.041.0318, TMP 2016.041.0319, TMP The species has often been placed in synon- 2016.041.0320, TMP 2016.041.0322, and TMP ymy with Volviceramus involutus (or its Ameri- 2016.041.0323. Single, double-valved unnumbered can synonym, V. umbonatus ). Both species differ, specimen from Cardinal River, 96.8 m. however, in their ontogenetic development and DIAGNOSIS. Noncoiled Volviceramus with LV consequent morphological characteristics. strongly oblique and weakly inflated in juvenile The juvenile parts of LVs may easily be taken stage, growing almost orthoclinally, with strong for a Cremnoceramus . The difference is clearly inflation in adult stage. RV strongly inflated for seen when the ligament plate is preserved, or genus, with regular, widely spaced rugae, and when the specimen is preserved as with both shallow radial sulcus on its disc. valves. This may be the reason for reports of DESCRIPTION. The species is strongly inequi- Cremnoceramus from the interval characterized valve, noncoiled Volviceramus , attaining large otherwise by Volviceramus (see, e.g., Kauffman et size, with strongly inflated LV up to 30 cm in al., 1993; Collom, 2001). maximum h length. The LV shows characteristic OCCURRENCE: Volviceramus exogyroides is change in growth direction, leading to the develknown widely in the North American Western opment of the juvenile and adult stages, some- Interior. It is also known from Europe, where it times, with well-developed geniculation. The was described as Inoceramus obliquus by Glazu- juvenile valve, up to 100 mm of axial length, nova (1972). The species was reported (although growths obliquely, with δ angle ca. 45°, then, in without illustration) from the southern and east- the adult stage, it changes its growth to markedly ern margins of the East European craton (e.g., less oblique. The juvenile stage is subrectangular Aliev and Kharitonov, 1981; Aliev and Pavlova, in outline, and moderately to weakly inflated. 1983), but it was never illustrated. The strong inflation characterizes the adult stage.

The adult stage varies in the L/H ratio, ranging

Volviceramus cardinalensis , sp. nov. from L-elongated, subrectangular specimens to subquadrate ones. The RV is relatively large, with

Figures 16 , 17

strongly inflated disc, distinctly oblique. The disc TYPE SPECIMENS: The holotype is TMP is separated from the posterior auricle, along a 2016.041.0317, upper middle Coniacian of the well-developed auricular sulcus. Sheep River section; paratypes: 14 specimens The juvenile stage of the LV is almost smooth; from various localities (see Material). the adult stage is covered with subregular, widely ETYMOLOGY: After Cardinal River, western spaced, low rugae. The RV is regularly, strongly Alberta, where one of the paratypes was rugate on the disc; the rugae do not continue collected. over the posterior auricle. The rugae are dis- MATERIAL: Fifteen specimens in total. Four tinctly narrower than interrugae spaces. specimens from Bighorn Dam: TMP 2016.041.0399, The holotype, TMP 2016.041.0317 (figs. 16, loose, but located approximately in the interval 17), is a huge (estimated maximum h is 180 mm), double-valved specimen, apparently nal to Volviceramus involutus (Soweby) in Colundeformed, with parts of shell in the liga- lom 2001: pl. 15, fig. 1; TMP 96.53.1, LV, original ment area preserved. The L of the juvenile to Volviceramus involutus (Soweby) in Collom stage (fig. 17B) of the LV is ca. 110 mm, and 2001, pl. 15, fig. 2; and TMP 87.56.13, doubleits H is ca. 60 mm. This part is weakly inflated, valved specimen, original to Volviceramus aff. with juvenile b = 18 mm, smooth, growing koeneni (Müller) in Collom 2001: pl. 15, fig. 3.

moderately obliquely, at δ = 45°. The beak is TYPE LOCALITY: Bad Heart Formation, Kakut strongly prosogyrous, curved anteriorly. The α Creek (for details of location, see Collom, 2001). angle is 105°. Although there is no distinct MATERIAL: Our material consists of two specgeniculation, at h = 120 mm the valve starts imens, both LVs: TMP 2016.041.0439 from Biggrowing perpendicularly to the juvenile stage. horn Dam, 91.5 m; TMP 2016.041.0245 from The adult stage is subrectangular, longer than West Thistle Creek, 107.5 m. Two other specihigh (H is only 110 mm at L = 170 mm). mens, TMP 2016.041.0313 and TMP REMARKS. Volviceramus cardinalensis , sp. 2016.041.0326, from Sheep River, are referred to nov., resembles V. exogyroides . It differs from the herein as cf. stotti .

latter in its subrectangular juvenile outline, DIAGNOSIS: Moderately inflated and moderinstead of suboval, and lower inflation. More- ately inequivalve Volviceramus , of moderate size, over, the juvenile of V. exogyroides is usually rounded, prosocline, with ornament, composed regularly rugate, changing to almost smooth in of raised growth lines, with superimposed, low, adult stage. In contrary, V. cardinalensis is almost widely spaced, subregular concentric rugae.

smooth in the juvenile stage, and changes its ETYMOLOGY: After Donald F. Stott, the preemiornament to distinctly rugate in the adult. nent Canadian geologist and researcher of the OCCURRENCE: The species seems to appear Cretaceous of the Canadian Western Interior.

very low in the middle Coniacian and ranges to MEASUREMENTS: See table 1.

the lower upper Coniacian. DESCRIPTION: This is a moderately inequivalve Volviceramus species, with both valves Volviceramus stotti , sp. nov. regularly inflated, strongly prosocline, straight. LV is larger and more inflated, growing domi- Figure 18 nantly posteroventrally. The beak is pointed, pars 2001. Volviceramus involutus (Sowerby, curved anterodorsally; it projects above the hinge 1828). Collom: 475, pl. 15, figs. 1, 2, 4, 5. line. The valve outline is parabolical. The anterior [only] margin is relatively short (AM/h between 0.40 2001. Volviceramus aff. koeneni [in text: Volvice- and 0.45). The anterior wall is steep to overhangramus koeneni ] ( Müller, 1888). Collom: ing, rounded. The anteroventral margin is 474, pl. 15, fig. 3. rounded, broadly convex; ventral margin is rounded. The posterior auricle is small, well sep- TYPE SPECIMENS: Holotype is TMP 96.19.13, arated from the disc, particularly in the RV; less double valved, moderately large; well preserved so in the LV. The ligament is strong; the resilifers (original to Volviceramus involutus (Soweby) in as observed on one of the specimens illustrated Collom, 2001: pl. 15, figs. 4, 5); paratypes: TMP in Collom (2001: pl. 15, fig. 1) are narrow and 2016.041.0439, and TMP 2016.041.0245; both rectangular, with narrow interresilifer plates.

internal molds of LVs, with fragments of shell The ornament is composed of regular to subpreserved; moreover: GSC 117324, LV, an origi- regular, round-edge rugae, superimposed by FIG. 17. Volviceramus cardinalensis , sp. nov. TMP 2016.041.0317, Wapiabi Formation, Sheep River, 144 m, A, lateral view of the LV; B, lateral view of the juvenile part of the LV. Both photographs are ×0.7.

sharp-edged growth lines, well visible both on outer shell surface and on internal mold.

REMARKS: The weak to moderate inequivalveness (the feature inferred from the characteristics of the ligamental plate), moderate to strong inflation of the LV, and a peculiar ornament, make this species different from any other Volviceramus species known. In general architecture V. stotti , sp. nov., resembles V. koeneni , however, the latter is distinctly inequivalve, with RV having a very distinct ornament, composed of sharp-edged, strong concentric rugae, with variably developed radial ribs.

OCCURRENCE: The species appears relatively high in the succession, close to the appearance level of Sphenoceramus subcardissoides , which marks the base of the upper Coniacian, and ranges to the top of CA16, in the middle part of the substage.

Figures

FIG. 11. Volviceramus koeneni (Müller, 1888), TMP 2016.041.0184, double-valve specimen, Wapiabi Formation, Chungo Creek, 45.5 m, A, dorsal view, B, lateral view of the LV, C, anterior view, D, lateral view of the RV. All photographs are ×0.95.

FIG. 12. Volviceramus involutus (Sowerby, 1828), TMP 2016.041.0243, LV, Wapiabi Formation, West Thistle Creek, 72.5 m, A, lateral view of the adult stage, B, anterior view, C, oblique, posterodorsal view, D, dorsal view, the photographs are ×1.

FIG. 13. Volviceramus exogyroides (Meek and Hayden, 1862), TMP 2016.041.0415, LV, Wapiabi Formation, Bighorn Dam, interval 50–60 m, A, lateral view of the juvenile stage, B, lateral view of the adult stage, C, anterior view. All photographs are ×1.0.

FIG. 14. A portion of the Muskiki Member exposed in Sheep River (fig. 11), illustrating typical sandier-upward successions (arrows) bounded by flooding surfaces. The regionally mappable surface CS3 is indicated.

FIG. 15. A. Overview of surface CS1 exposed at river level at the mouth of Oldfort Creek (fig. 10). At right, a coarse-grained wave ripple composed of granules and small pebbles of chert and quartz rests sharply on regional erosion surface CS1. Traced laterally over only 3 m, the coarse lag pinches out and surface CS1 is manifest simply as a sharp mud-on-mud contact; scale bar = 20 cm. B. Detail of the coarse-grained wave ripple.

FIG. 16. Intraclastic pebble lag resting on surface SS0 at Thistle Creek west (fig. 5). A. General view of siderite pebbles seen from above; scale bar in each image = 20 cm. B. Detail of panel A showing pitted, bioeroded surface of a siderite pebble. C. Side view of conglomerate showing clasts filling a shallow erosional trough (arrows).

FIG. 18. A. Overview of the lower part of the Coniacian succession at Burnt Timber Creek (fig. 9) illustrating depositional cyclicity and bounding surfaces E7 and CS1 to CS5. Note the prominent sandier-upward succession culminating in surface CS4. B. Overview of part of the Sheep River canyon (fig. 11). The CS4 surface caps an upward-coarsening package that, in this view, is repeated by a thrust fault; Walaszczyk (circled) provides an indication of scale. C. Detailed view of the subtle, but sharp CS4 surface that is mantled with a few mm of chert and phosphate pebbles and granules and separates bioturbated siltstone and very fine-grained sandstone below from silty clay above.