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Species Sphenodiscus pleurisepta Conrad 1857

[1]
[2]
[1] 7a-c Ifrim et al. (2005) [2] 5e Ifrim et al. (2005)

Diagnosis / Definition:
Ifrim et al. (2005):
Description. The shell is oxycone and very involute (U/D is about 0.04) with an intermediate expansion rate. The whorl section is compressed, with WB/WH approximately 0.30. The overhanging umbilical walls bend narrowly into slightly concave inner flanks. Whorl breadth is greatest at mid-flank. The outer flanks converge towards the very narrowly rounded venter. The test is faintly ornamented with a row of bullae at mid-flank (4 to 5 per quarter whorl) and a row of weak crescent ventrolateral ribs (6 to 7 per quarter whorl). The two rows are linked by feeble ribs. The suture line is moderately incised. The E/L saddle is incised by two adventive lobes.
Cobban & Kennedy (1995):
DESCRIPTION.- This species is rare in the Prairie Bluff Chalk, occurring as phosphatic fragments of phragmocones that have whorl heights of up to 44 mm. Whorl section oxycone with whorl breadth to height ratio of up to 0.4. Small, slightly bullate midlateral tubercles present, and twice as many outer lateral bullae that merge into a concave crescentic rib on outermost flank. A very feeble, straight, prorsiradiate rib links tubercles. Suture with narrow-stemmed saddles and up to 10 auxiliary elements on umbilical lobe.
Landman et al. (2004):
DESCRIPTION.- AMNH 47118 is a phragmocone 69.8 mm in diameter with part of the innermost flanks missing and most of the venter worn off (fig. 22). The specimen is involute with a very small umbilicus. The umbilical wall is steep and convex and the umbilical shoulder is sharply rounded on the adapical end of the specimen. The inner flanks are concave and the middle and outer flanks are broadly rounded on the adapical end of the specimen. Rectiradiate, straight, broad ribs are visible on the adapical onehalf of the specimen. There is a row of five radially elongated nodes on the midflanks with a distance of approximately 12 mm between the two most adoral nodes. Two nodes are preserved on the outer flanks on the right side.
Discussion / Comments:
Ifrim et al. (2005):
Type: The holotype is USNM 9888, which is the specimen of Conrad (1857, p. 159, pl. 15, fig. 1) by original designation. This specimen is said to be from “Jacun, 3 miles below Laredo”, although it may have been found in the Escondido Formation of the Rio Grande region in Maverick County, Texas (see Stephenson, 1941, 1955). Material: Nine crushed fragments of phragmocones from the base of the middle member of the Cárdenas Formation in the Arroyo de la Atarjea and at the railway section near Cárdenas, one fragment from the Tanque Formation south of Reata, Coahuila, ten specimens from the upper Escondido Formation at Cuevas Creek near Eagle Pass, Texas. Occurrence: This Maastrichtian species is common to abundant in the Cárdenas and Escondido Formations in Trans-Pecos, Texas, and northeastern Mexico (Böse, 1928; Stephenson, 1941, 1955). It was also described from northeastern Texas (Kennedy and Cobban, 1993b), Mississippi and Alabama, Missouri (Stephenson, 1955), Tennessee (Kennedy and Cobban, 2000), and Maryland (Kennedy et al., 1997). In the Western Interior, this species was recorded from the Baculites clinolobatus to Jeletzkytes nebrascensis ammonite zones (e.g., Kennedy et al., 1996; Landman and Cobban, 2003). Discussion: Sphenodiscus pleurisepta differs from the almost smooth S. lobatus by its stronger ornamentation. It differs from Coahuilites sheltoni Böse by a narrower whorl section (smaller WB/WH ratio) and a much more acute venter at comparable diameters.
Cobban & Kennedy (1995):
MATERIAL.- One specimen, USNM 463 1 15, plus several small fragments. TYPE.- The holotype is USNM 9888, said to be from "Jacun, 3 miles below Laredo," but probably from the Escondido Formation of the Rio Grande Region, probably in Maverick County, Texas (Stephenson, 1941, 1955). DISCUSSION.- Presence of two rows of tubercles in early growth distinguishes S. pleurisepta from S. lobatus, as noted above; it differs from Coahuilites sheltoni Bose (1928), described below, in its compressed, oxycone whorl section, rather than parallel sided with broad, fastigiate venter. OCCURRENCE.- Maastrichtian Prairie Bluff Chalk at locality 16 near Starkville, Mississippi. The species also occurs in the Escondido Formation in Trans-Pecos Texas and northern Mexico, Corsicana Formation in northeast Texas; Owl Creek Formation in Missouri, Mississippi and Tennessee; and the Severn Formation in Maryland. In the Western Interior, it occurs in Hoploscaphites nicolletti and Jeletzkytes nebrascensis Zones, and Landman and Waage (1993) record S. ?lenticularis from the Hoploscaphites birkelundi Zone in the Fox Hills Sandstone in Wyoming and Colorado.
Landman et al. (2004):
TYPE.- The holotype is USNM 9888, said to be from ‘‘Jacun, 3 miles below Laredo’’, but probably from the Escondido Formation in the Rio Grande Region, Maverick County, Texas (Stephenson, 1941, 1955). MATERIAL.- AMNH 47118 from the New Egypt/Hornerstown formational contact, AMNH loc. 3345, Parkers Creek, near Eatontown, Monmouth County. DISCUSSION.- The presence of two rows of nodes on the flanks distinguishes Sphenodiscus pleurisepta from the widely occurring Sphenodiscus lobatus. Cobban and Kennedy (1995) discussed the synonymy of S. pleurisepta and its differences from congeneric species. Because this species has an unusually long range (the entire upper Maastrichtian), it is possible that more than one species is masquerading under this name. It is probably a good idea to closely compare samples of this species from opposite ends of its stratigraphic range. OCCURRENCE.- New Egypt/Hornerstown formational contact, Parkers Creek, near Eatontown, Monmouth County. Sphenodiscus pleurisepta has not previously been reported from New Jersey. It also occurs in the Crosswicks Creek Drainage in southwestern Monmouth County (Landman et al., in prep. b). Elsewhere on the Gulf and Atlantic Coastal Plains, this species is known from the Owl Creek Formation in Missouri, Mississippi, and Tennessee (Kennedy and Cobban, 2000), the Prairie Bluff Chalk in Mississippi (Cobban and Kennedy, 1995), the Corsicana Formation in northeast Texas (Kennedy and Cobban, 1993), and the Severn Formation, Prince Georges and Kent counties, Maryland (Kennedy et al., 1997; Landman et al., 2004). It is known from the Escondido Formation in Trans-Pecos Texas and northern Mexico (Stephenson, 1941, 1955). In the Western Interior, this species occurs in the Hoploscaphites birkelundae Zone of the Pierre Shale in Meade and Pennington counties, South Dakota (Kennedy et al., 1996; Larson et al., 1997), the Fox Hills Formation in Niobrara County, Wyoming (Kennedy et al., 1996), and the upper part of the Pierre Shale and Fox Hills Formation in Weld County, Colorado (Kennedy et al., 1996; Landman and Cobban, 2003).
Synonym list:
Ifrim et al. (2005):
1857 Ammonites pleurisepta Conrad. - Conrad : p.159 pl. 15, fig. 1
1861 Ammonites pedernalis Binkhorst. - Binkhorst : p.21 pl. 5a1, figs. 1a-b only
? 1898 Sphenodiscus pleurisepta Conrad. - Böhm : 193-197 pl. 7, figs. 1, 1a-b
1928 Sphenodiscus pleurisepta Conrad. - Böse : p.304 pl. 17, figs. 2-5
1941 Sphenodiscus aff. pleurisepta Conrad. - Stephenson : p.436 pl. 95, figs. 1-4
1977 Sphenodiscus pleurisepta Conrad. - Wolleben : p.392 pl. 3, fig. 24
1993 Sphenodiscus pleurisepta Conrad. - Kennedy & Cobban : p.58 figs. 1a-c,2,3t (with additional synonymy)
1995 Sphenodiscus pleurisepta Conrad. - Cobban & Kennedy : p.12 fig. 8.5 (with full synonymy)
1996 Sphenodiscus pleurisepta Conrad. - Kennedy et al. : p.11 figs. 4a,5-12
1997 Sphenodiscus pleurisepta Conrad. - Kennedy et al. : p.9 figs. 9j, 11-14
2003 Sphenodiscus pleurisepta Conrad. - Landman & Cobban : p.17 figs. 12-15
2005 Sphenodiscus pleurisepta Conrad. - Ifrim et al. : 55, 59 fig. 5, figs. 7a-c, figs. 8a-d,h-i
Cobban & Kennedy (1995):
1857 Ammonites pleurisepta Conrad. - Conrad : p.159 pl. 15, fig. 1
p 1861 Ammonites pedernalis Binkhorst. - Binkhorst : p.21 pl. 5al, fig. 1a, b only
1898 Sphenodiscus pleurisepta Conrad. - Böhm : p.193 pl. 7; fig. 1, 1a, 1b
1903 Sphenodiscus pleurisepta Conrad. - Hyatt : p.59 pl. 3, fig. 7-15; pl. 4; pl. 5, fig. 1-3; pl. 6, fig. 6
? 1904 Sphenodiscus pleurisepta Conrad. - Lasswitz : p.231 pl. 14, fig. 3
1908 Sphenodiscus pleurisepta Conrad. - Grossouvre : p.22 pl. 1; fig. 8
1910 Sphenodiscus pleurisepta Conrad. - Grabau & Shimer : p.215 fig. 1490a-d
1921 Sphenodiscus pleurisepta Conrad. - Grabau : text-fig. 1756e-h
1924 Sphenodiscus pleurisepta Conrad. - Deussen : pl. 12, fig. 3
1928 Sphenodiscus pleurisepta Conrad. - Böse : p.304 pl. 17; fig. 2-5
1938 Sphenodiscus pleurisepta Conrad. - Roman : p.503
1940 Sphenodiscus aff. pleurisepta Conrad. - Stephenson & Monroe : p.268 pl. 13; fig. 6
1941 Sphenodiscus pleurisepta Conrad. - Stephenson : p.436 pl. 95; fig. 1-4
1955 Sphenodiscus pleurisepta Conrad. - Stephenson : p.135 pl. 24; fig. 1-4?
1955 Sphenodiscus pleurisepta Conrad. - Reyment : p.89 fig. 44b, c
1993 Sphenodiscus pleurisepta Conrad. - Kennedy & Cobban : p.58 fig. 1a-c, 2, 3t
1995 Sphenodiscus pleurisepta Conrad. - Cobban & Kennedy : p.11 fig. 8.5
Landman et al. (2004):
1857 Ammonites pleurisepta Conrad. - Conrad : p.159 pl. 15; fig. 1
1962 Sphenodiscus lenticularis Owen. - Kellum : p.68 pl. 4, fig. 3, 4; pl. 5, fig. 1; pl. 6, fig. 1, 2
1995 Sphenodiscus pleurisepta Conrad. - Cobban & Kennedy : p.12 fig. 8.5 [with full synonymy]
1996 Sphenodiscus pleurisepta Conrad. - Kennedy & Cobban : p.11 fig. 4A, 5-12
2004 Sphenodiscus pleurisepta Conrad. - Landman et al. : p.50 fig. 22
Stratigraphy - relative ages:
Maastrichtian: ()
Maastrichtian: Cobban & Kennedy (1995)
References:

Conrad,T.A.. (1857):
Descriptions of Cretaceous and Tertiary fossils.
In: Report on the United States and Mexican boundary survey, U.S. 34th congress 1st session, Senate Ex Document 108 and House Ex Document Vol. 135(1) Eds: Emery, W.H.. p. 140-174

Binkhorst,J.T.. (1861):
Monographie des gastropodes et des céphalopodes de la Craie Supérieure du Limburg.
In: Maastricht and Muller Frères Eds: Muquardt, G.. p. 17,83,44

Böhm,J. (1898):
Über Ammonites pedernalis v. Buch . Zeitschrift der Deutschen Geologischen Gesellschaft Vol. 50 p. 183-201

Hyatt,A.. (1903):
Pseudoceratites of the Cretaceous . U.S. Geological Survey Monograph Vol. 44 p. 1-351

Lasswitz,R.. (1904):
Die Kreide-Ammoniten von Texas . Geologische und Palaeontologische Abhandlungen Vol. 10 p. 223-259

Grossouvre,d.A.. (1908):
Description des ammonites du Cretace Superieur du Limbourg Belge et Hollandais et du Hainault . Mem. Mus. r. Hist. nat. Belg Vol. 4 p. 1-39

Grabau,A.W.. and Shimer,H.W.. (1910):
North American Index Fossils. , Invertebrates Vol. 2 p. 1-909

Grabau,A.W.. (1921):
A Textbook of Geology, Part 2.
In: Historical Geology p. 1-976

Deussen,A.. (1924):
Geology of the Coastal Plain of Texas west of Brazos River . U.S. Geological Survey Professional Paper p. 126, 139

Böse,E.. (1928):
Cretaceous ammonites from Texas and northern Mexico . University of Texas Bulletin Vol. 2748 p. 143–357

Roman,F.. (1938):
Les ammonites jurassiques et cretacees. Essai de genera. . p. 554

Stephenson,L.W.. and Monroe,W.H.. (1940):
The Upper Cretaceous deposits [Mississippi] . Mississippi Geological Survey Bulletin Vol. 40 p. 296 pp.

Stephenson,L.W.. (1941):
The larger invertebrates of the Navarro Group of Texas (exclusive of corals and crustaceans and exclusive of the fauna of the Escondido Formation) . University of Texas, Bulletin Vol. 4101 p. 641 pp

Stephenson,L.W.. (1941):
The larger invertebrates of the Navarro Group of Texas (exclusive of corals and crustaceans and exclusive of the fauna of the Escondido Formation) . University of Texas Bulletin Vol. 4101 p. 641

Reyment,R.A. (1955):
The Cretaceous Ammonoidea of southern Nigeria and the southern Cameroons . Geological Survey of Nigeria Bulletin Vol. 25 p. 112

Stephenson,L.W.. (1955):
Owl Creek (Upper Cretaceous) fossils from Crowleys Ridge, Southeastern Missouri . United States Geological Survey Professional Paper Vol. 274 p. E97-E140

Kellum,L.B.. (1962):
Upper Cretaceous Mollusca from Niobrara County . Wyoming. Papers of the Michigan Academy of Science, Arts and Letters Vol. 47 p. 37-81

Wolleben,J.A.. (1977):
Paleontology of the Difunta Group (Upper Cretacous– Tertiary) in northeastern Mexico . Journal of Paleontology Vol. 51(2) p. 373–398

Kennedy,W.J.. and Cobban,W.A.. (1993):
Maastrichtian ammonites from the Corsicana Formation in northeast Texas . Geological Magazine Vol. 130(1) p. 57–67

Cobban,W.A.. and Kennedy,W.J.. (1995):
Maastrichtian ammonites chiefly from the Prairie Bluff Chalk in Alabama and Mississippi . Journal of Paleontology Vol. 69(5) p. 1-40

Kennedy,W.J..; Landman,N.H.. and Cobban,W.A.. (1996):
The Maastrichtian ammonites Coahuilites sheltoni Böse, 1928, and Sphenodiscus pleurisepta (Conrad, 1857), from the uppermost Pierre Shale and basal Fox Hills Formation of Colorado and Wyoming . American Museum Novitates Vol. 3186 p. 1–14

Kennedy,W.J.. and Cobban,W.A.. (1996):
Maastrichtian ammonites from the Hornerstown Formation in New Jersey . Journal of Paleontology Vol. 70(5) p. 798–804

Kennedy,W.J..; Landman,N.H.. and Cobban,W.A.. (1997):
Maastrichtian ammonites from the Severn Formation of Maryland . American Museum Novitates Vol. 3210 p. 1–30

Landman,N.H.. and Cobban,W.A.. (2003):
Ammonites from the upper part of the Pierre Shale and Fox Hills Formation of Colorado . American Museum Novitates Vol. 3388 p. 1–45

Landman,N.H..; Johnson,R.O.. and Edwards,L.E.. (2004):
Cephalopods from the Cretaceous/Tertiary Boundary Interval on the Atlantic Coastal Plain, with a Description of the Highest Ammonite Zones in North America, Part 2: Northeastern Monmouth County, New Jersey . Bulletin of the American Museum of Natural History Vol. 287 p. 1-107

Ifrim,C..; Stinnesbeck,W.. and Schafhauser,A.. (2005):
Maastrichtian shallow-water ammonites of northeastern Mexico . Revista Mexicana de Ciencias Geológicas Vol. 22(1) p. 48-64

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