Nostoceras (Nostoceras) alternatum Tuomey 1854 from: Ifrim, C..Stinnesbeck, W..López-Oliva, J.G.. (2004): Maastrichtian cephalopods from Cerralvo, north-eastern Mexico . Palaeontology Vol. 47(6) p. 1575–1627 | . |
Notice: This catalogue page may contain unedited data.
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Species Nostoceras (Nostoceras) alternatum Tuomey 1854 |
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[1] Text-figs. 14a-b Ifrim et al. (2004) [2] text-fig. 16a-c Ifrim et al. (2004)
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| Alternative name: |
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| Diagnosis / Definition: |
Cobban & Kennedy (1995):
DESCRIPTION.-
USNM 463118, from locality 13, is a body chamber
with maximum preserved whorl height of 15.5 mm. Upper
whorl face concave to accommodate lower whorl face of previous
whorl; outer whorl face broadly rounded, juncture of outer
and lower whorl faces narrowly rounded, lower whorl face broadly
rounded. Ribs arise at upper whorl suture, are coarse, straight
and prorsiradiate across flanks and link in pairs at strong tubercles
at juncture of outer and lower whorl faces. An equal
number of coarse, radially elongated tubercles lie close to umbilical
margin. The two rows link across a concave zone by weak
zig-zag ribs. Tubercles next to umbilicus give rise to coarse single
ribs that extend across inner side of whorl, weakening progressively.
Sutures not seen.
Ifrim et al. (2004):
Description: Sinistral and dextral coiling. Moderate1y evolute and trochospiral. Apica1 angle of 45-55 degrees and
intermediate expansion rate result in an open umbi1icus on the abapica1 side. This umbi1icus spans c. 21 per cent of the
whorl diameter. Whorl cross section is rhomboida1 and WB/WH c. 1·0-1·2. Approximate1y 25 single ribs per whorl
are present internally and ventrally, and fork into pairs at sharp bullae on the lower flank or precise1y on the whorl
contact. Where test is preserved these bullae are extended to form short triangular spines which rest in the interspaces
of ribs of the succeeding whorl. A second row of tuberc1es or bullae is located on the inner whor1 contact. The two rows
of bullae form a concave mou1d between them that accommodates the succeeding whorl. The suture line is simple and
asymmetrie. The EIL sadd1e is broad, rectangular, 1itt1e incised and asymmetrically bifid. LlU, Land U are narrower
and symmetrically bifid. |
| Discussion / Comments: |
Cobban & Kennedy (1995):
TYPES.-
These were from Noxubee County, Mississippi, but
are lost.
MATERIAL.-
One specimen, USNM 463118.
DISCUSSION.-
Cobban (1974b) revised N. (N.) alternatum, the
distinctive features of which are the presence of a simple rib on
the outer whorl face with a row of long septate (tubercles on
internal molds) at the juncture of outer and lower whorl surfaces,
and a second row close to the umbilicus on the lower whorl
face.
OCCURRENCE.-
This species is the index to the lower Maastrichtian
N. (N.) alternatum zone (Cobban and Kennedy, 199 1 b),
and occurs in the Prairie Bluff Chalk at locality 13 in Mississippi;
the Navesink Formation at Atlantic Highlands, New Jersey; the
Ripley Formation in Mississippi, Alabama and Georgia; and
the Nacatoch Sand in Arkansas.
Ifrim et al. (2004):
Remarks: The species resembles N (N) approximans, N (N) hyatti and N (N) helicinum, species that do
not have spines but rows of tubercles instead. These tubercles are located ventrolaterally with a short
distance to the contact between succeeding whorls. In addition, all other species of Nostoceras have
rounded whorl sections instead of rhomboidal. The ornament resembles that of N (N) rugosum, which
differs from N (N) alternatum in having a smaller apical angle and lower expansion rate. Cobban (l974b)
and Cobban and Kennedy (l99Ib) described a size dimorphism characterized by uncoiling of the final
hook at different sizes. Unfortunately no final hook is preserved among the Cerralvo specimens so that this
dimorphism cannot be observed.
Occurrence: Nostoceras (Nostoceras) alternatum (Tuomey) is an upper Lower Maastrichtian biozonal marker in the
Ripley Formation of Mississippi, Alabama and Georgia (Cobban 1974a; Cobban and Kennedy 1991b). The species has
also been reported from the Maastrichtian Nacatotch Sand in Arkansas (Cobban and Kennedy 1991a) and the
Navesinsk Formation in New Jersey (Cobban 1974b). |
| Systematics: |
36
Ordo Ammonoidea
Subordo Ancyloceratina
Superfamilia Turrilitaceae
Familia Nostoceratidae
Genus Nostoceras
Subgenus Nostoceras (Nostoceras)
Species Nostoceras (Nostoceras) alternatum
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Ordo Ammonoidea
Subordo Ancyloceratina
Superfamilia Turrilitaceae
Familia Nostoceratidae
Genus Nostoceras
Subgenus Nostoceras (Nostoceras)
Species Nostoceras (Nostoceras) alternatum
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| Synonym list: |
Cobban & Kennedy (1995):
Ifrim et al. (2004):
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| Stratigraphy - relative ages: |
Maastrichtian: Ifrim et al. (2004)
lower Maastrichtian: Cobban & Kennedy (1995)
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| References: |
Tuomey,M.. (1854):
Description of some new fossils from the Cretaceous rocks of the Southern States . Proceedings of the Academy of Natural Sciences Philadelphia Vol. 7(5) p. 167-172
Conrad,T.A.. (1860):
Descriptions of new species of Cretaceous and Eocene fossils of Mississippi and Alabama . Journal of the Academy of Natural Sciences, Philadelphia Vol. 4 p. 275-298
Gabb,W.M.. (1861):
Synopsis of the Mollusca of the Cretaceous Formation, including the geographical and stratigraphical range and synonymy . Proceedings of the American Philosophical Society Vol. 8 p. 57-257
Cobban,W.A.. (1974):
Some ammonoids from the Ripley Formation of Mississippi, Alabama and Georgia . United States Geological Survey, Journal of Research Vol. 2 p. 81-88
Cobban,W.A.. (1974):
Ammonites from the Navesink Formation at Atlantic Highlands, New Jersey . United States Geological Survey Professional Paper Vol. 845 p. 1-46
Cobban,W.A.. and Kennedy,W.J.. (1991):
Upper Cretaceous (Maastrichtian) ammonites from the Nostoceras alternatum zone in southwestern Arkansas . United States Geological Survey, Bulletin Vol. 1985 p. E1-E6
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
Ifrim,C..; Stinnesbeck,W.. and López-Oliva,J.G.. (2004):
Maastrichtian cephalopods from Cerralvo, north-eastern Mexico . Palaeontology Vol. 47(6) p. 1575–1627
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