Sphenodiscus lobatus Tuomey 1854 from: Ifrim, C..Stinnesbeck, W..Schafhauser, A.. (2005): Maastrichtian shallow-water ammonites of northeastern Mexico . Revista Mexicana de Ciencias Geológicas Vol. 22(1) p. 48-64 . |
Notice: This catalogue page may contain unedited data.
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Species Sphenodiscus lobatus Tuomey 1854 |
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[1] 4d-g Ifrim et al. (2005) [2] 6 Ifrim et al. (2005) [3] Ifrim et al. (2005) [4] 5a-d Ifrim et al. (2005)
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Diagnosis / Definition: |
Ifrim et al. (2005):
Description. Compressed, involute, oxycone shell with
a tiny umbilicus of about 3% of the diameter. The venter
is fastigiate or narrowly rounded and grades into slightly
convex flanks. Maximum whorl breadth is at midflank.
Towards the umbilicus the flank is slightly concave. The
shell surface is smooth or may bear faint, low, broad,
concave ribs which are crescent on the outer flank but,
straight on the inner flank where visible. Our material
contains some body chambers, but no complete aperture is
preserved. The first lateral saddle of the suture line, E/L, is
trifid, auxiliary saddles are numerous and entire with the
exception of the outer one or two.
Cobban & Kennedy (1995):
DESCRIPTION.-
Fragments rare in Prairie Bluff Chalk; most are
short sections of phragmocone that have whorl heights of up to
75 mm, derived from oxycone shells with whorl breadth to
height ratios of around 0.4. Shell surface smooth, or may bear
faint, low, broad, concave, crescentic ribs on outer flank. Sutures
include trifid first lateral saddle, and up to 10 auxiliary saddles
on umbilical lobe, eight of which may have entire terminations.
Other saddles narrow stemmed with variously incised sometimes
subphylloid terminations.
Kennedy & Cobban (1996):
DESCRIPTION.-
All specimens fragmentary internal molds of
phragmocones with whorl heights of up to 110 mm. Earliest
growth stages seen represented by NJSMl1328a, a juvenile with
estimated original diameter of 23-24 mm. In this and other
fragments shell is very compressed and oxycone; surface of mold
smooth or with traces of morsiradiate striae and riblets. Suture
line includes numerous aixiliary and adventitious elements, as
is typical for genus.
Landman et al. (2004):
DESCRIPTION.-
MAPS A2002a9 is one-third
whorl of a large phragmocone (not illustrated).
The whorl width and height at the adoral
end of the specimen are approximately 66.6
mm and 164.0 mm, respectively; the ratio of
whorl width to height is 0.41. The flanks are
very broadly rounded and converge to an
acute venter. Part of the suture on the adapical
end of the specimen is illustrated (fig.
25A).
MAPS A2002a8 is a large specimen, 285
mm in diameter, with the adoral end slightly
crushed in (figs. 23, 24). Most of the specimen is phragmocone with barely less than
one-eighth whorl of body chamber attached.
However, part of the rest of the body chamber
was still present but was not collected in
the field because it was too crushed. Three
oval to circular depressions appear on the
midflanks of the body chamber on the left
side, the largest of which is approximately
16 mm in diameter. The inner flanks are
nearly flat and slightly divergent, the midflanks
are very broadly rounded and subparallel,
and the outer flanks are nearly flat and converge to an acute venter. The whorl width
and height near the base of the body chamber
are approximately 35.2 mm and 170 mm, respectively,
although the whorl width is underestimated
due to crushing; the ratio of
whorl width to height is 0.21. The flanks are
smooth without any nodes. The suture has a
very broad and shallow external lobe with a
low, little incised median saddle (fig. 25B). |
Discussion / Comments: |
Ifrim et al. (2005):
Type: The holotype is lost (fide Stephenson, 1941, p. 434).
It was from Noxubee County, Mississippi.
Material: 34 specimens from the Cerro del Pueblo Formation
at Rincón Colorado, Coahuila.
Occurrence: This Maastrichtian species was described
from the Escondido Formation in northeastern Mexico and
Trans-Pecos, Texas (Böse, 1928), Alabama, and Mississippi
(Cobban and Kennedy, 1995), and northeast Texas (Kennedy
and Cobban, 1993b). Other records are from North Carolina,
Maryland, New Jersey, Israel and Nigeria (fide Cobban and
Kennedy, 1995). In the Western Interior, S. lobatus was
recorded from the Hoploscaphites nicolletii and Jeletzkytes
nebrascensis ammonite zones and may also exist in the H.
birkelundi zone (see Kennedy et al., 1997).
Discussion: According to Cobban and Kennedy (1995)
and Kennedy et al. (1997), this species is morphologically
variable. Kennedy et al. (1997) include S. lenticularis
intermedius into the synonymy of S. lobatus. Sphenodiscus
pleurisepta, another common species in the Gulf of Mexico
area, clearly differs by a stronger ornamentation.
Cobban & Kennedy (1995):
TYPE.-
The holotype, from Noxubee County, Mississippi, is
lost (tide Stephenson, 194 1, page 434).
MATERIAL.-
Five specimens, USNM 463 109-463 1 14.
DISCUSSION.-
A second Sphenodiscus present in the Prairie
Bluff Chalk is S. pleurisepta (Conrad, 1857, page 159, plate 15,
figure 1; see below). This differs from S. lobatus in having midlateral
and outer lateral tubercles when young linked by sickle
shaped ribs. The outer lateral tubercle develops into a crescentic
rib in middle and later growth.
OCCURRENCE.-
Maastrichtian, Prairie Bluff Chalk at locality 45
in Wilcox County, Alabama, and at localities 21 and 24 in
Noxubee County, Mississippi. It also occurs in the Escondido Formation in Trans-Pecos Texas and northern Mexico; Corsicans
Formation in northeast Texas; upper part of Ripley Formation
in Mississippi; Providence Sand in the Chatahoochee
River area of eastern Alabama; Peedee Formation in North
Carolina; Severn Formation in Maryland; Red Bank Sand and
Tinton Sand of New Jersey; and in the Western Interior. Elsewhere,
the species is known from Israel and Nigeria.
Kennedy & Cobban (1996):
TYPE.-
The holotype, from Noxubee County, Mississippi, is
lost (fide Stephenson, 1941, p. 434).
DISCUSSION.-
See Cobban and Kennedy (1995) for a discussion
of the present species and its synonyms and differences
from allied species.
MATERIAL.-
More than 50 fragments including NJSM 103 15,
11328a-z, cc, ee, ff, from the main fossiliferous layer of the
Hornerstown Formation at the Inversand Marl Pit, Gloucester
County, New Jersey.
OCCURRENCE.-
Escondido Formation in Trans-Pecos Texas and
northern Mexico; Corsicana Formation in northeast Texas; upper
part of Ripley Formation in Mississippi; Prairie Bluff Chalk
in Alabama and Mississippi; Providence Sand in the Chattahoochee
River area, Alabama and Georgia; upper part of Peedee
Formation in North Carolina; Severn Formation in Maryland;
Red Bank Sand and Tinton Sand in New Jersey. In the Western
Interior the species occurs in the Hoploscaphites nicolletii and
Jeletzkytes nebrascensis zones, and may also be present in the underlying H. birkelundi zone.
Landman et al. (2004):
TYPE.-
The holotype, from Noxubee County,
Mississippi, is lost (fide Stephenson,
1941: 434).
MATERIAL.-
There are two specimens:
MAPS A2002a8 and A2002a9 from the Tinton
Formation, AMNH loc. 3348, 0.2 km
north of the intersection of Water Street and
Tinton Avenue, Tinton Falls, Monmouth
County, New Jersey.
DISCUSSION.-
These specimens lack the two
rows of nodes characteristic of Sphenodiscus
pleurisepta and are referred to Sphenodiscus
lobatus. Cobban and Kennedy (1995) fully
discussed S. lobatus and the differences with
congeneric species. The shallow circular depressions
and crushed body chamber may indicate
predation.
OCCURRENCE.-
Tinton Formation, near Tinton
Falls, northeastern Monmouth County,
New Jersey (Weller, 1907; Reeside, 1962;
see also Gallagher, 1993). Sphenodiscus lobatus
has also been reported in New Jersey
from the MFL at the Inversand Marl Pit,
Gloucester County (Gallagher, 1993; Kennedy
et al., 1995; Kennedy and Cobban,
1996). Elsewhere on the Gulf and Atlantic
Coastal Plains, this species is known from
the Corsicana Formation in northeast Texas
(Kennedy and Cobban, 1993); the upper part
of the Ripley Formation in Mississippi; the
Prairie Bluff Chalk in Alabama and Mississippi
(Cobban and Kennedy, 1995); the Providence
Sand in the Chattahoochee River area,
Alabama and Georgia; the upper part of the
Peedee Formation in North Carolina (Landman
et al., 2004); and the Severn Formation
in Prince Georges County, Maryland (Kennedy
et al., 1997). 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 nicolletii and Jeletzkytes
nebrascensis Zones of the Fox Hills Formation
in north-central South Dakota (Landman
and Waage, 1993) and in the J. nebrascensis
Zone of the Pierre Shale in southeastern
South Dakota and northeastern Nebraska
(Kennedy et al., 1998).
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Systematics: |
36 Ordo Ammonoidea
Subordo Ammonitina
Superfamilia Acanthocerataceae
Familia Sphenodiscidae
Subfamilia Sphenodiscinae
Genus Sphenodiscus
Species Sphenodiscus lobatus
44 Classis Cephalopoda
Subclassis Nautiloidea
Ordo Ammonoidea
Subordo Ammonitina
Superfamilia Acanthocerataceae
Familia Sphenodiscidae
Genus Sphenodiscus
Species Sphenodiscus lobatus
46 Ordo Ammonoidea
Subordo Lytoceratina
Superfamilia Acanthocerataceae
Familia Sphenodiscidae
Species Sphenodiscus lobatus
48 Ordo Ammonoidea
Subordo Ammonitina
Superfamilia Acanthocerataceae
Familia Sphenodiscidae
Genus Sphenodiscus
Species Sphenodiscus lobatus
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Synonym list: |
Ifrim et al. (2005):
1995 Sphenodiscus lobatus Tuomey. - Cobban & Kennedy : p.12 figs. 6.2-6.3, 8.4, 8.6-8.11, 12.18-12.19, 16.16-16.17
Cobban & Kennedy (1995):
1903 Sphenodiscus lobatus Tuomey. - Hyatt : p.66 pl. 6, fig. 1, 2;
pl. 7, fig. 1, 2;
pl. 9, fig. 11-13
1995 Sphenodiscus lobatus Tuomey. - Cobban & Kennedy : p. 9, 11, 19, 24 fig. 6.2, 6.3, 8.4-8.11, 12.18, 12.19, 16.16, 16.17
Kennedy & Cobban (1996):
1995 Sphenodiscus lobatus Tuomey. - Cobban & Kennedy : p.12 fig. 6.2, 6.3, 8.4, 8.6-8.11, 12.18, 12.19, 16.16, 16.17 [with full synonymy]
Landman et al. (2004):
1995 Sphenodiscus lobatus Tuomey. - Cobban & Kennedy : p.12 fig. 6.2, 6.3, 8.4, 8.6-8.11, 12.18, 12.19, 16.16, 16.17 [with full synonymy]
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Stratigraphy - relative ages: |
Maastrichtian, Ifrim et al.: ()
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References: |
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