Browsing by Author "Cobban, William A., 1916-2015."

Now showing 1 - 18 of 18

Open Access
Additions to the ammonite fauna of the Upper Cretaceous Navesink Formation of New Jersey. American Museum novitates ; no. 3306
(New York, NY : American Museum of Natural History, 2000) Kennedy, W. J. (William James); Landman, Neil H.; Cobban, William A., 1916-2015.; Johnson, Ralph O.
New fossil collections provide additional information about the late Campanian and Maastrichtian ammonites from the Navesink Formation of New Jersey. Late Campanian ammonites include Pseudophyllites indra (Forbes, 1846), Nostoceras (N.) approximans (Conrad, 1855) (of which Nostoceras (N.) stantoni Hyatt, 1894, is a synonym), Nostoceras (N.) hyatti Stephenson, 1941, Nostoceras (N.) pauper (Whitfield, 1892), Didymoceras cf. D. draconis (Stephenson, 1941), Exiteloceras rude n. sp., Hoploscaphites pumilus (Stephenson, 1941), and Jeletzkytes cf. J. nodosus (Owen, 1852). Maastrichtian ammonites from the Navesink Formation include Pachydiscus (P.) neubergicas neubergicus (Hauer, 1858), Kitchinites sp., Nostoceras (N.) alternatum (Tuomey, 1854), Baculites sp., Eubaculites cf. E. labyrinthicus (Morton, 1834), Eubaculites sp.?, Jeletzkytes cf. J. plenus (Meek, 1876), Jeletzkytes criptonodosus Riccardi, 1983, and Discoscaphites gulosus (Morton, 1834). These faunas are correlated with those of Western Europe, the Gulf Coast, and the Western Interior of the United States. The older fauna from the basal phosphatic beds of the Navesink Formation at the classic Atlantic Highlands locality is referred to the Nostoceras (N.) hyatti zone. It is late Campanian in age and equivalent to the Nostoceras (N.) pozaryskii/Belemnella langei zone in Europe and the Baculites jenseni zone in the United States Western Interior. In addition, these beds contain ammonites that range into the early Maastrichtian, as well as Pachydiscus (P.) neubergicus, whose appearance marks the base of the Maastrichtian. Thus, these phosphatic beds represent a condensed sequence that spans the late Campanian to early Maastrichtian. Ammonites also occur at other localities in the Navesink Formation in New Jersey, and correspond to higher levels in the Maastrichtian. The youngest ammonite known from the Navesink Formation, Discoscaphites gulosus, from Sewell, New Jersey, indicates a correlation with the Hoploscaphites nicolletii or Jeletzkytes nebrascensis zone of the Western Interior.
Open Access
Ammonites from the upper part of the Pierre Shale and Fox Hills Formation of Colorado. American Museum novitates ; no. 3388
(New York, NY : American Museum of Natural History, 2003) Landman, Neil H.; Cobban, William A., 1916-2015.
The upper part of the Pierre Shale and Fox Hills Formation were deposited in the late Cretaceous (Maastrichtian) Western Interior Seaway. They crop out in a belt that roughly parallels the Front Range of the Rocky Mountains from Douglas to Weld County, Colorado. These rocks consist of sandy shales and sandstones and are overlain by the nonmarine Laramie Formation. A sparse assemblage of ammonites is present consisting of Coahuilites sheltoni Böse, 1928, Sphenodiscus pleurisepta (Conrad, 1857), Trachybaculites sp. cf. T. columna (Morton, 1834), Hoploscaphites birkelundae Landman and Waage, 1993, Hoploscaphites sp. cf. H. birkelundae, Jeletzkytes dorfi Landman and Waage, 1993, and Jeletzkytes sp. cf. J. dorfi. Hoploscaphites birkelundae and Jeletzkytes dorfi define the H. birkelundae Zone in the Western Interior, which represents the lower part of the Upper Maastrichtian. These rocks are thus equivalent in age to the Fox Hills Formation in Niobrara County, Wyoming, and older than the type Fox Hills Formation in north-central South Dakota. An analysis of the ratio of ⁸⁷Sr/⁸⁶Sr in a belemnite from this zone in Morgan County, Colorado, yields a value of 0.707790 ± 0.000008 (2-sigma SE), nearly identical to that of a bivalve from the same zone in Niobrara County, Wyoming (McArthur et al., 1994). The western shoreline of the seaway during the time of H. birkelundae extended as far west as northwestern Colorado and southwestern Wyoming.
Open Access
Ammonites from the Weno limestone (Albian) in northeast Texas. American Museum novitates ; no. 3236
(New York, NY : American Museum of Natural History, 1998) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Gale, A. S.; Hancock, J. M.; Landman, Neil H.
The Weno Limestone of northeast Texas is an upper Albian unit that has previously been imprecisely dated in terms of the European standard zonal sequence. Ammonite faunas, chiefly from the lower Weno, show it to be equivalent to a part of the lowest Mortoniceras (Subschloenbachia) rostratum Subzone of the highest Albian Stoliczkaia dispar Zone of Europe on the basis of the presence of M. (S.) rostratum (J. Sowerby, 1817), together with Engonoceras serpentinum (Cragin, 1900), Engonoceras aff. subjectum (Hyatt, 1903), Cantabrigites aff. subsimplex (Spath, 1933), Mortoniceras (Angolaites) drakei (Young, 1957), Mortoniceras (Angolaites) wintoni (Adkins, 1920), Stoliczkaia (Stoliczkaia) argonautiformis (Stoliczka, 1864), Neophlycticeras (Neophlycticeras) sp., Anisoceras armatum (J. Sowerby, 1817), Anisoceras perarmatum Pictet and Campiche, 1861, and Mariella (Wintonia) sp. Mortoniceras (Subschloenbachia) Spath, 1921, is regarded as the senior synonym of Durnovarites Spath, 1932, and Mortoniceras (Angolaites) Spath, 1932, as the senior synonym of Drakeoceras Young, 1957. Most previous studies have interpreted the ammonites of the Weno Limestone as predominantly endemic to Texas. However, Mortoniceras (Angolaites) was originally described from Angola, S. (S.) argonautiformis from southern India, and M. (S.) rostratum and the species of Cantabrigites, Neophlycticeras, and Anisoceras from western Europe.
Open Access
Campanian ammonites from the Tombigbee Sand Member of the Eutaw Formation, the Mooreville Formation, and the basal part of the Demopolis Formation in Mississippi and Alabama. American Museum novitates ; no. 3201
(New York, N.Y. : American Museum of Natural History, 1997) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Landman, Neil H.
Open Access
Engonoceratid ammonites from the Glen Rose limestone, Walnut clay, Goodland limestone, and Comanche Peak limestone (Albian) in Texas. American Museum novitates ; no. 3221
(New York, NY : American Museum of Natural History, 1998) Kennedy, W. J. (William James); Landman, Neil H.; Cobban, William A., 1916-2015.
Ammonites of the family Engonoceratidae, commonly referred to as pseudoceratites because of their distinctive suture, are locally abundant in rocks of early to mid-Albian age in Texas, but have received little or no attention since their original description. Ten species are dealt with in the present publication in the following order: Engonoceras elegans, n. sp., Engonoceras gibbosum Hyatt, 1903, Engonoceras stolleyi Böhm, 1898, Engonoceras hilli Böhm, 1898, Engonoceras complicatum Hyatt, 1903, Parengonoceras roemeri (Cragin, 1893), Metengonoceras inscriptum Hyatt, 1903, Metengonoceras ambiguum Hyatt, 1903, Protengonoceras gabbi (Böhm, 1898), and Platiknemiceras flexuosum, n. sp.
Open Access
The heteromorph ammonite Didymoceras cochleatum (Meek and Hayden, 1858), from the Pierre Shale of South Dakota and Wyoming. American Museum novitates ; no. 3268
(New York, NY : American Museum of Natural History, 1999) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Landman, Neil H.
The middle Campanian (Upper Cretaceous) zone of Baculites gregoryensis Cobban, 1951 in south-central South Dakota and eastern Wyoming has yielded numerous fragments of a distinctive species of Didymoceras characterized by initial loose planispiral whorls followed by loose helical whorls, and finally by a slightly pendant body chamber. These fragments are referred to Didymoceras cochleatum (Meek and Hayden, 1858), a species based on one-half of a septate whorl from the helical growth stage. This species is abundant in the Gregory Member of the Pierre Shale along the Missouri River Valley in South Dakota, rare in the Red Bird Silty Member of the Pierre Shale in eastern Wyoming, and very rare in the Rock River Formation in southeastern Wyoming.
Open Access
Impressions of the attachment of the soft body to the shell in late Cretaceous pachydiscid ammonites from the Western Interior of the United States. American Museum novitates ; no. 3273
(New York, NY : American Museum of Natural History, 1999) Landman, Neil H.; Lane, Jennifer A.; Cobban, William A., 1916-2015.; Jorgensen, Steven D.; Kennedy, W. J. (William James); Larson, Neal L.
Late Cretaceous pachydiscid ammonites Menuites oralensis Cobban and Kennedy, 1993 and Menuites portlocki (Sharpe, 1855) complexus (Hall and Meek, 1856) from the Western Interior of the United States show four kinds of markings on the phragmocone and body chamber. These markings are preserved on internal molds that retain traces of the original shell, mostly the inner prismatic layer. (1) Transverse lines appear on the surface of the inner prismatic layer and extend adorally as far as midway onto the adult body chamber. They consist of a sequence of regularly spaced iridescent lines that usually cross the venter with a marked adoral projection, forming a chev-ronlike pattern. The transverse lines do not follow the shape of the apertural margin. Viewed in close-up, these lines appear as narrow bands of nacre; the adoral edge of each band is ragged and the adapical edge thins out and disappears. (2) A longitudinal band occurs on the flanks and extends from the umbilicus to about two--thirds whorl height. It appears on the surface of the inner prismatic layer. (3) A mid-ventral band extends for several tens of millimeters adoral of the ultimate septum and terminates in an unpaired scar. It appears on the internal mold and is visible below the inner prismatic layer. (4) A pair of dorsal scars occurs on the internal mold several millimeters adoral of the ultimate septum. Each scar is boomerang-shaped and extends from the dorsal margin to just ventral of the umbilical shoulder. We hypothesize that the transverse line formed at the adapical margin of the zone of nacreous secretion in the middle of the body chamber. They may have represented narrow bands of mantle attachment. The longitudinal band demarcated a broad area of nacreous secretion on the flanks, which may have represented an additional area of mantle attachment. During growth, both the transverse lines and the longitudinal band were overlain by the inner prismatic layer (and are thus now visible on the surface of this layer on partially exfoliated shells). The mid-ventral scar and dorsal scars just adoral of the ultimate septum are the sites of attachment of the soft body at the adapical end of the body chamber. These sites developed on the inside surface of the inner prismatic layer (and are thus now visible on the internal mold below the inner prismatic layer, if present).
Open Access
Jaws of late Cretaceous placenticeratid ammonites : how preservation affects the interpretation of morphology. American Museum novitates ; no. 3500
(New York, NY : American Museum of Natural History, 2006) Landman, Neil H.; Tsujita, Cameron J.; Cobban, William A., 1916-2015.; Larson, Neal L.; Tanabe, Kazushige.; Flemming, Roberta L.
We describe upper and lower jaws of Placenticeras Meek, 1876, from the Upper Cretaceous (Upper Campanian) Bearpaw Shale and Pierre Shale of the Western Interior of North America and lower jaws of the related ammonite Metaplacenticeras Spath, 1926, from the Campanian Yasukawa Formation of Hokkaido, Japan. One lower jaw is preserved inside the body chamber of Placenticeras costatum Hyatt, 1903. The other jaws are isolated but are generally associated with fragments of placenticeratid shells. The jaws from North America are attributed to Placenticeras meeki Böhm, 1898, and P. costatum, while those from Japan are attributed to Metaplacenticeras subtilistriatum (Jimbo, 1894). All of the jaws are presumed to be from adults. The jaws of Placenticeras attain lengths of up to 95 mm. They are preserved as steinkerns with a thin film of black material, representing diagenetically altered chitin. X-ray diffraction analysis of samples of this material indicates that it consists of magnesium-rich calcite, pyrite, and amorphous material (organic compounds). The upper jaw is approximately the same length as the lower jaw and is U-shaped, with narrow wings that converge anteriorly to a dome-shaped hood. The lower jaw is composed of two lamellae. The outer lamella is broad and consists of two wings terminating in a bilobate posterior margin. The inner lamella is one-half the length of the outer lamella. The two lamellae are separated except in the apical region and along the sides. The junction between the lamellae appears as a U or V-shaped outline on the anterior portion on the ventral surface of the jaw. This junction is especially conspicuous in specimens in which part of the inner lamella has eroded away. In crushed specimens, the lower jaw is subquadrate in shape. In specimens that retain some or all of their original curvature, the central portion is gently convex and the sides bend steeply dorsally. The rostrum projects slightly anteriorly and dorsally and there is a thickened rim of chitin along the anterior margin where the two lamellae are doubled over. A small indentation appears at the apical end and, in most specimens, develops into a midline slit that extends posteriorly 10-15 mm. However, as shown in well-preserved specimens and based on comparisons with the jaws of closely related ammonites, this slit represents the remnants of a narrow ridge on the ventral side of the inner lamella. This ridge is surrounded by an elongate boss of thickened chitin, which corresponds to a depression on the dorsal side. The ventral surface of the outer lamella bears a midline ridge with a central groove, which essentially forms a continuation of the ridge on the inner lamella. The ventral surface of the outer lamella is ornamented with thin, radial striations and irregular broad undulations paralleling the posterior margin. The posterior end is generally incomplete, probably as a result of predation or postmortem degradation, and the lateral margins are commonly creased, indicating postmortem plastic deformation. The lower jaws of Metaplacenticeras subtilistriatum are much smaller than those of Placenticeras but are otherwise similar in morphology. However, they retain pieces of a very thin, fibrous outer layer comprising two plates. X-ray diffraction analysis of samples of this layer indicates that it consists of calcite enriched in magnesium. Each plate covers the ventral surface of one of the wings and terminates at the midline ridge. Based on the close affinity of Metaplacenticeras and Placenticeras, and in comparison with published descriptions of placenticeratid jaws from elsewhere, we hypothesize that similar plates covered the lower jaws of all placenticeratids, although these plates have not been found in any Placenticeras material from North America. The thin nature and fibrous microstructure of this layer would have made it susceptible to mechanical breakage and chemical dissolution. Furthermore, jaws are internal structures embedded in the buccal bulb. The micro-environment within this bulb may have promoted dissolution of the outer calcitic layer of the lower jaw. The presence of a pair of calcitic plates (aptychi) and a midline ridge with a central groove on the outer lamella of the lower jaw are unique features of the lower jaws of the Aptychophora Engeser and Keupp, 2002. Although differences in preservation obscure this similarity, the lower jaws of placenticeratids conform to the description of aptychus-type jaws. However, unlike the thick calcitic aptychi of other Ammonitina, the thin calcitic aptychi of placenticeratids probably did not function as opercula and would have served simply to strengthen the lower jaw. The jaws of placenticeratids were probably designed for biting and cutting food rather than for passively collecting and straining plankton. Other data about the habitat and mode of life of placenticeratids are consistent with this interpretation. These ammonites probably inhabited surface waters and were capable of pursuing and attacking sluggish prey. An ecological analog of placenticeratids may be the modern ocean sunfish Mola mola (Linnaeus, 1758), which inhabits surface waters and feeds on gelatinous zooplankton.
Open Access
Late Campanian (Cretaceous) heteromorph ammonites from the Western Interior of the United States. Bulletin of the AMNH ; no. 251
([New York] : American Museum of Natural History, 2000) Kennedy, W. J. (William James); Landman, Neil H.; Cobban, William A., 1916-2015.; Scott, George Richard.
Heteromorh ammonites of the families Nostoceratidae Hyatt, 1894, and Diplomoceratidae Spath, 1926, are common to abundant in sediments deposited in the western and central parts of the U.S. Western Interior Seaway during the early late Campanian. The indices of successive zones of Didymoceras nebrascense (Meek and Hayden, 1856a) (oldest), Didymoceras stevensoni (Whitfield, 1877), Exiteloceras jenneyi camacki, n. subsp., Exiteloceras jenneyi jenneyi (Whitfield, 1877) and Didymoceras cheyennense (Meek and Hayden, 1856a) are revised, as are Nostoceras monotuberculatum Kennedy and Cobban, 1993a (D. nebrascense and D. stevensoni zones), Oxybeloceras crassum (Whitfield, 1877) (D. stevensoni and E. jenneyi zones), and Spiroxybeloceras meekanum (Whitfield, 1877) (D. cheyennense zone). Solenoceras elegans, n. sp. (D. stevensoni and E. jenneyi zones), Solenoceras bearpawense, n. sp. (D. nebrascense zone), and Solenoceras larimerense, n. sp. (E. jenneyi zone) are also described.
Open Access
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 ; no. 3186
(New York, N.Y. : American Museum of Natural History, 1996) Kennedy, W. J. (William James); Landman, Neil H.; Cobban, William A., 1916-2015.
Open Access
Maastrichtian ammonites from the Severn Formation of Maryland. American Museum novitates ; no. 3210
(New York, N.Y. : American Museum of Natural History, 1997) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Landman, Neil H.
Open Access
New ammonoid records from the Merchantville Formation (Upper Cretaceous) of Maryland and New Jersey. American Museum novitates ; no. 3193
(New York, N.Y. : American Museum of Natural History, 1997) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Landman, Neil H.; Johnson, R. O.
Open Access
New records of acanthoceratid ammonoids from the Upper Cenomanian of South Dakota. American Museum novitates ; no. 3161
(New York, N.Y. : American Museum of Natural History, 1996) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Landman, Neil H.
Open Access
A new species of Hoploscaphites (Ammonoidea, Ancyloceratina) from cold methane seeps in the Upper Cretaceous of the U.S. Western Interior. (American Museum novitates, no. 3781)
(American Museum of Natural History., 2013-09-23) Landman, Neil H.; Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Larson, Neal L.; Jorgensen, Steven D.
We describe Hoploscaphites gilberti, n. sp. (Ammonoidea: Ancyloceratina), from the Upper Cretaceous (middle-upper Campanian) Pierre Shale spanning the zones of Baculites scotti and Didymoceras nebrascense in Colorado, Wyoming, Montana, and South Dakota. This species is strongly dimorphic and is characterized by a compressed whorl section, with a rounded to elongate outline in lateral view. The apertural angle is approximately 50° in macroconchs. The body chamber is ornamented with fine flexuous ribs, umbilicolateral bullae, and ventrolateral tubercles. Hoploscaphites gilberti, n. sp., most closely resembles H. gilli Cobban and Jeletzky, 1965, but differs from this species in several important features: (1) the flanks of the body chamber are nearly subparallel rather than steeply convergent toward the venter, (2) the ventrolateral tubercles are larger and more numerous, and (3) the ribs are more widely spaced. Hoploscaphites gilberti, n. sp., is abundant at "tepee buttes" in the Pierre Shale, which are now interpreted as cold methane seeps.
Open Access
A revision of the Turonian members of the ammonite subfamily Collignoniceratinae from the United States Western Interior and Gulf Coast. Bulletin of the AMNH ; no. 267
(New York, NY : American Museum of Natural History, 2001) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Landman, Neil H.
The Collignoniceratinae of the U.S. Western Interior first appear in the Lower Turonian and range through the Middle, and most of the upper, Turonian. For most of their range they are important biostratigraphic indicators. A review of their biostratigraphic distribution is provided and this is followed by a revision and/or discussion of the following taxa: Cibolaites molenaari Cobban and Hook, 1983, Collignoniceras woollgari woollgari (Mantell, 1822), C. woollgari regulare Haas, 1946, C. vermilionense (Meek and Hayden, 1860), C. jorgenseni n. sp., C. percarinatum (Hall and Meek, 1856), C. praecox (Haas, 1946), Collignonicerites collisniger n. gen., n. sp., Prionocyclus hyatti (Stanton, 1894), P. albinus (Fritsch, 1872), P. macombi Meek, 1876, P. bosquensis Kennedy, 1988, P. wyomingensis Meek, 1876, P. novimexicanus (Marcou, 1858), P. quadratus Cobban, 1953, P. germari (Reuss, 1845), P. pluricostatus n. sp., Prionocyclites mite Kennedy, 1988, and Reesidites minimus Hayasaka and Fukada, 1951. Collignoniceras woollgari, Prionocyclus hyatti, P. macombi, P. wyomingensis, P. novimexicanus, P. quadratus, and P. germari have been designated as zonal species in many publications, but aside from C. woollgari, P. hyatti, and P. wyomingensis,most of these species have not been well described in terms of their intraspecific variation. In many species, there is a gracile and a robust form, which may represent sexual dimorphs, but in most instances, the sample size of adult specimens is too small to prove this.
Open Access
Santonian ammonites from the Blossom Sand in northeast Texas. American Museum novitates ; no. 3332
(New York, NY : American Museum of Natural History, 2001) Kennedy, W. J. (William James); Landman, Neil H.; Cobban, William A., 1916-2015.
The Blossom Sand is a lateral equivalent of the Austin Chalk Group, developed in Fannin, Lamar, and Red River counties in northeast Texas. Ammonites from this unit are Placenticeras syrtale (Morton, 1834), Baculites sp. cf. haresi Reeside, 1927, and Glyptoxoceras texanum, n. sp. The general aspect of the Placenticeras assemblage suggests a late Santonian age for this unit.
Open Access
Scaphites of the "nodosus group" from the Upper Cretaceous (Campanian) of the Western Interior of North America. (Bulletin of the American Museum of Natural History, no. 342)
(American Museum of Natural History., 2010) Landman, Neil H.; Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Larson, Neal L.
Scaphitid ammonites (scaphites) are common in the Upper Cretaceous Pierre Shale and Bearpaw Shale of the Western Interior of North America. We redescribe Hoploscaphites nodosus (Owen, 1852) and H. brevis (Meek, 1876) from the Baculites compressus–B. cuneatus zones of the upper Campanian. The types of both of these species were collected in the mid-19th century in what was then called Nebraska Territory, and included parts of present-day South Dakota, North Dakota, and Montana. Based on our present knowledge of the distribution of these species, the type material was probably collected from the B. compressus–B. cuneatus zones in the Pierre Shale at Sage Creek, a tributary of the Cheyenne River, Pennington County, South Dakota. Traditionally, the more robust, more coarsely ornamented scaphites (comprising the "nodosus group") from the Pierre Shale and Bearpaw Shale were assigned to Jeletzkytes Riccardi, 1983, and the more slender, more finely ornamented scaphites were assigned to Hoploscaphites Nowak, 1911. However, our large collections of these scaphites from the Baculites compressus–B. cuneatus zones reveal a complete intergradation between the two morphological extremes, and for many specimens, the choice of genus is arbitrary. In addition, our studies of other biostratigraphic zones in the Pierre Shale and Bearpaw Shale reveal that cooccurring species of these two "genera" share more in common with each other than they do with congeneric species from other horizons. Furthermore, contrary to earlier assumptions, Jeletkytes is not endemic to the Western Interior Basin of North America and occurs, for example, in the U.S. Atlantic Coastal Plain and Europe. We thus provisionally treat Jeletzkytes as a junior subjective synonym of Hoploscaphites. This expanded definition of Hoploscaphites is consistent with present-day concepts of other scaphitid genera such as Discoscaphites Meek, 1876, and Trachyscaphites Cobban and Scott, 1964...
Open Access
Two species of Placenticeras (Ammonitina) from the Upper Cretaceous (Campanian) of the Western Interior of the United States. American Museum novitates ; no. 3173
(New York, N.Y. : American Museum of Natural History, 1996) Kennedy, W. J. (William James); Cobban, William A., 1916-2015.; Landman, Neil H.