Cretaceous Ammonites Research Articles

Report on the 5th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the Kilian Group (Ankara, Turkey, 31st August 2013)

The 5th meeting of the IUGS Lower Cretaceous Ammonite Working Group (the Kilian Group) held in Ankara, Turkey, 31st August 2013, discussed the Mediterranean ammonite zonation, and its calibration with different ammonite zonal schemes of the Boreal, Austral and Central Atlantic realms. Concerning the standard zonation, that corresponds to the zonal scheme of the West Mediterranean province, some changes have been made on two stages. For the Valanginian, the Busnardoites campylotoxus Zone was abandoned; the upper part of the lower Valanginian is now characterised by the Neocomites neocomiensiformis and Karakaschiceras inostranzewi zones. For the upper Barremian, the former Imerites giraudi Zone is here subdivided into two zones, a lower I. giraudi Zone and an upper Martellites sarasini Zone. The I. giraudi Zone is now subdivided into the I. giraudi and Heteroceras emerici subzones, previously considered as horizons. The current M. sarasini and Pseudocrioceras waagenoides subzones correspond to the lower and upper parts of the M. sarasini Zone, respectively. The Anglesites puzosianum Horizon is kept. The Berriasian, Hauterivian, Aptian and Albian zonal schemes have been discussed but no change was made. The upper Hauterivian zonal scheme of the Georgian (Caucasus) region (East Mediterranean province) has been compared with the standard zonation. Discussions and some attempts at correlations are presented here between the standard zonation and the zonal schemes of different palaeobiogeographical provinces: the North-West European area for the Valanginian and Hauterivian, the Argentinean region for the Berriasian, Valanginian and Hauterivian, and the Mexican area for the Valanginian–Hauterivian and Aptian–lower Albian. The report concludes with some proposals for future work.

Organic Origin of Pseudosutures in Late Cretaceous Ammonites

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New ammonoid taxa from the Lower Cretaceous Giumal Formation of the Tethyan Himalaya (Northern India)

AbstractKnowledge of the Early Cretaceous ammonoids of the NW‐Himalayas was poor until recent discoveries. Intense sampling from the Giumal Formation exposed near the village of Chikkim (Spiti Valley, Himachal Pradesh, India) led to the recognition of a new Early Cretaceous ammonoid fauna. The succession consists of arenitic sandstone interbedded with shale that was deposited by turbidity currents on an unstable shelf in the Early Cretaceous. Ammonoids have been obtained only from sandstone beds in the lower one‐third and close to the top of the c. 350‐m‐thick section. Eight new ammonoid taxa (1 genus and 7 species) are described: Sinzovia franki sp. nov. (rare), Giumaliceras giumaliense gen. et sp. nov. (abundant), Giumaliceras bhargavai gen. et sp. nov. (rare), Neocomites (Eristavites) platycostatiformis sp. nov. (rare), Cleoniceras oberhauseri sp. nov. (abundant), Australiceras himalayense sp. nov. (rare) and Deshayesites fuchsi sp. nov. (rare). Sinzovia and Deshayesites are reported for the first time from the Tethyan Himalaya. According to the biostratigraphic relevance of some ammonoid taxa described here, the age of the Giumal Formation can be constrained from Berriasian (Giumaliceras assemblage) to Aptian (Cleoniceras assemblage). The discovery of the new fauna substantiates the significance of the Giumal Formation around Chikkim and facilitates comparison with faunal assemblages from other regions in the Tethys Ocean and beyond.

Nearly circular, oval and irregular holes in Cretaceous ammonoids from Nigeria

Nearly circular-, oval- and irregular-shaped holes are present in a collection of Late Cretaceous ammonoid cephalopods from southern Nigeria. Two competing hypotheses have been advanced to explain these holes: one is they were produced by diagenetic crushing of limpet home scars and the other is that they are predator's teeth marks. The latter explanation appears to be the best explanation for some of the damage seen in the Nigerian specimens. The suspected predator for some of the specimens was probably an unidentified reptile based on the diameters of the holes. Insofar as we are aware, this is the first recorded predatory damage reported on Cretaceous ammonoids from West-Central Africa.

The climate of the Late Cretaceous: New insights from the application of the carbonate clumped isotope thermometer to Western Interior Seaway macrofossil

We apply the carbonate clumped isotope thermometer (Δ47) to macrofossils from the Baculites compressus (∼73.5Ma) and the Hoploscaphites nebrascensis (∼67Ma) ammonite zones of the Western Interior Seaway (WIS) of North America, and nearby coeval terrestrial and open marine environments. The carbonate clumped isotope thermometer is based on a single-phase isotope exchange equilibrium that promotes the ‘clumping’ of two heavy isotopes together within a single carbonate molecule as temperature decreases. Due to the thermometer's isotopic independence from water, coupled measurements of Δ47 and the bulk oxygen isotopic composition of a carbonate (δ18Oc) enable the reconstruction of both paleotemperature and the isotopic composition of the water in which the organisms grew. Before applying the technique to the aragonite shells of fossil marine organisms (mostly ammonites, but also some gastropods, bivalves, and one belemnite), we measure the clumped isotopic composition of modern nautilus and cuttlefish, two of the nearest living relatives to the Cretaceous ammonites. Modern cephalopods exhibit disequilibrium isotope effects with respect to Δ47, but not δ18Oc, therefore a simple correctional scheme is applied to the Late Cretaceous macrofossil data before reconstructing paleotemperatures. Diagenesis is also assessed by visual preservation and previously measured Sr concentrations (Cochran et al., 2003). Temperatures reconstructed for the Late Cretaceous Western Interior Seaway range from 16.4±3.5°C for an offshore Interior Seaway environment from the H. nebrascensis zone to 24.2±0.4°C for the B. compressus ammonite zone. The seaway itself has an isotopic composition of approximately −1‰ (relative to VSMOW), the expectation for an ice-free global ocean average, while a nearby freshwater environment has an isotopic composition approaching −20‰. We compare the attributes of the reconstructed climate to predictions based on Late Cretaceous climate models and previous reconstructions of the seaway, and also assess the sensitivity of our results to the modern cephalopods correction by comparisons to suitable modern analogs. Finally, our clumped isotope data are consistent with cooling between the Late Campanian and Maastrichtian, as also seen in benthic foraminfera δ18O.

The Last Cretaceous Ammonites in Latin America

Sections yielding late Maastrichtian ammonite assemblages are rare in Latin America and precise biostratigraphic correlation with European type sections remains difficult. In all, the extinction pattern of ammonites appears to differ between sites in southern high latitudes and those in the tropics to subtropics. In austral sections of Chile, and possibly also in southern Argentina, diverse assemblages range throughout most of the substage and then show a gradual decline prior to the Cretaceous—Paleogene (K—Pg) boundary. Further north, in northeast Brazil, only two genera (Diplomoceras, Pachydiscus) range into the uppermost Maastrichtian, but disappear within the last 0.3 Ma of the Cretaceous. In tropical sections of Columbia and Mexico, the decline of ammonites started earlier and Sphenodiscus is the last ammonite known to occur in the late Maastrichtian. In all sections revised here the disappearance of ammonites was completed prior to the end of the Maastrichtian and was thus independent of the asteroi...

The radula of the Late Cretaceous scaphitid ammonite Rhaeboceras halli (Meek and Hayden, 1856)

Abstract: Radular teeth occur between the jaws in two specimens of the Late Cretaceous scaphitid ammonite Rhaeboceras halli (Meek and Hayden, 1856) from the Western Interior of the United States. The detailed morphology of the teeth has been revealed by propagation phase contrast X‐ray synchrotron microtomography. Each row of the radula of R. halli consists of a total of seven teeth (a central rachidian, two pairs of lateral and one pair of marginal teeth), as in other known ammonoid radulae, although the central tooth could not be confirmed in the specimens examined. The lateral teeth are multicuspid and robust, and the marginal teeth are long (4.6 mm) and slender. In overall morphology, the heterodont and ctenoglossan radula of R. halli is similar that of Jurassic and Cretaceous ammonites with the same aptychus‐type lower jaw, that is, the Aptychophora. This discovery reveals the range of variation in radular morphology, which could be related to ecological or phylogenetic factors. It also invalidates the hypothesis that the hook‐like structures in R. halli previously described are radular elements.

Different modes of migration among Late Cretaceous ammonoids in northwestern Hokkaido, Japan: evidence from the analyses of shell whorls

The thickness ratios of shell whorls (=whorl breadth/shell diameter) in the ammonoidsDamesites sugata(Forbes, 1845),Hypophylloceras subramosum(Shimizu, 1934), andGaudryceras tenuiliratumYabe, 1903 from Late Cretaceous outer shelf deposits in the Kotanbetsu area of northwestern Hokkaido, Japan, were examined in order to determine their mode of migration. The thickness ratios ofD. sugatadiffer significantly with depth on the outer shelf environment but show no significant difference laterally at a similar depth. These results suggest thatD. sugatadid not frequently migrate to different depths on the outer shelf environment but tended to live and migrate laterally at a similar depth on the outer shelf. The thickness ratios ofH. subramosumandG. tenuiliratumshow no significant difference between different depths on the outer shelf environment or for lateral direction at a similar depth. This suggests thatH. subramosumandG. tenuiliratumfrequently migrated at different depths on the outer shelf environment and laterally at a similar depth. There is no difference in hatchling diameters in all the examined species at different depths on the outer shelf environment, suggesting that the thickness ratios became manifest after the post-hatchling stage due to limited migration, which would have been in a nektobenthic habitat. The various modes of migration in the study area are reconstructed in this study, suggesting diversified paleoecology of Late Cretaceous ammonoids.

Early Cretaceous ammonite fauna of Catanduanes Island, Philippines

Nine Aptian to early Albian ammonoid species, apparently from the Yop Formation, in Catanduanes Island, Philippines, are described herein: Goretophylloceras sp., Eogaudryceras (Eotetragonites) sp., Notosilesitoides philippinensis gen. et sp. nov., Miyakoceras tanohatense, Neosilesites nepos, Neoastieria? sp., Marshallites miyakoensis, Colombiceras cf. satowi and Colombiceras sp. This is the first systematic palaeontological report of Cretaceous ammonoids from the Philippines. Among the described species, Notosilesitoides philippinensis is proposed as a new genus and species. This fauna shows close similarity to that of the Tomochi Formation, Choshi Group, and the Miyako Group in Japan. These faunas were in a warm current regime that extended from the equator. The age and palaeogeographical significance of the assemblage is discussed.

Geochronological constraints on post-extinction recovery of the ammonoids and carbon cycle perturbations during the Early Jurassic

This paper presents the first quantitative study of the Early Jurassic recovery of ammonoids after the end-Triassic mass extinction based on detailed U–Pb ID-TIMS (isotope dilution thermal ionization mass spectrometry) geochronology from ash bed zircons placed within a clear phylogenetical and biochronological framework at the subzonal and species level. This study was triggered by the discovery of a rich Peruvian succession of ammonites, deposited concomitantly with an unusually large number of ash beds. Two major phases of rediversification are observed during the Psiloceras spelae and Angulaticeras zones that correspond to positive peaks in the δ13Corg curve, providing a possible link between biodiversity and the global carbon cycle.In the case of the post-extinction recovery, the development of the earliest Hettangian ammonites occurs within the genus Psiloceras, which begins with the occurrence of P. spelae and then explodes into worldwide development of smooth psiloceratids of the Psiloceras planorbis group s.l. This rapid biodiversification likely occurred less than 100ka after the end-Triassic crisis; the genus Psiloceras occupied all the possible ecological niches worldwide, from the Pacific deep waters to the NW European shallow deposits and also in some rare Tethyan occurrences like at Germig in Tibet. This global dispersion allowed the differentiation of the group in several major phyla, the Schlotheimiidae, Discamphiceratinae, Arietitidae and Lytocerataceae, which were the roots of all other Jurassic and Cretaceous ammonites.

Paleogeography of Cretaceous ammonoids of the Pacific coast of Russia

This work presents the results of a study of the biogeographical distribution of Late Albian-Maastrichtian ammonites, found in sequences of the Pacific coast of Russia. The taxa typical of the Pacific Realm were identified, and their distribution traced beyond the borders of this region. In addition, species-migrants, distributed within the studied area were established. As a results of our works, a high level of endemism of ammonite fauna of the East of Russia was noted (75–88% of endemic species, on average). The bipolarity, previously established in the distribution of ammonoids within the Pacific Paleobiogeographical Realm, as well as their high regional provincialism, was confirmed.

Variable growth modes in Late Cretaceous ammonoids: implications for diverse early life histories

Examination of ontogenetic changes in the septal angle of Late Cretaceous ammonoids (ten species representing seven superfamilies and four suborders) reveals four patterns: 1) a single abrupt change in septal angle; 2) two abrupt changes in septal angle; 3) cyclic fluctuations in septal angle throughout ontogeny; and 4) an almost constant septal angle throughout ontogeny. These various septal-angle patterns in Late Cretaceous ammonoids are in contrast with modern and fossil nautiloids, which have the common pattern displaying a single abrupt change in septal angles. Although the abrupt change of septal angles in nautiloids corresponds with the hatching event from the egg, change of septal angles in the examined ammonoids is hypothesized to correspond not to hatching but to the change from a planktic to a nektobenthic habit demarcated by the post-embryonic stage. Therefore, the variable patterns of septal angles within ammonoids suggest a diverse set of early life histories.

Lower Cretaceous ammonites from the Neuquén Basin, Argentina: A new heteromorph fauna from the uppermost Agrio Formation

Although the Agrio Formation (Valanginian–Early Barremian) yields rich ammonite faunas at many levels, the highest beds are very sparsely fossiliferous. However, intensive collecting over the years has yielded a sparse fauna of heteromorph ammonites that are completely new to Argentina. Three taxa are represented, Sabaudiella riverorum sp. nov., Curacoites rotundus gen. et sp. nov. and Hamulinites? sp. The fauna is placed in a new ammonite zone of Sabaudiella riverorum and dated as latest Hauterivian–Early Barremian.

Confidence intervals for the duration of a mass extinction

A key question in studies of mass extinctions is whether the extinction was a sudden or gradual event. This question may be addressed by examining the locations of fossil occurrences in a stratigraphic section. However, the fossil record can be consistent with both sudden and gradual extinctions. Rather than being limited to rejecting or not rejecting a particular scenario, ideally we should estimate therangeof extinction scenarios that is consistent with the fossil record. In other words, rather than testing the simplified distinction of “sudden versus gradual,” we should be asking, “How gradual?”In this paper we answer the question “How gradual could the extinction have been?” by developing a confidence interval for the duration of a mass extinction. We define the duration of the extinction as the time or stratigraphic thickness between the first and last taxon to go extinct, which we denote by Δ. For example, we would like to be able to say with 90% confidence that the extinction took place over a duration of 0.3 to 1.1 million years, or 24 to 57 meters of stratigraphic thickness. Our method does not deny the possibility of a truly simultaneous extinction; rather, in this framework, a simultaneous extinction is one whose value of Δ is equal to zero years or meters.We present an algorithm to derive such estimates and show that it produces valid confidence intervals. We illustrate its use with data from Late Permian ostracodes from Meishan, China, and Late Cretaceous ammonites from Seymour Island, Antarctica.

Discovery ofAinoceras(Ammonoidea) from the Upper Cretaceous Futakawa Formation in the Aridagawa Area, Wakayama, Southwestern Japan

Abstract. Late Cretaceous heteromorph ammonoids, Ainoceras kamuy and Ainoceras paucicostatum, were discovered for the first time from the Futakawa Formation in the Aridagawa area, Wakayama, southwestern Japan. Other molluscan fossils such as Eupachydiscus sp., Gaudryceras aff. striatum, “Gigantocapulus” transformis, Sphenoceramus nagaoi, Sphenoceramus orientalis and Inoceramus balticus also cooccur with Ainoceras, and together they indicate the lower Campanian Stage. Recently, the middle Turonian—Santonian and upper lower Campanian—Maastrichtian litho- and biostratigraphy in the Aridagawa area was established. Therefore, the lower Campanian strata in the study area fill the gap between them and supplement the Upper Cretaceous stratigraphy in the Aridagawa area. The results of this study advance the biostratigraphy and correlation of the marine Cretaceous strata in the northwestern Pacific region.

Report on the 4th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the “Kilian Group” (Dijon, France, 30th August 2010)

The 4th Kilian Group meeting (Dijon, France, 30th August 2010) focused on the Aptian and Albian Stages. For the Aptian, a two-fold division of the stage was adopted for the Mediterranean area with a boundary between the Dufrenoyia furcata and Epicheloniceras martini Zones. The main changes to the zonal scheme concern the Lower Aptian with: the introduction of a Deshayesites luppovi Subzone in the upper part of the Deshayesites oglanlensis Zone; the replacement of Deshayesites weissi by Deshayesites forbesi as new index-species of the second interval zone; the introduction of a Roloboceras hambrovi Subzone in the upper part of the D. forbesi Zone; and the subdivision of the D. furcata Zone into the D. furcata and Dufrenoyia dufrenoyi Subzones. For the Albian, the upper part of the Douvilleiceras mammillatum Zone (Lower Albian) is now characterized by a Lyelliceras pseudolyelli Subzone. The main amendments concern the Upper Albian. The base of this substage is defined by the base of the Dipoloceras cristatum Zone. Above it, the Upper Albian zonal scheme comprises in stratigraphic order the Mortoniceras pricei, Mortoniceras inflatum, Mortoniceras fallax, Mortoniceras rostratum, Mortoniceras perinflatum and Arrhaphoceras briacensis Zones.

Microstructure and mineralogy of the outer calcareous layer in the lower jaws of Cretaceous Tetragonitoidea and Desmoceratoidea (Ammonoidea)

Tanabe, K., Landman, N.H. & Kruta, I. 2011: Microstructure and mineralogy of the outer calcareous layer in the lower jaws of Cretaceous Tetragonitoidea and Desmoceratoidea (Ammonoidea). Lethaia, Vol. 45, pp. 191–199. Based on the differences in their relative size, overall shape, structure and the degree of development of an outer calcified covering, lower jaws of the Ammonoidea have been classified into four morphotypes: normal, anaptychus, aptychus and rhynchaptychus types. However, detailed microstructural and mineralogical comparison of these morphotypes has not yet been addressed. This article documents the results of SEM and XRD observations of the lower jaws of three Late Cretaceous ammonoid species belonging to the Tetragonitoidea (Anagaudryceras limatum) and Desmoceratoidea (Pachydiscus kamishakensis and Damesites aff. sugata), based on excellent material preserved in situ within the body chamber, and retaining an aragonitic shell wall. The lower jaws of the three species are assigned to an intermediate form between anaptychus and aptychus types for the first two species and the rhynchaptychus type for the third species. Their black, presumably originally chitinous outer lamella is wholly covered with a calcareous layer. The calcareous layer is composed of aragonite in D. aff. sugata and A. limatum, and calcite in P. kamishakensis. The microstructure of the outer calcareous layer differs among the three species, i.e. granular in A. limatum, spherulitic prismatic in D. sugata, and prismatic in P. kamishakensis, all of which can be distinguished from the lamellar and spongy structure of the outer-paired calcitic plates of the typical aptychus-type lower jaws in some Jurassic and Cretaceous Ammonitina and Ancyloceratina. Our study suggests that most Jurassic and Cretaceous ammonoids possessed an outer calcareous layer in their lower jaws, although its mineralogy, microstructure and relative thickness vary among different taxa. □Ammonoidea, Cretaceous, Desmoceratoidea, lower jaw, microstructure, Tetragonitoidea.

Jurassic–Cretaceous boundary ammonite Blanfordiceras (Mollusca: Cephalopoda) from Fortissimo-1 Wildcat Well, Browse Basin, Northwest Shelf, Australia

Jurassic–Cretaceous ammonites are particularly robust fossil tools in global stratigraphy and correlation. The successive evolution and extinction of these cephalopod mollusks was so rapid that many ammonite zones are no more than one million years in duration. A well-preserved ammonite specimen from the Fortissimo-1 core, Browse Basin, NW Australia is assignable to the widespread latest Jurassic dimorphic berriaselline genus, Blanfordiceras Cossmann, recorded previously from the Spiti area, Nepal, Tibet, Madagascar, Papua-New Guinea, Antarctica, and southern South America. This is the first report of ammonites of this age in the Australian region. The evolute shell of an estimated 90-100 mm diameter (when extrapolated) and pronounced ornamentation of variably bifurcating, curvilinear and flexuous ribs, intercalated with simple, non-bifurcating ribs, is consistent with Blanfordiceras wallichi (Gray, 1832), which has traditionally been restricted to the uppermost Tithonian Stage, ca. 146.5-145.5 Ma, but may well have survived into the earliest part of the Berriasian. The first recorded occurrence of this ammonite in Australia fills an anomalous absence in the paleobiogeographic distribution of Jurassic–Cretaceous boundary ammonites in the Indo-SW Pacific Subrealm with important implications for the calibration of offshore rocks and wells in Australia.

Phenotypic plasticity of Acanthoscaphites tridens (Late Cretaceous ammonites): additional data

The concept of phenotypic plasticity of the temporal species Acanthoscaphites tridens s. str., as recently proposed by myself is elaborated upon, in response to issues raised in a commentary to the original paper. The terms phenomorphic class and dominant phenotype are explained in greater detail, as well as the evaluation of phenotypic plasticity in studies for extinct species.

Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido, Japan: implication for planktic duration at early ontogenetic stage

Tajika, A. & Wani, R. 2011: Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido, Japan: implication for planktic duration at early ontogenetic stage. Lethaia, Vol. 44, pp. 287–298. Intraspecific variations of the early shell dimensions (ammonitella and protoconch diameters) of two Late Cretaceous (earliest Campanian) ammonoid species (Gaudryceras tenuiliratum and Hypophylloceras subramosum) from the Haboro and Ikushumbetsu areas, Hokkaido, Japan, show no significant difference between these areas that are approximately 110 km apart. The geographic distributions of G. tenuiliratum and H. subramosum are supposed to be mainly controlled by the flotation and transportation during the embryonic stage within floating egg masses and/or post-embryonic stage because of their small hatchling sizes (1.18–1.46 mm in diameter for G. tenuiliratum, and 0.91–1.13 mm in diameter for H. subramosum), suggesting these two ammonite species at the embryonic and/or post-embryonic stages were transported at least 110 km. Postulating that the velocity of palaeocurrent around the Haboro and Ikushumbetsu areas during the Cretaceous Period was 0.25 m/s, similar to those in the modern ocean current flowing off the eastern Pacific coast of Hokkaido, the egg masses and/or hatchlings of G. tenuiliratum and H. subramosum were buoyant and transported more than 5 days. The preliminary comparison of hatchling size through time suggests that the hatching sizes of H. subramosum in Hokkaido increased slightly from the Middle Turonian until the earliest Campanian (during about 7 Myr). □ammonoid, hatchling, paleoecology, variation, Cretaceous.