Ammonoidea Research Papers - Academia.edu (original) (raw)

"The principal conch parameters—whorl expansion rate, whorl overlap rate, umbilical width, and whorl thickness—of Early and Middle Devonian ammonoids have been extensively investigated. Stratophenetic analyses show long-term trends in... more

"The principal conch parameters—whorl expansion rate, whorl overlap rate, umbilical
width, and whorl thickness—of Early and Middle Devonian ammonoids have been extensively investigated.
Stratophenetic analyses show long-term trends in the transformations of these characters
over long periods of time, but sudden and rapid reversals can also be observed. On the basis
of these four quantifiable conch parameters and supplementary qualitative characters, ten ammonoid
morphs were distinguished. Reconstruction of the evolutionary history of these morphs
reflects the existence of two major phylogenetic lineages, both already visible in Early Devonian
faunas. The agoniatitid lineage is characterized by slow character development and leads to the
Frasnian gephuroceratids; the anarcestid lineage displays rapidmorphological evolution that leads
to the late Givetian pharciceratids as well as the Middle and Late Devonian tornoceratids. Morphological
evolution is interpreted as partly limited by geometrical and physical constraints."

Ammonoids had high evolutionary rates and diversity throughout their entire history and played an important role in the high-resolution subdivision of the Mesozoic, but much of their palaeobiology remains unclear, including the brooding... more

Ammonoids had high evolutionary rates and diversity throughout their entire history and played an important role in the high-resolution subdivision of the Mesozoic, but much of their palaeobiology remains unclear, including the brooding habitat. We present our study of the first recorded ammonite embryonic shell clusters preserved with calcified embryonic aptychi in situ within the body chambers of mature macroconch shells of the Early Aptian (Early Cretaceous) ammonite Sinzovia sazonovae. The following support the idea that the clusters are egg masses, which developed inside ammonite body chambers: the absence of post-embryonic shells and any other fossils in these clusters, the presence of the aptychi in all embryonic shell apertures and peculiarities of adult shells preservation. These facts confirm earlier speculations that at least some ammonoids could have been ovoviviparous and that, like many modern cephalopods, they could have reproduced in mass spawning events. The aptychi of ammonite embryonic shells are observed here for the first time, indicating that they were already formed and calcified before hatching. Our results are fully congruent with the peculiar modes of ammonoid evolution: quick recovery after extinctions, distinct evolutionary rates, pronounced sexual dimorphism and the nearly constant size of embryonic shells through ammonoid history. We assume that adaptation to ovoviviparity may be the reason for the presence of these features in all post-Middle Devonian ammonoids.

Two sections were sampled and measured at Mdâour-El-Kbîr (Dra Valley, western Anti-Atlas) and at eastern Ouidane Chebbi (Tafilalt, eastern Anti-Atlas). In situ elements of two partially limonitized and one carbonatic fauna were found in... more

Two sections were sampled and measured at Mdâour-El-Kbîr (Dra Valley, western Anti-Atlas) and at eastern Ouidane
Chebbi (Tafilalt, eastern Anti-Atlas). In situ elements of two partially limonitized and one carbonatic fauna were found
in both sections. We report this fauna from the upper Merzâ-Akhsaï Formation and the lower Mdâour-el-Kbîr Formation
at Mdâour-el-Kbîr for the first time. Based on these faunas, we recorded a correlation of the early Emsian (Zlíchovian)
strata in the Tafilalt and the Dra Valley regions, which are about 350 km apart. Additionally, new ammonoid finds
(Teicherticeras cf. senior, Lenzites gesinae, Weyeroceras angustus) are figured and described including the stratigraphic
context. The diagnoses of Lenzites gesinae and Weyeroceras angustus are emended. Tabulate corals (Michelinia
mdaourensis sp. nov., Petridictyum sp.) found in both the Tafilalt and Dra Valley are figured and described for the first
time. • Key words: early Emsian, Ammonoidea, Tabulata, Micheliniidae, biostratigraphy, Anti-Atlas, Morocco.

Ammonites of the genus Santafecites Etayo-Serna and subgenus Olcostephanus (Viluceras) Aguirre-Urreta and Rawson are described for the first time from Chile. The succession of Olcostephaninae from the Chañarcillo Basin of northern Chile... more

Ammonites of the genus Santafecites Etayo-Serna and subgenus Olcostephanus (Viluceras) Aguirre-Urreta and Rawson are described for the first time from Chile. The succession of Olcostephaninae from the Chañarcillo Basin of northern Chile is described in the light of new collections and revision of historical material. The occurrence of mixed Andean and Mediterranean faunas supports the correlations proposed with the ammonite scales of the Neuquén Basin and the Mediterranean Province.

The findings of fossilized ammonite soft tissues are extremely rare, so each specimen may be important for understanding the anatomy of these cephalopods. This paper deals with soft tissue fragments and imprints preserved in the rear part... more

The findings of fossilized ammonite soft tissues are extremely rare, so each specimen may be important for understanding the anatomy of these cephalopods. This paper deals with soft tissue fragments and imprints preserved in the rear part of the body chamber of the Middle Jurassic ammonite Cadoceras stupachenkoi (Mitta) from Central Russia. At the base of the body chamber of this ammonite in front of the last septum, a mantle fragment with clearly visible longitudinal fibers and imprints of the palliovisceral ligament are preserved. In front and slightly to the side of the mantle fragment, a small area with branched structures is located; probably, these structures are fragments of gills.
In general, the structure of the soft tissues in the rear part of the ammonite body looks very similar to that of modern nautilids, with one exception: mantle fibers are not directed forward as observed in Nautilus, but to the mid-ventral line, probably to the ventral muscle.

From thinly laminated marlstones of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north-west Germany), 17 sediment-compacted baculitid... more

From thinly laminated marlstones of the Hesseltal
Formation, representing the Late Cenomanian Oceanic
Anoxic Event (OAE) 2, at Lengerich in the Teutoburger
Wald (Westfalen, north-west Germany), 17 sediment-compacted
baculitid ammonites with carbonised and partially
phosphatised soft parts are recorded. Some preserve remains
of the buccal mass, including jaws (occasionally articulated)
and radulae, as well as of the cephalic cartilage, such as eye
capsules. Such have not yet been recorded previously for the
order Ammonoidea. In addition, originally unmineralised
parts found preserved in these specimens include extensive
portions of the digestive tract, the siphonal tube, false colour
patterns (megastriae), as well as traces of what would appear
to be the oviduct. At the same levels, patches with numerous
isolated horny upper and rarer lower jaws as well as radulae
occur; these may represent regurgitates or faeces of larger
predators. The cephalopod remains described were deposited
in an epicontinental setting, possibly at palaeodepths between
200 and 600 m. In this particular Late Cretaceous fossil
Lagersta¨tte, upper jaws and anaptychi of ammonites rank
among the commonest fossils.

ARMBRUSTER, J. & KLUG, C.

Complete ammonoid mouth parts including both mandibles and the radula are rare. A newly prepared specimen of Ceratites penndorfi of the late Anisian from the Franconian Muschelkalk reveals one such anaptychus-type jaw apparatus including... more

Complete ammonoid mouth parts including both mandibles and the radula are rare. A newly prepared specimen of Ceratites penndorfi of the late Anisian from the Franconian Muschelkalk reveals one such anaptychus-type jaw apparatus including several more or less clearly recognisable structures such as the shapes and proportions of the inner and outer lamellae of both mandibles. The lower mandible has a short inner and a long outer lamella with an ovoid outline, while the upper mandible has a slightly arched rostrum and the inner lamella carries two wings. The radula, as far as it is preserved, appears to be homodont with oblique, simply conical, monocuspidate teeth. Some other structures are here illustrated, described and interpreted as both mandibles and oesophageal remains. Additional structures of organic origin are preserved such as the radula, but others are difficult to interpret. Some, if not all, of these structures also were body parts of the ceratite, such as perhaps the radular support and/or the oesophagus. All mouthparts, which are preserved in the specimen described herein, are carbonised except for the radula remains, which are phosphatic. The taphonomy of ceratite mouth parts in the Muschelkalk is shortly discussed.

The acrioceratid ammonite genus Toxoceratoides Spath has long been used to accommodate any late Barremian or Aptian species that show morphological similarities with its type species Toxoceratoides royeri (d'Orbigny). The revision of T.... more

The acrioceratid ammonite genus Toxoceratoides Spath has long been used to accommodate any late Barremian or Aptian species that show morphological similarities with its type species Toxoceratoides royeri (d'Orbigny). The revision of T. royeri and its allied species T. rochi Casey has convinced us that new genera should be introduced for some Aptian forms that were previously referred to Toxoceratoides. These are Klingerites gen. nov. (type species: Toxoceratoides? haughtoni Klinger & Kennedy), Richardreymentella gen. nov. (type species: Ancyloceras patagonicum Stolley), Immelites gen. nov. (type species: Tonohamites multituberculatus Immel & Guoxiong), Jenslehmannella gen. nov. (type species Jenslehmannella bangestanense gen. et sp. nov.). This contribution also reconsiders the taxonomic value of Tonohamites Spath, Colomboceratoides Etayo Serna and Raymondcaseyites Avram. The new taxonomic treatment proposed herein outlines the diversity and provincialism of the Acrioceratidae during Aptian times and questions the alleged cosmopolitan distribution of Toxoceratoides.

The Prionocyclus germari Zone is recognized for the first time in the Vocontian Basin. The upper part of the " calcaires blancs a silex " of the western Dieulefit syncline is characterized by the zonal index and a diverse ammonite fauna,... more

The Prionocyclus germari Zone is recognized for the first time in the Vocontian Basin. The upper part of the " calcaires blancs a silex " of the western Dieulefit syncline is characterized by the zonal index and a diverse ammonite fauna, as well as inoceramids of the Mytiloides scupini Zone. The co-occurring het-eromorph ammonites Hyphantoceras (Hyphantoceras) flexuosum (Schlüter, 1872) and H. (H.) ernsti Wiese, 2000 suggest a correlation with the Heteromorph Beds and the flexuosum Sequence of northern Ger-many. The co-occurrence of Prionocyclus germari (Reuss, 1845) and the bivalve Didymotis sp. in the overlying " gr es jaunes " suggests a correlation with the Didymotis Sequence of northern Germany. The presence of the nannofossil Broinsonia parca expansa Wise & Watkins, 1983 and absence of younger marker species indicate the upper Turonian to lower Coniacian nannofossil zone UC9c. The boundary between the " calcaires blancs a silex " and the " gr es jaunes " is interpreted as a sequence boundary linked to a eustatic rise of sea level. The event is correlated with the flexuosumeDidymotis sequence boundary of northern Germany and can be traced in northern Spain and the Czech Republic. Vocontiiceras vocontiense nov. gen. et sp. of the Family Collignoniceratidae shows a distinct ontogeny: an involute juvenile stage with Reesidites-like ornamentation and a single row of ventrolateral tubercles, and a smooth adult stage with a persistent keel and a short rostrum. The new species probably represents an evolutionary link between the subfamilies Collignoniceratinae and Barroisiceratinae.

Evolution of the coiled ammonoid conch from the uncoiled bactritid conch was probably coupled with changes in ma− noeuvrability and swimming velocity. The gradual transformation of uncoiled to coiled ammonoid conchs has essential... more

Evolution of the coiled ammonoid conch from the uncoiled bactritid conch was probably coupled with changes in ma− noeuvrability and swimming velocity. The gradual transformation of uncoiled to coiled ammonoid conchs has essential functional consequences. The radical change in conch geometry during phylogeny but also in ontogeny of early ammonoids implies a shift of the aperture from an original roughly downward, via a downward oblique and an upward oblique to an upward orientation, presuming a neutrally buoyant condition of the ammonoid animal. Similar trends were reconstructed for the three main ammonoid lineages in the Middle Devonian, the agoniatitid, the anarcestid, and the tornoceratid lineages. This allowed an increase in manoeuvrability and in the maximum horizontal swimming speed.

Thin, dark, probably phosphatic coatings were found on the dorsum in front of and sometimes behind the aperture of 50 specimens of Paraceratites and Ceratites (Ammonoidea) belonging to 14 species and subspecies and in three specimens of... more

Thin, dark, probably phosphatic coatings were found on the dorsum in front of and sometimes behind the
aperture of 50 specimens of Paraceratites and Ceratites (Ammonoidea) belonging to 14 species and subspecies and in
three specimens of Germanonautilus, all from theMiddle Triassic of Germany. The proportions, occurrences, position,
outline, and preservation in fossil Nautiloidea and Ammonoidea (originally organic matter) of this structure support
the hypothesis that it is homologous with the black layer in Recent Nautilus and Allonautilus. It is not yet possible to
test whether these cephalopods show homologous styles of the development of these structures or whether the black
layer can be identified in a common ancestor. In contrast to many ammonoids, Ceratites, Paraceratites, most
Palaeozoic ammonoids, and some Mesozoic ammonoids probably did not have lower mandibles that were suitable for
the closure of the aperture. They probably possessed a dorsally extending mantle (supracephalic mantle fold) and a
hood, as in Recent Nautilus and Allonautilus, that was attached to the black layer. This interpretation is corroborated by
a similar morphology of the black layer in an adult specimen of the nautilid Cenoceras from the South German Middle
Jurassic and three specimens of Germanonautilus from the South German Middle Triassic (both Nautiloidea).

A new type of shell damage on Late Jurassic ammonite Kachpurites fulgens is described. The new type of shell malformation consists of small elongated pits, arranged in groups on the surface of ammonite shell and concentrated near the... more

A new type of shell damage on Late Jurassic ammonite Kachpurites fulgens is described. The new type of shell malformation consists of small elongated pits, arranged in groups on the surface of ammonite shell and concentrated near the terminal aperture. The examination of the pits demonstrated no signs of drilling, biting, or healing of punctures. The shell layers in the pits are bent downward without changing in thickness. At the same time the pits, in some cases, significantly distort the shape of the shell walls. Deformed growth lines are associated with some of the pits. All of this supports the hypothesis that the pits had been formed by epifauna located at a flexible uncalcified part of the periostracum in the apertural region of the growing ammonite shell. It is likely that epizoan attachment led to the deformation of the thin periostracum film and to the distortion of the growing shell wall. The nature of epizoans is discussed, but remains unclear due to their rather poor preservation. The relationship between epizoans and ammonites is also an open question: they could have been parasites, but other types of biotic relationships cannot be entirely ruled out.

Based on new material collected from the Risan Aneiza Formation at Gabal Maaza (Maghara area, Sinai), the occurrence of the cosmopolitan Albian genus Douvilleiceras is unequivocally documented for the first time in Egypt. Douvilleiceras... more

Based on new material collected from the Risan Aneiza Formation at Gabal Maaza (Maghara area, Sinai), the occurrence of the cosmopolitan Albian genus Douvilleiceras is unequivocally documented for the first time in Egypt. Douvilleiceras orbignyi, a species known to characterise the middle to uppermost lower Albian of Western Europe, is identified. The taxonomy, palaeogeography and population dynamics of the hypernodose forms of Douvilleiceras, e.g. the "aequinodum" group of the literature are discussed.

In the Tuorasis Formation section of the lower reaches of Lena River (Northern Verkhoyansk Region, Kharaulakh ridge) were first found of the goniatite Svetlanoceras, defined as S. strigosum (Ruzhencev), which had previously been known... more

In the Tuorasis Formation section of the lower reaches of Lena River (Northern Verkhoyansk Region, Kharaulakh ridge) were first found of the goniatite Svetlanoceras, defined as S. strigosum (Ruzhencev), which had previously been known only in the Southern Urals. Kharaulakh Svetlanoceras were found at the same level with numerous Bulunites mezhvilki Andrianov (the species-index of the same ammonoids Beds of the Lower Permian in the Verkhoyansk Region) and with single Eoasianites maximovae (Andrianov). The finds of S. strigosum indicates migration of the South Ural Ammonoids in the Kharaulakh subzone of the Verkhoyansk water area of Khorokytian age and suggests the Asselian age of the Khorokytian Ammonoids Asociatian, which characterizes the Bulunites mezhvilki Beds of the Khorokytian Horizon in the Verkhoyansk Region.

The aim of this paper is to document the ammonite fauna of the upper part of the Late Tithonian collected at the key section of Le Chouet (Drome, SE France). Emphasis is laid on new and poorly known Ataxioceratidae, Himalayitidae and... more