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"The Cephalopod Macrosystem: A Historical Review, the Present State of Knowledge, and Unsolved Problems: 3. Classification of Bactritoidea and Ammonoidea"
Abstract
A new classification is proposed in which Bactritoidea and Ammonoidea are considered as subclasses. The subclass Bactritoidea
includes a single order, Bactritida. The subclass Ammonoidea includes ten orders: Anarcestida (suborders Agoniatitina, Auguritina,
Anarcestina, Gephurocerina, Timanocerina, and Prolecanitina), Tornocerida, Goniatitida (with suborders Goniatitina and Cyclolobina),
Praeglyphiocerida, Clymeniida (with suborders Gonioclymeniina and Clymeniina), Medlicottiida, Ceratitida (with suborders Paraceltitina,
Otocerina, Meekocerina, Sagecerina, Ptychitina, Ceratitina, Pinacocerina, Megaphyllitina, Arcestina, and Lobitina), Phyllocerida,
Lytocerida (with suborders Lytocerina and Turrilitina), and Ammonitida (with suborders Psilocerina, Haplocerina, Stephanocerina,
Cardiocerina, and Ancylocerina).
... Systematics of higher ammonite taxa used herein is based on Besnosov and Michailova (1991) with some additions from Kvantaliani et al. (1999) and Shevyrev (2006). As aptychi usually occurred outside the host conchs and their relation to ammonoid taxa are unclear, generic and species names used for aptychi are separate from those of ammonoid shells and treated as parataxa (Engeser and Keupp 2002). ...
... Keupp and Mitta 2013 Dorsoplanitidae Fig. 7 Aptychi distribution among the selected Middle Jurassic-Early Cretaceous ammonite lineages. Ammonoid suborders and evolution of lineages are given after Besnosov and Michailova (1991), Page (2008) and Shevyrev (2006); spelling of suborder is given after Shevyrev (2006) Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites ...
... Keupp and Mitta 2013 Dorsoplanitidae Fig. 7 Aptychi distribution among the selected Middle Jurassic-Early Cretaceous ammonite lineages. Ammonoid suborders and evolution of lineages are given after Besnosov and Michailova (1991), Page (2008) and Shevyrev (2006); spelling of suborder is given after Shevyrev (2006) Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites ...
... Systematics of higher ammonite taxa used herein is based on Besnosov and Michailova (1991) with some additions from Kvantaliani et al. (1999) and Shevyrev (2006). As aptychi usually occurred outside the host conchs and their relation to ammonoid taxa are unclear, generic and species names used for aptychi are separate from those of ammonoid shells and treated as parataxa (Engeser and Keupp 2002). ...
... Die Ammonitengattung Aulacostephanus im Oberjura (Taxonomie, Stratigraphie, Biologie). suborders and evolution of lineages are given after Besnosov and Mikhalova (1991), Page (2008) andShevyrev (2006); spelling of suborder is given after Shevyrev (2006 Click here to download Figure Rogov_fig. 6_new_br_1layer.tif ...
... Die Ammonitengattung Aulacostephanus im Oberjura (Taxonomie, Stratigraphie, Biologie). suborders and evolution of lineages are given after Besnosov and Mikhalova (1991), Page (2008) andShevyrev (2006); spelling of suborder is given after Shevyrev (2006 Click here to download Figure Rogov_fig. 6_new_br_1layer.tif ...
Here we are providing a review of aptychi records in ammonites of Boreal origin or that inhabited Boreal/Subboreal basins during the Bathonian - Albian with special focus on new records and the relationship between the evolution of ammonite conch and aptychi. For the first time we figure aptychi that belong to Aulacostephanidae, Virgatitidae, Deshayesitidae, Craspeditinae and Laugeitinae. A strong difference between aptychi of micro- and macroconchs of co-occurring Aspidoceratidae is shown, which, along with their shell morphologies suggests niche divergence of these dimorphs. Aptychi of Aptian Sinzovia (Aconeceratidae) should be tentatively ascribed to Didayilamellaptychus, while their previous assignment to rhynchaptychi was caused by misidentification. Aptychi of Middle Jurassic - Early Cretaceous Boreal and Subboreal ammonites are characterized by a very thin calcareous non-porous outer layer lacking distinct ribs and tubercles (only radial striae sometimes occur), and mainly should be assigned to Praestriaptychus. Some ammonoid groups (i.e. Ancylocerina and Desmoceratoidea) are characterized by the presence of different aptychi types irrespective of their shell shape. This fact could indicate that bivalved praestriaptychi could have easily transformed into single-valved "anaptychi" and vice versa. Size and form of aptychi in relation to those of the aperture of ammonite conchs vary within different lineages and at least some Stephanoceratoidea and Perisphinctoidea have aptychi significantly smaller than the aperture diameter.
... The ammonoid suture has long been a subject of palaeontologists' attention because of its great taxonomic utility (Arkell 1957;Miller et al. 1957;Kullmann & Wiedmann 1970;Wiedmann & Kullmann 1981;Korn & Klug 2002;Korn et al. 2003;Shevyrev 2006), morphogenetic wonder (Seilacher 1975;Westermann 1975;Bayer 1978;García-Ruiz et al. 1990;Hewitt et al. 1991;Hammer 1999) and puzzling functional morphology (Westermann 1958(Westermann , 1975Henderson 1984;Hewitt & Westermann 1986, 1987Jacobs 1990;Weitschat & Bandel 1991;Oló riz & Palmqvist 1995;Saunders 1995;Seilacher & LaBarbera 1995;Saunders & Work 1996Daniel et al. 1997;Oló riz et al. 1997;Hassan et al. 2002;Lewy 2002;Pérez-Claros 2005;Pérez-Claros et al. 2007;De Blasio 2008). The suture is the curved line of intersection between the external shell wall and a series of septa that partition the phragmocone internally into phragmocone chambers. ...
... The lobes are classified into several categories according to their primary positions. The pattern of their arrangement, as well as nature of its ontogenetic change, is used as a taxonomic characteristic of ammonoids (Arkell 1957;Kullmann & Wiedmann 1970;Lehmann 1981;Wiedmann & Kullmann 1981;Korn & Klug 2002;Korn et al. 2003;Shevyrev 2006). ...
... Most phylloceratine species seem to have obtained these characteristics in such way that they partly followed the phylogenetic legacy from ancestral ammonoids; however, more derived lytoceratine and ammonitine ammonoids appear to have obtained these characteristics via a more drastic reform. A diagnostic sutural characteristic, appropriate for distinction of the Lytoceratina and Ammonitina from the Phylloceratina, is the incised dorsal lobe (Kullmann & Wiedmann 1970;Shevyrev 2006), rather than features of the external suture. Lobe splitting near the umbilical seam, as seen typically in the Phylloceratina, is also found in the Lytoceratina and Ammonitina (Kullmann & Wiedmann 1970;Wiedmann & Kullmann 1981). ...
Ubukata, T., Tanabe, K., Shigeta, Y., Maeda, H. & Mapes, R.H. 2009: Eigenshape analysis of ammonoid sutures. Lethaia, Vol. 43, pp. 266–277.A morphometric method based on eigenshape analysis is proposed for characterizing the morphospace of widely varied ammonoid suture shapes. The analysis requires initially the placement of a suture line in an x–y coordinate system, with the ventral and umbilical extremes located on the x-axis. Series of x- and y-coordinates along the suture line are used as descriptors. The coordinate data are summarized into the two largest principal components using eigenshape analysis. A total of 115 species belonging to six ammonoid orders, spanning from the Devonian to the Cretaceous, was utilized in the present analysis. The analysis, using y-coordinate data, revealed differences in morphological variation in suture shape among taxa within the Mesozoic ammonitids: the Lytoceratina and Ammonitina were characterized by small negative values of the first eigenshape scores, whereas the Phylloceratina (the sister group of the Lytoceratina plus Ammonitina), as well as the Triassic ceratitids and Palaeozoic ammonoids, have a wide range of the first eigenshape scores. The pattern of data obtained from many different ammonoid species, as plotted on eigenshape axes in the morphospace constructed based on y-coordinate data, reveals a plesiomorphic aspect of suture shape in some phylloceratine species with respect to other ammonitids. □Ammonoids, eigenshape analysis, morphometrics, suture line.
... We consider ammonoids as a subclass including seven orders in the Paleozoic: (Bogoslovskaya et al., 1990;Leonova, 2002;Shevyrev, 2006;etc.). ...
... The order Anarcestida (Emsian-Famennian) includes the earliest ammonoids, which are widely accepted to have originated from Bactritida, a small group of cephalopods treated as an independent superorder (Shimansky, 1962;Teichert and Moore, 1964), or subclass (Shevyrev, 2005(Shevyrev, , 2006, or as an order in the subclass of ammonoids (Schindewolf, 1968;Wiedmann and Kullmann, 1980;Barskov, 1989, etc.). Anarcestida gave rise to all other orders of the subclass Ammonoidea. ...
... Early representatives, originating from prolecanitids, had evolute medium-sized shells, with a primitive suture (genus Paraceltites ). Of ten suborders recognized by major types of sutural ontogeny (Shevyrev, 1986(Shevyrev, , 2006, two existed in the Permian. The most characteristic morphological feature of Permian ceratitids was the absence of subspheroconic and spheroconic forms, which at that time were widespread among goniatitids. ...
Ecological specialization of Paleozoic ammonoid orders is discussed along with changes in the ecological structure of the
ammonoid assemblages in the Early Devonian-Late Permian. Two large cycles of change in the ecological structure, Devonian
and Carboniferous-Permian are recognized.
... Although a sensible system of cephalopods at the megataxon level has been intensively sought since the mid-20th century, no agreement has been achieved on the number of orders and subclasses, i.e., on the body plans within the archetype of the class (Flower and Kümmel, 1950;Flower, 1964;Zhuravleva, 1961, Donovan, 1964;Teichert, 1967Teichert, , 1988Zeiss, 1969;Zhuravleva, 1972;Salvini-Plawen, 1980;House, 1981;Drushchits and Shimansky, 1982;Starobogatov, 1983;Leonova, 2002;Shevyrev, 2005Shevyrev, , 2006aShevyrev, , 2006betc.). Approaches to classification have been very varied, which is reflected in the subdivision of the class into between two and eight subclasses. ...
... There is more consistency in the understanding of the orders, although the number of recognized orders varies from 15 to 30. The latest review of the macrosystem was undertaken by Shevyrev (2005Shevyrev ( , 2006aShevyrev ( , 2006b). Unfortunately, this system, like those proposed earlier, is nothing more than another shuffling of orders, some of which is widely accepted, and some is only accepted by a few authors. ...
... According to this classification (Bogoslovskaya et al., 1990;Leonova, 2002;Shevyrev, 2006b; etc.), Anarcestida Miller et Furnish, 1954 (Devonian) is the earliest ammonoid order. Anarcestida gave rise to other orders of Ammonoidea. ...
... Keupp and Mitta 2013 Dorsoplanitidae Fig. 7 Aptychi distribution among the selected Middle Jurassic-Early Cretaceous ammonite lineages. Ammonoid suborders and evolution of lineages are given after Besnosov and Michailova (1991), Page (2008) and Shevyrev (2006); spelling of suborder is given after Shevyrev (2006) northeastern part of the peninsula and La-gnu, Changwat Satun in the southwest (6°N, 102 0 E). The uppermost Ordovician strata presented at the latter locality have been proposed as Pa Kae Formation (Wongwanich et al. 1983;DMR 2001) (Table 1). ...
... Keupp and Mitta 2013 Dorsoplanitidae Fig. 7 Aptychi distribution among the selected Middle Jurassic-Early Cretaceous ammonite lineages. Ammonoid suborders and evolution of lineages are given after Besnosov and Michailova (1991), Page (2008) and Shevyrev (2006); spelling of suborder is given after Shevyrev (2006) northeastern part of the peninsula and La-gnu, Changwat Satun in the southwest (6°N, 102 0 E). The uppermost Ordovician strata presented at the latter locality have been proposed as Pa Kae Formation (Wongwanich et al. 1983;DMR 2001) (Table 1). ...
In September 2014, the 9th International Symposium Cephalopods—Present and Past (ISCPP) and the 5th International Coleoid Symposium were held at the University of Zurich. The numerous contributions from two joint symposia fill more than one special issue. After the first special issue, which was published in 2015 in the Swiss Journal of Palaeontology (Vol 134, Issue 2), the present second special issue also contains contributions from all fields of research on fossil and Recent cephalopod. In this editorial, we provide a short obituary honouring Fabrizio Cecca and report from the three conference field trips.
... Three subfamilies of Stephanoceratidae have been commonly distinguished: Stephanoceratinae Neumayr, 1875, Garantianinae Wetzel, 1937, and Cadomitinae Westermann, 1956(e.g., Westermann 1956, b, 1967Arkell et al. 1957;Schindewolf 1957Schindewolf , 1961Schindewolf -1968Géczy 1966;Westermann and Riccardi 1979;Callomon 1981Callomon , 1985Tintant and Mouterde 1981;Pavia 1983a, b;Sandoval 1983;Fernandez-Lopez 1985, 2014Page 1993Page , 1996Page , 2008Sandoval et al. 2000;Dietze et al. 2001Dietze et al. , 2010Chandler and Dietze 2004;Moyne and Neige 2004;O'Dogherty et al. 2006;Shevyrev 2006;Schlögl et al. 2006;Chandler et al. 2013). The Stephanoceratinae show increasing diversification during the lower Bajocian and pandemic distribution in the Tethys-Panthalassa Realm, from the Mediterranean-Caucasian to the East-Pacific subrealms. ...
... The septal suture is usually complex, with a retracted umbilical lobe in the macroconchs, but slightly more simplified in the microconchs. The first lateral saddle E/L is asymmetric and higher than L/U 2 (Moyne and Neige 2004;Shevyrev 2006;Page 2008;Howarth 2013;Fernandez-Lopez 2014). ...
Two new Bajocian stephanoceratid subfamilies are distinguished based on morpho-structural criteria and phyletic patterns. At the Aalenian/Bajocian transition, Stephanoceratinae of the genus Albarracinites are the source of the earliest species of Mollistephanus and of the new Mollistephaninae lineage that includes three successive genera: Mollistephanus, Paramollistephanus gen. nov. and Phaulostephanus. The Mollistephaninae span across the Mediterranean-Caucasian Subrealm during the lower Bajocian, but Paramollistephanus is pandemic to both the Mediterranean-Caucasian and East Pacific subrealms during the Propinquans Zone. The Frebolditinae evolved from Paramollistephanus in the lower Bajocian, beginning with Freboldites and giving rise to diverse genera such as Parabigotites, Patrulia, Bajocia, Subcollina and Parastrenoceras that occur into the upper Bajocian of both the East Pacific and Mediterranean-Caucasian subrealms. Palaeobiogeographical and phylogenetic data of these two subfamilies support an active Bajocian Central-Atlantic Seaway, the so-called Hispanic Corridor, as a bidirectional, biodispersal route driven by changes of the relative sea level. Several bioevents of appearance, immigration and dispersal, associated with the range expansion of ammonoid taxa, were effective (Paramollistephanus in the latest Laeviuscula Zone, Subcollina in the latest Humphriesianum Zone, and Parastrenoceras in the earliest Niortense Zone). Based on life-history strategy, morpho-structural and functional criteria, the dimorphic Caumontisphinctes-Infraparkinsonia pair seems to be the origin of the Parkinsoniidae. The Mollistephaninae and Frebolditinae show small adult size, scarcity of fossils, and low stratigraphic persistence and constancy; however, they present some pandemic genera of the Tethys-Panthalassa Realm and display high resolution for time correlation between the western Tethyan and eastern Pacific marine basins of separate bioprovinces.
... I consider ammonoids as a subclass that includes seven Paleozoic orders. There were four ammonoid orders in the Permian: (1) Tornoceratida Wedekind, 1918, which existed from the Mid Devonian to the end of the Permian (suborders Tornoceratina Wede kind, 1918;Pseudohaloritina Leonova, 2002;Agath iceratina Leonova, 2002); (2) Goniatitida Hyatt, 1884, Early Carboniferous-end of the Permian (sub orders Goniatitina Hyatt, 1884; Adrianitina Cyclolobina Leonova, 2002); (3) Prolecanitida Miller et Furnish, 1954, existing from the Early Car boniferous to the beginning of the Triassic (suborders Prolecanitina Miller et Furnish, 1954;Medlicottiina Zakharov, 1984); (4) Ceratitida Hyatt, 1884, existing from the beginning of the Middle Permian to the end of the Triassic (Permian suborders Paraceltitina Shevyrev, 1968;Otoceratina Shevyrev et Ermakova, 1979) (Bogoslovskaya, Zhuravleva, and Shimansky, 1990;Shevyrev, 2005Shevyrev, , 2006etc.). ...
... The early members, originating from prolecanitids, had evolute medium sized shells, with a primitive suture (genus Paraceltites). Of 10 suborders recognized based on the main types of sutural outline (Shevyrev, 1986(Shevyrev, , 2006, two existed in the Permian. The diversification of cer atitids was in the Triassic. ...
This monograph analyzes all available data on the biostratigraphic and biogeographical distribution of Permian ammonoids and the ecological interpretation of morphological changes in this group. Ammonoid assemblages of various regions at successive stages of the Permian are examined. Four major stages are substantiated in the evolution of Permian ammonoids. The most contentious stages in the Permian evolution of the group are extensively discussed.
... Furthermore, many orthoceratoids possess cameral and endosiphuncular deposits, although both characters are absent in the earliest members. The subclass has already been accepted by different authors in the past, although opinions on its extent varied [39,55,56]. ...
Background: Despite the excellent fossil record of cephalopods, their early evolution is poorly understood. Different, partly incompatible phylogenetic hypotheses have been proposed in the past, which reflected individual author’s opinions on the importance of certain characters but were not based on thorough cladistic analyses. At the same time, methods of phylogenetic inference have undergone substantial improvements. For fossil datasets, which typically only include morphological data, Bayesian inference and in particular the introduction of the fossilized birth-death model have opened new possibilities. Nevertheless, many tree topologies recovered from these new methods reflect large uncertainties, which have led to discussions on how to best summarize the information contained in the posterior set of trees.
Results: We present a large, newly compiled morphological character matrix of Cambrian and Ordovician cephalopods to conduct a comprehensive phylogenetic analysis and resolve existing controversies. Our results recover three major monophyletic groups, which correspond to the previously recognized Endoceratoidea, Multiceratoidea, and
Orthoceratoidea, though comprising slightly different taxa. In addition, many Cambrian and Early Ordovician representatives of the Ellesmerocerida and Plectronocerida were recovered near the root. The Ellesmerocerida is para- and polyphyletic, with some of its members recovered among the Multiceratoidea and early Endoceratoidea. These relationships are robust against modifications of the dataset. While our trees initially seem to reflect large uncertainties, these are mainly a consequence of the way clade support is measured. We show that clade posterior probabilities and tree similarity metrics often underestimate congruence between trees, especially if wildcard taxa are involved.
Conclusions: Our results provide important insights into the earliest evolution of cephalopods and clarify evolutionary pathways. We provide a classification scheme that is based on a robust phylogenetic analysis. Moreover, we provide some general insights on the application of Bayesian phylogenetic inference on morphological datasets. We support earlier findings that quartet similarity metrics should be preferred over the Robinson-Foulds distance when higher-level phylogenetic relationships are of interest and propose that using a posteriori pruned maximum clade credibility trees help in assessing support for phylogenetic relationships among a set of relevant taxa, because they provide clade support values that better reflect the phylogenetic signal.
... Subsequently, they were split into the Turrilitina and Ancyloceratina (Doguzhaeva & Mikhailova, 1982;Besnossov & Mikhailova, 1983), which was accepted by most subsequent workers (see Wright et al., 1996). Later, Shevyrev (2006) assigned them to the Lytoceratoidea and Ammonitida. Vermeulen (2005) added the Protancyloceratina. ...
Heteromorphs are ammonoids forming a conch with detached whorls (open coiling) or non-planispiral coiling. Such aberrant forms appeared convergently four times within this extinct group of cephalopods. Since Wiedmann's seminal paper in this journal, the palaeobiology of heteromorphs has advanced substantially. Combining direct evidence from their fossil record, indirect insights from phylogenetic bracketing, and physical as well as virtual models, we reach an improved understanding of heteromorph ammonoid palaeobiology. Their anatomy, buoyancy, locomotion, predators, diet, palaeoecology, and extinction are discussed. Based on phylogenetic bracketing with nautiloids and coleoids, hetero-morphs like other ammonoids had 10 arms, a well-developed brain, lens eyes, a buccal mass with a radula and a smaller upper as well as a larger lower jaw, and ammonia in their soft tissue. Heteromorphs likely lacked arm suckers, hooks, tentacles , a hood, and an ink sac. All Cretaceous heteromorphs share an aptychus-type lower jaw with a lamellar calcitic covering. Differences in radular tooth morphology and size in heteromorphs suggest a microphagous diet. Stomach contents of heteromorphs comprise planktic crustaceans, gastropods, and crinoids, suggesting a zooplanktic diet. Forms with a U-shaped body chamber (ancylocone) are regarded as suspension feeders, whereas orthoconic forms additionally might have consumed benthic prey. Heteromorphs could achieve near-neutral buoyancy regardless of conch shape or ontog-eny. Orthoconic heteromorphs likely had a vertical orientation, whereas ancylocone heteromorphs had a near-horizontal aperture pointing upwards. Heteromorphs with a U-shaped body chamber are more stable hydrodynamically than modern Nautilus and were unable substantially to modify their orientation by active locomotion, i.e. they had no or limited access to benthic prey at adulthood. Pathologies reported for heteromorphs were likely inflicted by crustaceans, fish, marine reptiles, and other cephalopods. Pathologies on Ptychoceras corroborates an external shell and rejects the endocochleate hypothesis. Devonian, Triassic, and Jurassic heteromorphs had a preference for deep-subtidal to offshore facies but are rare in shallow-subtidal, slope, and bathyal facies. Early Cretaceous heteromorphs preferred deep-subtidal to bathyal facies. Late Cretaceous heteromorphs are common in shallow-subtidal to offshore facies. Oxygen isotope data suggest rapid growth and a demersal habitat for adult Discoscaphites and Baculites. A benthic embryonic stage, planktic hatchlings, and a habitat change after one whorl is proposed for Hoploscaphites. Carbon isotope data indicate that some Baculites lived throughout their lives at cold seeps. Adaptation to a planktic life habit potentially drove selection towards smaller hatchlings, implying high fecundity and an ecological role of the hatchlings as micro-and mesoplankton. The Chicxulub impact at the Cretaceous/Paleogene (K/Pg) boundary 66 million years ago is the likely trigger for the extinction of ammonoids. Ammonoids likely persisted after this event for 40-500 thousand years and are exclusively represented by heteromorphs. The ammonoid extinction is linked to their small hatchling sizes, planktotrophic diets, and higher metabolic rates than in nautilids, which survived the K/Pg mass extinction event.
... Ruzhencev (1940Ruzhencev ( , 1950 suggested that Vidrioceras (initial genus for the superfamily Cycloloboidea, which existed in the second half of the Late Carboniferous) evolved from the genus Eoasianites (suborder Goniatitina, superfamily Neoicocertoidea) based on the similarity in the ontogeny of the suture and the shell shape. Ruzhencev (see Ruzhencev and Bogoslovskaya, 1978) suggested that the initial taxa of other superfamilies (Shumarditoidea and Marathonitoidea) of the suborder Cyclolobina (Leonova, 2002;Shevyrev, 2006) evolved from one of the members of the family Glaphyritidae (suborder Goniatitina, superfamily Somoholitoidea). It should be noted that many species of the genera Glaphyrites and Eoasianites are very similar to one another, and this complicates precise delineation of their characters in juveniles. ...
Abstract—This paper provides a review of the evolution of opinions on the composition and history of the
development of the family Vidrioceratidae Plummer et Scott, 1937, which played an important role in the
Carboniferous–Permian ammonoid biota. The division of the group into subfamilies, for which the generic
composition is determined and the morphogenetic trends are reconstructed, is reinterpreted. The status and
species composition of the genera Pamirites Toumanskaya and Prostacheoceras Ruzhencev are emended. The
familial assignments of the “problematic” genera Leites Bogoslovskaya, 1990, Jilingites Liang, 1982, and Per
itrochia
Girty, 1908 are revised.
... Instead of the ventral lobe, they formed a ventral saddle (Fig. 5), which was associated with a dorsal, rather than a ventral (as in most other groups), siphon. After the radiation of the "archaic diversity" of the Devonian ammonoids of the orders of Anarcestida with five sub-orders and Clymeniida with two suborders (Shevyrev, 2006), a serious biotic crisis occurred led to an extinction of almost all Devonian ammonoid taxa. The only exception was the order Tornoceratida, and the Devonian-Carboniferous boundary was crossed by a few taxa with a simple ventral lobe, and these gave rise to new large groups of ammonoids. ...
The history of Paleozoic ammonoids can be subdivided into two large intervals: Devonian and Carboniferous–Permian. There were two major evolutionary pathways: changes in the external shell morphology and changes in the suture, a character observed only in cephalopods. Almost all major shell types and ornamentation appeared at early stages of the evolution of the subclass Ammonoidea (archaic diversity). The suture in ancient taxa in this group was represented by virtually all known types, except for the complexly dissected suture lines of the “Mesozoic type” that appeared only at the end of the Paleozoic. During the time of the subclass’s existence, Devonian morphotypes recurrently appeared in different orders. The senile diversity was associated with the diversification of exotic taxa at the end of the Ammonoidea evolution.
... b Fig. 8 Besnosov and Michailova (1991), Page (2008) and Shevyrev (2006)] and distribution of sutural pseudoinversion ...
New records of ammonites showing poorly known sutural anomaly, so-called sutural pseudoinversion, are discussed. For the first time, sutural pseudoinversion was found in non-heteromorph Jurassic and Lower Cretaceous ammonoids, which are belonging to 10 genera (Dorsetensia, Indosphinctes, Erymnoceras, Pictonia, Aspidoceras, Kachpurites, Craspedites, Delphinites, Nikitinoceras and Immunitoceras) and 8 families (Sonniniidae, Pseudoperisphinctidae, Pachyceratidae, Aulacostephanidae, Aspidoceratidae, Craspeditidae, Neocomitidae and Parahoplitidae). Two types of sutural pseudoinversion were recognized: normal sutural pseudoinversion, in which the outline of small elements in lobes and saddles is fully reversed, and transitional sutural pseudoinversion, characterized by changes in the outline of folioles only. Usually, sutural pseudoinversion occurs in the terminal part of the phragmocone and becomes especially clear on the last sutures near the body chamber, but in some studied specimens sutural pseudoinversion appears in middle whorls and can be traced further up to the last visible sutures. Sutural pseudoinversion could not be caused by mechanical compression of saddles due to sutural asymmetry or strong development of sculptural elements as Bayer (Lethaia 11:307–313, 1978) assumed. Pseudoinversion is usually (although not always) visible in all sutural elements. Although pseudoinversion is known in those taxa with strong sutural asymmetry, pseudoinversion and asymmetry often affected different specimens. Influence of hydrostatic overpressure during the septal formation as well as parasite infestation on development of sutural pseudoinversion is considered to be unlikely. Instead, an abnormality appears to be a case of homeotic mutation, possibly caused by transcription errors in polarity genes. Much more common occurrence of sutural pseudoinversion in ammonites than it was expected previously suggest that it could be a relatively common phenomenon that needs increased attention in the future.
... Instead of the ventral lobe they had a ventral saddle resulting from the dorsal, rather than the ventral, (as in most ammonoids) siphuncle (genus Clymenia, etc). Following the "archaic diversity" of the sutures of Devonian ammonoids assigned to the order Anarcestida with five suborders and Clymeniida with two suborders (Shevyrev, 2006), four large groups were formed by the beginning of the Carboniferous, each characterized by a particular evolutionary trend and receiving an ordinal rank. ...
The history of the appearance and evolution of the suture, one of the major structural elements of the shells of ammonoids (a subclass of Cephalopoda), is briefly discussed. Its morphology is considered in the Devonian Anarcestida, the first members of which are very similar to the ancestral Bactritoidea, in the Late Devonian Clymeniida, the Devonian–Permian Tornoceratida, the Carboniferous–Permian Prolecanitida and Goniatitida, and the Permian Ceratitida. Three major trends in the evolution of the suture are recognized in the order Goniatitida, which were instrumental in the subdivision of this order into suborders. Variations of elements of the sutures allow the recognition of the familial, generic, and specific ranks.
... As argued convincingly by Landman (1982) and Holland (1988), however, it is highly unlikely that ancient Greeks could have had significant familiarity with Nautilus, if only because its geographic range is so distant from the Mediterranean. 25 This history of the study of ammonites is taken largely from Jenyns (1835); Nelson (1968); Shevyrev (2006); and Romano (2014). 26 Owen (1832). ...
Ammonites were among the first life restorations of invertebrate fossil animals. These restorations appeared at around the same time (the 1830s)—and were executed by some of the same artists and scientists—as the earliest restorations of fossil vertebrates. As was the case for many of these vertebrates, ammonite restorations underwent major changes over the next century. These changes were associated with shifts in which living species were used as the basis for comparison with the extinct ammonites. The first models were argonauts (paper nautilus), because at the time they were better known than living Nautilus. By the mid-nineteenth century, Nautilus began to be used as a model, but with an ‘argonaut mode’ of life (floating on the surface). More modern-looking, subsurface restorations first appeared in the late nineteenth and early twentieth centuries. The issue of ‘taxonomic uniformitarianism’ remains a fundamental challenge for efforts to understand ammonite biology today, and this is reflected in the...
... superfamily Hammatoceratoidea Schindewolf, 1964 that gave rise to Otoitidae Mascke, 1907, which 1952;Westermann 1956Westermann , 1964aWestermann , 1993Westermann , 1995Arkell et al. 1957;Geczy 1966;Westermann & Riccardi 1979;Callomon 1981;Tintant & Mouterde 1981;Pavia 1983;Sandoval 1983;Fernandez-Lopez 1985;Page 1996Page , 2008Sandoval et al. 2000;Dietze et al. 2001Dietze et al. , 2010Chandler & Dietze 2004;Moyne & Neige 2004;O'Dogherty et al. 2006;Shevyrev 2006;Howarth 2013). ...
Several tens of specimens of Lower Bajocian Albarracinites (type species A. albarraciniensis Fernandez-Lopez, 198523.
Fernandez-Lopez, S.R. 1985. El Bajociense en la Cordillera Ibérica. Thesis Departamento Paleontologia, Universidad Complutense Madrid, 850 pp.View all references), including microconchs and macroconchs from the Iberian Range, have been studied. This ammonite genus ranges in the Iberian Range from at least the Ovale Zone to the uppermost Laeviuscula Zone of the Lower Bajocian (Middle Jurassic). The macroconch counterpart is thought to be a group of stephanoceratids previously attributed to Mollistephanus, Riccardiceras and other new forms described in this paper. Two chronologically successive species of Albarracinites have been identified: A. albarraciniensis and A. submediterraneus sp. nov. The evolution of the Albarracinites lineage represents a hypermorphic peramorphocline starting from depressed, small and slender serpenticones of A. westermanni, to larger planorbicones with more cadiconic phragmocones and body chamber of subcircular cross section belonging to A. submediterraneus sp. nov., through A. albarraciniensis Fernandez-Lopez. In contrast, Mollistephanus planulatus (Buckman), M. cockroadensis Chandler & Dietze and M. mollis Buckman represent a peramorphocline by acceleration, producing adults of similar size but more compressed and with increasing ontogenic variation of shell ornament. Albarracinites and Mollistephanus subsequently developed two opposite peramorphoclines or gradational series of morphological changes undergoing greater development and ontogenic variation. These two genera show diverse palaeobiogeographical distributions too. Albarracinites is rarely recorded in the Mediterranean and Submediterranean from the Discites to the Laeviuscula Zone, whereas Mollistephanus is more common in north-western Europe and other biochoremas of the western Tethys from the Discites Zone to the Sauzei Zone. Albarracinites seems to be the earliest stephanoceratid lineage in western Tethys, branching off from the otoitid Riccardiceras by proterogenetic change and resulting in paedomorphosis at the Aalenian/Bajocian boundary.http://zoobank.org/urn:lsid:zoobank.org:pub:09B95E3C-00E7-4A9E-907B-656255AA7B00
... Therefore, within the superfamily Haploceratoidea (zitteL, 1884) of the suborder Haplocerina (BeSnoSov & michaiLova, 1983; cf. ShevYrev, 2006; paGe, 2008), besides the basal families Lissoceratidae (douviLLe, 1885) and Oppeliidae (douviLLe, 1890), the family Hebetoxyitidae (Buckman, 1924 in 1909-1930) evolved during the late Aalenian and early Bajocian. ...
New findings of lower Bajocian, haploceratid ammonites (Cephalopoda, Mollusca) of the genus Hebetoxyites from the Albarracin area are described and revised alongside specimens previously collected from the Iberian Range. Three species have been identified: H. hebes Buckman, H. incongruens Buckman and H. mouterdei Fernández-López. Indigenous populations of these Tethyan species in the Iberian carbonate platform system, including macroconchs and microconchs, are interpreted as immigration and colonization of shallow-water marine environments by Submediterranean taxa during a short interval of the early Bajocian. As peramorphic result of palingenetic evolution, a chronocline from strongly ribbed, stout forms of the Ovale Zone (including H. mouterdei), to oxycones with blunt, simple or irregularly branched ribbing of the Laeviuscula Zone (including H. incongruens), through intermediate forms belonging to H. hebes, has been recognized. These successive species of Hebetoxyites provide a basis for correlation and subzonal division of the Ovale and Laeviuscula zones in the Iberian Range.
... The rank and taxonn omy of this group are still debated. They have been treated as a family (Korn and Klug, 2002), superfamily (Furnish et al., 2009), suborder (Ruzhencev, 1957Ruzhencev, , 1960 Bogoslovsky, 1971; Bogoslovskaya et al. (1990), and order (Leonova, 2002; Shevyrev, 2006). Such a large discrepancy in the classification rank results from an insufficient number of publications on this group and especially a lack of data on its sutural ontogeny. ...
The history of the taxonomy and classification of the Famennian genus Praeglyphioceras Wedekind, 1908 and the family Praeglyphioceratidae are discussed. The sutural ontogeny of this genus, which is examined for
the first time for two species of the genus, supports the high taxonomic rank of praeglyphioceratids. This family is mostly
related to primitive Prionoceratoidea. A new species, Praeglyphioceras korobkovi sp. nov., is described from the delphinus Zone (Prolobites-Platyclymenia Genozone) of the Aktyubinsk Region of Kazakhstan.
Keywordsammonoids–
Praeglyphioceras
–new species–Famennian–
delphinus Zone
... In our understanding, the superfamily Cycloloboidea should be included in the suborder Cyclolobina along with the superfamilies: Shumarditoidea, Maratonitoidea, and Popanocera toidea (Leonova, 2002). The separation of the subor der Cyclolobina was supported by Shevyrev (2006). The genetic affinity of all four superfamilies is indi cated by characteristic morphological characters, which can be traced in each of them in various combi nations at various evolutionary stages. ...
The development of views on the phylogeny of the family Cyclolobidae Zittel, 1895 is discussed. The generic composition is
emended, phylogenetic links are indicated, a new version of the phylogenetic scheme is proposed, and phylogeny of the key
genera is traced at species level. The sutural ontogeny of the genus Mexicoceras is examined, its placement in the family Cyclolobidae is supported, and its position in the phylogenetic reconstruction of
the family is determined.
Key wordsAmmonoidea-Cyclolobidae-systematics-phylogeny-ontogeny-sutural line-Permian
Ammonoids from the Besano Formation published by Airaghi in 1912 kept at the Museo Kosmos in Pavia. The ammonoids from the Besano Formation described by Airaghi in two works in 1912, belonging to the collections of the Museo di Storia Naturale di Milano, as well as many other historical collections stored in this museum, have been lost during World War II. However, some plaster casts of these specimens were recently found among the material stored in the new Museo Kosmos in Pavia during a reorganization of the deposits. The plaster casts, probably made by Airaghi, were obtained from the original specimens corresponding to some species erected by Airaghi and coming from the mine of Tre Fontane (Mt. San Giorgio, Switzerland). Lacking original specimens and related stratigraphic data, the present material is herein reclassified and considered as complementary for the corresponding neotypes, previously stated by Rieber in 1973. Among the taxa not revised in literature, two new combinations are here proposed: Serpianites marianii (Airaghi 1912) and ?Nevadites bassanii (Airaghi 1912). With these plaster casts we also uncovered some original specimens never described. The majority of the material is paired with the original labels by Airaghi. These ammonoids are characteristic of the lower and upper Secedensis Zone (Upper Anisian, Middle Triassic) of the Besano Formation. It is very likely the herein described specimens were collected in the beds belonging to the Secedensis Zone of the mine Tre Fontane which have been completely removed in the first years of excavation activity. [Article in Italian]
For the taxon comprising all Devonian to Cretaceous ammonoids, a variety of conflicting names with different authorship and taxonomic rank are available and have been repeatedly cited. Here, we review the primary literature and suggest the appropriate name, authorship and date of publication; we suggest the rank of a superorder for the ammonoids. The monophylum including all Devonian to Cretaceous ammonoids is here called Ammonoida. For the traditional suborder Ammo-nitina comprising Jurassic and Cretaceous forms the taxonomic rank of an order named Ammonitida is suggested to match the ranking of Palaeozoic ammonoid groups. Although the International Rules of Zoological Nomenclature only cover categories from subspecies to superfamily levels, similar procedures are applied to the higher taxonomic categories described here in order to avoid further inconsistencies in cephalopod taxonomy.
An exhaustive study of existing data on the relationship between egg size and maximum size of embryonic shells in 42 species of extant cephalopods demonstrated that these values are approximately equal regardless of taxonomy and shell morphology. Egg size is also approximately equal to mantle length of hatchlings in 45 cephalopod species with rudimentary shells. Paired data on the size of the initial chamber versus embryonic shell in 235 species of Ammonoidea, and 1 Spirulida demonstrated that, although there is a positive relationship between these parameters in some taxa, initial chamber size cannot be used to predict egg size in extinct cephalopods; the size of the embryonic shell may be more appropriate for this task. The evolution of reproductive strategies in cephalopods in the geological past was marked by an increasing significance of small-egged taxa, as is also seen in simultaneously evolving fish taxa.
Over one hundred specimens assigned to three species of the cephalopod genus Bactroceras (=Eobactrites) from the Ordovician of the Prague Basin (Czech Republic) have been studied in detail. Preservation of the material allows study of external features including the embryonic shell, as well as some internal structures of the shell. Muscle scars, described for the first time in Bactroceras, show a simple, unpaired and low, dorsally-situated lobe (“orthoceridan” type of muscle scars). The type species of the genus, Bactroceras avus, is synonymized with B. sandbergeri based on strong similarities in the outer morphology of the shell and the position and internal structure of the siphuncle. A new species of Bactroceras from Bolivia is erected: B. boliviensis. Orthoceras interpolatum Barrande, 1870, from the Upper Ordovician of Bohemia, is assigned to Bactroceras; it is one of the stratigraphically youngest species of the genus. The assignment of Orthoceras gossei Etheridge to Bactroceras is rejected. Convergence with bactritids and the classification of Bactroceras as the oldest known member of the order Orthocerida is discussed. The exact stratigraphic occurrences of Bactroceras are refined, and the palaeobiogeographic significance of the genus is evaluated. It suggests origin of the genus in high-latitude margins of Gondwana, and its expansion to low-latitude regions during the Ordovician as part of the early radiation of pelagic cephalopods.
Three genera and seven species belonging to the subfamily Zigzagiceratinae (family Perisphinctidae) are described from the Lower Bathonian of France and Saudi Arabia. Intraspecific dimorphism is recognized. A revision of the genus Franchia proposed by Sturani (1967), based on the syntypes and new specimens from south-east France, is presented. Franchia arkelli Sturani, Franchia subalpina sp. nov., Protozigzagiceras torrensi (Sturani), Protozigzagiceras tethycum sp. nov., Protozigzagiceras flexum sp. nov. and Protozigzagiceras densum sp. nov. are described from the Digne–Castellane region of south-east France. Megazigzagiceras subarabicum, gen. et sp. nov. is described from the Dharma region of Saudi Arabia. The successive Early Bathonian species of Franchia and Protozigzagiceras herein identified in West Tethyan areas, as members of the Mediterranean–Caucasian Subrealm, formed lasting separate peramorphoclines characterized by increasing hydrodynamic coiling of the shell. In contrast, rapid proterogenesis originated and diversified the earliest Bathonian zigzagiceratin lineages, giving paedomorphic members, commonly neotenic and more scarcely progenetic. Procerites–Siemiradzkia seems to be the oldest zigzagiceratin member in the French Subalpine, Iberian and Lusitanian basins, branched off by paedomorphosis from leptosphinctins at the Bajocian–Bathonian transition. The Mediterranean–Caucasian genera Franchia, Zigzagiceras, Zigzagites and Wagnericeras branched from successive species of Protozigzagiceras, in turn, a direct derivative of Procerites. The oldest lineages of the clade Zigzagiceratinae evolved by iterative, rapid, paedomorphic changes and additional, lasting, peramorphic modifications during the Early Bathonian.
Lytoceratites together with Phylloceratites are often described as “conservative”. However, the origin and monophyly of lytoceratid
ammonites as well as their role in the evolution of all ammonites is under constant debate. In this work, the Lytoceratoidea investigated
on generic level for the presence of a septal lobe. Included into this investigation is the verification of relevant literature and the
registration of the collected literature in a database system. Furthermore material from public and private collections was studied.
The investigation reveals that all Lytoceratoidea are characterised by the presence of a septal lobe which constitutes their monophyly
(cp. Arkell et al., 1957). The septal lobe represents a consistent morphological character that appeared in the lowermost Jurassic and
is present in the uppermost Cretaceous members of Lytoceratoidea. It was noticed that the septal lobe appeared earlier in ontogeny and
was stronger developed in most of the stratigraphical younger representatives compared to Jurassic members (acceleration). In addition,
further characters have been investigated and tested for their phylogenetic significance. It turned out that most of these characters e. g.
whorl section, course and number of constrictions are homoplastic or highly variable within one genus. Finally, six characters (septal
lobe, parabolic ribs, fimbriation, shape of adult lateral lobe, primary suture, jaw type) have been kept for stratocladistic analyses.
With this method the phylogeny within the Lytoceratoidea was enlightened as far as possible. Within the family Lytoceratidae five
monophyletic subfamilies are retained : Ectocentritinae, Pleuroacanthinae, Lytoceratinae, Alocolytoceratinae and Megalytoceratinae.
The monophyly of the second family Tetragonitidae is based on the distribution of the quinque- and sixlobate primary suture line and
the development of a rhynchaptychus (Engeser & Keupp, 2002). Within the Tetragonitidae two subfamilies (Gaudryceratinae and
Tetragonitinae) and one tribus Gabbioceratini are retained. This work has been the first critical-systematical review for the whole group
within the last forty years. As a main result of this investigation fifteen genera have been excluded from Lytoceratoidea, seventeen
genera have been regarded as junior subjective synonyms. A sexual dimorphic couple is presented for Anagaudryceras (M) and
Anagaudryceras (Zelandites [m]) for the first time in addition to the two well known of Lytoceras (M). Thirty genera have been retained
as valid lytoceratid taxa. For some genera e. g. Lobolytoceras and Protetragonites the stratigraphic distribution has been extended
significantly. “Trachyphyllites” costatus is included into Analytoceras hermanni and represents a typical Lower Jurassic lytoceratid
member. It appears that the Lytoceratoidea are derived from psiloceratids at the Triassic-Jurassic-boundary as already stated by Guex
(1987).
The author assents the statement of Guex (1987) and regards the Lytoceratoidea as members of Ammonitina. Tetragonitidae are
derived from Protetragonites. Both taxa develop non-fimbriate ribs in contrast to contemporary lytoceratids. Protetragonites fraasi
from the Oxfordian (Upper Jurassic) represents the oldest member of that genus. Judging from the two characters sixlobate primary
suture and septal lobe, discussed above, Lytoceratoidea represent the most advanced ammonoid group.
In the second part of this thesis the functional significance of the septal lobe was investigated. It was planned to calculate the ratio of
chamber volume against its surface. For this purpose a Gaudryceras specimen in hollow preservation was scanned using computer
tomography at the “Bundesanstalt für Materialforschung und -prüfung” (Berlin). The ammonite was digitalised at “Konrad-Zuse-
Institut” (Berlin) using AM IRA®. Unfortunately, the resolution was too low for the project. The positive effect of the ratio of chamber
volume against its surface caused by the septal lobe can therefore only be assumed. It is supposed that the septal lobe increases the
efficiency of the hydrostatic apparatus.
Several ammonite fossil assemblages from Sierra de Albarracín (Teruel, Castilian Branch) contain abundant specimens of the Ovale and Laeviuscula zones (lower Bajocian, Middle Jurassic), including microconchs and macroconchs of the characteristic genus Albarracinites. Over 1500 ammonites from the type horizon of the species A. albarraciniensis, in the outcrop of Masada Toyuela, have been studied.
Ammonites are commonly preserved as phosphatized, calcareous, concretionary internal moulds (mean size = 50.5 mm) of unflattened shells, partially or completely filled with relatively heterogeneous mudstone to wackestone sediment. Incomplete, fragmented phragmocones with calcitic septa are the dominant remains, generally bearing traces of rounding, incrustation and bioerosion. Taphonomic data, such as the predominant taphonomic populations of type 3, composed of reelaborated, relatively heterogeneous concretionary internal moulds, isolated concretionary body chambers and hollow ammonites, bearing traces of abrasion, bioerosion and encrusting organisms, are indicative of low rate of sedimentation and occasional high rate of sediment accumulation, due to sedimentary winnowing and bypassing interrupted by storm depositional events, in shallow-water marine environments. The exceptional occurrence of taphonic populations of type 2 belonging to Albarracinites and Hebetoxyites, with dominant shells of pre-adults and absence of juveniles, suggests autochthonous biogenic production of shells by indigenous populations of Sub-Mediterranean taxa at the Iberian platform system.
In the outcrop of Masada Toyuela, the Albarracinites beds correspond to a condensed section, developed in shallow-water, open-marine, carbonate environments of the External Castilian platform. The sharp, irregular base of beds and the normal grading of reworked elements suggest these carbonate deposits were affected by tractive currents, scouring and redeposition. Limestone beds represent storm-related sedimentary events, whereas the local marly intervals represent background-sedimentation time-intervals of winnowing and bypassing on the seafloor. This condensed section is composed of at least four, decimetric or centimetric, expanded-deposit intervals, stacked and showing an overall thinning upward, which constitute a deepening sequence developed during two biochrons. Taphonomic results also corroborate the development of an incipient-deepening phase, which represents the first episode of a deepening half-cycle of third order, in the Albarracín area within the Castilian platform, during the Ovale and Laeviuscula biochrons (early Bajocian).
In this work the main directions of study of ontogeny and phylogeny of Paleozoic ammonoids are discussed, and the results of studies of the Permian families of this subclass are presented. It is shown that the morphogenetic evolution of taxa of different rank is caused by manifestation of major phylogenetic moduses and their various combinations. Thus, development can proceed in the direction of morphological complexity and in the direction of simplification. The conclusion about the role of family in the evolutionary history of ammonoids, which depends on the complexity of its structure, was made: the more complex it is, the greater the perspective taxon can be for formation of new groups of the supraspecific rank.
Paleozoic ammonoids have attracted much less attention from professional and amateur paleontologists than Mesozoic ammonoids. Because of the Variscan folding in Europe, the classical area of investigation, Devonian and Carboniferous material from Europe is often rather poorly preserved. As a result, few collectors of the 19th and early 20th century have focused their attention on these fossils. In recent decades, however, as our knowledge of Paleozoic ammonoids has expanded, it has become more and more apparent that the evolution and systematics of Paleozoic forms are as complex as those of Mesozoic ones. For example, the number of Devonian genera rose from about 80 in the Treatise of 1957 to a present figure of more than 200.
The main evolutionary trends in the Permian ammonoids are traced, and the systematics of this group is revised at the ordinal, family, and generic levels. All Permian species and their stratigraphie and geographic ranges are listed. The phylogenetic relationships within all Permian ammonoid families are discussed. For a number of them, new phylogenetic reconstructions are made.
We investigated the morphology and microstructure of the early whorls of goniatites with aragonitic preservation from the Upper Carboniferous Buckhorn Asphalt (Oklahoma, USA). These specimens probably all belong to the same species or to several closely related species. The ammonitella diameter is approximately 0.8 mm and the ammonitella angle is approximately 360°. The initial chamber is ellipsoidal and is surrounded by the first whorl of the ammonitella. The outer surface of the ammonitella is smooth without any trace of ornamentation or growth lines. In contrast, growth lines and lirae are present on the postembryonic shell. The dorsal end of the initial chamber terminates in a thick flange. There is an elongate muscle scar on the inside surface of the initial chamber above the flange. The wall of the initial chamber consists of three layers, the outermost of which is the dorsal wall of the next whorl. The wall of the first whorl of the ammonitella consists of
four layers:
1) Inner prismatic layer (= the mural part of the proseptum and subsequent septa).
2) Middle granular/subprismatic layer (= the wall proper of the ammonitella).
3) Very thin outer prismatic layer.
4) Dorsal wall of the next (postembryonic) whorl.
The wrinkle layer first appears on the ventral surface of the initial chamber near the ammonitella edge. This layer is the outer component of the dorsal wall and disappears on the postembryonic shell. In median cross-section the proseptum and second septum are closely spaced on
the dorsal side. The proseptum is prismatic and the second septum is nacreous. There are many similarities between the ammonitellas of these goniatites and those of Mesozoic ammonoids, implying a similar mode of embryonic development. However, there are also several important differences relating to the shape of the ammonitella and its ornamentation. This variation in the morphology of the ammonitella can be used for phylogenetic analysis.
Ammonoids retain a record of growth in their shells, and, therefore, material is readily available for studies of early ontogeny. Such studies were performed first in the mid-19th century and have been pursued with vigor ever since. Using optical and scanning electron microscopy, ammonoid workers have described the morphology of the early whorls and have attempted to reconstruct the sequence of early ontogenetic development and to identify the embryonic shell.
Ammonites are externally shelled cephalopods and range in geologic age from the Devonian to the Late Cretaceous. They comprise nine orders that may be informally grouped into the paleo-, meso-, and neoammonoidea. The paleoammonoidea consists of the Devonian-Permian goniatites, anarcestids, clymeniids, and prolecanitids. The mesoammonoidea or ceratites range from the Permian to the Triassic. The neoammonoidea consists of the phylloceratids, lytoceratids, ammonitids, and ancyloceratids and ranges from the Jurassic to the Cretaceous.
A general classification of cephalopods, a vast group of extinct and living mollusks with unique biological organization and a rich evolutionary history is proposed. Major schemes of the classification in this group are considered and analyzed. The earliest cephalopods are assigned to the subclass Ellesmeroceratoidea. Other cephalopods are divided into seven subclasses: Endoceratoidea, Actinoceratoidea, Nautiloidea, Orthoceratoidea, Bactritoidea, Ammonoidea, and Coleoidea. This macrosystem most fully reflects the morphological diversity and major developmental trends in cephalopod mollusks. Short diagnoses of the above subclasses are proposed.
The ammonoid order Prolecanitida constitutes a relatively small (43 genera, ∼250 species) but long-ranging lineage (Lower Carboniferous-Triassic, ∼108 m.y.), which narrowly survived the P/Tr extinctions and provided the stock from which were derived all later Mesozoic ammonoids. Prolecanitids were a minority among Late Paleozoic ammonoids, which were dominated by the Goniatitida, and showed many features that set them far apart from their contemporaries, including (1) long-term, gradual changes in shell geometry (W-D-S); (2) the most strongly constrained morphospace of any Paleozoic ammonids examined to date; (3) an eight-fold increase in mean suture complexity (three times that of Pennsylvanian goniatitids); (4) high correlations between shell geometry, shell and septal thickness, and suture complexity; (5) short body chambers and as a consequence, high aperture orientations; (6) indications that cameral liquid may have been used for buoyancy control; and (7) a genus longevity that averaged 14.7 m.y. compared with 5.7 m.y. in Upper Carboniferous goniatitids, and that appears to have been unrelated to suture complexity. Prolecanitids showed a pervasive tendency to increase suture complexity (in the clade as a whole as well as within subclades and in more than 90 percent of ancestor-descendant genera), thus arguing a case for a driven complexity trend. The uniqueness of the prolecanitids calls into question whether they and their Mesozoic descendants, ceratites and ammonites, were strictly analogous to Paleozoic goniatites.
Zusammenfassung In Lehrbüchern der Paläontologie findet sich häufig der Hinweis, dass der Begriff "Ammonit" bereits von PLINIUS dem Älteren (23 oder 24–79 n. Chr.) in seiner "Naturalis historiae" verwendet wurde. Ob damit tatsächlich Ammoniten gemeint waren, war allerdings bereits vor mehr als hundert Jahren in Frage gestellt worden; Steinkerne einer großen Schnecke (Natica sp.) aus dem Eozän Ägyptens entsprechen offensichtlich viel besser der kurzen Beschreibung bei PLINIUS. Die Möglichkeit, dass der phönikische Gott Baal Hammon zusammen mit dem ägyptischen Gott Amun für die Her-leitung des Begriffes "Ammonit" in Frage kommt, wird diskutiert. *) Vortrag beim 3. Symposium "Geschichte der Erdwissenschaften in Österreich", 27.–29. September 2001, Hallstatt, Oberösterreich. Abstract In textbooks on palaeontology the statement that the term "ammonite" had first been used by PLINY the Elder (23 or 24–79 A.D.) in his "Naturalis historiae" can frequently be found. Whether this term does really refer to ammonites was questioned already more than hundred years ago; steinkerns of a large gastropod (Natica sp.) from the Eocene of Egypt obviously fit much better the short description given by PLINY. The possibility that the Phoe-nician god Baal Hammon together with the Egyptian god Amun may be involved in the origin of the term "ammonite" is discussed.
Mit Tafel 3—6 und Abb. 14—47 im Text und auf 2 Beilagen 2. Die eigentlichen Desmoceratinae der höheren Unterkreide weisen einen andersartigen, aber bereits bekannten Lobenbildungsmodus auf. In ähnlicher Weise wie bei den Perisphincten (Abb. 5) wird auch bei der typischen Gattung Desmoceras (Abb. 14) in einem sehr frühen Stadium der Lobenboden des Uj verbreitert und durch eine mediane Aufsattelung gespalten (Abb. 14b). Erst danach (Abb. 14c) wird im Sattel U 2 U lv der erste Metalobus angelegt. Dieser U 3 verbleibt im Verlaufe der weiteren Entwick lung auf der Flanke, der U lT dagegen in der Internsutur, in absoluter Ent sprechung der bei den Perisphincten beobachteten Verhältnisse. Ebenfalls übereinstimmend verhält sich der U 4 , der symmetrisch zur Naht weiter auf spaltet und damit zum Suspensivlobus wird (Abb. 14g). Die resultierende Lobenformel E L U 2 U 3 U 4 = S U lv U ld I charakterisiert neben den jüngeren Desmoceratinae des Apt, Alb und der Oberkreide auch die Puzosiinae, Kossmaticeratidae, Pachydiscidae 1 und wohl auch die Diaziceratidae 2 . Stellvertretend für alle diese Formen sei hier nur die Lobenentwicklung von Parasilesites (Abb. 15) wiedergegeben, der von seinem Autor (R. IMLAY 1959) den Silesitidae zugerechnet wurde. Statt dessen bestehen jedoch offensichtliche Beziehungen zur Gattung Pu-%osia, mit der die bisherigen Parasilesites-Arten auch generisch vereinigt wurden. Die Gattung IMLAY'S ist daher besser den Puzosiinae zuzuordnen.
Intra- and interspecific variation in the early internal shell features of ammonoids has been examined in 14 Late Cretaceous species representing four suborders on the basis of large samples from Hokkaido (Japan) and the U.S. Western Interior Province. Our observations indicate that quantitative characters such as the size of the initial chamber and ammonitella, the length of the prosiphon, and the ammonitella angle exhibit moderate variation within species. The ranges of variation partly overlap among species, indicating
that these characters are not suitable for studies of the higher-level systematics of ammonoids, but may sometimes help diagnose species. In contrast, there is much less variation within species with respect to qualitative characters such as the shape of the prosiphon, the presence or absence of accessory threads of the prosiphon, the shape of the caecum, and the initial position of the siphuncle. Examination of these characters shows that they appear to be stable at the superfamily level for the Ammonitina, but variable among species in the Lytoceratina. Thus, these characters are potentially more useful for higher-level phylogenetic analysis.
Intra- and interspecific variation in the early internal shell features of ammonoids has been examined in 14 Late Cretaceous species representing four suborders on the basis of large samples from Hokkaido (Japan) and the U.S. Western Interior Province. Our observations indicate that quantitative characters such as the size of the initial chamber and ammonitella, the length of the prosiphon, and the ammonitella angle exhibit moderate variation within species. The ranges of variation partly overlap among species, indicating that these characters are not suitable for studies of the higher-level systematics of ammonoids, but may sometimes help diagnose species. In contrast, there is much less variation within species with respect to qualitative characters such as the shape of the prosiphon, the presence or absence of accessory threads of the prosiphon, the shape of the caecum, and the initial position of the siphuncle. Examination of these characters shows that they appear to be stable at the superfamily level for the Ammonitina, but variable among species in the Lytoceratina. Thus, these characters are potentially more useful for higher-level phylogenetic analysis.
Major classifications of nautiloid cephalopods are critically reviewed. It is suggested that this cephalopod group is subdivided
into 5 subclasses and 17 orders: Ellesmeroceratoidea (including the orders Plectronocerida, Protactinocerida, Yanhecerida,
and Ellesmerocerida), Endoceratoidea (including the orders Endocerida and Intejocerida), Actinoceratoidea (including the order
Actinocerida), Nautiloidea (with the orders Basslerocerida, Tarphycerida, Lituitida, Discosorida, Oncocerida, and Nautilida),
and Orthoceratoidea (including the orders Orthocerida, Ascocerida, Dissidocerida, and Bajkalocerida). The above orders are
briefly described.
The Principles of Systematics, System, and Phylogeny of Paleozoic Ammonoids (Akad
- V E Ruzhencev
The Ontogeny of Permian Pronoritidae and Medlicottiidae and the Problem of the Origin of Ceratites,” in Systematics and Evolution of Invertebrates of the Russian Far East (Dal’nevost
- D Yu
Mollusks, Cephalopods: 2. Ammonoids (Ceratites and Ammonites)
- Fundamentals
- Paleontology
Evolution of Septal Necks in Ammonoids
- V V Drushchits
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