Cephalopods in the marine ecosystems of the Paleozoic

Барсков, И. С.; Boiko, M. S.; Konovalova, V. A.; Леонова, Т. Б.; Nikolaeva, Svetlana

doi:10.1134/s0031030108110014

Cited by 30 publications

(26 citation statements)

References 33 publications

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“…No consensus has been reached concerning the number of orders and subclasses, and their classification is therefore unsettled. Achieving a relatively stable state of classification in this macrosystem will depend not only on morphology, but also on evaluation of the disparity of morphological features and interpretation of the functional significance of this disparity (Barskov et al 2008). However, to recognize the major evolutionary patterns in non-ammonoid cephalopods, more intensive studies of their early ontogeny is necessary.…”

Section: Systematic Partmentioning

confidence: 99%

“…He stated that the contraction of the retractor muscles in orthocerids attached to the dorsal side of the shell close to the last septum "could not be used to expel water from the mantle cavity for swimming by jet propulsion, as in Nautilus" (p. 391). Considering the superficial similarity of Sphooceras and some other straightshelled cephalopods to some coleoids, it seems possible that the mantle was also liberated to become a muscular pumping organ that led to much more powerful jet propulsion, enabling rapid swimming (see also Barskov et al 2008).…”

Section: Ecology Of Sphoocerasmentioning

confidence: 99%

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"An endocochleate experiment" in the Silurian straight-shelled cephalopod Sphooceras

Turek¹,

Manda²

2012

Bull. Geosci.

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Sphooceras truncatum (Barrande, 1860), a Silurian straight-shelled cephalopod with a short finger-shaped shell, is one of a few cephalopods in which natural truncation of the apical part of the phragmocone from the rest of the conch is confirmed. Periodic natural removal of the apical part of the shell (4 to 5 phragmocone chambers) preceded formation of a terminal callus and a calcareous plug closing the septal foramen. The apical callus probably originated by fusion of the truncation septum with episeptal deposits. These structures temporarily formed the new apex on which two additional calcareous layers had been secreted. A unique specimen preserves a colour pattern in the convex apical region, which proves that the shell in Sphooceras was temporarily completely surrounded by mantle extending from the body chamber, i.e. the cephalopod was at least temporarily endocochleate. The co-occurrence of different growth stages of S. truncatum together with one type of short juvenile orthoceracone shell, with a maximum of eight phragmocone chambers and a very small subglobular initial chamber indicates that these embryonic shells may belong to Sphooceras. Two other genera are discussed, both previously included in the family Sphooceratidae: Disjunctoceras Gnoli in Kiselev, 1992 and Andigenoceras Gnoli in Kiselev, 1992. The newly discovered thickening of the apex in "Disjunctoceras" disjunctum, the type species of Disjunctoceras, indicates that this species does not differ substantially from Sphooceras and should be reassigned to this genus. Similarly, representatives of Andigenoceras also possess characteristic features of Sphooceras. Sphooceras has many features characteristic for modern cephalopods: short, thin-walled, semi-internal shell; phragmocone reduced to only a few chambers; uncalcified connecting rings; apical callus (a structure analogous to the belemnite rostrum); retractor muscle scars situated dorsally; very small protoconch without cicatrix. In some exceptionally well-preserved cephalopods with orthoceracone shell radula with seven rows of teeth were observed. All these features support the thesis that some straight-shelled cephalopods are evolutionarily closer to coleoids than nautiloids and their separation from nautiloids is legitimate. Vascular imprints on the surface of the cameral deposits provide further support for their primary origin and the existence of a cameral mantle. The character of cameral deposits in Sphooceras demonstrates that the systematic value of these structures in other straight-shelled cephalopods, a subject of controversy, has limited value. The morphology of Sphooceras also demonstrates that the boundary between endocochleate and ectocochleate cephalopods is not sharp, i.e. internalisation of the shell in cephalopods occurred repeatedly.•

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Section: Systematic Partmentioning

confidence: 99%

Section: Ecology Of Sphoocerasmentioning

confidence: 99%

"An endocochleate experiment" in the Silurian straight-shelled cephalopod Sphooceras

Turek¹,

Manda²

2012

Bull. Geosci.

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“…Ecological interactions between nautilids and ammonoids have recently been discussed including their early co-occurrence in the Early Devonian (Barskov et al 2008, Klug et al 2010, Manda & Turek 2011. Possible interaction between the two groups may aid understanding of the evolutionary pattern of ectocochleate cephalopods.…”

Section: Competition Nautilids Versus Ammonites And/or Ecological Sumentioning

confidence: 99%

“…Nevertheless, the vast majority of these endemic taxa are demersal nautilids (e.g. Barskov et al 2008, Manda & Turek 2009b, Turek & Manda 2011 and endemism in coiled nautilids is quite rare. The distribution pattern of Cretaceous Deltocymatoceras to some degree corresponds to recent nautilids and reflects a decrease in steeled nautilids in late Mesozoic ecosystems.…”

Section: Distribution Pattern Of Deltocymatoceras and Its Implicationsmentioning

confidence: 99%

“…Keeled venters are also commonly found in ammonoids, for example in representatives of the order Prolecanitida. Barskov et al (2008Barskov et al ( , p. 1228 mentioned that streamlined (compressed) shell shape together with a keel indicates good manoeuvrability in various shelf environments. The keel in several cephalopod groups thus played a different role, but the basic function seems to be stability control.…”

Section: Functional Morphology and Ontogenymentioning

confidence: 99%

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The endemic and morphologically remarkable nautilid genus Deltocymatoceras Kummel, 1956 from the Late Cretaceous of Central Europe

Frank¹,

Wilmsen²,

Košťák³

2013

Bull. Geosci.

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The endemic Late Cretaceous nautilid genus Deltocymatoceras Kummel, 1956 is represented by Deltocymatoceras leiotropis (Schlüter, 1876) and D. rugatum (Fritsch & Schlönbach, 1872). Characteristic for this genus is a bulbous involute shell with strong radial ribbing and a ventral keel, which appears in post-juvenile ontogenetic stages. The combination of these morphological features is unique among post-Palaeozoic nautiloids. Both species are restricted to the Late Turonian-Middle Coniacian of Central Europe and England. Until now, the type species D. leiotropis was known based only on the holotype specimen. This specimen is re-described with revised occurrence and for the first time photographically illustrated. The only preserved syntype from the type specimens of D. rugatum was re-discovered during this revision and more than thirty other specimens were studied. Representatives of Deltocymatoceras show clear morphological changes during their ontogeny and acquisition of maturity, most notably the appearance of a ventral keel in premature stages and its disappearance at maturity. The hypothesis of a close phylogenetic affinity of Deltocymatoceras to the genus Cymatoceras Hyatt, 1884 is based on similar morphological features such as the suture, ribbing, shell shape and early ontogenetic development. The ventral keel is quite an exceptional feature of morphology in post-Palaeozoic nautiloids. In particular the combination with an involute depressed shell is only shared with representatives of the genus Angulithes Montfort, 1808 (Cretaceous-Palaeogene) and Gryponautilus Mojsisovic, 1902 (Triassic). The combination with a compressed and evolute planispiral shell is more common in Palaeozoic and some post-Palaeozoic nautiloids. The ventral keel is discussed here in relation to its functional aspects (hydrodynamic stability) in combination with the strong radial ribbing (protection of the shell against mechanical damage). The appearance of the genus concurred with the late Turonian shallowing/cooling associated with the "Hyphantoceras Event" and the availability of an ecologic niche (i.e., absence of medium-sized, keeled ammonites at that time). Low abundance, an endemic occurrence, and the very short stratigraphic range of the genus (~3.5 Ma) reflect the limited evolutionary success of the Deltocymatoceras lineage.• Key words: Nautilida, taxonomy, phylogeny, ontogeny, palaeogeography, functional morphology, biostratigraphy. May 17, 2013; published online September 12, 2013; issued October 31, 2013. Jiří Frank, Institute of Geology and Palaeontology, Faculty of Science, Charles University, Albertov 6, 128 43 Praha 2, and National Museum, Department of Palaeontology, Václavské náměstí 68, 115 79 Praha 1, Czech Republic; jiri_frank@nm.cz • Markus Wilmsen, Senckenberg Naturhistorische Sammlungen Dresden, Museum für Mineralogie und Geologie, Sektion Paläozoologie, Königsbrücker Landstrasse 159, D-01109 Dresden, Germany; markus.wilmsen@senckenberg.de • Martin Košťák, Institute of Geology and Palaeontology, Facult...

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Palaeozoic Ammonoids – Diversity and Development of Conch Morphology

Korn

Klug²

2012

Earth and Life

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Cephalopods in the marine ecosystems of the Paleozoic

Cited by 30 publications

References 33 publications

"An endocochleate experiment" in the Silurian straight-shelled cephalopod Sphooceras

"An endocochleate experiment" in the Silurian straight-shelled cephalopod Sphooceras

The endemic and morphologically remarkable nautilid genus Deltocymatoceras Kummel, 1956 from the Late Cretaceous of Central Europe

Palaeozoic Ammonoids – Diversity and Development of Conch Morphology

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