Discosorids and Oncocerids (Cephalopoda) of the Middle Ordovician Kunda and Aseri Regional Stages of Baltoscandia and the early evolution of these groups

Kröger, Björn; Zhang, Yunbai; Isakar, Mare

doi:10.1016/j.geobios.2008.09.006

Cited by 24 publications

(25 citation statements)

References 6 publications

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“…5), which appeared in the earliest Ordovician ($480 Ma) and went extinct during the Paleozoic [50,51]. In contrast, the coleoids are hypothesised descendents of a specialised group of cephalopods with simple straight shells (the Orthocerida) [52,53].…”

Section: The Ancestor Of Extant Cephalopods -A Late-comer According Tmentioning

confidence: 99%

“…In contrast, the coleoids are hypothesised descendents of a specialised group of cephalopods with simple straight shells (the Orthocerida) [52,53]. The fossil record indicates a divergence between these hypothesised ancestors of Nautilus and the straight ancestors of coleoids by the early Palaeozoic ($480 Ma) [50,51,54].…”

Section: The Ancestor Of Extant Cephalopods -A Late-comer According Tmentioning

confidence: 99%

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Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules

2011

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Cephalopods are extraordinary molluscs equipped with vertebrate-like intelligence and a unique buoyancy system for locomotion. A growing body of evidence from the fossil record, embryology and Bayesian molecular divergence estimations provides a comprehensive picture of their origins and evolution. Cephalopods evolved during the Cambrian (∼530 Ma) from a monoplacophoran-like mollusc in which the conical, external shell was modified into a chambered buoyancy apparatus. During the mid-Palaeozoic (∼416 Ma) cephalopods diverged into nautiloids and the presently dominant coleoids. Coleoids (i.e. squids, cuttlefish and octopods) internalised their shells and, in the late Palaeozoic (∼276 Ma), diverged into Vampyropoda and the Decabrachia. This shell internalisation appears to be a unique evolutionary event. In contrast, the loss of a mineralised shell has occurred several times in distinct coleoid lineages. The general tendency of shell reduction reflects a trend towards active modes of life and much more complex behaviour.

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Section: The Ancestor Of Extant Cephalopods -A Late-comer According Tmentioning

confidence: 99%

Section: The Ancestor Of Extant Cephalopods -A Late-comer According Tmentioning

confidence: 99%

Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules

2011

Self Cite

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“…By comparison with the faunas of South China and Baltica, that of the Alborz is of very restricted diversity, which on current evidence lacks representatives of the Oncocerida, Tarphycerida, or Lituitida, all of which were thriving during the Darriwilian in South China and Baltica (King 1990(King , 1999Kröger et al 2009;Xiao et al 2006).…”

Section: Biostratigraphical and Palaeobiogeographical Significance Ofmentioning

confidence: 78%

“…-Following the recognition of a small, spherical or subspherical protoconch lacking a cicatrix in Isorthoceras (Kröger et al 2009(Kröger et al , 2011, assignment of this group to the Pseudorthocerataceae (Sweet 1964) or Pseudorthocerida (Kröger & Isakar 2006), no longer seems tenable and the Proteoceratidae were placed in the Orthocerida (Kröger et al 2011).…”

Section: Family Proteoceratidae Flower 1962mentioning

confidence: 99%

Review of the Early to Mid Ordovician orthoconic cephalopods from Iran

Evans¹,

Pour²,

Попов³

2012

Bull. Geosci.

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“…In the Nautilus type, the connecting ring is composed of an inner fibrous organic layer that originates from the nacreous layer of the septal neck, and an outer spherulitic -prismatic layer that takes its origin on the outer surface of the septal neck. In addition to recent Nautilus, this type of connecting ring also occurs in fossil ellesmerocerids, tarphycerids, oncocerids, endocerids, and nautilids (Mutvei 2002;Kröger & Mutvei 2005;Kröger et al 2009;Mutvei & Dunca 2010;Mutvei et al 2011). In the calcified-perforate type, the connecting ring consists of an outer spherulitic -prismatic layer as that in the Nautilus type, but the inner fibrous organic layer is replaced by a structurally modified calcareous layer with pore canals.…”

Section: Introductionmentioning

confidence: 97%

Silurian oncoceridOctamerella(Cephalopoda) from Gotland, Sweden

Mutvei

2011

GFF

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An actinosiphonate deposit with radial lamellae occurs in the siphuncle of several genera classified within the Oncocerida. Unique structural preservation of the connecting ring and the actinosiphonate deposit is here described in the oncocerid Octamerella sp. from the Silurian of Gotland, Sweden. The connecting ring of Octamerella is of the Nautilus type. It consists of an outer porous spherulitic-prismatic layer and an inner thin fibrous organic layer, the latter destroyed by diagenesis. The actinosiphonate deposit consists of two, structurally different, spherulitic-prismatic sublayers. The thin outer sublayer has a fragile porous structure and low mechanical strength, similar to the outer spherulitic-prismatic layer of the connecting ring. The inner spherulitic-prismatic sublayer that forms the actinosiphonate lamellae has a more rigid, less porous structure and higher mechanical strength than the outer sublayer. Each lamella is longitudinally traversed by a calcareous central plate that has a solid structure and consists of thin acicular crystallites that are orientated parallel to the long axis of the plate. The secretion of the actinosiphonate deposit probably began immediately after a new siphuncular segment was completed. The connecting ring together with the actinosiphonate deposit functioned as a reservoir and transport route for the cameral liquid improving the buoyancy regulation.

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Discosorids and Oncocerids (Cephalopoda) of the Middle Ordovician Kunda and Aseri Regional Stages of Baltoscandia and the early evolution of these groups

Cited by 24 publications

References 6 publications

Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules

Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules

Review of the Early to Mid Ordovician orthoconic cephalopods from Iran

Silurian oncoceridOctamerella(Cephalopoda) from Gotland, Sweden

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