Ammonoid Buoyancy

Hoffmann, René; Lemanis, Robert; Naglik, Carole; Klug, Christian

doi:10.1007/978-94-017-9630-9_16

Cited by 29 publications

(42 citation statements)

References 129 publications

(271 reference statements)

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“…For septal crowding related to the terminal countdown morphology (reaching the adulthood) these interpretations seem to be correct because reduced septal spacing is indeed known to be associated with reduced chamber volumes in adult Nautilus pompilius and Spirula spirula shells (Hoffmann et al . , , b; Lemanis et al . ).…”

Section: Discussionmentioning

confidence: 99%

“…Supplementing these traditional morphological data, recent tomographic studies (grinding‐ or computed tomography (CT)) of cephalopod shells have been published, dealing with completely new data, such as chamber volumes and chamber surface areas, in order to address questions about their palaeobiology, such as buoyancy control or septal function (Hoffmann et al . , , b; Tajika et al . , ; Lemanis et al .…”

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confidence: 99%

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Integrating 2D and 3D shell morphology to disentangle the palaeobiology of ammonoids: a virtual approach

et al. 2017

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Based on data derived from computed tomography, we demonstrate that integrating 2D and 3D morphological data from ammonoid shells represents an important new approach for investigating the palaeobiology of ammonoids. Characterization of ammonite morphology has long been constrained to 2D data, with only a few studies collecting ontogenetic data in 180°steps. Here we combine this traditional approach with 3D data collected from high-resolution nano-computed tomography. Ontogenetic morphological data on the hollow shell of a juvenile ammonite Kosmoceras (Jurassic, Callovian) was collected. 2D data was collected in 10°steps and show significant changes in shell morphology. Preserved hollow spines show multiple mineralized membranes never reported before, representing temporal changes in the ammonoid mantle tissue. 3D data show that chamber volumes do not always increase exponentially, as was generally assumed, but may represent a proxy for life events, such as stress phases. Furthermore, chamber volume cannot be simply derived from septal spacing in forms comparable to Kosmoceras. Vogel numbers represent a 3D parameter for chamber shape, and those for Kosmoceras are similar to other ammonoids (Arnsbergites, Amauroceras) and modern cephalopods (Nautilus, Spirula). Two methods to virtually document the suture line ontogeny, used to document phylogenetic relationships of larger taxonomic entities, were applied for the first time and present a promising alternative to hand drawings. The curvature of the chamber surfaces increases during ontogeny due to increasing strength of ornamentation and septal complexity. As this may allow for faster handling of cameral liquid, it could compensate for decreasing SA/V ratios through ontogeny.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Integrating 2D and 3D shell morphology to disentangle the palaeobiology of ammonoids: a virtual approach

et al. 2017

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“…; Hoffmann et al . ). We can therefore expect (with further correction) a more symmetrical and thus upright position than that depicted in Figure B (right, posterior view).…”

Section: Resultsmentioning

confidence: 97%

“…; Hoffmann et al . ). Reyment () explained that, although the Nautilus shell has a density of around 2.61–2.62 g/cm 3 , its septa contain less organic material and thus have densities of 2.93–2.94 g/cm 3 , corresponding to the specific density of aragonite in its pure state.…”

Section: Methodsmentioning

confidence: 97%

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Buoyancy of some Palaeozoic ammonoids and their hydrostatic properties based on empirical 3D-models

Naglik

Rikhtegar

Klug

2016

LET

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The interpretation of the function of the ammonoid phragmocone as a buoyancy device is now widely accepted among ammonoid researchers. During the 20th century, several theoretical models were proposed for the role of the chambered shell (phragmocone); accordingly, the phragmocone had hydrostatic properties, which enabled it to attain neutral buoyancy, presuming it was partially filled with gas. With new three‐dimensional reconstructions of ammonoid shells, we are now able to test these hypothetical models using empirical volume data of actual ammonoid shells. We investigated three Palaeozoic ammonoids (Devonian and Carboniferous), namely Fidelites clariondi, Diallagites lenticulifer and Goniatites multiliratus, to reconstruct their hydrostatic properties, their syn vivo shell orientation and their buoyancy. According to our models, measurements and calculations, these specimens had aperture orientations of 19°, 64° and 125° during their lives. Although none of our results coincide with the aperture orientation of the living Nautilus, they do verify the predictions for shell orientations based on published theoretical models. Our calculations also show that the shorter the body chamber, the poorer was the hydrodynamic stability of the animal. This finding corroborates the results of theoretical models from the 1990s. With these results, which are based on actual specimens, we favour the rejection of hypotheses suggesting a purely benthonic mode of life of ammonoids. Additionally, it is now possible to assess hydrodynamic properties of the shells through ontogeny and phylogeny, leading to insights to validate theoretical modes of life and habitat through the animal's life.

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Polymorphism in Late Cretaceous phylloceratid ammonoids: evidence from ontogenetic trajectories of septal spacing

Iwasaki

Wani

2019

Papers in Palaeontology

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The ontogenetic trajectories of septal spacing between succeeding chambers of two phylloceratid ammonoids, Hypophylloceras subramosum and Phyllopachyceras ezoense, from the Haboro and Kotanbetsu areas, north‐western Hokkaido, Japan, were analysed. The ontogenetic trajectories of septal spacing of H. subramosum demonstrate a general trend with large intraspecific variation: two cycles of increasing to decreasing spacing followed by almost constant spacing. The large intraspecific variation can be subdivided into three types, making this species polymorphic. The ontogenetic trajectories of septal spacing of P. ezoense also show intraspecific variation, but with a different trend: one cycle of increasing to decreasing spacing and an increasing trend after that. The intraspecific variation can be subdivided into two types, which suggests that this species is dimorphic, possibly sexually dimorphic. Dimorphism is supported by two observations: (1) the difference in the ontogenetic trajectories of septal spacing is only seen in the later ontogenetic stages; and (2) the two types co‐occur with comparable abundance throughout all stratigraphic horizons. Detailed analyses of ontogenetic trajectories of septal spacing may reveal polymorphism in other ammonoid clades.

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Ammonoid Buoyancy

Cited by 29 publications

References 129 publications

Integrating 2D and 3D shell morphology to disentangle the palaeobiology of ammonoids: a virtual approach

Integrating 2D and 3D shell morphology to disentangle the palaeobiology of ammonoids: a virtual approach

Buoyancy of some Palaeozoic ammonoids and their hydrostatic properties based on empirical 3D-models

Polymorphism in Late Cretaceous phylloceratid ammonoids: evidence from ontogenetic trajectories of septal spacing

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