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Foss. Rec., 21, 171-182, 2018
https://doi.org/10.5194/fr-21-171-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
07 Jun 2018
Rostrum size differences between Toarcian belemnite battlefields
Patrícia Rita, Kenneth De Baets, and Martina Schlott Geozentrum Nordbayern, Friedrich-Alexander Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
Abstract. Body size changes have been reported across crisis intervals. Belemnites – now considered extinct stem-decabrachians – have rarely been investigated for this purpose, and the few studies have resulted in ambiguous outcomes. Here we investigate two Toarcian belemnite accumulations in southern Germany from a morphometric point of view with the support of computed tomography data. The aim of this study is to test whether a difference in size can be observed between the rostra of the two studied samples, from individual lineage to community, and which proxy is more reliable. A significant decrease in median size from the Early Toarcian (Dactylioceras tenuicostatum Zone) to the Middle Toarcian (Haugia variabilis Zone) is recognized. This is observed at the community level of organization, considering the whole assemblage, but also within Passaloteuthis–Acrocoelites lineage, at the genus level. It is also demonstrated that diameter-based measurements or maximum preserved length are not reliable proxies for size, and therefore apical length or three-dimensional approximations, such as the geometric mean or the post-phragmocone volume, are more advisable. This is especially important when comparing specimens with markedly different rostrum shapes. Further studies are, however, still necessary to disentangle the mechanisms behind the reduction in rostrum size within the Toarcian and their putative environmental causes.
Citation: Rita, P., De Baets, K., and Schlott, M.: Rostrum size differences between Toarcian belemnite battlefields, Foss. Rec., 21, 171-182, https://doi.org/10.5194/fr-21-171-2018, 2018.
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Short summary
With the support of CT data, a morphometric analysis was performed with the aim of investigating the rostrum size differences between two Toarcian belemnite accumulations. A decrease in size from the Early Toarcian to the Middle Toarcian is recognized. It is also demonstrated that diameter-based measurements or maximum preserved length are not reliable proxies for rostrum size, and therefore apical length or three-dimensional approximations are more advisable.
With the support of CT data, a morphometric analysis was performed with the aim of investigating...
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