High diversity in the Triassic Cassian Formation

Conference contribution
(Abstract of lecture)


Publication Details

Author(s): Roden V, Hausmann IM, Seuß B, Nützel A, Kießling W
Publication year: 2018
Language: English


Abstract

The Middle to Upper Triassic Cassian Formation (Dolomites, Northern
Italy) is the most diverse early Mesozoic ecosystem worldwide. A
compilation of taxa described from the Cassian Formation contains 1336
species after revision. The species richness is very high compared with
other fossil lagerstätten known for their diversity. For example, 228
species are reported in the Early Cambrian Chengjiang biota, 280 from
the Upper Carboniferous Mazon Creek fauna, 491 from the Eocene London
Clay, 147 from the Lower Devonian Hunsrück Slate, a literature
compilation of the Upper Carboniferous Finis Shale of Texas yields 332
species, and a total of 861 animal species is reported from the Upper
Jurassic Solnhofen Formation. Although the Cassian Formation stands out
in the fossil context, a much higher species richness is recorded in
Recent tropical ecosystems. For example, a comprehensive survey in New
Caledonia, south-west Pacific, yielded 2738 species of molluscs alone
(P. Bouchet et al., 2002).
With gastropods comprising 70 % of mollusc species (53 % of all
species), it is clear that aragonite preservation has a large impact on
the diversity of the Cassian fauna. In general, fossil lagerstätten can
yield highly diverse communities due to preservational effects. To
assess the degree to which the Cassian diversity is driven by a
lagerstätten effect, we compare the proportion of stratigraphic
singletons among well-known lagerstätten (Chengjiang biota, Hunsrück
Slate, Mazon Creek fauna, Solnhofen, London Clay). Among those, the
Cassian Formation yields the lowest proportion of singleton genera
(17%), and next to lowest proportion of singleton species (68%).
The lagerstätten effect is therefore lower than in most other datasets.
We consequently conclude that intensive taxonomic work and
preservational bias are not the only factors contributing to the high
diversity. Beyond the large area (at least 500 km2) and variety of
environments covered by the Cassian Formation, yielding a very high beta
diversity (mean proportional dissimilarity of 0.94), as well as
aragonite preservation, the favorable living conditions in this tropical
reef-basin allowed a high dlyiverse fauna to flourish.


FAU Authors / FAU Editors

Kießling, Wolfgang Prof. Dr.
Lehrstuhl für Paläoumwelt
Roden, Vanessa
Lehrstuhl für Paläoumwelt
Seuß, Barbara Dr.
Lehrstuhl für Paläoumwelt


External institutions with authors

Ludwig-Maximilians-Universität (LMU)


How to cite

APA:
Roden, V., Hausmann, I.M., Seuß, B., Nützel, A., & Kießling, W. (2018). High diversity in the Triassic Cassian Formation. Paper presentation at GeoBonn2018, Living Earth, Bonn.

MLA:
Roden, Vanessa, et al. "High diversity in the Triassic Cassian Formation." Presented at GeoBonn2018, Living Earth, Bonn 2018.

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Last updated on 2019-24-04 at 05:21

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