Refined age and geological context of two of Australia’s most important Jurassic vertebrate taxa (Rhoetosaurus brownei and Siderops kehli), Queensland

Todd, Christopher N., Roberts, Eric M., Knutsen, Espen M., Rozefelds, Andrew C., Huang, Hui-Qing, and Spandler, Carl (2019) Refined age and geological context of two of Australia’s most important Jurassic vertebrate taxa (Rhoetosaurus brownei and Siderops kehli), Queensland. Gondwana Research, 76. pp. 19-25.

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Australia’s Jurassic vertebrate fossil record remains extremely sparse with only two dinosaur taxa and two temnospondyl amphibians identified to date. Of these, the spectacular and extremely well-preserved giant amphibian, Siderops kehli, and the only known pre-Cretaceous sauropod in Australia, Rhoetosaurus brownei, are perhaps the most important. The age of both specimens, and the stratigraphic context of Rhoetosaurus brownei, are weakly constrained and imprecisely defined, limiting our understanding of their evolutionary relationships within a broader Gondwanan context. To clarify and contextualise the evolutionary relationships and ages of these two iconic Jurassic taxa, we used UPb detrital zircon geochronology to date the sandstone matrix from around the bones of the historic museum specimens. The robust maximum depositional age for Siderops was calculated at 176.6 Ma ± 2 Ma, indicating that it is no older than late Toarcian, which refines existing biostratigraphic estimates. The Rhoetosaurus maximum depositional age was determined to be 162.6 ± 1.1 Ma, no older than early Oxfordian, demonstrating that the fossils are younger than expected, and definitely recovered from the Walloon Coal Measures.

Item ID: 61479
Item Type: Article (Research - C1)
ISSN: 1342-937X
Keywords: Jurassic, Rhoetosaurus brownei, Siderops kehli, Walloon Coal Measures, Evergreen Formation
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Copyright Information: © 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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A version of this publication was included as Chapter 4 of the following PhD thesis: Todd, Christopher Noel (2020) The sedimentary evolution of Permian to Cretaceous basins in Queensland, Australia: insights from lithostratigraphy, U–Pb zircon geochronology, sedimentary facies, and provenance analysis. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Research Council (ARC), James Cook University
Projects and Grants: ARC Jurassic Arc: Reconstructing the Lost World of Eastern Australia Project (DP180102851)
Date Deposited: 22 Jan 2020 04:21
FoR Codes: 37 EARTH SCIENCES > 3705 Geology > 370502 Geochronology @ 80%
37 EARTH SCIENCES > 3705 Geology > 370506 Palaeontology (incl. palynology) @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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