Ben Creisler
Recent papers:
We report the first definite specimen of a thalattosuchian crocodylomorph from the Portland Stone Formation of England. This specimen (an isolated tooth crown) can be referred to the teleosauroid genus Machimosaurus based on its conical shape, distinctive enamel ornamentation and lack of carinae. Understanding the faunal composition of the Portland Stone Formation is key to elucidating the distinct shift in crocodylomorph taxa that occurred during the Tithonian-to-Berriasian in Europe. One of the most striking aspects of this faunal shift is the hypothesised extinction of Teleosauroidea in Europe. The presence of Machimosaurus in the Portland Stone Formation supports the hypothesis that the localised marine regression in Europe at the JurassicâCretaceous boundary, and the resultant habitat loss, contributed to the absence of teleosauroids in Europe during the Berriasian. However, the fossil record of thalattosuchians during the Cretaceous is notorious scarce. We review the purported Cretaceous record of teleosauroids, and agree that closer to the equator this clade survived for at least 20 million years after the JurassicâCretaceous boundary.
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Zhiqiang Yu, Huaiyu He, Gang Li, Chenglong Deng, Haibing Wang, Xinxin Zhang, Qing Yang, Xiao-Ping Xia, Zhonghe Zhou & Rixiang Zhu (2019)
SIMS U-Pb geochronology for the Jurassic Yanliao Biota from Bawanggou section, Qinglong (northern Hebei Province, China).
International Geology Review (advance online publication)
doi:
https://doi.org/10.1080/00206814.2019.1707127 https://www.tandfonline.com/doi/full/10.1080/00206814.2019.1707127The Yanliao Biota is notable for producing rare and well-preserved Jurassic vertebrate fossils. Many discoveries in the Bawanggou section, northern Hebei Province have greatly enhanced our knowledge of important vertebrate fossils from the Yanliao Biota, including an arboreal euharamiyidan mammal, maniraptoran theropods, salamanders and pterosaurs. However, lacking of precise dating for the sediments bearing these fossils in the Bawanggou section hampered further understanding of the evolution of this biota. Here we report a chronology based on secondary ion mass spectrometry (SIMS) U-Pb zircon analyses from the Tiaojishan Formation bearing the Yanliao Biota in the Bawanggou section. Three bentonite layers dated to 159.0 Â 1.1 Ma, 159.5 Â 0.8 Ma, and 159.8 Â 0.8 Ma, respectively, were found to be interstratified with the fossil-bearing layer in this area. These data place the Yanliao Biota from Qinglong in the Oxfordian Stage of the Upper Jurassic and provide stringent constraints on vertebrates discovered in the Bawanggou section. Previous biostratigraphic studies and our geochronology show that fossil assemblage in the Bawanggou section is coeval with the Linglongta Biota (late Yanliao Biota) preserved in the Daxishan section (western Liaoning Province).
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This paper presents paleomagnetic data from the Paleozoic YaguarÃ-Buena Vista sedimentary succession, in Uruguay.
The paper discusses the similitudes of the fossiliferous content of the Buena Vista Formation in Uruguay and lithostratigraphic equivalent formations in Brazil.
The combination of the paleomagnetic, geochronologic, and paleontologic data constrained the age of the Buena Vista upper deposits to the Late Permian (Lopingian age).
Abstract
The Yaguarà and the Buena Vista formations from Uruguay are historically correlated to the Brazilian Rio do Rasto and Sanga do Cabral formations, respectively, as they have some lithostratigraphic similarities, indicating a Permo-Triassic or even Triassic age of the YaguarÃ-Buena Vista succession. However, they differ in the fossil indexes that characterize the faunistic communities present in both countries. A paleomagnetic work was carried out on some sections of the Buena Vista and the Yaguarà formations, as well as on some layers of bentonites, underlying the Buena Vista sediments. The alternating field and thermal demagnetization procedures revealed both normal and reversed magnetization components, but the samples showed evidence of secondary magnetic minerals and possibly remagnetizations. The calculated paleomagnetic pole for the YaguarÃ-Buena Vista Formation plots near to the poles for the Choiyoi magmatism that is believed to be responsible for the bentonite accumulation; it is also in agreement with other Permian paleomagnetic poles for South America. Based on the paleomagnetic results, the available radiometric data for the bentonites, and the fossiliferous content, a Late Permian (Lopingian) age is assigned to the YaguarÃ-Buena Vista rocks.
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