[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

[dinosaur] Early Triassic terrestrial tetrapod fauna + tetrapod tracks from Rhaetian in British Isles + .




Ben Creisler
bcreisler@gmail.com

Some recent Triassic-related papers:

====

Marco Romano, Massimo Bernardi, Fabio Massimo Petti, Bruce Rubidge, JohnHancox & Michael J.Benton (2020)
Early Triassic terrestrial tetrapod fauna: a review.
Earth-Science Reviews 103331 (advance online publication)
doi: https://doi.org/10.1016/j.earscirev.2020.103331
https://www.sciencedirect.com/science/article/abs/pii/S0012825220303779

NOTE: A free pdf should be posted here on Michael Benton's website are some point:

https://benton.blogs.bristol.ac.uk/publications/



The Permian-Triassic mass extinction (PTME, ca. 252 Mya) was one of the most severe biotic crises of the Phanerozoic, eliminating > 90% of marine and terrestrial species. This was followed by a long period of recovery in the Early and Middle Triassic which revolutionised the structure of both marine and terrestrial ecosystems, triggering the new ecosystem structure of the Mesozoic and Cenozoic. Entire new clades emerged after the mass extinction, including decapods and marine reptiles in the oceans and new tetrapods on land. In both marine and terrestrial ecosystems, the recovery is interpreted as stepwise and slow, from a combination of continuing environmental perturbations and complex multilevel interaction between species in the new environments as ecosystems reconstructed themselves. Here, we present a review of Early Triassic terrestrial tetrapod faunas, geological formations and outcrops around the world, and provide a semi-quantitative analysis of a data set of Early Triassic terrestrial tetrapods. We identify a marked regionalisation of Early Triassic terrestrial tetrapods, with faunas varying in both taxonomic composition and relative abundance according to palaeolatitudinal belt. We reject the alleged uniformity of faunas around Pangaea suggested in the literature as a result of the hot-house climate. In addition, we can restrict the "tetrapod gap" of terrestrial life in the Early Triassic to palaeolatitudes between 15ÂN and about 31ÂS, in contrast to the earlier suggestion of total absence of tetrapod taxa between 30ÂN and 40ÂS. There was fairly strong provincialism following the PTME, according to cluster analysis of a taxon presence matrix, entirely consistent with Early Triassic palaeobiogeography. Unexpectedly, the overall pattern for Early Triassic terrestrial tetrapod faunas largely reflects that of the Late Permian, suggesting that the recovery faunas in the Early Triassic retained some kind of imprint of tetrapod distributions according to palaeogeography and palaeoclimate, despite the near-total extinction of life through the PTME.

======


Nigel R. Larkin, Christopher J. Duffin, Steven Dey, Stephen Stukins & Peter Falkingham (2020)
The first tetrapod track recorded from the Rhaetian in the British Isles.
Proceedings of the Geologists' Association (advance online publication)
doi: https://doi.org/10.1016/j.pgeola.2020.07.012
https://www.sciencedirect.com/science/article/abs/pii/S0016787820300754


Terrestrial vertebrate trace fossils are relatively abundant in mid-to-late Triassic and early Jurassic deposits in the British Isles but to date none at all have been recorded from the Rhaetian, the final stage of the Triassic. This represents a persistent gap in the terrestrial ichnological record. We present the first Rhaetian track to be recognised in the British Isles, found at Aust Cliff on the south bank of the Severn Estuary near Bristol in SW England. This locality is well known for disarticulated remains of Rhaetian fossil reptiles including some terrestrial species but in 2006 a track (TECMAG0161) was found for the fist time. Although the specimen was found ex-situ the palynological data from the surrounding matrix confirms a Rhaetian age. The track was examined with CT scanning and photogrammetry. We tentatively assign the track to the ichnogenus Procolophonichnium based on size and digit proportions. The isolated nature of the specimen offers little concrete information about the track maker but such tracks have previously been attributed to parareptiles or therapsid trackmakers. The specimen adds a datapoint to an otherwise ichnologically empty period of time in the British Isles. The track also provides solid evidence for a [locally] terrestrial environment in a sequence that is otherwise considered predominantly marine or estuarine. This discovery suggests that there may be more such tetrapod tracks of Rhaetian age preserved, at least at Aust, and further searching will hopefully lead to the current minimal dataset being expanded.


====


Abdelkbir Hminna, Abdelouahed Lagnaoui, Tariq Zouheir, Hafid Saber & Joerg W. Schneider (2020)
Late Triassic ichnoassemblage from a playa-lake system of the Coastal Meseta, Morocco: Palaeoenvironmental and palaeoecological implications.
Journal of African Earth Sciences 103995 (advance online publication)
doi: https://doi.org/10.1016/j.jafrearsci.2020.103995
https://www.sciencedirect.com/science/article/pii/S1464343X20302466

Highlights

First comprehensive analysis ofTriassic invertebrate ichnofauna from Meseta.
The trace fossils were discovered mainly in the silting-up phase sediments of a playa lake.
Post-palaeozoic record of the Cruziana-Diplichnites-Rusophycus ichnoassociation.
The invertebrate ichnoassemblage is referred to the Scoyenia ichnofacies.
Opportunistic behaviours in temporarily or periodically inundated nonmarine environments.

Abstract

Here we present the first comprehensive ichnotaxonomic analysis of a Late Triassic playa system from the Sidi SaÃd Maachou Basin, Coastal Meseta (Western Meseta, Morocco). The Late Triassic deposits consist of sediments deposited in various nonmarine environments dominated by dry red-bed facies. These deposits yielded, so far, an ichnoassemblage consisting of the invertebrate ichnogenera Cochlichnus, Cruziana, Diplichnites, Rusophycus, Palaeophycus, and Taenidium associated with the tetrapod tracks Brachychirotherium and Rhynchosauroides. These invertebrate and vertebrate trace fossils are preserved in concave epirelief and convex hyporelief on upper and lower surfaces of laminated mudstones and fine-grained sandstones. The invertebrate ichnofossils were probably made subaqueously and indicate different behaviours of the tracemakers: walking (cursichnium, Acripes), resting (cubichnium, Rusophycus) and combined locomotion-feeding or plowing (pascichnium, Cruziana). Additionally, many other fossils are collected from the same formation, including plant impressions, rhizoliths and fish scales. The invertebrate ichnoassemblage described herein is referred to the Scoyenia ichnofacies, which indicates opportunistic behaviours in temporarily or periodically inundated nonmarine environments, such as playa systems, floodplains and lake margins. The invertebrate ichnoassemblage reported here is the first well documented from the Sidi SaÃd Maachou Basin and the Late Triassic of Morocco in general. The strata have a high potential to yield other ichnoassemblages, therefore further exploration is needed.

=======




Virus-free. www.avg.com