Ben Creisler
New papers in Historical Biology:
Tariq Zouheir, Abdelkbir Hminna, Hendrik Klein, Abdelouahed Lagnaoui, Hafid Saber & Joerg W. Schneider (2018)Â
Unusual archosaur trackway and associated tetrapod ichnofauna from Irohalene member (Timezgadiouine formation, late Triassic, Carnian) of the Argana Basin, Western High Atlas, Morocco.
Historical Biology (advance online publication)Â
DOI: 10.1080/08912963.2018.1513506
An archosaur trackway consisting of 10 successive pes imprints has been recovered from the Late Triassic Irohalene Member of the Timezgadiouine Formation (Argana Basin, Morocco). Footprints are tetradactyl-pentadactyl, and show an elongated âheelâ, probably enclosing the trace of digit V. The trackway lacks a manus impression, which could be due to bipedal progression of the trackmaker or be a preservational phenomenon. It is assigned to cf. Parachirotherium isp. based on similarities with the ichnogenus that has been described from the same stratigraphic unit. Other footprints of this assemblage are assigned to the ichnotaxa Grallator-Eubrontes (dinosauromorphs/crocodilian-stem archosaurs), Brachychirotherium isp. (crocodilian-stem archosaurs), Rhynchosauroides isp. (lepidosauromorphs/archosauromorphs), and indeterminate ichnotaxa. Associated with the footprints are numerous invertebrate traces such as Scoyenia gracilis. The ichnofauna of the Irohalene Member supports a cosmopolitan distribution of pentadactyl but functionally tridactyl chirotheres (Parachirotherium) and grallatorids across the Ladinian-Carnian boundary. Similar assemblages are known from the Germanic Basin and from Eastern North America. Furthermore, it documents the occurrence of very large Eubrontes trackmakers in the early Carnian. The depositional environment of the lower part of the Irohalene Member is interpreted as wet red beds of a flood basin transitional to a distal braid plain.
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Grzegorz Racki & Spencer G. Lucas (2018)Â
Timing of dicynodont extinction in light of an unusual Late
Historical Biology (advance online publication)Â
DOI: 10.1080/08912963.2018.1499734
Dicynodont therapsids are prominent elements of Triassic continental faunas, but the date of their demise is controversial, linked either to end-Carnian faunal turnover or to end-Triassic mass extinction. The second timing is based on a unique, giant dicynodont-theropod dinosaur fauna from Lipie ÅlÄskie, Poland, thought to be Rhaetian in age, due to conjectural botanical and conchostracan (but not tetrapod) evidence. On the other hand, an age assignment for the Lipie fauna to the mid-Norian (Revueltian) has been demonstrated recently by regional integrative stratigraphic data. To test once more this still debated age assignment, we recall the rationale of Georges Cuvier in the study of the fossil record (âthe best documents of Earthâs past are fossilized large tetrapodsâ). This approach was applied successfully 200 years ago to the species extinction dilemma. In light of the worldwide distribution of dicynodonts, the alleged compositional paradox of the âRhaetianâ fauna from Poland can be significantly reduced by its recognition as a more ânormalâ early-middle Norian assemblage. The simple megafaunal correlation appears to be conclusive. Thus, there was a major pulse of dicynodont extinction at the end of the Carnian, with the final extinction of the few remaining species happening in the Norian.