The content describes the discovery of a new giant stem tetrapod, Gaiasia jennyae, from high-palaeolatitude (around 55° S) early Permian-aged (about 280 million years ago) deposits in Namibia. This finding challenges the current hypotheses of early tetrapod evolution, which posit close ecological and biogeographic ties to the extensive coal-producing wetlands of the Carboniferous palaeoequator, with rapid replacement of archaic tetrapod groups by relatives of modern amniotes and lissamphibians in the late Carboniferous.
Gaiasia is represented by several large, semi-articulated skeletons characterized by a weakly ossified skull with a loosely articulated palate dominated by a broad diamond-shaped parasphenoid, a posteriorly projecting occiput, and enlarged, interlocking dentary and coronoid fangs. Phylogenetic analysis resolves Gaiasia within the tetrapod stem group as the sister taxon of the Carboniferous Colosteidae from Euramerica.
Gaiasia is larger than all previously described digited stem tetrapods and provides evidence that continental tetrapods were well established in the cold-temperate latitudes of Gondwana during the final phases of the Carboniferous–Permian deglaciation. This points to a more global distribution of continental tetrapods during the Carboniferous–Permian transition and indicates that previous hypotheses of global tetrapod faunal turnover and dispersal at this time must be reconsidered.
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by Claudia A. M... o www.nature.com 07-03-2024
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