Written by Prof. Roger Smith, Evolutionary Studies Institute, University of the Witwatersrand and Karoo Palaeontology, Iziko South African Museum
In a newly published article in Nature, an international team announced the discovery of a fossilized giant stem tetrapod in the arid heartland of Namibia. The team of South African, Namibian, Argentinian and US palaeontologists found the near complete 3-metre-long skeleton in the rocks exposed along the valley of the Ugab River in Damaraland.
Funded by PAST Africa, and the National Geographical Society of America, they were searching for evidence of the earliest four-legged animals to set foot on land in this part of the ancient supercontinent of Gondwana some 300 million years ago.
In 2018 the skeleton was taken to the Iziko South African Museum, in Cape Town to be painstakingly prepared by one of the team members, Sibusiso Mtungata, in the Karoo Fossil Laboratory. After 2 years of preparation and a further 3-years of study, the specimen was returned to Windhoek where it will soon be on display in the Geological Museum of Namibia.
The fossil preparation revealed that the large, flattened skull was highly ornamented with a very unusual structure of the palate with enormous backwardly curved fangs which also occur on the lower jaw, making its mouth unlike anything that had been found before. Initially identified as a large temnospondyl amphibian, after full preparation it became apparent that the skull displayed the primitive features of older, much less evolved, four-limbed animals, only known in older rocks from the northern hemisphere. They have named this new type of early tetrapod Gaiasia jennyae, the former after the locality, the latter in honour of the lifelong work of British palaeontologist Jennifer Clack.
The team have now revealed that this new species is the largest found to date of a group of ancient four-legged animals with fingers known as “basal tetrapods”. More importantly, previous finds have all come from the northern hemisphere which means that scientists will now have to include the southern continents in future research on the origin and early evolution of land living four-legged animals.
Title and Abstract as published in Nature
Giant stem tetrapod was apex predator in Gondwanan late Palaeozoic ice age
Current hypotheses of early tetrapod evolution 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 (ca. 307 Ma). These hypotheses draw on a tetrapod fossil record that is almost entirely restricted to palaeoequatorial Pangea (Euramerica)1,2. Here we describe a new giant stem tetrapod, Gaiasia jennyae, from high-palaeolatitude early Permian (ca. 280 Ma) deposits in Namibia that challenges this scenario. Gaiasia is represented by multiple large, semi-articulated skeletons characterized by a weakly-ossified skull with 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 Colosteida, a Carboniferous clade known from Euramerica. Gaiasia is larger than all known 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 tetrapods during the Carboniferous–Permian transition and indicates that prior hypotheses of global tetrapod faunal turnover and dispersal at this time2,3 may need to be reconsidered.
Scientific reference
Marsicano C.A. Pardo J.D., Smith R.M.H., Mancuso, A., Gaetano, L., Mocke, H. 2024. Giant stem tetrapod was apex predator in Gondwanan late Palaeozoic ice age. Nature
