image: An artist's reconstruction of the Waterloo Farm lagerstatte showing <em>Tutusius</em> at right and <em>Umzantsia</em> on the left." <em>Tutusius</em> is eying <em>Gondwanascorpio emzantsiensis</em> (the oldest terrestrial animal known from Gondwana), whereas <em>Umzantsia</em> is diving down to catch a small <em>Bothriolepis africana</em>. The coelacanths at bottom right are <em>Serenichthys kowiensis</em> (Africa's earliest fossil coelacanths from the world's earliest known coelacanth nursery). They are sheltering in a clump of charophyte algae of the species <em>Octochara crassa</em>. The hazy placoderm silhouettes in the background are <em>Groenlandaspis riniensis</em>. The distant trees and the trunk that <em>Tutusius</em> is resting on represent the progymnosperm tree <em>Archaeopteris notosaria</em>. All these taxa are described from Waterloo Farm. This material relates to a paper that appeared in the 8 June 2018 issue of <i>Science</i>, published by AAAS. The paper, by R. Gess at Rhodes University in Grahamstown, South Africa, and colleagues was titled, "A tetrapod fauna from within the Devonian Antarctic Circle." view more
Credit: Maggie Newman
It has long been presumed that the ancestors of all vertebrates - the amphibious, aquatic tetrapods that first colonized the land - evolved in warm tropical environments. Now, however, the unexpected unearthing of two ancient tetrapod fossils in South Africa, near polar latitudes, hints that four-limbed animals were more widespread in their early stages of evolution. To date, fossils of early tetrapods have only been uncovered in tropical regions, at latitudes that lie within 30° of the palaeoequator. The newly uncovered fossils suggest that scientists will have to broaden the range of environments in which they consider ancient tetrapods to have existed, which holds implications for understanding the evolution of these creatures. Here, Robert Gess and Per Erik Ahlberg described Tutusius umlambo and Umzantsia amazana, which were recovered from Waterloo Farm, near Grahamstown, South Africa. Accounting for how continents have shifted over time, this means that the two animals lived at a latitude of about 70°S about 350 million years ago, close to what today is the Antarctic. The authors note that the abundance and type of plants present at the site rule out the possibilities that the two tetrapods lived in a truly polar climate; however, the animals' proximity to the pole implies that they endured several months of complete winter darkness. Gess and Ahlberg say that the presence of tetrapods in such an environment raises the question of whether high-latitude environments played a distinctive role in the evolutionary transition between fish and four-limbed animals -- for example, these environments could have been drivers of evolutionary innovation or served as refuges for archaic taxa.
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Journal
Science