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
人们长期以来假定，所有脊椎动物的祖先—即首次在陆地扎根的两栖、水生四足动物—是在温暖的热带环境中演化出来的。然而，在南非靠近极地纬度附近意外出土的两个远古四足动物化石如今提示，这些有4个肢体的动物在其演化的早期要比以前认为的有更为普遍的存在。到目前为止，早期四足动物的化石仅发现于纬度为30⁰或不到的热带地区。这些新的化石表明，科学家必需拓宽他们认为的远古四足动物存在的环境范围，后者对了解这些动物的演化具有意义。Robert Gess和Per Erik Ahlberg在此描述了Tutusius umlambo和Umzantsia amazana，它们是在南非格雷厄姆斯敦附近的Waterloo Farm被发现的。考虑到大陆板块随着时间的移动，这意味着这两种动物在3.5亿年前左右所生活的纬度约在南纬70°，与如今的南极地区接近。作者指出，该地区存在的植物的丰度和类型排除了这两种四足动物生活在真正极地气候中的可能性；然而，这些动物与极地接近表明，它们在一年中会经历几个月时间的完全黑暗的冬天。Gess和Ahlberg说，鉴于四足动物存在于这样的环境中，这样的问题出现了：高纬度环境是否在鱼类与四个肢体动物间的演化转变中扮演着独特的角色；例如，这些环境可能是演化创新的驱动因子或它们成为古老生物类群的庇护场所。
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Journal
Science