美国芝加哥大学Neil H. Shubin团队近期取得重要工作进展，他们研究发现了加拿大北极地区晚泥盆世的一种新的elpistostegalian。该项研究2022年7月20日在线发表于《自然》杂志上。
在这里，研究人员报告了在加拿大北极地区晚泥盆纪时期发现的一种新的elpistostegalian，它在该群体中显示出惊人的差异。标本包括部分上颚和下颚、咽部、胸鳍和鳞片。这个新属在系统发育上与T. roseae和E. watsoni很接近，但与这两个分类群以及其他描述的四足动物有明显的区别。它的胸鳍显示出与其他鳞翅目动物不同的游泳特性，它的胸鳍缺乏在坚硬基质上以附属物为基础的支撑的过程、关节方向和肌肉疤痕。这种出乎意料的形态和功能多样性代表了之前隐藏的生态扩张，是对开阔水域的二次回归，靠近肢体脊椎动物的起源。
据介绍，在有肢脊椎动物起源研究中，一个根本的空白在于理解它们近亲的形态和功能多样性。虽然对elpistostegalians Panderichthys rhombolepis,Tiktaalik roseae和Elpistostege watsoni的分析揭示了在过渡过程中运动，进食和呼吸结构的一系列变化，但一块孤立的骨头，一个假定的肱骨，却有争议地暗示了它的形式和功能比现在所认识到的更广泛。
附：英文原文
Title: A new elpistostegalian from the Late Devonian of the Canadian Arctic
Author: Stewart, Thomas A., Lemberg, Justin B., Daly, Ailis, Daeschler, Edward B., Shubin, Neil H.
Issue&Volume: 2022-07-20
Abstract: A fundamental gap in the study of the origin of limbed vertebrates lies in understanding the morphological and functional diversity of their closest relatives. Whereas analyses of the elpistostegalians Panderichthys rhombolepis, Tiktaalik roseae and Elpistostege watsoni have revealed a sequence of changes in locomotor, feeding and respiratory structures during the transition1,2,3,4,5,6,7,8,9, an isolated bone, a putative humerus, has controversially hinted at a wider range in form and function than now recognized10,11,12,13,14. Here we report the discovery of a new elpistostegalian from the Late Devonian period of the Canadian Arctic that shows surprising disparity in the group. The specimen includes partial upper and lower jaws, pharyngeal elements, a pectoral fin and scalation. This new genus is phylogenetically proximate to T. roseae and E. watsoni but evinces notable differences from both taxa and, indeed, other described tetrapodomorphs. Lacking processes, joint orientations and muscle scars indicative of appendage-based support on a hard substrate13, its pectoral fin shows specializations for swimming that are unlike those known from other sarcopterygians. This unexpected morphological and functional diversity represents a previously hidden ecological expansion, a secondary return to open water, near the origin of limbed vertebrates.
DOI: 10.1038/s41586-022-04990-w
Source: https://www.nature.com/articles/s41586-022-04990-w
