ABSTRACT

The fossil record of temnospondyl amphibians in the immediate wake of the Permo-Triassic mass extinction captures extensive taxic and ecological diversity, with most records known from high paleolatitudinal settings. In southern Pangea, the most substantial records come from South Africa and Australia, with a total of over 20 taxa presently recognized. Temnospondyls have also been known from correlated horizons in the lower Fremouw Formation of Antarctica since the late 1960s, but these records are mostly fragmentary, thereby limiting taxonomic resolution to the family level and subsequent biostratigraphic correlations and comparisons between high-latitude basins. Here we report substantial new material of the amphibamiform Micropholis stowi, a relic dissorophoid previously known only from the Katberg Formation (Lystrosaurus declivis Assemblage Zone) of South Africa, from the lower Fremouw Formation. The exceptional preservation of the recently recovered material permits not only confident taxonomic referral but also tentative association of several individuals to the broad-headed morph of the taxon. The recognition of M. stowi in Antarctica represents only the fourth geographic occurrence of a dissorophoid from southern Pangea and supports the hypothesis that high-latitude environments served as refugia for temnospondyls during the mass extinction. In the case of M. stowi, such refugia permitted the persistence of a predominantly Permo-Carboniferous clade, and the Antarctic records discussed here further hint at a poorly sampled cryptic distribution, both of amphibamiforms in southern Pangea and of small-bodied temnospondyls in early Mesozoic deposits.

摘要

在二叠纪-三叠纪大灭绝之后的 temnospondyl 两栖动物化石记录记录了广泛的分类和生态多样性，大多数记录来自高古纬度环境。在南盘古大陆，最重要的记录来自南非和澳大利亚，目前共有 20 多个分类群被确认。自 1960 年代后期以来，人们还从南极洲 Fremouw 组下部的相关层位中发现了 Temnospondyl，但这些记录大多是零碎的，因此将分类学分辨率限制在科水平以及随后的高纬度盆地之间的生物地层相关性和比较。在这里，我们报告了大量的两栖动物Micropholis stowi 的新材料，一种以前仅在南非的 Katberg 组（Lystrosaurus declivis组合区）中发现的遗物 dissorophoid，来自较低的 Fremouw 组。最近恢复的材料的特殊保存不仅允许有信心的分类参考，而且允许几个个体与分类群的宽头形态的暂时联系。在南极洲对M. stowi的承认仅代表了盘古大陆南部dissorophoid的第四次地理事件，并支持了高纬度环境在大规模灭绝期间成为 temnospondyl 的避难所的假设。在M. stowi的情况下，这样的避难所允许以二叠纪-石炭纪为主的进化枝的持续存在，这里讨论的南极记录进一步暗示了一个采样不佳的隐蔽分布，包括南盘古的两栖类动物和早期中生代沉积物中的小体型 temnospondyls。