Museum of Comparative Zoology, Harvard University, Cambridge, MA, 02138, USA.
Department of Biology and Burke Museum, University of Washington, Seattle, WA, 98195, USA.
Commun Biol. 2020 Aug 27;3(1):471. doi: 10.1038/s42003-020-01207-6.
Antarctica has hosted a wide range of ecosystems over the past 500-million years. Early in the Mesozoic, the Antarctic portion of southern Pangaea had a more habitable climate, but its position within the polar circle imposed extreme photoperiod seasonality on its resident flora and fauna. It remains unclear to what degree physiological adaptations underpinned the ability of tetrapods to establish the terrestrial communities captured in the fossil record. Here we use regular and stressful growth marks preserved in the dentine of ever-growing tusks of the Early Triassic mammalian predecessor, Lystrosaurus, to test for adaptations specific to this polar inhabitant. We find evidence of prolonged stress indicative of torpor when compared to tusk samples from non-polar populations of Lystrosaurus. These preliminary findings are to our knowledge the oldest instance of torpor yet reported in the fossil record and demonstrate unexpected physiological flexibility in Lystrosaurus that may have contributed its survivorship through the Permo-Triassic mass extinction.
南极洲在过去的 5 亿年中承载了多种多样的生态系统。在中生代早期，盘古大陆的南极部分气候更加适宜居住，但它位于极圈之内，这对其居住的动植物造成了极端的光周期季节性影响。目前还不清楚生理适应在多大程度上支持了四足动物建立在化石记录中捕获的陆生群落的能力。在这里，我们使用保存在早期三叠纪哺乳动物先驱雷兽不断生长的獠牙牙本质中的常规和应激生长标记，来测试这种极地生物的特殊适应性。与来自雷兽非极地种群的獠牙样本相比，我们发现了表明进入蛰伏状态的长期应激的证据。这些初步发现据我们所知是化石记录中最早的蛰伏实例，证明了雷兽出人意料的生理灵活性，这可能有助于它在二叠纪-三叠纪大灭绝中幸存下来。
