The Mesonychia is a group of archaic carnivorous mammals of uncertain phylogenetic affinities with a Holarctic distribution during the Paleogene. Intensive fossil collecting efforts in the Bighorn Basin, Wyoming, have resulted in recovery of the largest sample and most complete specimens yet known of the mesonychid Dissacus praenuntius from the second biozone of the Wasatchian North American Land Mammal Age (Wa-0). The Wa-0 biozone corresponds to the body of the Paleocene-Eocene Thermal Maximum (PETM), a brief but intense global warming event that occurred ~56 myr ago that significantly impacted terrestrial mammal faunas, including dwarfing in many mammal lineages. To evaluate the potential response of this lineage to climate change, we compared the PETM sample of D. praenuntius with those recovered from just before the PETM in the last biozone of the Clarkforkian North American Land Mammal Age (Cf-3) and just after the PETM in the Wa-1 biozone. While the sample size is still too small to say with certainty, tooth size (as a proxy for body weight) of D. praenuntius appears to be smaller during the late PETM than during either the pre-PETM Cf-3, or post-PETM Wa-1 biozones, suggesting the possibility of a muted dwarfing response to the PETM. However, the pattern observed for D. praenuntius differs from that of many other PETM mammals, as the shift to smaller body size is less pronounced and may have only occurred in late Wa-0.

Mesonychia 是一组古老的食肉哺乳动物，具有不确定的系统发育亲缘关系，在古近纪期间具有全北分布。在怀俄明州比格霍恩盆地进行的大量化石收集工作，已经从瓦萨奇北美陆地哺乳动物时代 (Wa-0) 的第二个生物区中回收了迄今为止已知的最大样本和最完整的中爪类Dissacus praenuntius标本。Wa-0 生物区对应于古新世-始新世热最大值 (PETM) 的主体，这是一个短暂但强烈的全球变暖事件，发生在大约 56 年 以前，对陆地哺乳动物群产生了重大影响，包括许多哺乳动物谱系的矮化。为了评估该谱系对气候变化的潜在反应，我们比较了D. praenuntius的 PETM 样本那些在克拉克福克北美陆地哺乳动物时代（Cf-3）的最后一个生物区中的 PETM 之前和 Wa-1 生物区中的 PETM 之后。虽然样本量仍然太小，无法确定，但在PETM 后期，D. praenuntius 的牙齿尺寸（作为体重的代表）似乎比PETM 之前的Cf-3 或PETM 之后的要小Wa-1 生物区，表明可能对 PETM 产生无声的矮化反应。然而，观察到的D. praenuntius模式与许多其他 PETM 哺乳动物的模式不同，因为向较小体型的转变不太明显，可能只发生在 Wa-0 晚期。