Data from: Post Permo-Triassic terrestrial vertebrate recovery southwestern United States

Recovery of marine biodiversity following the Permo-Triassic extinction is thought to have been delayed relative to other mass extinctions. Terrestrial vertebrate biodiversity is said to have taken as much as 15 Myr longer to recover than the marine. The present study tests, at the scale of an individual fossil community, whether a disparity in biodiversity existed in the American Southwest, between the Moenkopi Formation, containing an early Middle Triassic (Anisian) terrestrial tetrapod fauna, and the Chinle Formation, containing a successor Late Triassic (Norian) tetrapod fauna. Taking Chinle faunal biodiversity to represent full biotic recovery, comparison of taxonomic and guild diversity of faunas from similar depositional and taphonomic environments in these two formations allowed us to assess the possibility of incipient terrestrial recovery of biodiversity in the Anisian. Comparisons were made between the Holbrook Member fauna of the Moenkopi, a unit best characterized as a low-sinuosity medium- to coarse-grained fluvial deposit, and each of four Chinle stratigraphic units, representing fluvial settings from sandy low-sinuosity to muddy high-sinuosity. Three metrics were applied: generic and familial taxonomic diversity and guild diversity; these were compared by rarefaction. Simpson and Shannon diversity metrics augmented the analysis. Units of extraordinary preservation in the Chinle—the so-called blue layers—were removed from the analysis. In all tests the biodiversity of the Holbrook Member fauna is within the variation seen in Chinle faunas. If the results of our study represent global conditions, they suggest that by at least early Anisian time (6 Myr after the P/T extinction) biodiversity had reached levels comparable to those seen in the Late Triassic. This potentially brings the terrestrial vertebrate recovery in line with the 4–8 Myr it took for recovery in the marine realm.学界普遍认为，相较于其他大灭绝事件，二叠纪-三叠纪灭绝事件（Permo-Triassic extinction）后的海洋生物多样性恢复进程显著延迟。有研究表明，陆生脊椎动物生物多样性的恢复耗时较海洋生物多出多达1500万年。本研究以单个化石群落为尺度，针对美国西南部的两套地层开展对比检验，以明确二者间是否存在生物多样性差异：其一为产出中三叠世早期（安尼期，Anisian）陆生四足动物群的莫恩科皮组（Moenkopi Formation），其二为产出晚三叠世（诺利期，Norian）后继四足动物群的钦利组（Chinle Formation）。本研究以钦利组动物群的生物多样性代表完全生物恢复状态，通过对比两套地层中沉积环境与埋藏学条件相似的动物群的分类多样性与功能群多样性，得以评估安尼期陆生生物多样性处于初步恢复阶段的可能性。本次对比选取莫恩科皮组的霍尔布鲁克段（Holbrook Member）——该地层单元以低弯曲度中-粗粒河流沉积为典型特征——与四个钦利组地层单元分别进行比对，这些钦利组地层单元涵盖了从砂质低弯曲度到泥质高弯曲度的各类河流沉积环境。本研究采用三类多样性测度指标：属级与科级分类多样性以及功能群多样性，并通过稀疏化分析（rarefaction）开展组间比较；同时辅以辛普森多样性指数与香农多样性指数（Simpson and Shannon diversity metrics）进行补充分析。此外，我们将钦利组中保存条件极为特殊的‘蓝色层’（blue layers）样本排除在本次分析之外。所有检验结果均显示，霍尔布鲁克段动物群的生物多样性处于钦利组动物群的自然变异范围之内。若本研究结果可代表全球同期的演化情况，则表明至少在安尼期早期（二叠纪-三叠纪灭绝事件发生后600万年），陆生生物多样性已达到与晚三叠世相当的水平。这一结论或将陆生脊椎动物的恢复时长修正至与海洋域400万至800万年的恢复时长相符的范围。