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.人们普遍认为，二叠纪-三叠纪灭绝事件（Permo-Triassic extinction）后海洋生物多样性的恢复，相较于其他大规模灭绝事件而言更为迟缓。据称陆地脊椎动物生物多样性的恢复比海洋系统要慢至多15百万年（Myr）。本研究以单个化石群落为尺度，针对美国西南部地区，检验包含早中三叠世安尼期（Anisian）陆地四足类动物群的莫恩科皮组（Moenkopi Formation），与包含后续晚三叠世诺利期（Norian）四足类动物群的钦利组（Chinle Formation）之间是否存在生物多样性差异。以钦利组的动物群生物多样性代表完全的生物恢复状态，通过对比这两个地层中沉积环境与埋藏学（taphonomic）环境相似的动物群的分类多样性与功能群多样性，我们得以评估安尼期陆地生物多样性是否处于初步恢复阶段。本次对比选取莫恩科皮组霍尔布鲁克段（Holbrook Member）的动物群——该段以低弯度中-粗粒河流沉积为典型特征——与钦利组的四个地层单元分别进行，这四个地层单元代表了从砂质低弯度到泥质高弯度的河流沉积环境。研究采用了三类指标：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）进行对比。辛普森（Simpson）与香农（Shannon）多样性指数进一步补充了分析内容。钦利组中保存状况极佳的岩层（即所谓的"蓝色层"）被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变异范围之内。若本研究结果代表全球普遍情况，则表明至少在安尼期早期（二叠纪-三叠纪灭绝事件后6百万年），陆地生物多样性已达到与晚三叠世相当的水平。这一结论或将陆地脊椎动物的恢复时长与海洋生态系统的4~8百万年恢复周期对齐。