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，二叠纪-三叠纪灭绝事件（Permo-Triassic extinction）后海洋生物多样性的恢复，相较于其他大灭绝事件而言更为滞后。已有研究表明，陆地脊椎动物生物多样性的恢复甚至比海洋慢多达15百万年（15 Myr）。本研究以单个化石群落为研究尺度，旨在检验美国西南部地区的莫恩科皮组（Moenkopi Formation，产出早三叠世中期安尼期（Anisian）陆地四足动物化石群）与钦利组（Chinle Formation，产出后续的晚三叠世诺利期（Norian）四足动物化石群）之间是否存在生物多样性差异。本研究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环境相似的动物群的分类多样性与生态类群多样性，得以评估安尼期陆地生物多样性是否处于初步恢复阶段。研究对比了莫恩科皮组霍尔布鲁克段（Holbrook Member）动物群（该地层单元以低弯度中-粗粒河流沉积为典型特征）与钦利组的四个地层单元，后者涵盖了从砂质低弯度到泥质高弯度的河流沉积环境。本研究采用三类统计指标：属级与科级分类多样性以及生态类群多样性，并通过稀疏分析法（rarefaction）进行对比。研究同时引入辛普森多样性指数（Simpson diversity）与香农多样性指数（Shannon diversity）以辅助分析。钦利组中保存质量极佳的地层单元——即所谓的“蓝色层”——被排除在本次分析之外。所有测试结果均显示，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。若本研究结果可代表全球情况，则表明至少在安尼期早期（二叠纪-三叠纪灭绝事件发生后6百万年（6 Myr）），陆地生物多样性已达到与晚三叠世相当的水平。这一结果或将陆地脊椎动物的恢复时长修正为与海洋生物恢复的4~8百万年（4-8 Myr）相符的区间。