Data from: Deep time diversity of metatherian mammals: implications for evolutionary history and fossil-record quality

Despite a global fossil record, Metatheria are now largely restricted to Australasia and South America. Most metatherian palaeodiversity studies to date are limited to particular subclades, time intervals and/or regions, and few consider uneven sampling. Here, we present a comprehensive new dataset on metatherian fossil occurrences (Barremian to end-Pliocene). These data are analysed using standard rarefaction and Share-holder Quorum Subsampling (including a new protocol for handling ‘Lagerstätten’-like localities). Global metatherian diversity was lowest during the Cretaceous, and increased sharply in the Paleocene, where the South American record begins. Global and South American diversity rose in the early Eocene then fell in the late Eocene, contrasting the North American pattern. In the Oligocene diversity declined in the Americas but this was more than offset by Oligocene radiations in Australia. Diversity continued to decrease in Laurasia with final representatives in North America (excluding the later entry of Didelphis virginiana) and Europe in the early Miocene, and Asia in the middle Miocene. Global metatherian diversity appears to have peaked in the early Miocene, especially in Australia. Following a trough in the late Miocene, the Pliocene saw another increase in global diversity. By this time, metatherian biogeographic distribution had essentially contracted to that of today.
Comparison of the raw and sampling-corrected diversity estimates, coupled with evaluation of ‘coverage’ and number of prolific sites, demonstrates that the metatherian fossil record is spatially and temporally extremely patchy. Therefore, assessments of macroevolutionary patterns based on the raw fossil record (as in most previous studies) are inadvisable.

尽管后兽下纲（Metatheria）拥有全球范围的化石记录，但现生类群如今主要局限于澳大拉西亚与南美洲。迄今为止，多数针对后兽类古生物多样性的研究仅聚焦于特定亚支系、时间区间或区域，且极少考虑采样不均的问题。本文提供一套时间跨度覆盖巴列姆期至上新世末期的后兽类化石产出综合数据集。本数据集采用标准稀疏化法与持股配额子采样法（包含一套全新的特异埋藏化石库（Lagerstätten）型遗址处理流程）开展分析。
全球后兽类多样性在白垩纪处于最低水平，古新世时大幅攀升——这一时期南美地区的后兽类化石记录首次出现。全球及南美后兽类多样性在始新世早期上升，随后在始新世晚期下降，这与北美地区的变化模式形成鲜明反差。渐新世时期，美洲的后兽类多样性有所下降，但这一降幅被同期澳大利亚地区的辐射演化大幅抵消。劳亚大陆的后兽类多样性持续降低：北美（不含后续迁入的弗吉尼亚负鼠（Didelphis virginiana））与欧洲的最后类群出现于中新世早期，亚洲则为中新世中期。全球后兽类多样性似乎在中新世早期达到峰值，尤以澳大利亚地区为甚。晚中新世出现多样性低谷后，上新世时期全球后兽类多样性再度回升。至此时，后兽类的生物地理分布已基本收缩至现今的分布范围。
通过对比原始数据与采样校正后的多样性估算结果，结合对‘覆盖度’及多产遗址数量的评估，可发现后兽类化石记录在空间与时间维度上均存在极强的斑块性。因此，基于原始化石记录开展宏观演化模式评估（如多数既往研究）的做法并不可取。