(Figure 2) Distribution of planktonic foraminifera in the upper Paleocene of DSDP Hole 93-605

Good faunal preservation in the upper part of the Planorotatites pseudomenardii Zone at Deep Sea Drilling Project Site 605, northwestern Atlantic, allows a biometric analysis of the upper Paleocene planktonic foraminiferal species Planorotatites pseudomenardii (Belli), a keeled species that probably developed from a middle Paleocene unkeeled Planorotalites form. Multivariate analysis shows a consistent separation of all Planorotatites specimens into two groups, which are differentiated by the presence or absence of a complete keel; other variables are only of minor importance. The keeled group coincides with P. pseudomenardii. We recognize only one unkeeled species, Planorotalites chapmani (Parr), with Planorotalites ehrenbergi (Bolli), Planorotalites imitata (Subbotina), Planorotalites planoconica (Subbotina), Planorotalites troelseni (Loeblich and Tappan), and Planorotalites hausbergensis (Gohrbrandt) as junior synonyms. P. chapmani ranges from the middle Paleocene to at least the top of the upper Paleocene. […]

在西北大西洋深海钻探项目605站位Planorotatites pseudomenardii层位上部，保存良好的生物化石，为对上新世上层浮游有孔虫物种Planorotatites pseudomenardii (Belli)的生物计量学分析提供了可能，该物种为一带状物种，可能源自中新世无带的Planorotalites型。多元统计分析表明，所有Planorotatites标本均呈现两个组别的明显分离，这两组别分别以是否存在完整带状为区分；其他变量则相对次要。带状组别与P. pseudomenardii相吻合。我们仅识别出一个无带状物种，即Planorotalites chapmani (Parr)，并将Planorotalites ehrenbergi (Bolli)、Planorotalites imitata (Subbotina)、Planorotalites planoconica (Subbotina)、Planorotalites troelseni (Loeblich and Tappan)以及Planorotalites hausbergensis (Gohrbrandt)视为其亚种。P. chapmani的分布范围从中新世中期至至少上新世上层顶部。