Data from: X-rays and virtual taphonomy resolve the first Cissus (Vitaceae) macrofossils from Africa as early diverging members of the genus

PREMISE OF THE STUDY: Fossilized seeds similar to Cissus (Vitaceae) have been recognized from the Miocene of Kenya, though some were previously assigned to the Menispermaceae. We undertook a comparative survey of extant African Cissus seeds to identify the fossils and consider their implications for the evolution and biogeography of Cissus and for African early Miocene paleoenvironments.

METHODS: Micro-computed tomography (µCT) and synchrotron-based X-ray tomographic microscopy (SRXTM) were used to study seed morphology and anatomy. Virtual taphonomy, using SRXTM data sets, produced digital fossils to elucidate seed taphonomy. Phylogenetic relationships within Cissus were reconstructed using existing and newly produced DNA sequences for African species. Paleobiology and paleoecology were inferred from African nearest living relatives.

KEY RESULTS: The fossils were assigned to four new Cissus species, related to four modern clades. The fossil plants were interpreted as climbers inhabiting a mosaic of riverine woodland and forest to more open habitats. Virtual taphonomy explained how complex mineral infill processes concealed key seed features, causing the previous taxonomic misidentification. Newly sampled African species, with seeds most similar to the fossils, belong to four clades within core Cissus, two of which are early diverging.

CONCLUSIONS: Virtual taphonomy, combined with X-ray imaging, has enabled recognition of the first fossil Cissus and Vitaceae from Africa. Early-divergent members of the core Cissus clade were present in Africa by at least the early Miocene, with an African origin suggested for the Cissus sciaphila clade. The fossils provide supporting evidence for mosaic paleoenvironments inhabited by early Miocene hominoids.

研究背景（PREMISE OF THE STUDY）：此前在肯尼亚中新世地层中发现了隶属于葡萄科（Vitaceae）、形态类似白粉藤属（Cissus）的化石种子，不过其中部分标本曾被归为防己科（Menispermaceae）。本研究通过对现存非洲白粉藤属种子开展对比调查以鉴定这些化石，并探讨其对白粉藤属演化、生物地理学以及非洲早中新世古环境的研究意义。

研究方法（METHODS）：本研究采用显微计算机断层扫描（micro-computed tomography, µCT）与同步辐射X射线断层扫描显微镜（synchrotron-based X-ray tomographic microscopy, SRXTM）对种子的形态与解剖结构进行研究。利用SRXTM数据集开展虚拟埋藏学（virtual taphonomy）分析，生成数字化化石以阐明种子的埋藏学过程。本研究通过已有的和新获取的非洲物种DNA序列，重建白粉藤属内的系统发育关系。通过非洲现生近缘类群推断其古生物学与古生态学特征。

主要结果（KEY RESULTS）：本次研究将这些化石归为4个白粉藤属新种，它们与4个现代演化支（clade）具有亲缘关系。化石所属的植物被推断为藤本植物，栖息于河流沿岸林地、森林与更为开阔的生境镶嵌分布的环境中。虚拟埋藏学揭示了复杂的矿物充填过程如何掩盖了种子的关键形态特征，从而导致此前的分类学误判。新采样的非洲物种中，种子形态与化石最为相似的类群隶属于核心白粉藤属（core Cissus）内的4个演化支，其中2个为早期分化支系。

研究结论（CONCLUSIONS）：结合X射线成像技术的虚拟埋藏学，使得非洲地区首例白粉藤属及葡萄科化石得以被识别。核心白粉藤属演化支的早期分化类群至少在早中新世时期就已存在于非洲，研究推测喜阴白粉藤演化支（Cissus sciaphila clade）起源于非洲。这些化石为早中新世人猿总科（hominoids）所栖息的镶嵌型古环境提供了佐证。