Revisions to the fossil sporophyte record of Marsilea
Revisions to the fossil sporophyte record of Marsilea
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DOI：
10.2478/acpa-2019-0005
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发表时间：
2019-06
影响因子：
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通讯作者：
E. Hermsen
中科院分区：
文献类型：
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作者：
E. Hermsen
摘要Marsilea的化石记录是具有挑战性的评估，部分原因是不可靠的报告和相互矛盾的意见有关的名称Marsilea和Marsileaceaephyllum的化石叶和小叶类似于现代Marsilea的正确应用。本研究检查的标本包括被指定为Marsileaceaephyllum johnhallii的材料，据称是美国堪萨斯下白垩纪达科他组中最古老的Marsileae样孢子体化石记录;在北美西部的几个晚白垩世和古新世地点发现的已灭绝的水生被子植物福图纳的叶子和叶轮;在美国科罗拉多和犹他州始新世绿色河组发现的类似Marsilea的叶子和小叶。因此，提出了几项分类上的改变。虽然Marsileaceaephyllum johnhallii被重新解释为一种水生被子植物，与福图纳属共享一些建筑特征，但Marsileaceaephyllum在这里被维持为一个独特的属，并有一个修正的诊断;在这种重新解释下，Marsileaceaephyllum这个名字不再适用于与Marsileaceae有亲缘关系的孢子体器官。三个有效的化石Marsilea种被确认的孢子体材料的基础上，包括特征的四小叶和网状脉小叶：Marsilea campanica（J. Kvaček &赫尔曼）Hermsen，comb。来自奥地利上白垩纪Grünbach组; Marsilea mascogos Estrada-Ruiz et al.，产于墨西哥上白垩统Olmos组; Marsilea sprungerorum Hermsen，sp. nov.，产于美国始新世绿色河组。根据小叶尺寸可将该种彼此区分开来。美国始新世瓦萨奇组的树叶，从Marsileaceaephyllum转移回Marsilea，虽然没有分配到一个化石物种。最后，从埃塞俄比亚渐新世Marsilea的出现被重新分配到Salvinia。因此，对Marsilea化石记录的关键评估表明：（1）最古老的带有Marsilea状叶子的Marsilaceous孢子体化石来自Campanian;（2）只有四个可靠的孢子体材料记录可归因于Marsilea;（3）最古老的分散Marsilea孢子已知来自渐新世。
Abstract The fossil record of Marsilea is challenging to assess, due in part to unreliable reports and conflicting opinions regarding the proper application of the names Marsilea and Marsileaceaephyllum to fossil leaves and leaflets similar to those of modern Marsilea. Specimens examined for this study include material assigned to Marsileaceaephyllum johnhallii, purportedly the oldest fossil record of a Marsilea-like sporophyte from the Lower Cretaceous of the Dakota Formation, Kansas, U.S.A.; leaves and leaf whorls of the extinct aquatic angiosperm Fortuna from several Late Cretaceous and Paleocene localities in western North America; and leaves and leaflets resembling Marsilea from the Eocene Green River Formation, Colorado and Utah, U.S.A. Literature on the fossil record of Marsilea was also reviewed. As a result, several taxonomic changes are proposed. Marsileaceaephyllum johnhallii is reinterpreted as an aquatic angiosperm that shares some architectural features with the genus Fortuna, although Marsileaceaephyllum is here maintained as a distinct genus with an emended diagnosis; under this reinterpretation, the name Marsileaceaephyllum can no longer be applied to sporophyte organs with affinities to Marsileaceae. Three valid fossil Marsilea species are recognized on the basis of sporophyte material that includes characteristic quadrifoliolate leaves and reticulate-veined leaflets: Marsilea campanica (J. Kvaček & Herman) Hermsen, comb. nov., from the Upper Cretaceous Grünbach Formation, Austria; Marsilea mascogos Estrada-Ruiz et al., from the Upper Cretaceous Olmos Formation, Mexico; and Marsilea sprungerorum Hermsen, sp. nov., from the Eocene Green River Formation, U.S.A. The species are distinguished from one another based on leaflet dimensions. Leaves from the Eocene Wasatch Formation, U.S.A., are transferred from Marsileaceaephyllum back to Marsilea, although not assigned to a fossil species. Finally, an occurrence of Marsilea from the Oligocene of Ethiopia is reassigned to Salvinia. A critical evaluation of the fossil record of Marsilea thus indicates that (1) the oldest fossil marsileaceous sporophytes bearing Marsilea-like leaves are from the Campanian; (2) only four credible records of sporophyte material attributable to Marsilea are known; and (3) the oldest dispersed Marsilea spores are known from the Oligocene.