Mallomonas skogstadii sp nov and M. bakeri sp nov.: Two new fossil species from the middle Eocene representing extinct members of the section Heterospinae?
Mallomonas skogstadii sp nov and M. bakeri sp nov.: Two new fossil species from the middle Eocene representing extinct members of the section Heterospinae?
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DOI：
10.7872/crya/v39.iss4.2018.511
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发表时间：
2018-11-01
影响因子：
1.3
通讯作者：
Siver, Peter A.
中科院分区：
文献类型：
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作者：
Siver, Peter A.
在加拿大北部靠近北极圈的始新世长颈鹿管地区，发现了两个新的同泌尿植物Mallomonas属的化石种M. skogstadii和M. bakeri。这两个新物种的鳞片都有一套共同的特征，包括一个椭圆形的肋骨环绕着大约一半的底板和大部分的圆顶，在后翼缘上有一系列厚的肋骨，但在盾上没有，一个薄的后缘，和一个平坦而浅的圆顶。此外，这两个物种都有两种类型的鳞片，体鳞片和顶鳞片。bakeri M.顶端鳞片形成一个独特的向前突出的圆顶，而skogstedii M.顶端鳞片与体鳞片在形状上有显著差异。skogstadii的鳞片比M. bakeri的鳞片更大，基板孔隙模式也不同，并且在相隔数百年的地层中发现了这两个分类群的遗骸。根据与现代种的比较，M. bakeri和M. skogstadii在较小程度上属于异棘科的基部代表。与每个物种相关的植物区系反映了酸性环境，可能是高溶解腐殖质含量。
Two new fossil species of the synurophyte genus Mallomonas, M. skogstadii and M. bakeri, are described from Giraffe Pipe, an Eocene locality situated near the Arctic Circle in northern Canada. Scales of both new species share a suite of characters, including an ovalshaped rib encircling approximately half of the base plate and most of the dome, a series of thick ribs on the posterior flange, but lacking on the shield, a thin posterior rim, and a flat and shallow dome. In addition, both species possess two types of scales, body scales and apical scales. Apical scales of M. bakeri form a unique forward-projecting dome, and those of M. skogstedii are significantly different in shape than the body scales. Scales of M. skogstadii are significantly larger and have a different base plate pore pattern than those of M. bakeri, and remains of both taxa were uncovered in strata deposited hundreds of years apart. Based on comparison made with modern species, M. bakeri, and to a lesser extent M. skogstadii, are placed into, and likely represent basal representatives of section Heterospinae. The floras associated with each species reflect acidic environments, probably high in dissolved humic content.