Eoangiopteris congestus sp. nov., a marattialean fern from the Lower Permian Taiyuan Formation of Wuda Coalfield, Inner Mongolia
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Abstract:
A new marattialean fern Eoangiopteris congestus sp. nov. is described from the volcanic tuff bed in the uppermost part of the Taiyuan Formation, within Wuda Coalfield, Inner Mongolia. It consists of organically connected Psaronius –type stem, Pecopteris –type vegetative fronds and Eoangiopteris –type fertile fronds. Vegetative fronds are tripinnate. Penultimate and ultimate pinnae are both linear. Pinnules are typically pecopterid, oblong in outline, with decurrent midvein and once–bifurcated lateral veins. Vegetative pinnules are attributable to Pecopteris orientalis (Schenk) Potonié type. Fertile pinnules are identical to these vegetative pinnules. Bilaterally symmetrical synangia are borne in a single row on each side of the midvein, closely arranged along the lateral veins, and composed of 6–8 sporangia that are attached to a parenchymatous receptacle. Sporangia are elongate and exannulate, fusiform in shape. The outer facing walls of the sporangia are two to three cells thick, while the inner facing walls are reduced to one cell thick. In situspores are trilete, oval to circular in shape with prominently microspinate sculpture. They are comparable to the dispersed miospore genus Apiculatisporites. The new discovery represents the stratigraphically earliest occurrence of Eoangiopteris in Cathaysia. In addition, these bilaterally symmetrical synangia are distinctly different from those radially symmetrical synangia (Asterotheca) which previously were considered to be the fertile organs of Pecopteris orientalis–type pinnules, suggesting one morphotype of fossil pinnule may correspondence to several types of fructifications in palaeobotanical researches.
