中国科学院南京地质古生物研究所机构知识库

Karkenia henanensis sp. nov. is found in association with ginkgoalean leaves of the Sphenobaiera type in the Jurassic Yima Formation, Henan, China. The material consists of five young strobili. The strobilus is compact, oblong to lanceolate, and contains more than 100 ovules. Ovules orthotropous, but incurved. The integument cuticle remains unknown, while it appears to be free from the nucellus in the greater part of the ovule. The megaspore membrane is composed of a thin, amorphous foot layer and a thick patterned layer. Bacula are irregularly arranged, finely granular in texture, but with electron-lucent lines in the matrix. Pollen grains found attached to the nucellus are of the Ginkgocycadophytus type. Comparisons have been made between the new species and the already described forms. The general morphology of the genus Karkenia is summarized with phenological consideration, taking into account the information obtained in the present study and in recent years as well. This is the first record of Karkenia in China. Possible records of this genus in China formerly described under Stenorachis are also enumerated. K henanensis is one of the few fossil ginkgoaleans of which the megaspore membrane ultrastructure has been studied. (C) 2002 Elsevier Science B.V. All rights reserved.