Cuticle ultrastructure of Pseudofrenelopsis gansuensis: Further taxonomical implications for Cheirolepidiaceae
Résumé
A study of the cheirolepidiaceous conifer Pseudofrenelopsis gansuensis from the Lower Cretaceous of Wangqing Jilin Province in China was conducted in detail using scanning and transmission electron microscopy techniques. In total, nine ultrastructural features were recognized for the cuticle of this fossil plant, which are helpful in the distinguishing between cuticles of ordinary epidermal cells, subsidiary cells, guard cells and hypodermal cells of the stomatal apparatus. A three dimensional reconstruction of the cuticle ultrastructure was obtained. Pseudofrenelopsis gansuensis is the second species of this genus for which the cuticle ultrastructure has been statistically examined with 30 measurements and estimated con␣dence interval values. The close comparison of the cuticle ultrastructure characters, including sta- tistical data, among Cheirolepidiaceae and other fossil conifers provides potential evidence of the taxonomic signi␣cance of this genus: ten characters are potentially valuable for speci␣c separation, eleven parameters for generic separation and three parameters seem also to be useful for Family determination. The differences in the chemical composition according to preliminary statistical element analyses of the cuticles based on three ratios in two species of Pseudofrenelopsis, P. dalatzensis and P. gansuensis, should also be examined in future studies.