摘要
本文描述黑龙江东部双鸭山-绥滨地区城子河组的银杏类化石6属14种(5新种)。多数属于银杏目,包括Ginkgoites baoshanensis sp. nov., G. elegans sp. nov., G.manchuricus(Yabe et Oishi), G. microphyllus sp. nov., G. cf. sibiricus (Heer) Seward, G. subadiantoides sp. nov., G.spp., Sphenobaiera qixingensis Zheng et Zhang, cf. Sph. pulchella (Heer) Florin, Toretzia shunfaensis sp. nov.等;属于茨康目的只Phoenicopsis (Phoenicopsis?) sp.,Ixostrobus heeri Prynada两种。
This paper deals with several specimens of ginkgophytes, paying particular attention to the characteristics of the cuticular structure. These specimens are part of the collection from the Chengzihe Formation in Shuangyashan Coalfield and Suibin Region of eastern Heilongjiang, separately belonging to Ginkgoites, Sphenobaiera, Toretzia, Phoenicopsis, and Ixostrobus, including Ginkgoiter baoshanensis sp. nov., G. elegans sp. nov., G. manchuricus (Yabe et Oishi), G. mircophyllum sp. nov., G. cf. sibiricus (Heer) Seward, G. subadiantoides sp. nov., G. spp., Sphenobaiera qixiangensis Zheng et Zhang, Sph. cf. pulchella (Heer) Florin, Toretzia shunfaensis sp. nov., Phenicopsis (Phoenicopsis?) sp. and Ixotrobus heeri Prynada.
Concerning the similarity of Mesozoic leaves to those of modern Ginkgo biloba, there are conflicts in the usage of the generic names Ginkgo and Ginkgoites; a species may bear different generic names in various documents. With the study of cuticles in recent years' the generic name Ginkgo seems to be more frequently used. Since not all of the fossil leaves of the Ginkgo type are related to the genus Ginkgo, the writer follows Seward (1919) regarding the generic name of Ginkgoites as a form genus for the Mesozoic leaves with certain resemblance to the leaves of modern Ginkgo, and the genus Ginkgo for the leaves resembling those of G. biloba in the morphology of leaf as well as in fructifications.
Description of new species Ginkgoites baoshanenss sp. nov. (Pl. Ⅱ, fig. 1; Pl. Ⅴ, figs. 12—14; text-fig. 1)
Lamina semi-circular, about 2.8cm high, with a petiole about 1.2mm broad, dissected by deep median sinus into two halves; each half more or less deeply divided 3—4 times into lanceolate ultimate segments, with their apex generally oblate, sometimes notched. Each ultimate segment with about 8 veins at intervals of 0.2—0.3ram.
Cuticle thick. Upper cuticle completely lacking stomata; epidermal cells elongated-polygonal but narrower on the margin of segment, with irregularly thickened walls but without median papillae. Lower cuticle slightly thinner than the upper, bearing numerous stomata confined to strips between veins; s tomatal strips usually two times as broad as strips without stomata. Cells over the veins like those of the upper cuticle in outline, irregularly arranged, in 4—5 rows, with papillae; anticlinal walls straight and irregularly thickened. Cells between veins indefinite, with stronger and hollow papillae. Stomata rounded to elliptical, surrounded by less than 8 subsidiary cells, each with a larger papilla arising inwards over the stomatal pit. Guard cells deeply sunken, usually concealed by papillae of subsidiary cells, with surface quite thinly cutinized; aperture about 10μm long, irregularly oriented.
Holotype: Pl. Ⅱ, fig. 1
This species is similar to G. sibiricus in shape, but in the latter, the segments are less in number and apart from each other, the apex of segment is rounded and the veins appear to be slightly convergent at the top of segment.
Ginkgoites elegans sp. nov. (Pl. Ⅰ, figs. 8—14; text-fig. 2)
Lamina nearly semi-circular, with a basal angle of about 220°, smaller, less than 1.5cm high, dissected by a deep median sinus into two halves, each divided into 4 main segments, and then further divided 1—2 times into oblong ultimate segments, with their apex broadly rounded. Each segment carrying 5—6 rather marked veins.
Upper cuticle consisting wholly of isodiametric polygonal cells; nerve-courses unmarkd; no Stomatal strips much broader than strips without st flat and smooth periclinal walls and well-marked, straight and evenly thickened anticlinal walls. Lowercuticle slightly thinner than the upper, bearing numerous stomata which are rounded or squarish, scattered confined to strips between veins. Stomatal strips much broader than strips without stomata. Nerve-course represented by 4—5 rows of rectangular cells with very thickly cutinized walls. Cells between veins often indistinct in outline, appearing to be irregularly polygonal, mostly with hollow papilla and unevenly thickened. Guard cells sunken, surrounded by 4—5 rectangular or polygonal subsidiary cells, each with papilla arising from the inner border and pointing inwards.
Holotype: Pl. Ⅰ, fig. 8.
The present species approaches to Ginkgo delicata Samylina from the Lower Cretaceous of Zyrianka Coal Basin, USSR (Samylina, 1967, p. 136, Pl. Ⅰ, figs. 3—12), but it is easily distinguishted by the size of leaves and the epidermal features from the latter in which the leaves are larger with upper and lower cuticles not only on the nerve-course but also between veins, all bearing larger and conspicuous central papillae. In the shape of leaf and the dissection of lamina, it bears a certain resemblance to Ginkgoites tylensis E. Lebrdev from the Lower Cretaceous of easter Siberia (Doludenko and Lebedev, 1972, p. 91, fig. 5; Lebedev, 1974, p. 73, Pl. 18, figs. 6—8; rex-fig. 33) But in the latter, the apex of segment is rounded and the broadest portion is not close to it. Moreover, its epidermal structure still remains unknown. The specimens described as G. sibirica by Chen et al. (1988, p. 67, Pl. 34, figs. 6—10) from Fuxin, Liaoning appear to be more similar to the present species than G. sibirica.
Ginkgoites microphyllus sp. nov. (Pl. Ⅱ, figs. 2—16; text-fig. 3)
Leaf smaller, with a petiole. Lamina flabellate, 1.4—2.2cm high, usually divided asymmetrically by a deep median sinus into two halves; each half further divided 1—2 (occasionally 3) times into lanceolate or elongated-elliptical ultimate segments, with their apex rounded, sometimes notched. Veins unsatisfactorily shown, with 8—12 in each segment.
Cuticles thick. Upper cuticle with no papille and stomata, composed of elongated cells. Cells along the vein narrower, with surface strongly cutinized but not papillate; anticlinal walls straight or somewhat undulated and irregularly thickened. Lower cuticle thinner than the upper, composed of 5—7 rows of rectangular and elongated cells with straight or somewhat undulated walls. Cells between veins unmarked, probably polygonal, with hollow papillae and undulate walls. Stomata scattered between veins, irregularly oriented, rounded or elliptical. Guard cells sunken; subsidiary cells 5—7 in number, each bearing a larger papilla over the stomatal pit.
Holotype: Pl. Ⅱ, fig. 10.
This species quite resembles G. sibiricus, although much smaller in size. It is also comparable with G. pusilla and G. flabellate from eastern Siberia (Heer, 1876, 1880), but can be distinguished from them by the flabellae leaf, the lanceolate or elongated-elliptical segment and more crowded veins. Besides, in the latter two species the epidermal features are still unknown up to now.
Ginkgoites subadiantoides sp. nov. (Pl. Ⅲ, figs. 1—9; Pl. Ⅳ, figs. 1—10; Pl. Ⅴ, figs. 1Ⅸ8; Pl. Ⅵ, fig. 10)
Leaf generally larger, with a petiole. In the larger leaves, lamina semi-cirular or nearly semicirular, usually deeply divided into two halves and then each half further divided 1—2 times into the cuneate segments or not divided, with anterior margin of segment nearly straight or notched; in the smaller ones, lamina flabellate, undivided and with entire or irregularly notched margin.
Cuticle thick. Upper cuticle with polygonal or elongatedpolygonal and rectangular cells; nervecourses indistinct. Surface of cell normally without papilla and stomata but occasionally with the occurrence of incompletely developed ones; anticlinal walls almost straight and thickly cutinized. Lower cuticle slightly thinner than the upper, in most preparations without papilla, and sometimes partly with a few hollow papillae between veins, but in incufficiently oxidized preparations showing larger and clearly marked papillae on the whole surfface. Strip along veins distinct, composed of 8—14 rows of elongated cells; cells between veins rectangular or polygonal, periclinal and anticlinal walls all thickly cutinized. Stomata confined to interstitial region, scattered, with rounded or elliptical outline and surrounded by 4—8 polygonal or squarish subsidiary cells, each with a very large papilla. Papillae often situated near the stomatal pit, pointing inwards and thus concealing it. Guard cells sunken, thinly cutinized along the aperture with irregular orientation.
The specimens of this species are very abundant in our collection. They can not be separated from the specimens described under Ginkgoites adiantoides (Unger) or Ginkgo adiantoides (Unger) by different authors in the form and the size of lamina. In the epidermal structure the original specimens of the latter have not been known, while the specimens described under the same name by several palaeobotanists are not quite identical with each other and so they are generally considered as complex species. In the new species Ginkgoites pgradiantoides established by Samylina (1967) for the leaves from the Zirianka Coal Basin, the form is identical with G. adiantoides, with the epidermal structure recognized in detail. The present species also bears some resemblances but with some differences between them. In the latter the veins are rare, the lower cuticle bears clearly marked hollow papillae but the upper cuticle bears no or some inconspicuous ones, the strip along veins is narrower and the cells between veins are mostly squarish or polygonal. While in the former the veins are rather dense, the upper cuticle never bears papillae and in most preparations no papillae are found on the epidermal cells of the lower cuticle, either, except a few in the insufficiently oxidized preparations; besides, the strip along veins is wider and the cells between veins are rectangular or elongated-polygonal in outline. It is very difficult to distinguish the present species from the living species Ginkgo biloba in the form and the size of lamina, but they are dif erent in epidermal structure.
Based on appeara
出处
《古生物学报》
CAS
CSCD
北大核心
1992年第2期232-248,277-282,共17页
Acta Palaeontologica Sinica
基金
国家自然科学基金(4850039)
关键词
银杏类化石
城子河组
黑龙江
eastern Heilongjiang, Shuangyashan-Suibin, Chengzihe Formation, Early Cretaceous, Ginkgophytes.
