摘要
近年作者(1988—1990)在辽阳兰家寒武纪崮山组发现了笔石生物群,新建Dendrograptusliaoyiangensis sp.nov..D.liaoyiangensis latus subsp.nov.,Callograptus lanjiaensis sp.nov.。其特征为笔石个体小,枝短粗,具附着盘,胞管简单,固着底栖,分布局限,具有地方色彩,是目前已发现的最古老的笔石生物群。根据前人研究结果(穆恩之、林尧坤)和作者的研究认为,寒武系风山组Dictyonema wu-tingshanense是原始漂浮笔石,在太子河流域出现层位最低;凤山组燕州段笔石属底栖和漂浮的混合生态笔石群。同时作者在辽东半岛南部寒武系凤山组湾湾沟段和下楸树沟段发现笔石生物群,新建Dictyonema jin-zhouense sp.nov.Callograptus viminalis sp.nov.C.lashushanensis sp.nov.。作者的研究表明,太子河流域寒武系崮山组的笔石是最古老的笔石,因而太子河流域很可能是太平洋型和大西洋型笔石动物群的发源地。
During studies on Cambrian graptolites in 1988-1990, graptolites were first found from Gushan Formation at Lanjia, Liaoyang, and some new species were erected, namely, Dendrograptus liaoyongensis sp. nov., D. liaoyangensis latus subsp, nov., Callograptus lanjiaensis sp. nov.. A section was mapped for Fengshan Formation of the Upper Cambrian in Wutingshan, graptolites in Yanzhou Member were collected across the section. Consulting predecessors (Mu Enzi, Lin Yaokun), Dictyonema wutingshanense is confirmed to be primitive floating graptolites at the lowest horizon in Taitze River Basin, graptolites from Yanzhou Member of Fengshan Formation are considered to belong to mixed ecology colony of benthon and neuston. A layer of graptolites found in Wanwangou Member of Fengshan Formation are Dictyonema jinzhouense sp. nov., D. wutingshanense Mu, Callograptus lashushanensis sp. nov., C. viminalis sp. nov.; anothor layer in Xiaqiushugou Member are Dictyonema kelanense Lin, Callograptus sp., Dendrograptus sp.; the third layer 2m above Xiaqiushugou Member are Dictyonema flabelliforme, Airograptus 'furciferus (Ruedemann). There are three graptolites zone, established in southern Liaodong Peninsula, from Wanwangou Member of Fengshan Formation, Cambrian to the bottom of Yeli Formation, Ordovician. The boundary of Cambrian and Ordovician is lined between Dictyonema kelanense zone and Airograptus furciferus zone. So far, Gushan Formation in Taitze River Basin is the oldest graptolite-bearing strata. Yanzhou Member of Fengshan Formation is the lowest horizon for Dictyonema wutingshanense as the most primitively floating graptolite and also for the two species of Airograptus paragenetic with it. With the graptolites of above-mentioned two genuses evoluting, their horizon uprises from Taitze River Basin south to southern Liaodong Peninsula, Shandong, North Jiangshu, North Anhui. It shows that is multiplying and spreading route for graptolite, and probably it is originating and multiplying route for the Pacific-and Atlantic-type graptolite fauna. In Taitze River Basin, the graptolites were thriving from Cambrian to the early stage of Ordovician and some key genuses and species were complete. Through the study on the Cambrian graptolites in East Liaoning, the birth place can be exactly affirmed to be Taitze River Basin of Liaoning. Description of new species Dictyonema jinzhouense sp. nov. (pl. Ⅴ, fig. 6) Rhabdosome large, fan-like in form, over 40mm in length, more than 28mm in width. Stips straight with a width of 0.4mm. Two main stips short, less 1mm in length. Branching subparallel at a small angle and irregular, with 6-7 branches in 5mm. Dissepiments few, at an angle with stips. Thecae not very clear. Autothecae being tube-like and apertural margins even, with 5-6 thecae in 5mm. A long stalk, over 20mm in length. Comparison: The new species seems belonging to the genus Callograptus in the general features, but dissepiments few. It is more closely allied to the genus Dictyonema, but differs from the former in laterally branching and having a long stalk. Callograptus lashushanensis sp. nov. (pl. Ⅴ, fig. 5; pl. Ⅵ, figs. 4, 6) Rhabdosome cone-like in form, 9mm in length and 7mm in width, with a spherical floating bubble of 0.8mm in diameter at the proximal end. Stips a little curved with a uniform width of 1-0.7mm. Branching dichotomously with 7 branches in 5mm. no dissepiment and hinge. Thecae clear, being exceedingly slender tubes. Apertural margins even, supragenicular wall straight, overlapping 1/3 thecal length, with 7-9 thecae in 5mm. Comparison: In the form of rhabdosome, features of stips and thecae, the new species resembles Callograptus pennatus Lin of Fengshan Formation, Upper Cambrian, Xiaoxianzhuangli, Anhui, but differs from the former in. the floating bubble. Callograptus viminalis sp. nov. (pl. Ⅵ, fig. 7) Rhabdosome wicker-like, 12mm in height and 5mm in width. A plate-like basal disc at the proximal end, measuring 1mm in diameter, 0. 07mm in height. A 0.5mm longstalk growing at the basal disc, three main stips branching from the stalk, and branches parallel upward, re-branching 1-3 times, numbering 7 branches in 5mm, with the width of 0.5mm, distance between branches large. Thecae clear, being tubes, apertual margins and supragenicular wall even, overla- pping half thecal length, with 10 in 5mm, bithecae not clearly seen. Comparison: The new species is similar to Callograptus pennatus Lin in the form but differs from the new species in the plate-like basal disc, short stalk with 3 stips, and dense arrangement of thecae. Callograptus lanjiaensis sp. nov. (pl. Ⅰ, figs. 2, 3, 4) Rhabdosome taper-like in form, 10mm in height and 8mm in width, stalk short and thick with 0.3mm in length. Branches parallel, curved upward. Branching distance gra- dualy increasing from proximal to distal end: the first being 1mm, the second 2-3mm, the third 5mm. Branching belt obvious. Distance between branches being over 0.3-0.5 mm, with 16 in 10mm. No dissepiment and thecae not clearly seen. Comparison: In branching style and distance, the new species and Callograptus? toitzehoensis Mu are similar, but differs from the former in wide rhabdosome, large distance between branches, and curved branches. Dendrograptus liaoyangensis sp. nov. (pl. Ⅰ, figs. 1, 5; pl. Ⅱ, figs. 2, 6; pl. Ⅲ, figs. 1, 4, 5, 7, 10) Rhabdosome grove-like in form, measuring 17mm in height and 18mm in width, A plate found at the proximal end, 0.5-0.7mm in diameter. Main stip short, two stips bran- ching from the distal end of the main stip at 60°, then re-branching 5-6 times forming grove. Branching distance various from 1mm at proximal end to 2mm at distal end forming obviously branching belt. Branching angle small at 30°-50°. Branches thick, with a uniform width of 0.5mm. Thecae obviously seen, tube-like, 1.7mm in length and 0.5mm in width across its aperture, apertural margins even, ventral margins slightly concave, overlapping one- half, numbering 4 in 5mm. Bithecae tube-like also, 1.5mm in length, 0.2mm in width, alternate in arrangement. Comparison: The new species is similar to Dendrograptus yini Mu in the form of rhabdosome and branching features, but differs from the new species in the wide rhabdosome, thick stips and obviously branching belt at distal ends. Dendrograptus liaoyangensis latus subsp. nov. (pl. Ⅱ, figs. 1, 4, 5, 7) Rhabdosome wide and large, grove-like in form, 9mm in height, 24mm Jn width. The main stips short with the length of 2mm, two stips stretching from the main stips, 4-6 times branching at 1.5mm with the branching distance of 2.5mm. Two main stips at an angle of 60°, while the third branching at 180°. A lateral branch of 2mm in length found at 0.5mm of each main stips. Thecae and bithecae clear, the former tube-like, 1.5mm in length, 0.2mm in width across its aperture, apertural margins shallow and even, ventral margins straight; the latter thin and long, 1mm in length, O.12mm in width, alternating in arrangement, similar to the former in shape. Comparison: The new species is similar to Dendrograptus liaoyangensis sp. nov., but differs obviously in shape.
出处
《辽宁地质》
1991年第2期97-129,98-129,共33页
关键词
笔石纲
寒武纪
辽宁
Eastern Liaoning Cambrian Gushan Formation Fenshan Formation Graptolite Birth place
