摘要
宽背虫(Bathynotus)这一早寒武世晚期相当重要的三叶虫属,是由Hall(1860)据美国佛蒙特州Georgia镇下中寒武统Georgia组所产B. holopyge的标本而建立的,后来,Walcott又据模式标本对其眼叶、面线等构造进行了补充描述和讨论(1886,p.191)。由于对Hall的模式标本观察认识不同。
The genus Bathynotus was erected by Hall(1860). After being supplemented and revised by Walcott (1886) and Resser and Howell (1938), its definition was tending towards perfection. Now it is included in the family Bathynotidae, under the suborder Bathynoina and the order Redlichiida(Moore ed., 1959).So far, Bathynotus includes 11 species and 1 conformis, namely, B. holopyga Hall, 1860; B. namanensis Lerm., 1940; B. granulatus Lerm., 1940; B. rotundus Semshko, 1969; B. fortis Semshko, 1969; B. kueichouensis Lu, 1963; B. nanjiangensis Zhang Tairong, 1981; B. hunanensis Liu, 1982; B. hubeiensis Sun, 1982; B. gaotonensis Zhang Quanzhong et al,, 1984; B. elongatus Zhao et al., 1987 and B. cf. holopyga. Among them, there are six species in China.Bathynotus. is widely distributed; besides in the Appalachian Mts. of North America, it has also been found in the southern and southwestern fringe of Siberia; Wushi in Xinjiang, eastern Guizhou, northern Hunan, southeastern Hubei, southern Anhui, and northern Zhejiang of China; and the southern part of the Northern Territory, Australia. Most of the areas are situated in the transitional zone from the stable to active regions of Cambrian. It is apparent that the distribution of Bathyotus is very regular.In North America, Bathynotus has been found in the Bonnia-Olenellus zone, which belongs to the upper part of the Lower Cambrian, corresponding to the Tsanglangpu stage and the Longwangmiao stage of China (Zhou Zhi-yi and Yuan Jin-liang, 1982). In Siberia, the conditions are a little complicate. There seem to be two horizons of Bathynotus. One is associated with Namania, Ingledella, etc., which undoubtedly belongs to Lower Cambrian (Suvorova, 1961; Pokrovskya, 1961; Karasev et al., 1966; Repina, 1972). The other is discovered from the Edelstenaspis-Kooteniella zone of the uppermost part of the Lenaian, which can be compared with the transitional beds of Lower-Middle Cambrian in China (Zhou Zhi-yi and Yuan Jin-liang, 1982). The cases in China are similar to those in the Soviet Union, in most localities, Bathynotus is associated with Kunmingaspis, Chiltidilla (Xiang Li-wen, 1981) or with Kunmingaspis, Mufushania and Redlichia (Sun Zhen-hua, 1982). In the Kaili area of Guizhou, besides Kunmingaspts, Mufushania and Redlichia, Bathynotus is associated with Nangaops. Since there are arguements about the age of the transitional beds, which in fact involve the division of the boundary between Lower and Middle Cambrian, the upper boundary of the Bathynotus cannot be determined. Many specimens of Bathynotus have also been collected from a place 20m below the transitional beds in the Kaili area. It is obvious that Redlichia appears in the Tsanglangpu stage and Bathynotus in the world appears in the Longwangmiao stage, i.e., later than Redlichia, and both genera died out almost contemporaneously in the transitional stage from Early to Middle Cambrian.The Kaili area of Guizhou is situated in the transitional region between the Yangtzi region and the Jiangnan region (Lu Yan-hao et al., 1974; Lu Yan-hao, 1979; Zhou Zhi-yi et al., 1979, 1980). There are abundant specimens of Bathynotus in the lower part of the Kaili Formation (Lower-Middle Cambrian). The well-preserved specimens are very rare in the world. There are also some specimens of the holaspid period, providing material for studying the ontogeny of Bathynotus.The trilobites of Bathynotidae here described were collected from the lower part of the Kaili Formation (Lower—Middle Cambrian) in the Kaili area. They consist of 1 genus, 4 species, 2 indeterminable species and 1 indeterminable genus or species, including 1 new species, Bathynotus sinensis sp. nov.Description of new species Bathynotus sinensis Zhao et Huang sp. nov. (Pl. Ⅰ, figs. 1—9; Pl. Ⅱ, flgs. 6, 7; Text-fig. 2)Diagnosis: Dorsal exoskeleton elongately ovate. Holotype 17.1mm long. Glabella conical, broadly rounded in front, concave inward on both sides. 2 pairs of glabellar furrows shallow; fixigenae narrow. Palpebral lobes long; palpebral furrows broad and deep, with a node in the middle of occipital ring. Brim absent; anterior border short(tr.). Librigenae narrow (tr.); librigenal spine very long. Hypostom pentagonal. Thorax with 13 segments; axothorax very broad (tr.), with median nodes. Pleural lobes narrow. Pygidium semielliptical, axial lobe convex, with 2—3 segments; terminal segment with postaxial ridge; pygidial border low, with central part of posterior margin slightly concave inward.Comparison: This species is closely similar to B. hunanensis Liu, 1982, but in the latter, the glabella is slightly shorter, and is not concave inwards on both sides, the genal spine is short, and the pygidium is broader (tr.). It is also similar to B. holopyga Hall, 1860, but differs in having broader glabella and axothorax, shorter genal spines, narrower pleural lobes and broader axis of pygidium. It may be compared with B. hubeiensis Sun, 1982, but in the latter, the glabella is broader, with front rounded, the occipital furrow and posterior glabellar furrows are deeper, the genae are broader (tr.), and the genal spines are shorter.Locality and horizon: Danzhai County, Kaili area, Guizhou; lower part of Kaili Formation (Lower and Middle Cambrian).
出处
《古生物学报》
CAS
CSCD
北大核心
1990年第1期43-53,共11页
Acta Palaeontologica Sinica
