摘要
本文描述的化石材料是笔者于1987年在四川广元宣河宁强组内采得。经笔者鉴定和描述的计有海绵类Calycocoelia profunda sichuanensis subsp. nov.和托盘类Calathium sp.。Receptaculitids是表示以Receptaculites属为代表的一类海生生物的名字。Receptaculires是Deshayes(1828)从法文的属名Receptaculite(Defrance, 1827)改拼而成的。尼捷茨基(Nitecki)在1967年和1972年的文章已详细论及这个属名的沿革。1932年Waterlot描述比利时中泥盆统Receptaculites neptuni Defrance(它是Receptaculites的模式种)的标本时,从他提供的插图中,表明这种生物的个体呈杯状、瓶状和瓮状,其腔口是向上的。1962年科学出版社出版的《英汉动物学词汇》(第375页)把Receptaculites翻译为“
Summary
The present study is based on the materials collected from Xuanhe, a small village in Guangyuan County, N. W. Sichuan by the writer in 1987. The collection contains sponges (a new subspecies Calycocoelia profunda sichuanensis) and receptaculitids (Calathium sp. indet.)
According to their restudy of the biostratigraphy of Ningqiang and Guangyuan in recent years, the Chinese geologists suggested a late Early Silurian (Telychian) age for the Ningqiang Formation. In the past, Silurian sponges and receptaculitids have not yet been reported in Chinese palae-ontological literature. It is interesting that the Silurian sponges and receptaculitids from the Yangzi Platform are used as supplementary evidence for Silurian biostratigraphic correlation between East Asia and North America.
Description of Species Phylum Porifera Grant, 1827 Class Demospongea Sollas, 1875 Order Lithistida Schmidt, 1870 Suborder Tetracladina Zittel, 1878 Family Anthaspidellidae Miller, 1889 Genus Calycocoelia Bassler, 1927 Calycocoelia profunda sichuanensis subsp, nov. (Pl. Ⅰ, figs. 1, 2; Pl. Ⅱ, figs. 1, 2)
Description A cylindrical or conico-cylindrical fragmental sponge body poorly preserved, with part of it slightly silicified, prossessed of only a tubular spongocoelom, approximately 80mm high, broken at the base and top, gently but smoothly expanding upwards from subcylindrical basal stalk, approximetely 28 mm in diameter in the lower part and 32 mm in diameter in the upper part. Spongocoelom circular, gently broadening with a width ranging from 13 mm in lower part to 15 mm in upper part, exactly centered, and filled with matrix. Thickness of body wall on all sides ranging from 7mm in lower part to 8mm in upper part.
External surface of body generally corrugated due to alternations of superimposed circular apertures and vertically lined terminals of skeletal strands, and partially covered with bioclastic sediments. Surface of spongocoelom also composed of both apertures and skeletal strands.
Radial canals nearly straight in transverse section. Canals horizontal, inclining, usually spaced 0.5—0.8mm apart longitudinally. Circular apertures of canals in both exteral surface of body and surface of spongocoelom equal-sized, about 0.5 mm in diameter. Other skeletal openings in body wall triangular to rectanglar (tr.), different in sizes, restricted by the stacked ladder-like series consisting of spicules and strands or by irregular spicules, and filled with matrix. Both continuities and positions of openings affected by spacings of canals and strands.
Skeletal structure of sponge body characteristic of Anthasipellidae. Body skeletons mainly composed of ladder-like series made up of dendroclones generally 0.025—0.05mm in diameter and 0.5—0.6mm in length. Ray tips of dendroclones in neighbouring series sometimes fused to form rod-shaped strands. Strands in flabelliform arrangement representing the most conspicuous vertical structures. Upward strands branching inward to meet the spongocoelom surface and outward to meet the body surface at acute angles respectively. Strands usually 0.1mm in diameter in transverse section, arranged in a row (i. e., in a dotted-line transversely), with every two rows usually 0.3—0.4mm apart, constituting a group which is similar to a perforate septum of rugose corals; groups numbering 62 in the sponge body, separating the canals respectively.
Remarks Ivanovski (1963) described a species of rugose corals under the name of Calostylis profundum from the Lower Silurian strata in Siberia. Judged from the skeletal features in Ivanovski's description and figures, the Siberian form does not belong to rugose corals but to sponge; it should be assigned as a species to the genus Calycocoelia of lithistids. The Siberian form is similar to those from Sichuan in shape and size of body and canal system of body wall. It seems that both Siberian and Sichuan forms are closely related but probably not conspecific, and therefore the writer proposes a new subspecific name of Calycocoelia profunda sichuanensis for the Sichuan form which shows a close relationship to the Siberian form (Ivanovski, 1963).
Locality and horizon Xuanhe of Guangyuan County, N. W. Sichuan; Ningqiang Formation, upper Lower Silurian.
Receptaculitids Family Soanitidae Miagkova, 1965 Genus Calathium Billings, 1865 Calathium sp. (Pl. Ⅱ, figs. 3, 4)
Description External form of body unclear. Two sections of parallel slices, 20 mm apart in Figs. 3a and 3b showing internal structures.
Fig. 3a showing two fragmentary bodies. Bigger body with an incomplete elliptic section, about 22 mm in short diameter and only 26 mm in long diameter. A ring-like chamber dividing the body wall into two parts: inner wall incomplete and thin, about 0.2mm in thickness while outer one 0.8 mm in thickness, with a denticulate inner margin; both walls 3.5—4.5mm apart. Radial shafts incomplete, scattered in the ring-like chamber, meeting both outer and inner walls at a right angle. Central coelom incompletely elliptic in outline, 20×11mm in diameter, with some meandroid organisms deposited in it.
Small body also incompletely elliptic in section, 20×15 mm in diameter. Outer wall thick, commonly 0.5 mm in thickness with a denticulate inner margin. Inner wall thin, 0.1—0.2 mm in thickness. A few incomplete radial shafts scattered in the ring-like chamber. Central coelom irregularly elliptic in outline, containing some meandroid organisms and bioclastics.
Fig. 3b showing the irregularly elliptic section of the bigger body (bigger section in Fig. 3b and bigger body in Fig. 3a being two sections of the same body), 16×12mm in diameter, outer wall with a denticulate inner margin, relatively thick (0.7—0.8mm in thickness). Obvious inner wall absent. Corresponding place to central coelom of body filled with meandroid organisms. Radial shafts incomplete and scattered in ring-like chamber.
Smaller section in Fig. 3b belonging to the same body with the smaller section in Fig. 3a, circular in outline, about 8 mm in diameter. Outer wall with a denticulate inner margin, 0.5 mm in thickness. Central coelom of body absent. Radial shafts rare and incomplete, scattered in the section of body.
Remarks The Sichuan form can be compared with Calathium egerodae (Nitecki, 1972) due to their similar features in the body section. Although there are incomplete section of the two sponge bodies, the form of calathid receptaculitids from Sichuan still can be assigned as Calathium sp. It is far impossible to make any detailed comparison of both forms due to the lack of more materials of Calathium sp. from Sichuan.
Locality and horizon Ibid.
出处
《古生物学报》
CAS
CSCD
北大核心
1990年第5期581-591,657-658,共11页
Acta Palaeontologica Sinica
基金
国家自然科学基金4870090项目资助
为中英志留系研究项目的阶段成果之十二
