摘要
本文简述了海绵动物的基本特征,比较了硅质海绵与钙质海绵在骨针及骨骼结构上的不同,认为骨针性质与硬体骨骼结构是海绵分类的主要依据。据此把海绵动物划分为普通海绵纲(Class Demospongea)、六射海绵纲(Class Hexactinellida)、钙质海绵纲(Class Calcispongiae)、异射海绵纲(Class Heteractinida)和硬骨海绵纲(Class Sclerospongiae),并进一步讨论了不同类别海绵在地史时期的分布及演化。提出海绵除可作为判别环境的标志外,还是重要的造礁生物。地史时期由海绵形成的成礁期有3次,它们与不同类型碳酸盐岩隆的生成及油气的聚集有密切关系。
Taxonomy of fossil sponges at the highest level is based on the rigid skeleton, since the soft tissue is not preserved in the fossils. Most sponges have an internal skeleton, which may consist of 1) calcareous spicules; 2) siliceous spicules: 3) siliceous spicules and organic matter (spongin) or 4) spongin fibers only. In calcareous sponges, a few have calcareous non-spicular wall structures (Sphinctozoa), and a few have fibrous structures (Inozoa) in which calcareous spicules are embedded and cemented together. The following is an accepted classification of fossil sponges:
Phyllum: Porifera
Ⅰ. Class: Demospongea (Cambrian—Recent)
Skeleton composed of siliceous spicules and spongin, or spongin only. Megascleres being, oneto four-rayed spicules and microscleres including chelas, sigmas, toxons, forceps, sigmaspires and asters. Most microscleres not preserved in fossil demosponges.
1. Order: Keretosa (Recent)
2. Order: Monaxonida (Middle Cambrian—Recent)
3. Order: Choristida (Carboniferous—Recent)
4. Order Lithistida (Cambrian—Recent)
Ⅱ. Class: Hexactinellida (Late Proterozoic—Recent)
Megascleres mainly being hexactins and stauractins which are found in some earliest hexactinellids. Microscleres including hexasters and amphidiscs, with no spongin.
Ⅰ). Subclass: Hexasterophora: Microscleres are hexasters.
1. Order: Lyssacinosida (Ordovician—Recent)
2. Order: Hexactinosida (Permian—Recent)
3. Order: Lychniscosida (Triassic—Recent)
Ⅱ). Subclass: Amphidiscophora: Microscleres being amphidiscs.
Order: Amphidiscosida (Cambrian—Recent)
Ⅲ. Class: calcispongiae (=Calcarea) (Cambrian—Recent)
Framework composed of calcareous spicules and/or non-spicular skeleton. All spicules only of primary types such as monoactine, diactine, triactine and tetractine.
1. Order: Calcinea (Recent)
2. Order: Calcaronea (Carboniferous—Recent)
3. Order: Pharetronida (Cambrian—Recent)
1) Suborder: Inozoa (Permian—Recent)
2) Suborder: Sphinctozoa (Cambrian—Recent)
Ⅳ. Class: Heteractinida (Late Cambrian—Early Permian)
Skeleton composed of 3-, 4-, 6- or 8-rayed calcareous spicules which may be interlocked and or embedded in a solid non-spicular skeleton, with no spongin. Ⅴ. Class: Sclerospongiae (Permian—Recent)
Sponges with a skeleton composed of siliceous spicules and spongin fibers as well as a basal massive skeleton of calcium carbonate occurring as either aragonite or calcite.
The oldest isolated spicules of Hexactinellida are found in Late Proterozoic (Doushantuo Formation), South China; some first entire hexactinellid sponges are from the Middle Cambrian (Burgess Shale), West Canada. These earliest hexactinellids have got a single layer of parallel stauractins, and a more complex form, with two or more layers of parallel hexactins, appearing in the Upper Cambrian. A general evolutionary trend from early thin-walled form to later thick-walled form can be seen in this group. From Ordovician, hexactinellids developed into two branches: a): the branch with a large and broad central spongocoel such as the genera Brachiospongia and Pyruspongia; b) the branch with the central spongocoel reduced and degenerated, such as the genus Pettersonia. PostPaleozoic hexactinellids became a conservative group, in which only a few tenuous lineages seemed to have crossed the Permian and Triassic boundary. Most hexactinellids limited their extent to deeper marine facies.
The principal demosponges are found in Lower Cambrian (Chiungchussu Formation), Yunnan, China, mostly consisting of monaxonic forms. The lithistids occupied a supremacy during the Ordovician. In fact, they constituted the most important reef-builders with a wide distribution, but they became a small group at the end of the Devonian, probably due to the development of stromatoporoids and other reef-building organisms. Non-lithistids of Demospongea have undergone a slow and continuous evolution. Three evolutionary trends are evident in demosponges: 1) Thin-walled sponges developed into forms with thicker, more massive walls (similar to patterns seen in Hexactinellids); 2) Thin-walled sponges without canal system developed into forms with thick walls equipped with a canal system; and 3) Simple assemblages of spicules developed into more complex regular frameworks. Today demosponges have persisted as a major class of sponges. They occupy environments ranging from warm, shallow subtidal, high energy to quiet, cold oceanic deeps, and from modern seas to freshwater ponds and lakes.
In calcareous sponges, Inozoa seemed to have spread out from the Tethys Region where they suddenly appeared in the uppermost Lower Permian of Sicily. A similar high diversity is found in Upper Permian reefs of Tunisia and China. The evolution of this group still remains obscure, not only because of their scanty fossil records, but also because of their generalized nature. Sphinctozoa were the most important reef builders during Late Paleozoic and Mesozoic. They first appeared in Cambrian and then developed into a large group during the Late Paleozoic. A general trend in the evolution of Sphinctozoa is the development of increasing chambers and filling structure. The earliest genera have almost empty chambers while complex forms have various filling tissues and numerous chambers. Their development in species diversity in geological times is similar to that of Inozoa: the highest diversity was in the Permian, with a gap in the Lower Triassic; while the second peak was in the Upper Triassic, with a gap from Middle Liassic to the uppermost Middle Jurassic.
出处
《古生物学报》
CAS
CSCD
北大核心
1991年第6期772-785,共14页
Acta Palaeontologica Sinica
基金
国家青年自然科学奖励基金
关键词
海绵
分类
演化
sponge, rigid Skeleton, classification, evolution, distribution
