Ziegler B, Rietschel S. (1970). Phylogenetic relationships of fossil calcisponges. In: Fry WG (ed) The Biology of the Porifera. Zoological Society of London, Academic Press London, pp 23-40.

277325

Ziegler B, Rietschel S

1970

Publication

Proceedings of the 1st International Sponge Conference

Available for editors   [request]

Fossil calcareous sponges differ from the majority of modern Calcarea in one important feature; they possess firm skeletons stiffening the animals' bodies. Most modern Calcisponges possess loose spicules embedded separately in the soft tissue. Fossil representatives of apparently the same organization as these living species have been known since Lower Carboniferous. They are, however, likely to have existed since Cambrian or perhaps even Precambrian times. From this conservative stock several offshoots arose which had the common tendency to produce stiffened skeletons. The means, however, of realizing this were varied. In two lineages, the Palaeozoic Octactinellida and the mainly Mesozoic Pharetronida, then spicular skeleton was maintained. In the first group the firm skeleton was formed by entangling large many-rayed spicules, in the second by cementing the spicules and building up fibres. In two other lineages, the Lower Cambrian Archaeocyatha and the mainly Permian and Triassic Sphinctozoa, the spicular skeleton was replaced by non-spicular walls. Thus, four offshoots from the main stock may be recognized, three of which are extinct, while a few genera of the fourth still persist. Unfortunately, the common phylogenetic origin of some of these offshoots cannot be proven.

Porifera

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