Cretaceous sponges from the Campanian of Misburg and Höver |
Siphonia | Goldfuss 1833 |
Some small Siphonia species are difficult to distinguish macroscopically from certain small forms of Phymatella, particularly Phymatella sphaeroides. This is due to similarities in the skeletal structure. The main differences are in the internal canalization, which is invisible unless the specimen is destroyed. However, Siphonia lacks the constrictions near the base of the sponge body, which are typical for Phymatella, and there are subtle differences in the skeletal structure.
Considerable "taxonomic chaos" exists for Siphonia and the related genera Jerea, Thecosiphonia, and Polyjerea. The problem of identifying and naming a particular specimen is further aggravated by the high morphological variability of Siphonia and the other species. E.g., many juvenile forms of Siphonia have no paragaster, but instead a group of oscula at their apex, while adult individuals tend to have a deep, tubular paragaster.