Dead sponge fragments in modern sponge reefs on the British Columbia shelf contain an assemblage of foraminifera that differs entirely from that found in Jurassic sponge reefs at the species level. At the genus level, there is a slight resemblance among some long-ranging taxa. There is on the contrary a strong resemblance when the foraminifera’s relationship to the sponge meshwork is considered. In both periods, there are taxa that tend to get trapped and laced into the meshwork, others that attach to it and some that engulf it as they grow. In the Jurassic, there are essentially four laced-in taxa: Thurammina sp., Tolypammina sp., S. haeusleri and B. tuberculata. However, Thurammina is the only taxon to be impaled. In the modern oceans, Thurammina papillata is still common but totally absent from our sponge reefs. A number of modern species get trapped, impaled or attached, some arenaceous (Gaudryina, Karreriella) and some calcareous (Lobatula, Ramulina). Lobatula did not exist back in the Jurassic but Ramulina did. The species of Ramulina reported from the Jurassic are not found inside sponge fragments, but Bullopora tuberculata, another irregular polymorphinid, is common and can be considered trapped or laced in.

Crithionina is abundant in the modern attached fauna; it is a primitive genus that probably existed in Jurassic times but did not fossilize. The genus Tritaxis, except for some differences at the species level, seems to be the same and live in the same way, then and now. Tolypammina is virtually absent from modern sponge fragments: the few thin tubes we find probably do not occupy the same niche. The Jurassic Subbdelloidina haeusleri is quite close morphologically to the modern Placopsilina spongiphila and grows approximately in the same way; it probably fed in the same way too, from the substrate.

One of the most striking differences between modern and Jurassic reefs is the absence of attached miliolids such as the Jurassic Vinelloidea, "Tubiphytes" and Nodophthalmidium. The cool and dark waters off British Columbia are probably the main factor explaining the near-absence of miliolids. The disappearance, after the end of the Jurassic, of sponge mounds cemented by stromatolitic microbial crusts may have caused the extinction of Vinelloidea, which was narrowly adapted to this environment.

The arenaceous/calcareous ratio is higher among the assemblages closely associated with dead sponge meshwork than in the surrounding mud. This is true in the Recent and even more so in the Jurassic. There are many biases that may affect quantitative estimates however: counting bias (see Methods), postmortem etching, irregular silicification of Jurassic assemblages and the fact that paleontologists working on the Jurassic may have different sampling methods or targets depending on the goal of their research.

Modern foraminiferal assemblages of the "loose" type consist mostly of smaller specimens of calcareous species that are found in large numbers in the region: Epistominella vitrea, Bolivina decussata, Eponides pusillus, Seabrookia earlandi and Angulogerina spp. Their presence may be in part accidental and should be distinguished from the typical sponge fragment dwellers. The Spirillina and Lenticulina found in the assemblage extracted by etching probably represent the Jurassic "loose" fauna.

The most characteristic species in our material is Ramulina siphonifera. The genus Ramulina is rare but widespread in the Recent, but has never been reported growing in a similar trapped or impaled fashion. In the Jurassic, the closely related Bullopora tuberculata does grow attached or intertwined with the meshwork. Ramulina siphonifera may completely engulf sponge meshes and tightly wrap silica rods with its wall in the same way Thurammina does in the Jurassic. This is a clear case of convergent evolution implying that at least some niches inside the sponge reef environment have not changed, even though the setting of our modern reefs, with its cool temperate waters, clastic sedimentation, food chain based on diatoms, and absence of bacterial mats is quite different from that of the Jurassic sponge reefs.

Modern dead sponge assemblages as a whole show definite resemblance with some assemblages reported from the deep-sea and characterized by attached-encrusting species, mostly arenaceous, growing on hard substrate, away from clastic sedimentation but surrounded by precipitation of dissolved minerals. These can be observed on hydrothermal vents, phosphatic hardgrounds, manganese nodules and dead tests of large foraminifera. The similarity is greatest with settings where chemical/physical stress is least and where oxides are being deposited , such as settings characterized by manganese nodules and dead foraminiferal tests.