Sponge reefs were common on Earth millions of years ... The phylum's golden age appears to have been the Jurassic period, 150 to 200 million years ago, when hexactinellid glass sponges built ...

This was the Jurassic, which took place 199 ... and coil-shelled ammonites were abundant. Coral reefs grew in the warm waters, and sponges, snails, and mollusks flourished. Microscopic, free ...

However, prodelta sedimentation did affect two of the three major Late Jurassic reef/mound types – siliceous sponge and thrombolitic-microbial slope mud mounds – but not coral reefs nor the oolitic ...