Tithoniidae is an extinct family of

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

References

* Thuy B, Gale AS, Kroh A, Kucera M, Numberger-Thuy LD, Reich M, et al. (2012) Ancient Origin of the Modern Deep-Sea Fauna. PLoS ONE 7(10): e46913. doi:10.1371/journal.pone.0046913 Prehistoric echinoderm families {{paleo-echinoidea-stub