The Echinoid Directory

 Cidaroids with:

• Interambulacra with single large primary tubercle with large to massive mamelon that increases in size adapically. This tubercle often, but not always, imperforate and non-crenulate.
• Pore-pairs narrow and non-conjugate.
• Spines stout; fusiform, clavate or glandiform, often massively so.

Lower Jurassic (Toarcian) to Recent; Europe, North America, North Africa, Ukraine, West Pacific.

The lack of any non-ambulacral plates in the peristome (known only for Cretaceous to Recent Tylocidaris) and the coarse aboral mamelons that typically have a reduced perforation differentiate this from other Cidaridae and Rhabdocidaridae. The Triassic Leurocidaris also has massive imperforate mamelons, but is distinguished by having no scrobicular tubercles and a very different style of ambulacral tuberculation.

Ikeda, H. 1936. Preliminary notice on a new family of the Cidaroidea. Annotationes Zoologiicae Japonenses 15, 486-489.