The Echinoid Directory

Order Hemicidaroida Beurlen, 1937


Calycina with:

  • apical disc relatively small; dicyclic or hemicyclic. Periproct subcircular with smooth edges (periproctal plates not indenting apical ring);
  • ambulacral plating trigeminate to polygeminate, with all elements extending from adradial to perradial suture;
  • primary tubercle overlaps all elements beneath ambitus; reduced to overlapping two of the three elements or simple adapically;
  • primary tubercles in ambulacral zones significantly smaller than those of interambulacral zones;
  • primary tubercles perforate and usually crenulate (may be effectively smooth);
  • peristome much larger than apical disc; with phyllodes and deep buccal notches.
Lower Jurassic (Plliensbachian) to Lower Cretaceous (Aptian), Europe, Middle East, India.
Classification and/or Status Taxon not employed by Kroh & Smith (2010)
Like acrosalenids in having ambulacral tubercles very much smaller than interambulacral tubercles, perforate and crenulate tubercles and simple plate compounding with all elements extending to the perradius, but differing in having a rounded periproct without angular elements forming an integral part of the apical disc circlet.

Beurlen, K. 1937. Revision der Seeigel aus dem norddeutschen Jura. II, Die regulären Seeigel. Abhandlungen der Preussischen Geologischen Landesanstalt, 174, 6-149, 1 pl.