The Echinoid Directory

Family Clypeidae Lambert, 1898,

Diagnosis

A basal grade of Neognathostomata with:

  • apical system compact, tetrabasal with four gonopores; a few small complemental plates generally present but not separating posterior ocular plates;
  • periproct enclosed within or in direct contact with apical disc and opening into anal sulcus;
  • petals well developed, of equal length, outer pores slit-like, strongly conjugate; ambulacral pores double below petals;
  • phyllodes well developed, pore pairs in arcs of three, the inner tending to form a discrete series; no buccal pores.
Range
Middle to Upper Jurassic (Bajocian-Kimmeridgian); Europe, Middle East, probably more widely distributed.
Classification and/or Status Irregularia, Microstomata, Neognathostomata stem group

Probably a paraphyletic grade.
Remarks
Basal Microstomata that were previously placed in both the families Clypeidae Lambert, 1898 and Nucleolitidae Agassiz & Desor, 1847 and which have their periproct either still enclosed by the apical disc plates, or at least remaining in contact with the posterior ocular plates. Phylogenetic analysis (Barras, 2007) suggests that this may be a grade taxon.

Lambert, J.  1898. Note sue les échinides de la Craie de Ciply. Bulletin de la Société belge de Géologie, de Paléontologie et d'Hydrologie, 11, 141-190, pls 2-5.

Barras, C. G. 2007. Phylogeny of the Jurassic to Early Cretaceous 'Disasteroid' Echinoids (Echinoidea; Echinodermata) and the origins of Spatangoids and Holasteroids. Journal of Systematic Palaeontology 5, 134-161.