IRREGULAR ECHINOIDS—AN INSUFFICIENTLY KNOWN GROUP

Authors

  • WANDA JESIONEK-SZYMAÑSKA

    1. Palaeozoological Institute of the Polish Academy of Sciences (Zaklad Palcoyoologii Polskiej Akademii Nauk), Warszawa 22, Zwirki i Wigury 93, Poland, July 15th 1967.
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Abstract

Some aspects of echinoid evolution from an endocyclic towards an exocyclic apical system, in the light of embryological and palaeontological data, are discussed. A primitive feature—imbrication of interamhulacral plates in Jurassic irregular echinoids, recently described—proves once more that this group is insufficiently known. Every revision of taxonomic or phylogenetic concepts concerning this group of echinoids should be preceded by careful morphological analysis of the material.

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