Pelanechinus corallina
... that the shell of the extinct sea urchin Pelanechinus corallina was composed of separate groups of fused plates which resulted in its being flexible?
... that the <a href="./Test_(biology)" id="mwdA" rel="mw:WikiLink" title="Test (biology)">shell</a> of the <a href="./Extinction" id="mwdQ" rel="mw:WikiLink" title="Extinction">extinct</a> <a href="./Sea_urchin" id="mwdg" rel="mw:WikiLink" title="Sea urchin">sea urchin</a> <i id="mwdw"><b id="mweA"><a href="./Pelanechinus" id="mweQ" rel="mw:WikiLink" title="Pelanechinus">Pelanechinus corallina</a></b></i> was composed of separate groups of fused plates which resulted in its being flexible?