The oldest echinoderm faunas from Gondwana show that echinoderm body plan diversification was rapid

Articulated echinoderm faunas with at least four markedly differentiated body plans are documented by about 510 Ma; this is an articulated-fauna datum, not the origin time of Echinodermata.

Diagnostic isolated stereom ossicles occur in the Delgadella anabara Zone of Cambrian Series 2, Stage 3, approximately 520–525 Ma on the source's 2013 calibration; they are skeletal microfossils, not articulated echinoderm bodies.

Echinodermata is profiled as a phylum while Yanjiahella’s proposed stem placement remains contested and is not used as direct ancestry.

The highlighted earliest articulated faunas are Gondwanan samples; they do not define a global centre of origin or complete Cambrian distribution.

The earliest samples document multiple marine body plans but do not support one ancestral diet, locomotor mode or ecological guild for the phylum.

Diagnostic stereom occurs as isolated ossicles before articulated faunas with at least four differentiated body plans by about 510 Ma.

The 510–0 Ma profile range begins with robust articulated faunas; older isolated stereom and contested Yanjiahella material do not set the body-fossil endpoint.