Follow five evidence boundaries that keep isolated skeleton, contested affinity, articulated bodies and modelled crown time distinct.
每一步标明所依据的主张，引用列于下方。交互探索状态可在完整应用中打开；故事本身仍是编辑综合。
Cambrian Stage 3 stereom ossicles directly record echinoderm skeletal microstructure, but isolated elements do not reveal one complete body plan or a phylum origin date.
The source-reported numerical calibration is approximate and older than the atlas's current chart.
claim:taxon:echinodermata:earliest-stereom-ossiclesYanjiahella was recovered as a stem echinoderm in one analysis, but a published reanalysis found no unambiguous echinoderm synapomorphy or stereom, so it does not set the range.
Competing matrices are evidence of disagreement, not permission to select a convenient endpoint.
claim:taxon:echinodermata:yanjiahella-affinityBy about 510 Ma, articulated echinoderms preserve at least four markedly differentiated body plans, supplying a more robust body-fossil datum than isolated stereom.
A robust sampled fauna is still not the first evolutionary instant of Echinodermata.
claim:taxon:echinodermata:articulated-faunas-510maThe unproblematic crinoid record begins in the middle Tremadocian, while the oldest articulated holothurian used here is late Darriwilian; each class keeps its own specimen and stratigraphic boundary.
Different preservation histories prevent one class record from standing in for every echinoderm class.
claim:taxon:crinoidea:tremadocian-record · claim:taxon:holothuroidea:darriwilian-articulated-recordDarriwilian bothriocidaroid plates anchor total-group Echinoidea, whereas phylogenomic analyses place the crown near the Carboniferous–Permian transition under model-dependent clocks.
A fossil occurrence and a modelled divergence answer different questions and remain separate in the atlas.
claim:taxon:echinoidea:ordovician-stem-record · claim:taxon:echinoidea:crown-origin