Move from an articulated stem gnathostome to lamprey and hagfish total-group fossils without turning specimen occurrences into crown origins or PBDB first appearances.
Each step names its evidence claims, with references below. Interactive Explorer states are available in the full application; the narrative remains an editorial synthesis.
IVPP V300001 and twenty referred Xiushanosteus specimens expose an approximately 436 Ma placoderm-grade body and mosaic skull roof. Abundance in one Lagerstätte does not make the animal a direct ancestor or a global first appearance.
Articulation strengthens anatomical association; it does not convert a stem-grade taxon into a crown ancestor.
claim:event:chongqing-xiushanosteus-complete-bodyHolotype AM5750 preserves a large oral disc, fourteen circumoral teeth and a branchial basket at roughly 360 Ma. These structures diagnose total-group lamprey anatomy, not parasitism, migration or an ammocoete lifecycle.
A body fossil can preserve adult-like structures while leaving lifecycle and crown-node timing unresolved.
claim:event:famennian-priscomyzon-oral-discFMNH PF15373 and PF8472 preserve a roughly 310–307 Ma cyclostome–hagfish mosaic, but different preservation and equivocal structures require a stem or putative total-group reading. The separate Myxini navigation node therefore does not inherit this age.
Total-group occurrence and crown-group range are separate evidence objects.
claim:event:mazon-creek-myxinikela-stem-hagfish