The oldest gnathostome teeth

Twenty-three isolated Qianodus duplicis tooth whorls, including holotype IVPP V26641, occur in the late Aeronian Ozarkodina guizhouensis biozone of the Rongxi Formation at approximately 439 Ma and provide direct evidence of jawed-vertebrate dentition; they support a stem-chondrichthyan occurrence, not a crown-shark body, the origin of jaws or a global FAD.

Qianodus duplicis is represented by twenty-three isolated tooth whorls and was recovered as a stem chondrichthyan; it is not an articulated crown shark.

The Qianodus tooth whorls come from the late Aeronian Rongxi Formation at Leijiatun, Guizhou, China; this single sample does not establish a global distribution.

The whorls document tooth development and histology, but diet, prey, locomotion, body size and habitat preference cannot be recovered from the isolated elements.

Qianodus whorls preserve non-shedding teeth added lingually in offset rows, with histology examined from named specimens including IVPP V26641.

The displayed approximately 439 Ma point is the late Aeronian Rongxi Formation sample and is not a global Chondrichthyes first appearance.

The Chondrichthyes display begins at the approximately 439 Ma Qianodus tooth-whorl sample as an evidence-linked stem-chondrichthyan anchor and continues to living members at 0 Ma; isolated teeth do not establish a crown-chondrichthyan global first appearance, a complete lineage range or direct ancestry.

Qianodus tooth whorls from late Aeronian strata at approximately 439 Ma anchor the 439–0 Ma Gnathostomata route; isolated dental elements provide a minimum sampled occurrence, not the origin of jaws, crown age or global FAD.

The Stem-chondrichthyan evidence route navigation entity is source-linked only to the named specimen, dataset and analysis dossiers already cited by its range ledger. Its displayed span is a study-bounded route or sample envelope, not a biological taxon, ancestor sequence, global FAD/LAD or exact origin interval.