Living-species clocks, fossil-integrated total-evidence dating and historical-biogeography models provide different views of cycad timing and range contraction.
Represented range330.4–Present Ma
Content packagegymnosperms
PBDBtxn:56134
Evidence boundary
Automated checks cover structure, identifiers, translations and links only; maintainer and external expert review are not complete.
Claim ledger
taxonomy · medium
Coiro et al. combine molecular data from living cycads with leaf morphology from living and fossil taxa in a Bayesian total-evidence analysis to study cycad biogeographic history; its sampled topology is not an immutable total-group topology.
claim:taxon:cycadophyta:taxonomybiogeography · medium
Fossil-integrated modelling supports broader high-latitude occupation followed by contraction, but ancestral areas and extirpation counts remain model-dependent.
claim:taxon:cycadophyta:biogeographyecology · medium
Living cycads are terrestrial primary producers across varied habitats; the profile does not infer one fossil habitat or ecological cause for diversification.
claim:taxon:cycadophyta:ecologymorphology · medium
The cited total-evidence datasets combine living cycad characters with fossil leaf taxa; leaf assignments and character coding remain explicit analytical inputs.
claim:taxon:cycadophyta:morphologyfossil-range · medium
Cycadophyta is displayed at 330.4–0 Ma only as a total-evidence model-to-living navigation interval: 330.4 Ma is the fossilized birth–death posterior median for crown Cycadales (95% HPD 296.2–358.9 Ma), not a directly observed fossil FAD.
claim:taxon:cycadophyta:fossil-range
Known limits
A missing branch or fossil occurrence does not imply biological absence. Internal nodes are not calibrated divergence estimates.
PBDB mapping requires concept review because the pinned lineage is incompatible with the local expected parent Gymnospermae.