A cladistic analysis of ammonoids spanning the Permian–Triassic boundary tests survival and turnover in that sampled interval; it neither covers all Ammonoidea nor fixes their origin and extinction endpoints.
claim:taxon:ammonoideaAmmonoids across the Permian/Triassic boundary: a cladistic perspective
McGowan, A.J.; Smith, A.B.
Year2007
Source roleprimary-study
DOI / ID10.1111/j.1475-4983.2007.00653.x
Fitness and scope
taxonomy · topology · range
Cladistic analysis of sampled boundary-crossing ammonoids; it addresses survival and turnover near one interval, not the full Ammonoidea range.
Claim ledger
McGowan and Smith sample Middle–Late Permian and Induan ammonoids across the Permian–Triassic boundary, supporting a Roadian-to-end-Induan study window of 274.4–250.8 Ma rather than the full Ammonoidea range, a divergence date or continuous global occupancy.
claim:taxon:ammonoidea:source-bounded-range-rc50