The early evolution of synapsids, and the influence of sampling on their fossil record

Ophiacodontidae is one of the named early-synapsid families tracked in a sampling-standardized Permian diversity analysis, which reports its decline and disappearance from the sampled record without supplying an exact global family origin or extinction instant.

Brocklehurst and colleagues explicitly analyse “pelycosaurian-grade” synapsids as an early, non-crown sampling grade; the atlas therefore retains Pelycosauria only as a historical navigation grade, not a monophyletic ancestor taxon.

A family-level occurrence analysis distinguishes Therapsida from the historical pelycosaurian grade and finds therapsids diversifying while several early-synapsid families decline; this sampled pattern does not date the clade’s origin or imply direct descent from any sampled genus.

Pelycosauria is displayed at 308–260 Ma only as the review's historical pelycosaurian-grade sample, not a monophyletic taxon range. The interval is a source-bounded sample window, not a global FAD, LAD, divergence date, continuous occupancy claim or direct-ancestor assertion.

Therapsida is displayed at 283.3–259.5 Ma only as the sampled diversification interval in that analysis, not the origin, survival or full duration of Therapsida. The interval is a source-bounded sample window, not a global FAD, LAD, divergence date, continuous occupancy claim or direct-ancestor assertion.

Ophiacodontidae is displayed at 308–272 Ma only as the family-level sampled record in the diversity analysis, not exact global endpoints. The interval is a source-bounded sample window, not a global FAD, LAD, divergence date, continuous occupancy claim or direct-ancestor assertion.