K-Pg Bottleneck

This timeline entry records the second major demographic compression in the archive's deep-time dragon history. The K-Pg event is treated as a true Thermosynapsida bottleneck, but not as a repetition of the end-Permian in identical form. The lineage survives again through buffered habitats, yet the demographic and morphological consequences differ by clade and medium.

Claims

c0001 - By about 80 Ma Thermosynapsida reaches its Mesozoic peak of family and geographic diversity

The archive treats the Late Cretaceous, around 80 Ma, as the high-water mark of Thermosynapsida global presence. All five principal families are established, body size spans multiple orders of magnitude, and populations occupy nearly every major landmass and ocean basin through combinations of cave colonization, cliff-edge dispersal, and marine expansion.

c0002 - The K-Pg event is buffered by subterranean and deep-ocean habitats rather than by open-surface resilience

The archive interprets Chicxulub survival through the same broad principle that operated at the P-T boundary: geothermal caves and deep marine refugia absorb the shock of surface collapse. The difference is duration. K-Pg impact winter is catastrophic but shorter than the Permian recovery interval, so the lineage experiences a severe contraction rather than the longer near-reset modeled for the end-Permian.

c0003 - Post-K-Pg body-size reduction is treated as a survival bias toward smaller individuals

The fossil record is read as showing a systematic reduction in post-K-Pg body size relative to late Cretaceous maxima. The archive's explanation is simple and selective: smaller individuals require less energy to survive the reduced-food interval, while the largest high-caloric-demand animals are more likely to be lost during the bottleneck.

c0004 - Deep-ocean Thalassodraconidae appears least disrupted across the boundary

Among the major families, deep-ocean Thalassodraconidae is treated as the least affected by the K-Pg boundary. The archive attributes that relative continuity to hydrothermal-vent dependence and to insulation from the immediate collapse of surface food webs that hit terrestrial and coastal lineages more directly.

c0005 - Paleocene-Eocene warmth reshapes sex-bias and flight refinement after the bottleneck

The archive treats the Paleocene-Eocene recovery as more than demographic rebound. Warmer caves are modeled as biasing TSD-competent populations toward female-heavy cohorts, selecting for modifier alleles that restore balance, while Volucridraconidae benefits from post-bottleneck small size and warm atmospheric conditions that improve sustained flight efficiency.