We resolve the long-standing paradoxes of Jurassic gigantism—including the extreme body size of sauropod dinosaurs—by demonstrating their size cannot be maintained under present-day gravity. Unsatisfied with incomplete biological or atmospheric explanations, we introduce the Jurassic Gravity Framework (JGF). Our quantitative physical model explicitly holds the universal gravitational constant G, Earth’s mass, and radius invariant, fully compatible with all tight astrophysical constraints. This is achieved by modeling the local effective gravitational acceleration gₑff (t) through brane-inspired models (screening mechanisms), which permit gₑff (t) to undergo rare, episodic fluctuations across geological timescales. Our model achieves a present-day screening accuracy within 1 × 10−7, satisfying Lunar Laser Ranging (LLR) constraints. The framework is uniquely parsimonious as it explains those enigmas using a single physical variable. Using finite-element analysis (FEA) and allometric stress laws, we derive a robust biomechanical constraint: the survival of these taxa required gₑff ≲ 0. 85 g0 during the Mesozoic Era. This figure, validated by Sobol analysis, transforms the fossil record into a Fossil Gravimeter. Mapping this empirically derived constraint yields a novel, non-astronomical restriction on the fundamental parameter space of beyond-standard-model physics, opening new horizons of research.
Domenico Frijio (Tue,) studied this question.