The Lifetime Cardiac-Cycle Invariant in Endothermic Vertebrates: A 230-Species Comparative Dataset, Statistical Validation, and Explicit Falsifiability Criteria

A pygmy shrew ($\mathit{\text{Suncus}}\mathit{\text{etruscus}}$, $\approx 2$,g) sustains a resting heart rate near $\mathrm{1,000}$,beats,min${}^{-1}$ and dies within two years; an African elephant ($\approx \mathrm{4,000}$,kg) beats at $28$,beats,min${}^{-1}$ and lives seven decades. Their chronological lifespans differ by a factor of 35, yet each accumulates close to ${10}^9$ cardiac cycles before death – a near-constancy first noted by Rubner~(1908) and quantified by Lindstedt and Calder~(1981)~\cite{lindstedt1981}, but never subjected to multi-clade statistical testing, phylogenetic correction, or explicit falsifiability criteria with a large modern dataset. We address this gap with a curated 230-species vertebrate dataset spanning non-primate placentals ($n=43$), primates ($n=18$), marsupials and monotremes ($n=19$), duty-cycle-corrected bats ($n=31$), dive-corrected cetaceans ($n=12$), birds ($n=78$), and Arrhenius-corrected ectotherms ($n=26$), and subject the log-invariant $\mathrm{\ell }={\log }_{10}(N^{\text{\hspace{0.17em}⁣}\star })$ – where $N^{\text{\hspace{0.17em}⁣}\star }=f_{H}L\times \mathrm{525,960}$ cardiac cycles – to four independent tests.