Data from: Reconstructing the mass and thermal ecology of North American Pleistocene tortoises

Researchers often interpret the presence of tortoises in Pleistocene
assemblages as evidence of an interglacial age, based on an assumption
that these fossils indicate thermic climates, as modern giant tortoises
require. Since the Paleocene, tortoises have been common components of
terrestrial fossil assemblages and have repeatedly evolved species of
giant size. Whereas extant giant tortoises are found only on islands off
the coasts of South America and Africa, at least two species persisted in
North America until the terminal Pleistocene. These tortoises,
Hesperotestudo crassiscutata and Gopherus ‘hexagonatus,’ both of which
reached carapace lengths of >1m, were distributed across the
southern United States. This study provides new metrics to derive
quantitative weight estimates from measurements of the tortoise shell. The
linear measurement of 69 anatomical features of the shell of 108 live
tortoises indicate that the regression between straight carapace length
and weight is most significant, with a maximum r2 > 0.99. This
regression is useful for tortoises that weigh between 1.8 and 339 kg. This
mass estimate coupled with a heat dissipation rate derived from
thermoregulation modeling provides estimates of how long tortoises can
maintain a viable body temperature at low ambient temperatures. Depending
on size, a tortoise can survive a maximum of 2.3 to 33 hours of freezing
temperatures, which corresponds to a mean annual temperature ≥ 22° C and a
mean winter low temperature ≥ 7.5° C. This analysis infers warmer
temperatures at Pleistocene sites with fossil tortoise occurrences than
previous qualitative estimates.