Reconstructing the mass and thermal ecology of North American Pleistocene tortoises
| Autor: | Donald A. Esker, Steve L. Forman, Dava K. Butler |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
0106 biological sciences
010506 paleontology Ecology Tortoise Pleistocene biology Paleontology Thermal management of electronic devices and systems Thermoregulation biology.organism_classification 010603 evolutionary biology 01 natural sciences Hesperotestudo Extant taxon Interglacial Carapace General Agricultural and Biological Sciences Ecology Evolution Behavior and Systematics Geology 0105 earth and related environmental sciences |
| Zdroj: | Paleobiology. 45:363-377 |
| ISSN: | 1938-5331 0094-8373 |
| DOI: | 10.1017/pab.2019.6 |
| Popis: | 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 crassiscutataandGopherus“hexagonatus,” both of which reached carapace lengths of >1 m, 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 measurements of 69 anatomical features of the shells of 108 live tortoises indicate that the regression between straight carapace length and weight is most significant, with a maximumr2> 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. |
| Databáze: | OpenAIRE |
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