The tooth of Belize's first fossilized terrestrial giant sloth exposes its world


By analyzing a tooth from the earliest remains of an extinct giant sloth found in Belize, the researchers uncovered insight into the animal's dietary adaptations as reported by the local climate. In fossilized animals such as lack of dental enamel, the authors found, dental layers are affected differently by long sedimentary processes; so they say, if isotopic analyzes are conducted on any other dental layer than internal orthodental, the conclusions are likely to be imprecise. While exploring a water-filled sinkhole in central Belize, divers discovered the fossilized remains of an extinct giant earth sloth (Eremotherium laurillardi). As lazy teeth grow throughout an individual's life, studying changes in stable isotope patterns along the length of the tooth can shed light on their diet and exposure to the weather. With this in mind, Jean T. Larmon and colleagues examined stable isotope data of carbon (δ13C) and oxygen (δ18O) from 58 samples derived from a single tooth of E. laurillardi, which complemented with cathodoluminescence analysis to evaluate the reliability of the data. These samples were taken from three layers of apatite of the tooth – the cementum, as well as the outer and inner layers of orthodental. The authors found a remarkable variation in the δ13C results when comparing the layers, which suggests that these layers are affected differently by chemical and physical processes as they become fossilized. In this case, the authors found that the inner layer of orthodental is more resilient and therefore likely to return the more accurate results. Knowing this, Larmon et al. used a "vacuum milling" technique on a weak acid to date this inner layer of orthodental, and concluded that the tooth's age was about 27,000 years before the present – a time when the Earth was cold during the Last Maximum Glacial. In addition, fluctuations in the proportions of δ18O along the tooth show a distinct pattern of two short moist seasons divided by a longer dry season, indicating that laziness lived for annual periods of aridity. Larmon et al. say that the highest δ13C values ​​when δ18O values ​​are the lowest may mean that grasses and shrubs probably comprised a large amount of lazy diet during the rainy season. The data suggest that the animal's diet varied seasonally, that giant land sloths in Belize were likely opportunistic feeders. Their diversified diet would have increased their habitat and distribution, say the authors.


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