Therizinisaurus cheloniformis Archosauria: Saurischia: Segnosauria: Theresinosauridae Locality: Nemegetu, Gobi Desert, southeastern Mongolia Age: Late Cretaceous (Late Campanian-Early Maastrichtian), 74 million years ago  The segnosaurs come only from the Late Cretaceous of Mongolia and China and are not studied well enough because of the insufficient fossil record. They were large or medium-sized bipedal plant-eaters with a relatively small head, massive body and stout hindlimbs. Very long and powerful forelimbs in segnosaurs possessed giant claws that might be up to 80 centimeters (2.6 feet) long, like in Therezinosaurus from Mongolia. For many years Therezinosaurus cheloniformis presented paleontologists with a puzzle. Evidently somehow related to the theropods or carnivorous dinosaurs, the function of their large claws and their attendant forelimbs was a mystery. Certainly, they had to belong to animals quite unlike Tarbosaurus baatar with its highly reduced forelimbs and yet they were animals clearly in the same size catagory. Material that has recently come to light in China suggests that these animals were as atypical of the large carnivorous dinosaurs as pandas are atypical of bears. Like pandas, they were probably gentle herbivores. They used their large forelimbs and claws to pull down branches on which to browse. The claws with the horny sheath that would have fitted over the outside of the bone may have been up to one meter long. Paleontologists have even suggested that therezinosaurs may have used the huge claws for ripping into ant nests. This is unlikely however because of the abscence of social insects in the Mesozoic. The large gut size would further confirm the herbivorous nature of this animal. This picture of Therezinosaurus cheloniformis as browsers in a forest agrees well with the view that conditions in Central Asia had become much more moist than what they had been like 10 million years before these dinosaurs lived.
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