can you name a few other species from that period you mentioned earlier?
Hadrosaurs, ankylosaurs and ceratopsians
Late Cretaceous
In the Late Cretaceous, the hadrosaurs, ankylosaurs, and ceratopsians experienced success in Asiamerica (Western North America and eastern Asia). 
how many years ago was the thescelosaurus in existence? More than 66 million years ago which period was that? Late Cretaceous period describe this creature's physical characteristics. Its size has been estimated in the 2.5–4.0 m range for length, a weight of 200–300 kilograms and it may have been sexually dimorphic, with one sex larger than the other in which region were their fossils discovered? Niobrara County, Wyoming, USA who discovered them? John Bell Hatcher and William H. Utterback were these fossils recovered and preserved somewhere in an institution? Smithsonian Institution's National Museum of Natural History were there any body organs of this creature recovered? Remnants of a four-chambered heart and an aorta but these conclusions have been disputed
wiki:13066052
Late Cretaceous [SEP] Non-Avian Dinosaurs
In the Late Cretaceous, the hadrosaurs, ankylosaurs, and ceratopsians experienced success in Asiamerica (Western North America and eastern Asia). Tyrannosaurs dominated the large predator niche in North America. They were also present in Asia, although were usually smaller and more primitive than the North American varieties. Pachycephalosaurs were also present in both North America and Asia. Dromaeosaurs shared the same geographical distribution, and are well documented in both Mongolia and Western North America. Additionally therizinosaurs (known previously as segnosaurs) appear to have been in North America and Asia. Gondwana held a very different dinosaurian fauna, with most predators being abelisaurs and carcharodontosaurs; and titanosaurs being among the dominant herbivores.