<P> While skin impressions from a Tyrannosaurus rex specimen nicknamed "Wyrex" (BHI 6230) discovered in Montana in 2002, as well as some other giant tyrannosauroid specimens, show at least small patches of mosaic scales, others, such as Yutyrannus huali (which was up to 9 meters (30 ft) long and weighed about 1,400 kilograms (3,100 lb)), preserve feathers on various sections of the body, strongly suggesting that its whole body was covered in feathers . It is possible that the extent and nature of feather covering in tyrannosauroids may have changed over time in response to body size, a warmer climate, or other factors . In 2017, based on skin impressions found on the tail, ilium and neck of the "Wyrex" (BHI 6230) specimen and other closely related tyrannosaurids, it was suggested that large - bodied tyrannosaurids were scaly and, if partly feathered, these were limited to the dorsum . </P> <P> A study in 2016 proposed that large theropods like Tyrannosaurus had teeth covered in lips like extant lizards instead of bare teeth like crocodilians . This was based on the presence of enamel, which according to the study needs to remain hydrated, an issue not faced by aquatic animals like crocodilians or toothless animals like birds . </P> <P> Based on comparisons of bone texture of Daspletosaurus with extant crocodilians, a detailed study in 2017 by Thomas D. Carr et al. found that tyrannosaurs had large, flat scales on their snouts . At the center of these scales were small keratinised patches . In crocodilians, such patches cover bundles of sensory neurons that can detect mechanical, thermal and chemical stimuli . They proposed that tyrannosaurs probably also had bundles of sensory neurons under their facial scales and may have used them to identify objects, measure the temperature of their nests and gently pick - up eggs and hatchlings . Although the study did not explicitly discuss the evidence for or against lips, many major news outlets considered it as evidence against tyrannosaurs having lips . Comparisons with crocodilian facial tissue and Thomas D. Carr's personal interpretation of the findings were cited as support for the conclusion that tyrannosaurs did not have lips . </P> <P> Henry Fairfield Osborn, president of the American Museum of Natural History, named Tyrannosaurus rex in 1905 . The generic name is derived from the Greek words τύραννος (tyrannos, meaning "tyrant") and σαῦρος (sauros, meaning "lizard"). Osborn used the Latin word rex, meaning "king", for the specific name . The full binomial therefore translates to "tyrant lizard the king" or "King Tyrant Lizard", emphasizing the animal's size and perceived dominance over other species of the time . </P>

When did tyrannosaurus rex rule as apex predator