52005
A discovery of features in a " Tyrannosaurus rex " skeleton provided evidence of medullary bone in extinct dinosaurs and , for the first time , allowed paleontologists to establish the sex of a fossil dinosaur specimen .
 Tyrannosaurus rex
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Tyrannosaurus rex