This question’s stated answer would be Barnum Brown, a male American paleontologist, not a female scientist.
Brown discovered the first documented Tyrannosaurus rex fossils in 1902 in Montana and found a nearly complete skeleton in 1908. He worked for the American Museum of Natural History and became one of the most productive fossil hunters of the early twentieth century. The species had been named by Henry Fairfield Osborn in 1905 from Brown’s earlier material.
Mary Anning was a pioneering female fossil collector, but she is associated especially with marine reptiles such as ichthyosaurs and plesiosaurs, not the first nearly complete T. rex skeleton. Dorothy Hill was an Australian geologist and paleontologist known for coral research.
This question therefore fails the topic requirement and should not be included in a batch about famous female scientists without being rewritten around a female paleontologist and a fact specifically supported by her work.