why couldn't the dinosaur skull be dated with either c14 or u238

carbon-14 cannot be used to date dinosaur  because radiocarbon dating  can only measure ages in the ranges of 50,000 years. radiometric dating using uranium-234 is not possible because uranium does not occur in dinosaur, it only exist in rocks and earth, though uranium-238 has a half-life longer of 4.468 billion years.