As time passed , Anning 's confidence in her knowledge grew , and in 1839 she wrote to the Magazine of Natural History to question the claim made in an article , that a recently discovered fossil of the prehistoric shark Hybodus represented a new genus , as an error since she had discovered the existence of fossil sharks with both straight and hooked teeth many years ago .
She remarked in her diary : As time passed , her confidence in her knowledge increased , and in 1839 she wrote to the Magazine of Natural History to question their claim that a hooked tooth of the prehistoric shark Hybodus represented a new discovery .