Yes, the writer can make this addition after the sixth sentence.
The writer was saying that paleontologist Elmer Riggs argued that the Brontosaurus was of the same genus as the Apatosaurus, only a younger version.
After this statement, he can add the basis on which the paleontologist made this argument.
So, the writer can make the addition stated above.
Learn more about logical writing here:
https://brainly.com/question/1460072