Complex sentence: The genus name "Aphanacanthe"--not "Aphanacanthus" as the original spelling takes priority--would have taken precedence over the current genus name "Tetractenos", however it lacks a diagnosing description and is hence a "nomen nudum".
Split into simpler sentences: The genus name "Aphanacanthe"--not "Aphanacanthus", as the original spelling takes priority--would have taken precedence over the current genus name "Tetractenos". However, it lacks a diagnosing description and is hence a "nomen nudum".