The guideline at WP FAUNA Monotypic taxa is pretty clear about this All other fauna including all other fossil fauna should always be represented at the lowest ranked taxon which the article inclusively covers Examples Confuciusornithidae not Confuciusornithiformes Bullockia maldonadoi not Bullockia For whatever reason this is unfortunately opposite to the recommendation of WP FLORA A genus with a single species is treated at the article for the genus