I wrote this tiny snippet back in the day and a long time ago discovered that they’re called tautonyms, they basically represent the “type” of a given genus. I wrote about it recently with respect to the many birds that I’ve photographed with tautonymic binomials. Also, some more recent items on tautonyms here and here.
Rattus rattus (black rat) is coming to a town near you, while Gallus gallus (wild chicken) has got scientists all in a flap (you’ll find out why later this week). Then there’s Bubo bubo (the eagle owl)…Buteo buteo (common buzzard), and many others. Some tautonyms are trebled – Gorilla gorilla gorilla, being the Western Lowland Gorilla.
UPDATE Christie Wilcox just mention Boops boops on twitter, it’s a seabream colloquially called a bogue.