Interesting. ("Unken" -- another great name. Onomatopoeic?)
(The best is *Pelobates*, though: KrÃtenfrosch -- toadfrog!)
I'm suddenly reminded that the phenomenon extends to other types of technical term as well. Where English has "the Lower Cretaceous", German has "die Unterkreide" -- "the underchalk".
(Also "untere Kreide".)