Dual appendages:

Fossil find reveals world’s oldest penises: “A perfectly preserved shellfish fossil over 100 million years old has revealed a surprising feature – the oldest penis in the world. The fossil, a one millimetre-wide crustacean called an ostracod, was found in Brazil and examined by David Siveter at the University of Leicester. It was preserved with its shell open displayed another surprise – not one but two penises…” New Scientist