Dinosaurs - Fundamental Matters 

THIS ARTICLE informed me about something I didn't know, that I didn't know - an unknown unknown. Unlike mammals who have two openings "down there" dinosaurs have only one! We have one for reproduction and one for expulsion of faeces. Dinosaurs and similar have a multi purpose opening called a cloaca.

This is not commonly found in the fossil record, but a chance encounter in a Frankfurt museum with psittacosaurus - a herbivorous dinosaur of labrador size, related to triceratops - gave the opportunity to study a cloaca more closely.

And the conclusion drawn was that the animals bottom was designed, among more prosaic functions, for display. Which gives me pause for reflection.

The fossil concerned

This discovery was part of the study of psittacosaurus. There is a very interesting video HERE which goes into some detail of how to make a dinosaur.