Did dinosaurs urinate?

[Rexy]

Mammals produce liquid urine whilst birds produce uric acid which is excreted along with faeces as a semisolid waste. But what about dinosaurs? Did they have a urinary bladder like mammals or did they produce uric acid like birds? Personally, I would assume that, since birds are their closest living relatives, dinosaurs produced uric acid.

[Newt]

I think Darren Naish covered this in depth on Tetrapod Zoology at some point, but my brief search did not recover it. The upshot was that dinosaurs most likely had bird-like uric-acid excretion. That said, at least some birds do sometimes excrete liquid urine; you can find videos online of ostriches peeing.


Non-avian sauropsids, including squamates, turtles, and crocodilians, have more flexible nitrogenous waste strategies and may produce various combinations of ammonia, urea, and uric acid depending on availability of water or other factors. Crocodilians produce equal amounts of urea and uric acid in the egg, but switch to mostly ammonia with smaller amounts of urea and uric acid post-hatching; this is probably an aquatic adaptation, as they don't need to concentrate their wastes to save water. I think it's quite likely that dinosaurs were similarly flexible.

[andrewsaurus rex]

Newt has summed it up very well.  I did some research on this a while ago and the basic answer is, as usual with dinosaurs, no one knows.

However, I feel the most likely answer is that dinosaurs used a strategy similar to reptiles except for the more avian like dinosaurs, which were probably more like ostriches (ie they had liquid waste and solid waste, excreted separately)..which is not dramatically different from reptiles.

However, one conclusion I did come to was that regardless of the strategy, both the liquid waste and solid were probably off white in colour.  Even birds that eat meat like owls and eagles produce white coloured waste and many reptiles do as well.  However, there are exceptions (as always), for example cassowary waste is often multi coloured.

[Bowhead Whale]

Birds' solid waste is not white: I had budgies in my home during all my childhood and let me tell you that their solid waste was greenish grey in color; only their uric acid was white. Sparrows that come in my yard also have dark greenish grey solid waste aside their white uric acid. And it is the same for pigeons (I've seen their wastes many times). Among all birds I have met and seen waste of, none had white solid waste. Only their uric acid is white. Solid waste is always dark greenish grey.