Life on Earth is not infinitely variable, but at times it seems to get pretty close. Even within the relatively conservative vertebrate body plan we see extremes such as whales, sauropods, hummingbirds, eels and bats. That’s pretty good all things considered. The extremes are fun and interesting and give us an insight into just what evolution is capable of. For palaeontologists this quite handy – it’s not uncommon to come across something that looks totally implausible in a fossil and then realise that actually there is a living animal with a similar feature out there. That can give a bit of confidence that the interpretation of the anatomy or function is correct.
Of course not every extreme is usual and not every exception to the rule is one to follow, but it is a good idea to have a grasp of what is out there. A case in point here (and a chance to drift off from archosaurs just a little and show off a cool mammal skeleton) is the truly colossal orbits of a bushbaby. It could be easy to look at the orbits of say, an anuroganthid pterosaur, and think that they can’t *possibly* have had eyes that big. And yet, in comparison to this little critter, they are not actually that big.