In the second film there was the 'tauntaun' on the ice planet Hoth, and as a hairy mammal-like animal with the body plan of a bipedal carnivorous dinosaur that was an intriguing invention. Otherwise, not many in the early stages came across as great exobiological inventions. In fact, quite a few some could not be taken seriously at all: just think of the gigantic snake-like animal living in an asteroid (in a vacuum!), large enough to have the Millennium Falcon fly between its teeth. Or take the 'Sarlacc', a carnivorous monster buried in the sand on Tatooine: all you see of it is a gigantic mouth in a pit in the sand, reminiscent of an antlion but scaled up to a gigantic level. Its very existence implies that there are lots of rather stupid animals ready to stumble into it maws. No-one would take such a creature seriously from a biological point of view, and no-one should; it's not what the films are about.
Still, there is a book about the animals in the Star wars universe, showing someone cared. It is called 'The Wildlife of Star Wars. A Field Guide', by Terryl Whitlatch and Bob Carrau. Terryl Whitlatch has been working as a 'creature designer' for several of the Star Wars films. Typing her name into Google results in so many hits that I do not need to provide many links. Still, here is one with a video interview, and here are two on character design (one and two).
The 'Wildlife' book first came out in 2001. I had somehow missed it completely until recently, when a reprint was issued. I found another book of hers showcasing other work, not related to Star Wars: 'Animals Real and Imagined'.
The Star Wars book seems to have many creatures in it that did not appear in the films as far as I know. I have to be careful here, as the three newest films (I, II and III) did not make much of an impact on me, aimed as they seemed to be at children. I suspect that most of the animals in the book were not in the films at all, which would imply that Ms Whitlatch had more or less free reign in designing them.
The sillier animals such as Giant Space Slugs of over 900 meters long, and the above-mentioned sarlacc occur in the book, should you wish to know more about them. The animals that I assume to be Ms Whitlatch's inventions were much more to my liking. In a way they conform to the general exobiological theme of Star Wars. In it, intelligent beings are almost always humanoid, with two legs, two arms and a sort of alien-looking head that is rather larger than the standard Earth issue human head. The films started when digital creature design did not exist, and alien design followed time-honoured principles, involving actors in rubber suits. Hence the big heads.
Ms Whitlatch's aliens more or less follow such principles. The book deals with life on several planets, but you will not be able to determine their planet of origin by looking at their body plan: an animal could come from one planet as well as from the next. Whereas nearly all intelligent beings are humanoid, animals also share many design principles with Earth animals. Quite a few are 'mammaloid', meaning they look a lot like mammals with odd heads. There are also plenty of aviforms and reptiloids, as well as combinations of designs. It is interesting to compare this design strategy with that of Mr Broadmore's Victorian Venusian life forms discussed recently: these were specifically designed to evoke a sense of displacement, i.e. of 'alienness'. Instead, Ms Whitlatch's life forms might be just around the corner. That makes them more believable, but inevitably less alien.
Regardless of the degree of their 'alienosity', the animals are all superbly well drawn, with an intimate knowledge of animal anatomy and behaviour. The 'Animals Real and imagined' book contains drawings of existing animals in addition to fantasy ones, proving once more that Ms Whitlatch is a very skilled artist. I will go through a few of her drawings, scanned from the two books. As I did not wish to damage the books, I had to crop some drawings a bit, for which I apologise (you could all get the books yourselves...).
These are Motts from the planet Naboo, revealing how mammalian their body plan is. The way the legs fold, the number of joints, the general shape of the head, all these things say 'earth mammal'; 'ungulate' in fact. But look at the ease with which their poses are captured, and the green thingy walking away from the motts is much more 'alien'!
Also from Naboo, these gullipuds are, as the text says, amphibians. They resemble puffer fish or indeed, some Earth amphibian in being able to inflate their bodies. I like the sense of humour in this and other drawings.
Click to enlarge; copyright Lucasfilm Ltd.
The tree-dwelling Shaupaut. This is another mammaloid. Its elongated fingers are apparently used to 'fish' for avians flying by.
These animals are apparently extinct. They are labelled as stalking birds from Alderaan, and are obviously modelled on large African ground living birds, called 'ground hornbills'. These walk in rows over open fields, hoping to disturb smaller animals so they can be caught and eaten. These birds are doing the exact same thing.
The text says that their span is about two meters, which means that they must be very heavy. Their bodies and thick tails look good, but do not appear to be designed to save weight. Light bones? A heavy atmosphere?
This one is not from the Star Wars book, but from the other one. It represents one of the few designs that I do not really like. The reason is that it reminds me too much of the six-legged forms in Avatar that I discussed earlier. Like the Avatar animals, this one does have six limbs, but not as three pairs with their own characteristics, but as one pair of hind legs and two pairs of identical front legs. In fact, their muscle anatomy shows the same problem as Avatar's thanator: the front limbs are, like those of Earth mammals, connected to the axial skeleton almost entirely by muscles. Note that the two sets of muscles seem to run through one another...
I would rather end with something I like better: the Nuna from Naboo, which is a very interesting and humorous drawing. The one on the left is a male, inflating his wattles and hissing to underline his dominance. You can see how well Ms Whitlatch combines animal anatomy with the expression of emotions. The emotions are very readable to us, which is probably not at all would you would expect from alien life forms. Then again, emotions help tell a story, and that is done very well here.