Since i really like squigs, and there are just very few models for
40k, i was confronted with a similar problem.
i got the following idea from another thread in some forum (don'task me wich, i confuse them all the times

)
1. buy small toy dinosaurs (keychain accessories etc.)
2. chop off the head and forward legs
3. sculpt squig jaw (or maybe use a trimmed ork head - pink horror heads are nice too)
i didnt get around to trying this out myself, but eventually i wil (already got me some dinos...)l
depending on the used dinosaurs you can get a good variety of poses and sizes.
i chose triceratops since i think the relative size of hind legs and tail is best, but some others will do as well (just trimm the tails, horns etc.)