Can having an intense interest in a particular subject (ie. Dinosaurs) be a sign of OCD in children?

Maybe, maybe not. Children may have an intense interest in a wide variety of things without meriting any pathological diagnosis. Also this intense interest in dinosaurs would not be enough to diagnose ocd, although it could be related. http://tinyurl.com/k2dftl4.
Kids behavior. Interest or obsession? Some children can get obsessed with a subject and are very bright about it, know all of its details but cannot get their mind off it, it could be asperger. But a mere interest is not abnormal and is usually a phase.