Dinosaurs are always a cool animal for young kids to learn about. They're fascinating!
I wonder if this connection that fossils = dinosaurs is due to the exposure at an early age without reference to other types of fossils. For example, at museums the first fossils typically shown are the attention getters: T-Rex, triceratops, etc. Also, bones are (arguably?) the most easily preserved part of an organism. So non-bony organisms are harder to come by, like plants, fish, insects, etc. These are usually imprints or carbon remains rather than eye-grabbing skeletons.
I just started a unit where the driving phenomenon is a new fossil. Many students asked what it is and that is what they are trying to figure out. We also talked about the variety of fossils: petrified, preserved remains, trace, etc.
I wonder what students would say fossils include? If we were to survey students, across various ages/grade levels, I wonder what patterns we'd see. Would younger studetns focus mostly on bones of dinosaurs? Would older students talk about more variety? Reminds me of a first grade unit where students believe that humans are not animals because they believe animals live in nature while humans do not. Also fascinating to see what the students are thinking and how they reason their ideas!