Mosasaurs are serpentine marine reptiles. They are not dinosaurs, but evolved from semi-aquatic squamates known as the "aigialosaurs", close relatives of modern-day monitor lizards.
Trilobite were prehistoric marine creatures related to the extant horseshoe crab. They were one of the first living creatures to develop compound eyes which gave them 180 degree vision.
The photos below are sample finish projects in one of our programs, Bones in a Box.