You can make two kinds of dinosaur fossils for -- or with -- your children. Impression fossils are flat and imprinted with objects boasting interesting patterns; creating these lets children experiment with textures, seeing results emerge immediately. Display impression fossils as souvenirs or decorations. Rock fossils contain hidden objects, so breaking them to get the treasure can be an activity at a dinosaur-themed party. They can also be used to stage an archeological dig in containers of sand or dirt, or hidden for an Easter egg-styled hunt.
Pat or roll dough into flat circles or ovals wide enough and long enough to fit the objects. The clay should be about 6 mm to 1.2 cm (1/4 to 1/2 inch) thick.
Press leaves, feathers, shells and other objects into the dough gently, stamping each clay disc with the shape and pattern of an object. A rolling pin might be useful for this. Layer objects like leaves and feathers to create more complex imprints.
Peel the objects off the clay and let the dough dry. Drying time will vary depending on the type of modelling material used.
Shape clay into balls large enough to contain the objects chosen to be the fossils, from about golf ball to tennis ball size.
Cut the clay balls in half.
Embed a plastic dinosaur, bone or shell into one of the halves of each dough ball. Hollow out space, if needed, to fit each "fossil."
Sandwich the other half of each dough ball on its mate to reform the ball. Hollow out more clay to fit the object, if needed.
Pinch and smooth the seam to seal the ball. Some clay might need a drop or two of water to close the seam. If the balls become misshapen, you don't need to fix them -- the misshapen blobs will dry to more closely resemble rocks.
Allow the dough to dry. Drying time will vary depending on the type of modelling material used.
Choose shells for the impression fossils that have texture like spirals or ridges. Keep dough contained to keep it from drying out if working with it for a long time. Spray delicate or brittle materials to be used in the rock fossils with cooking spray to make release of the objects from the rocks easier. Talk with your kids about how long ferns and shelled creatures, like the nautilus, have been on the earth -- long enough to have shared the world with dinosaurs. Using wishbones inside the rock fossils gives kids an extra surprise and a chance to make a wish.
Give children goggles or safety glasses before they break the rock fossils.