I kept my derasa clam shell after it died. It was about 6-7 years old. You can see the bottom outline of how big it was when I got it and I grew the rest. It spawned one day and died shortly after.
The boneyard has neat parts one can send their kindergartener to school with to hopefully edge out a silent win on show and tell day, it will at least edge out stick figure drawings. Send a kid to school with a dried starfish, seal the deal. Use a small one in case it gets eaten.