While germinating seeds in paper towels, I came upon a seed with two tap roots. They were much longer than any roots from its sister seeds and were already shedding the shell. When I inserted the seed into dirt, it split into two separate equal sized pieces. Couple days later, two sets of cotyledons have poked into the air. I've been using mostly clones, not seeds, so this was a surprise to me. Is this common/normal behavior?