 Mating in the tawny nurse shark is known to occur from July to August off Madagascar . Adult females have one functional ovary and two functional <unk> . The mode of reproduction is aplacental <unk> , meaning that the embryos hatch inside the uterus ; females in captivity have been documented depositing up to 52 non @-@ viable egg capsules , which has led to erroneous reports of this shark being <unk> . The egg capsules of this species are onion @-@ shaped , with thin , brown , translucent shells . The tawny nurse shark is the only carpet shark in which there is <unk> : once the developing embryos exhaust their supply of yolk , they <unk> on eggs produced by the mother and acquire the <unk> abdomen characteristic of such <unk> embryos . Unlike in <unk> sharks , the eggs consumed by the embryos are large and shelled rather than small and undeveloped . There is no evidence of sibling cannibalism as in the sand tiger shark ( <unk> <unk> ) . 
