Sesquizygotic Twins

Scientists stunned by discovery of 'semi-identical' twins

Quote:

A pair of twins have stunned researchers after it emerged that they are neither identical nor fraternal – but something in between. The team say the boy and girl, now four years old, are the second case of semi-identical twins ever recorded, and the first to be spotted while the mother was pregnant. The situation was a surprise to the researchers. An ultrasound of the 28-year old mother at six weeks suggested the twins were identical – with signs including a shared placenta. But it soon became clear all was not as it seemed...

Click the link. There's a diagram.

via International Skeptics Forum https://ift.tt/2H7c4g0