No doubt they were there previously but have since disappeared. This is a peony flower that is past its bloom cycle, as indicated by the presence of the very distinct seed pods. Older petals have already fallen off and dispersed.

No. These just opened up like this...

Seed pods will not appear until after pollination/fertilization of the plant parts and the flowers have to be fully open and mature for that to happen.

Could a couple of frosts have damaged the buds?

I agree with gardengal, it has to be an old bloom that's gone to seed. Does this plant have any buds left that haven't opened ? I would like to see a picture of an unopened bloom.

Couldn't it be a mutation where the flower self-pollinated and started developing seeds before opening? Mutations happen.

Thus is the way they opened. So disappointing.

This one just opened, it's the last one.

Yes, mutations can occur........but I have never heard of a mutation with an unopened flower bud achieving sexual maturity, pollinating itself AND developing seed pods (and a pretty advanced set at that) before opening! I'm not sure that is even botanically possible.

It is one of the intersectionals and it just does this. Sorry I do not remember which one as I do not collect them.

gardengal:

As far as I know, but I am not a botanist, autogamy is one of the ways Peonies self pollinate. I also know that in other plants (eg. Tomatoes) self pollination of that kind can take place even before the flower opens. Could it not have happened to op's plants? Is not Brown's Paeony an example of something similar?

Yes @windberry zone5a BCCanada, that's exactly what happened!!!
Will it always do this? This is a young plant in that it is its 3rd year here and only 2nd one blooming. Last year, the bloom was very very small and had a few petals. But this plant was really expensive (to me) and was supposed to produce massive double flowers.

If the carpels, which are the undeveloped seed pods, were not there before blooming there would be nothing for hybridizers to place pollen on. Those things in the center are carpels.

Will it always do this?

Agnes:

I can't say for sure, but I suppose the plant may produce normal flowers in the future. Why it happened is hard to say. In case of fasciation, which is another kind of deformity "Fasciation can be caused by hormonal imbalances in the meristematic cells of plants, which are cells where growth can occur. Fasciation can also be caused by random genetic mutation. Bacterial and viral infections can also cause fasciation." - Wikipedia.

Very likely the same explanation applies to your case.