The only pythons I've bred were Spotteds and Childrens many years ago but I have seen the late-showing vascularization with colubrid eggs many times. I work with Graybands, Mexicana ssp. and Pyros and it's so common that I never thought it was anything unusual so I can't really say if it's restricted to any certain species; I've definately seen it with the Graybands but I'm also pretty sure I've seen it with all those species I mentioned.
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