<prompt> Most common type of conjoint twin is -ThoracopagusOmphalopagusCraniopagusRachipagus  <response>: Ans. is a i.e., Thoracopagus o In case of monozygotic twins, the following possibilities may occur: If the division takes place within 72 hours after fertilization prior to morula stage the resulting embryos will have two separate placenta, chorions and amnions diamniotic - dichorionic twins If the division takes place between the 4th and 8th day after the formation of inner cell mass when chorion has already developed - diamniotic monochorionic twins develop. If the division occurs after 8th day of fertilization, when the amniotic cavity has already formed, a monoamniotic monochorionic twin develops. On extremely rare occasions, division occurs after 2 weeks of the development of embryonic disc resulting in the formation of conjoined twins, called as Siamese twins.o Four types of fusion may occur: Thorapagus - Most common Pyopagus posterior fusion Craniopagus cephalic Ischiopagus caudal 