Basically, it starts as a variation on the seahorse, once the ova are fertilized within the mother the embryoes are drawn back into the father who then carries them to term (there's actually a second, more gruesome stage to the process but that's probably a question for another time.) How w(c)ould this be done in a species of land-dwelling bipeds (still working on whether they're warm or cold-blodded)?

  • $\begingroup$ Kangaroo should qualify $\endgroup$ – user6760 Oct 3 '15 at 8:11

On Earth, the marsupials like kangaroos or koalas have an interresting system: the gestation period is very short, but they give birth to an undeveloped foetus that climbs by itself into the mother's pouch and keeps growing there, feeding from a nipple within this pocket. The male of some species like the tasmanian tiger even have a pouch too, although they do not use it for the babies. The obvious advantages are that the female is much less likely to die while giving birth, and is ready to be impregnated again after a short time.

If you go for an egg-laying species, the easiest I believe would be to have the female lay her eggs in the male's pouch with an appendage, the ovipositor. This is very similar to the seahorse system.

For a live-bearing species, the female could also give birth to the foetus with an appendage directly into the male's pouch. Or she can give birth to an undeveloped foetus that has to go by itself onto the male, then in his pouch. This implies that a kind of secondary sexual intercourse is required for the female to give birth. Lastly, the male can simply pick the newborn foetus and place it in his pouch.

Now, depending on how evolved your land-dwelling bipeds are, there could be a lot of specifics or rituals to each solution. Anyway it's either the female give the youngs to the male, the male takes the young from the female or the youngs go by themselves from the female to the male. There could also be a third party that take the youngs from the female and give them to the male, but this makes a minimum of three individuals for a natural reproduction.

  • $\begingroup$ We almost have that here on earth. The male Darwin's frog guards the eggs that the female deposits, and when the embryos start to move, he ingests the unborn tadpoles into his vocal sac and broods them there. $\endgroup$ – nigel222 Oct 3 '15 at 9:38
  • $\begingroup$ Also of note: Rheas (large flightless birds) where the male (alone or with other subservient males) guards the eggs and looks after the young, and Marmosets, where it's the father not the mother who does the child-rearing. $\endgroup$ – nigel222 Oct 3 '15 at 9:39
  • $\begingroup$ Interesting examples, but wouldn't work with what I have in mind. The alien is a live-bearing species that births a litter, but after the father takes the embryoes into his body and the parents seperate he kills and eats his mate (the gruesome next stage I mentioned in the question). $\endgroup$ – king of panes Oct 3 '15 at 19:23

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