One interesting thing I have heard is that amongst hyenas females have more androgens, and this is also visible in size, behavior etc. Must be an interesting kind of puberty.
Yep. While having different developmental payhways to making ova and sperm is ancient, pretty much everything else associated with biological sex is potentially mutable over evolutionary time (and even that can revert to hermaphrodite status).
I am unaware of any examples of normally functionally hermaphroditic mammals, and unaware of but less confident in the same for tetrapods (four limbed vertebrares that came onto land and their descendants). I am aware of tetrapod species that became almost entirely female, reproducing primarily by cloning. I am also aware of tetrapods that switch sex during their lifetimes, though you could call that a form of hermaphroditism. Tetrapods also exhibit all of the above methods of sex determination.
The pattern of hermaphroditism in ray finned fish, a very diverse and old vertebrate lineage, however suggests multiple conversion events back and forth some of which are recent. See http://evolution.berkeley.edu/evolibrary/images/hermaphroditismtree.gif . Of note, cichlid fish are listed as hermaphroditic on there but recently went through a huge evolutionary radiation and several of their sublineages have been caught in the act of reevolving most of the above sex determination systems.
One interesting thing I have heard is that amongst hyenas females have more androgens, and this is also visible in size, behavior etc. Must be an interesting kind of puberty.
Yep. While having different developmental payhways to making ova and sperm is ancient, pretty much everything else associated with biological sex is potentially mutable over evolutionary time (and even that can revert to hermaphrodite status).
Has that actually happened to anything amphibian or above?
I am unaware of any examples of normally functionally hermaphroditic mammals, and unaware of but less confident in the same for tetrapods (four limbed vertebrares that came onto land and their descendants). I am aware of tetrapod species that became almost entirely female, reproducing primarily by cloning. I am also aware of tetrapods that switch sex during their lifetimes, though you could call that a form of hermaphroditism. Tetrapods also exhibit all of the above methods of sex determination.
The pattern of hermaphroditism in ray finned fish, a very diverse and old vertebrate lineage, however suggests multiple conversion events back and forth some of which are recent. See http://evolution.berkeley.edu/evolibrary/images/hermaphroditismtree.gif . Of note, cichlid fish are listed as hermaphroditic on there but recently went through a huge evolutionary radiation and several of their sublineages have been caught in the act of reevolving most of the above sex determination systems.