In "Jurassic Park", they had to blame frog eggs used as part of the cloning process (I think it was frogs, wasn't it?) for the parthenogenesis. But apparently it happens in many lizard species, too. So in fact this might have happened even if they hadn't used frog eggs. I bet there are a lot of imaginary bioengineers breathing a sigh of relief over this one!
I thought (and I could very well be wrong) that in Jurassic Park they claimed that some of the females changed sex to become males. This also has a counterpart in other species, such as the Blue Groper.
It's been a while, but my recollection on this seems to match EFH's. There were initially only female dinosaurs, but parthenogenesis allowed the creation of male dinosaurs, who then breeded with the other dinos. So yes it was a surprise to the humans to discover that there were males and they were breeding, but individual dinos weren't changing gender. I think. It is interesting that the whole business about frog DNA may not have been necessary at all.
Although it may help for the short term survival of a species, it can't be a good tactic in the long run because it would slow down the evolutionary process by offering less chance to mix the genes up.
There will be glitches in my transition from being a saloon bar sage to a world statesman. - Tony Banks
Well, if the alternative is for an organism to simply die off without procreating, that would seem to offer even less chance to mix genes up. I agree that in general, sexual reproduction seems to be significantly advantageous, offering better opportunities to discover lucky genetic combinations which lead to greater chances of survival and further procreation. Plus, it's fun. But in the species that have exhibited parthenogenesis so far, it looks like they're quite happy to utilize sexual reproduction when possible... but they (females at least) are capable of parthenogenesis when males are not available. Maybe that's not the best option in general, but it beats dying with no descendants - at least from an evolutionary perspective.