Relating to or lacking an allantois, which is a membrane that forms around developing embryos in certain animals.
From Greek 'an-' (without) + 'allantois' (sausage-shaped). The 'allantois' comes from Greek 'allas' (sausage), as the membrane resembles a sausage in shape.
The allantois is a temporary organ that helps developing bird and reptile embryos breathe and manage waste—if an animal is 'anallantoic,' it never develops one, which tells scientists about evolutionary relationships!
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