However, the skulls are a mere 3.5 centimetres long, as they came from unhatched eggs. (newscientist.com)
Definition of fetus -LCB- IS -RCB- An unborn or unhatched offspring of a mammal, in particular an unborn human baby more than eight weeks after conception. (religion.blogs.cnn.com)
They are probably unhatched embryos of Lufengosaurus, which is a close relative of the sauropods, and grew up to 9 metres long (Nature, DOI: 10.1038 / nature11978). (newscientist.com)