The egg or the reptiles, what was before?

2023/06/16 Etxebeste Aduriz, Egoitz - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Zoologia
• Eboluzioa

The first reptiles may not lay eggs and the pups may be born directly. This is what researchers have deduced in a study published in the journal Nature Ecology & Evolution.

So far, it has been considered that the egg with shells was a key egg for vertebrates to do it from the water to the earth. Thus, the study of 51 fossil species and 29 living species shows that the ancestors of the main evolutionary lines of terrestrial vertebrates (reptiles, birds and mammals) did not lay eggs and that the embryos developed within the mother.

In fact, according to this study, the maintenance of embryos inside the mother was one of the first keys to the grounding of vertebrates, followed by the hard shell egg.