Pokémon Go changed the latter from 7 km eggs. While the pinkish yellow eggs usually carry baby Pokémon, they now only bind fossil Pokémon.
This means that Omanyte, Kabuto, Aerodactyl, Lileep, Anorith, Cranidos, Shieldon, Tirtouga, and Archen are the only Pokémon from the eggs you receive through the gifts of friends. With this step, none of this will come from other eggs and Riolu will now hatch 10 km eggs.
There is no set date for the end of this ancient bonanza, but you can use this opportunity to get a Cranidos crowd, if you're lucky. Its origin, the Rampardos, is one of the best rock-type attacks in the game. Basododon, a modified form of Shieldon, is also a pretty solid PvP Pokémon.
Tirtouga and Archen are still new additions to the game, so this is also a great opportunity to catch yourself and just enough candy to emerge. Of course, you may doubt and end up with an Omanyte or Lileep team that you no longer need.
Note that this change does not affect the 7 km eggs you may have received earlier today. Those will still have the old Pokémon in them, but any egg you get from friends from the start will now tie the old Pokémon.