'The event will run beginning today on all platforms until July 15th. As you traverse along the ground on any of the maps (the Island, The Center, Ragnarok, Aberration or Scorched Earth) you will come across fossil mounds which you are able to excavate. Inside the mounds, you'll find a few bones and if you're lucky you'll even find extra loot inside of one (signified by a special particle effect)! After you collect enough bones you’ll be able to craft several skins with the use of a Cooking Pot.'
Further reading at https://survivetheark.com/index.php?/articles.html/announcing-arkaeology-event-r837/
There are returning skins, the skeleton bone dino costumes:
Rex Bone Costume
Carno Bone Costume
Raptor Bone Costume
Bronto Bone Costume
Stego Bone Costume
Trike Bone Costume
Giganotosaurus Bone Costume
Quetzalcoatlus Bone Costume
Jerboa Bone Costume
Wyvern Bone Costume
The Tek Rex is, as the name implies, a rare, specially armored wild T-Rex that can achieve a higher level than its standard brethren. Previously isolated to just a cosmetic skin, these wild creatures will be roaming the ARKs (on maps where normal Rexes are present) and are yours for the taming, if you can handle it!
During this event all wild dinos have a chance to spawn with additional mutation colors: White, Yellow, Grey, and Black!