These are the Pokemon which are revived from fossils in game.
In Ewim's Verse Edit
Dex (Deoxys) owns the largest hospital/research complex in all the Regions. One of the divisions is dedicated to Project Recovery.
Project Recovery is the leading discovery project of the century. It's focus is on learning the truths of ancient cultures, history, and evolution for the sake of proper education, to learn from any past mistakes, to learn how cultures grow and fall through the eras, to learn the science behind how modern day Pokemon developed from their ancestors, and to help discover possible reasons why evolving Pokemon developed. After all, no Legendary Pokemon, whom are rumored to be the oldest of all Pokemon, can evolve or reproduce. And thus far, ancient Pokemon have shown to be capable of evolving only once. One of the main goals of the project is to discover when the first evolving Pokemon existed, how it came to be, how Pokemon gained additional evolutions, and why is it that not all modern day Pokemon have the same number of evolutions. More recently, an additional point of interest is the Mega Stones and their possible connection to these aspects.
The project's research is done primarily by reviving ancient Pokemon from fossils. Each of these revived Pokemon then progress through a series of stages.
Stage 1: Calm. This stage is designed to assist a newly revived Pokemon adjust to their new environment and to devise a method to handle aggressive Pokemon.
Stage 2: Communication. This stage is designed to establish a mode of communication with the revived Pokemon by either teaching the revived Pokemon the modern language or by learning the language of the revived Pokemon. Alternatively, pictures and written word are also utilized here. In addition to language, modern morals are also taught in order to ensure that the revived Pokemon does not inadvertently take an action that they would have done in their era but is illegal or immoral in this era, such as Pokemon/human sacrifices or various forms/intensity of sexual harassment.
Stage 3: Archive. This stage is designed to record all information, regardless of significance, that the revived Pokemon can recall and accurately share. This stage is also judged to be the point that the revived Pokemon is capable of understanding the concept, intricacies, laws, and moral standing behind Psychic mind reading and thus is able to truly consent to the process. This greatly helps improve both quantity and quality of information recalled by the revived Pokemon. There are some cases that the entire revived Pokemon's life has been recorded as a biography, in addition to varying amounts of detail of the different aspects of the civilization in which they lived.
Stage 4: Integration. This is the final stage, designed to help integrate the revived Pokemon into the new era. They are taught the laws and cultures of the Region they are interested in settling in, along with the Region's geography and history. They are also taught how to manage their lives, how to find a job, how to properly interact with modern Pokemon (including the current slang), and how to find a house in which to live. The revived Pokemon also has the option of staying with the scientists and the project by becoming a councilor, adviser, or psychiatrist in order to help other ancient Pokemon in Stage 1 or Stage 2. Whichever decision they make, they remain in contact with the project heads, on call in case there is another ancient Pokemon revived from their era or shares a common language with them.
In addition to the above, Project Recovery also makes advancement in the field of life restoration and prolongation, a side effect of which is also the discovery of cures to major and minor aliments, such as small pox or a few types of cancer.