Mysterious "Primal Pokémon"--ancestors who are the evolutionary link between two disparate species of Pokémon--have been appearing all across the Johto region. They will be listed and described here...
Primal Pokémon met so far (as of Part Seven)--
Six-Legged Stinger
Type: Bug/Poison
Common ancestor of Beedrill and Ariados
Known moves: Twineedle/Night Shade/Sticky Web/Poison Jab
Ability: Levitate
PrimalDex Entry: "In prehistoric times, Six-Legged Stinger was among the most fearsome Bug type predators. Able to fly at supersonic speeds, it can spit cobwebs and then jab its prey with its poison-tipped stingers. Its six legs are coated in a sticky serum that allows it to climb up almost any surface, allowing it to gain a vantage point to stake out its prey. Six-Legged Stinger's descendants split into two species after a niche was achieved by members of the species who were born without wings. These wingless Six-Legged Stingers became apex predators in the floors and canopies of forest, becoming the species of Ariados. Meanwhile, its aerially-inclined descendants became the modern species of Beedrill."
Roaring Serpent
Type: Dragon/Flying
Common ancestor of Dragonite and Salamence
Known moves: Dragon Rush/Safeguard/Crunch/Flamethrower
Ability: Serene Grace
PrimalDex Entry: "Roaring Serpent is a gentle giant that can live underwater, walk on land, and soar through the skies. It is known to comfort and care for smaller Pokémon, regardless of species. A global ice age caused the extinction of Roaring Serpent, as well as many other prehistoric Dragon type Pokémon. Some of its descendants evolved into Dragonite--which has a similar herbivorous diet and kind demeanor to Roaring Serpent. Other descendants evolved into the carnivorous and violent Salamence, part of a larger trend observed by scientists wherein descendants of previously herbivorous Dragon-types were forced to become predators due to the harsh conditions of the ice age leading to a global decimation of vegetation."
Poison Cannon
Type: Water/Poison
Common ancestor of Tentacruel and Octillery
Known moves: Octozooka/Smokescreen/Constrict/Sludge Bomb
Ability: Suction Cups
PrimalDex Entry: "Poison Cannon was the apex predator of the West Johto Sea in ancient times. It was able to swim at surprisingly fast speeds and capture its prey in its tentacles. It then blasted their prey point-blank with a poisonous gas with the force of a cannon. Poison Cannon's descendants split when some members of the species were born without the ability to produce poison. These poisonless descendants--which became the modern species of Octillery--found a niche within the ecosystem as they were able to mate more easily with other Water type Pokémon, as Poison Cannon was known to accidentally discharge poison during the process of breeding, which deterred many potential partners. Poison Cannon's other descendant, Tentacruel, retained its ability to secrete and spray poison."
Clownish Valiant
Type: Psychic/Fighting
Common ancestor of Mr. Mime and Gallade
Known moves: Barrier/Brick Break/Psycho Cut/Swords Dance
Ability: Prankster
PrimalDex Entry: "These incredibly intelligent Pokémon formed primitive societies in prehistory along with other Psychic type Pokémon, organizd in similar ways to modern human civilization. In these societies, Clownish Valiant served as both warriors and entertainers. In times of strife and war with other societies, it would wield its blade arms fiercely and summon invisible shields to gain the edge in combat. In times of peace, these usually fierce Pokémon would assume a jester-like demeanor and entertain younger Pokémon through its mime act. These two personality traits came into conflict among its descendants, with its warrior-like descendants becoming Gallade and its clown-like descendants becoming Mr. Mime."
Raging Snout
Type: Normal/Fighting
Common ancestor of Mankey and Lechonk
Known moves: Odor Sleuth/Karate Chop/Close Combat/Echoed Voice
Ability: Lingering Armoa
PrimalDex Entry: "These Pokémon were incredibly common in prehistoric time. Most of the time, Raging Snout is very docile and calm. It is a connossieur of fine smells--it had a highly-developed nose that can smell much better than even that of an Arcanine. This Pokémon likes to collect objects that smell good, having a special fondness for mushrooms. If someone tries to steal one of these items or emits a bad smell, Raging Snout with become balistic with anger and begin to attack them, pummeling them senselessly with its fists, only able to calm down if it smells something good. Its anger and ferocity made it a formidable Pokémon and adept at survival--its Mankey descendants inherited its latent rage and fighting abilities. Meanwhile, its Lechonk descendants inherited the Pokémon's mostly calm nature and advanced sense of smell."
Webbed Wings
Type: Water/Flying
Common ancestor of Golduck and Ducklett
Known moves: Aqua Jet/Hurricane/Psychic/Aerial Ace
Ability: Cloud Nine
PrimalDex Entry: "This Pokémon was a fearsome predator in ancient lakes, able to dive underwater and swim at high speeds thanks to its webbed hands and feet. It can catch fish and Bug Pokémon in its beak with ease. It is also covered with long, easily ruffled feathers and large wings, allowing it to fly--though it has difficulty gaining much altitude. Descendants of this Pokémon who focused on their adept swimming abilities evolved into the modern species of Psyduck and Golduck. Meanwhile, descendants that focused on flying became the modern Ducklett and Swanna."
Fiery Mountain
Type: Fire/Rock
Common ancestor of Charizard and Tyranitar
Known moves: Flamethrower/Outrage/Earthquake/Rock Slide
Ability: Intimidate
PrimalDex Entry: "This fearsome Pokémon was the apex predator of its day. Every other Pokémon feared Fiery Mountain due to its bad temper, insatiable appetite, and its vast arsenal of tools for hunting prey--it has sharp claws to slash through rock and trees, wings it can use to fly at deceptively highly speeds, and it even has the ability to breath fire from its mouth and from the holes all over its body. It has highly attuned senses and is a very light sleeper, liable to wake up within seconds if it hears any prey make noise within a few feet of where it is sleeping. However, even this Pokémon at the top of the food chain saw divergent paths for its descendants, mostly due to changes in diet. Its carnivorous descendants who still engaged in hunting became the modern Charmander line, preserving their wings and firebrething ability but shedding their heavy rock body to allow for easier movement. Other descendants of Fiery Mountain, however, mysteriously developed an appetite for minerals and rock. These descendants no longer needed to hunt and instead fed off mountains to survive--they became the modern Larvitar line, shedding their wings and hunting instincts."