It is not known to evolve into or from any other Pokémon.
Heatran on a wall
Heatran is a reddish-brown Pokémon resembling a tortoise and a ram. It is dotted with orange and gray spots, and it has metal bangles locked on its legs. Its four claws on each of its feet are in a cross formation. These claws allow it to dig deep into walls, and its feet allow it to stick to a surface, so it can hang and climb from walls and ceilings. Heatran has a gray underside, and its face is covered by an iron mask, with red-orange eyes uncovered. Whenever it is seen with its mouth open, an orange glow emanates from inside it. Because of its intense body heat, certain parts of its body are melted slightly out of shape. Boiling blood, like magma, circulates through its body. Heatran is a fierce guardian. Without the power of the Magma Stone, Heatran would rampage and cause the volcanic crater where it dwells to erupt. Heatran is the only known Pokémon that learns Magma Storm.
In Pokémon Adventures, Heatran is referred to as the "Lord of Stark Mountain." Heatran first appears in the Platinum chapter after Buck goes to Stark Mountain to try to prevent Team Galactic from getting to it first. However, after Buck removes the Magma Stone that sealed Heatran, Charon captures it and uses it to attack Buck. Charon takes Heatran to Eterna City to battle Regigigas, who had joined Diamond's team as Reg. The battle is interrupted when Charon decides to follow the rampaging Giratina back to the Distortion World. There, the battle between Heatran and Reg resumes, with the lake guardians assisting Reg. At the end of the arc, Buck announces that he would escort Heatran back to Stark Mountain. Cheryl and Mira agree to help. It first appeared in Clobbering Claydol.
In the Japanese version of Pokémon X and Y, two women in Jaune Plaza mimic the sounds of Pokémon. One mimics the sound of a Heatran while the other compliments her. However, this is mistranslated in the English version to say that there is a Lava Dome Pokémon here in Jaune Plaza.
Heatran has the lowest number of Egg cycles of all Legendary Pokémon, with 10.
Currently, Heatran is the only Pokémon not from Generation VII that cannot obtain its Hidden Ability.
Heatran is most likely based on volcanic remains. Its Steel type references how the Earth's inner core is made of solid metal under immense pressure. It may be also based on a generic volcano monster: in the ancient mythologies of most cultures volcano's eruption was explained by the presence of a fire monster inside it, often a dragon. It may also be based on a turtle, as the Pokémon Platinum Pokédex entry states that it is melted in parts because of its own heat and in the artwork, bits of metal, which may possibly be a melted shell, can be seen on its body. Due to the fact that it crawls on the ceiling and learns the move Bug Bite, it may also be based on some larger variants of insects, particularly cockroaches.